Cognitive Enhancement

Front Cell Neurosci 2019 Mar 19;13:74. doi: 10.3389/fncel.2019.00074. eCollection 2019.

Photobiomodulation and Coenzyme Q10 Treatments Attenuate Cognitive Impairment Associated With Model of Transient Global Brain Ischemia in Artificially Aged Mice.

Author information

Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
Department of Medical Physics, Tabriz University of Medical Sciences, Tabriz, Iran.
ProNeuroLIGHT LLC, Phoenix, AZ, United States.
Higher Educational Institute of Rab-Rashid, Tabriz, Iran.
Department of Medical Bioengineering, Tabriz University of Medical Sciences, Tabriz, Iran.
School of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom.
Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, United States.
Department of Dermatology, Harvard Medical School, Boston, MA, United States.
Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States.
Departments of Clinical Research and Nuclear Medicine, Odense University Hospital, University of Southern Denmark, Odense, Denmark.
Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.
Department of Neurology & Neurosurgery, McGill University, Montreal, QC, Canada.
Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States.


Disturbances in mitochondrial biogenesis and bioenergetics, combined with neuroinflammation, play cardinal roles in the cognitive impairment during aging that is further exacerbated by transient cerebral ischemia. Both near-infrared (NIR) photobiomodulation (PBM) and Coenzyme Q10 (CoQ10) administration are known to stimulate mitochondrial electron transport that potentially may reverse the effects of cerebral ischemia in aged animals. We tested the hypothesis that the effects of PBM and CoQ10, separately or in combination, improve cognition in a mouse model of transient cerebral ischemia superimposed on a model of aging. We modeled aging by 6-week administration of D-galactose (500 mg/kg subcutaneous) to mice. We subsequently induced transient cerebral ischemia by bilateral occlusion of the common carotid artery (BCCAO). We treated the mice with PBM (810 nm transcranial laser) or CoQ10 (500 mg/kg by gavage), or both, for 2 weeks after surgery. We assessed cognitive function by the Barnes and Lashley III mazes and the What-Where-Which (WWWhich) task. PBM or CoQ10, and both, improved spatial and episodic memory in the mice. Separately and together, the treatments lowered reactive oxygen species and raised ATP and general mitochondrial activity as well as biomarkers of mitochondrial biogenesis, including SIRT1, PGC-1?, NRF1, and TFAM. Neuroinflammatory responsiveness declined, as indicated by decreased iNOS, TNF-?, and IL-1? levels with the PBM and CoQ10 treatments. Collectively, the findings of this preclinical study imply that the procognitive effects of NIR PBM and CoQ10treatments, separately or in combination, are beneficial in a model of transient global brain ischemia superimposed on a model of aging in mice.


Coenzyme Q10; aging; global ischemia; learning and memory; mitochondrial biogenesis; neuroinflammation; transcranial photobiomodulation.

Lasers Med Sci. 2017 May 2. doi: 10.1007/s10103-017-2221-y. [Epub ahead of print]

Beneficial neurocognitive effects of transcranial laser in older adults.

Vargas E1, Barrett DW1, Saucedo CL1, Huang LD2, Abraham JA2, Tanaka H3, Haley AP1, Gonzalez-Lima F4.

Author information

Department of Psychology and Institute for Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Electrical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Psychology and Institute for Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA.


Transcranial infrared laser stimulation (TILS) at 1064 nm, 250 mW/cm2 has been proven safe and effective for increasing neurocognitive functions in young adults in controlled studies using photobiomodulation of the right prefrontal cortex. The objective of this pilot study was to determine whether there is any effect from TILS on neurocognitive function in older adults with subjective memory complaint at risk for cognitive decline (e.g., increased carotid artery intima-media thickness or mild traumatic brain injury). We investigated the cognitive effects of TILS in older adults (ages 49-90, n = 12) using prefrontal cortex measures of attention (psychomotor vigilance task (PVT)) and memory (delayed match to sample (DMS)), carotid artery intima-media thickness (measured by ultrasound), and evaluated the potential neural mechanisms mediating the cognitive effects of TILS using exploratory brain studies of electroencephalography (EEG, n = 6) and functional magnetic resonance imaging (fMRI, n = 6). Cognitive performance, age, and carotid artery intima-media thickness were highly correlated, but all participants improved in all cognitive measures after TILS treatments. Baseline vs. chronic (five weekly sessions, 8 min each) comparisons of mean cognitive scores all showed improvements, significant for PVT reaction time (p < 0.001), PVT lapses (p < 0.001), and DMS correct responses (p < 0.05). The neural studies also showed for the first time that TILS increases resting-state EEG alpha, beta, and gamma power and promotes more efficient prefrontal blood-oxygen-level-dependent (BOLD)-fMRI response. Importantly, no adverse effects were found. These preliminary findings support the use of TILS for larger randomized clinical trials with this non-invasive approach to augment neurocognitive function in older people to combat aging-related and vascular disease-related cognitive decline.

BBA Clin. 2016 Dec; 6: 113–124.
Published online 2016 Oct 1. doi:  10.1016/j.bbacli.2016.09.002
PMCID: PMC5066074

Shining light on the head: Photobiomodulation for brain disorders

Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA
Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA
Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA
Michael R. Hamblin: ude.dravrah.hgm.xileh@nilbmaH
?Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA.Wellman Center for PhotomedicineMassachusetts General HospitalBostonMA02114USA ude.dravrah.hgm.xileh@nilbmaH
Author information ? Article notes ? Copyright and License information ?
Received 2016 Sep 2; Revised 2016 Sep 27; Accepted 2016 Sep 29.


Photobiomodulation (PBM) describes the use of red or near-infrared light to stimulate, heal, regenerate, and protect tissue that has either been injured, is degenerating, or else is at risk of dying. One of the organ systems of the human body that is most necessary to life, and whose optimum functioning is most worried about by humankind in general, is the brain. The brain suffers from many different disorders that can be classified into three broad groupings: traumatic events (stroke, traumatic brain injury, and global ischemia), degenerative diseases (dementia, Alzheimer’s and Parkinson’s), and psychiatric disorders (depression, anxiety, post traumatic stress disorder). There is some evidence that all these seemingly diverse conditions can be beneficially affected by applying light to the head. There is even the possibility that PBM could be used for cognitive enhancement in normal healthy people. In this transcranial PBM (tPBM) application, near-infrared (NIR) light is often applied to the forehead because of the better penetration (no hair, longer wavelength). Some workers have used lasers, but recently the introduction of inexpensive light emitting diode (LED) arrays has allowed the development of light emitting helmets or “brain caps”. This review will cover the mechanisms of action of photobiomodulation to the brain, and summarize some of the key pre-clinical studies and clinical trials that have been undertaken for diverse brain disorders.

Keywords: Photobiomodulation, Low level laser (light) therapy, Ischemic stroke, Traumatic brain injury, Alzheimer’s disease, Parkinson’s disease, Major depression, Cognitive enhancement

Graphical abstract

Image 2


Photobiomodulation (PBM) as it is known today (the beneficial health benefits of light therapy had been known for some time before), was accidently discovered in 1967, when Endre Mester from Hungary attempted to repeat an experiment recently published by McGuff in Boston, USA [1]. McGuff had used a beam from the recently discovered ruby laser [2], to destroy a cancerous tumor that had been experimentally implanted into a laboratory rat. However (unbeknownst to Mester) the ruby laser that had been built for him, was only a tiny fraction of the power of the laser that had previously been used by McGuff. However, instead of curing the experimental tumors with his low-powered laser, Mester succeeded in stimulating hair regrowth and wound healing in the rats, in the sites where the tumors had been implanted [3], [4]. This discovery led to a series of papers describing what Mester called “laser biostimulation”, and soon became known as “low level laser therapy” (LLLT) [5], [6], [7].

LLLT was initially primarily studied for stimulation of wound healing, and reduction of pain and inflammation in various orthopedic conditions such as tendonitis, neck pain, and carpal tunnel syndrome [8]. The advent of light emitting diodes (LED) led to LLLT being renamed as “low level light therapy”, as it became more accepted that the use of coherent lasers was not absolutely necessary, and a second renaming occurred recently [9] when the term PBM was adopted due to uncertainties in the exact meaning of “low level”.

2.?Mechanisms of action of photobiomodulation

2.1. Mitochondria and cytochrome c oxidase

The most well studied mechanism of action of PBM centers around cytochrome c oxidase (CCO), which is unit four of the mitochondrial respiratory chain, responsible for the final reduction of oxygen to water using the electrons generated from glucose metabolism [10]. The theory is that CCO enzyme activity may be inhibited by nitric oxide (NO) (especially in hypoxic or damaged cells). This inhibitory NO can be dissociated by photons of light that are absorbed by CCO (which contains two heme and two copper centers with different absorption spectra) [11]. These absorption peaks are mainly in the red (600–700 nm) and near-infrared (760–940 nm) spectral regions. When NO is dissociated, the mitochondrial membrane potential is increased, more oxygen is consumed, more glucose is metabolized and more ATP is produced by the mitochondria.

2.2. Reactive oxygen species, nitric oxide, blood flow

It has been shown that there is a brief increase in reactive oxygen species (ROS) produced in the mitochondria when they absorb the photons delivered during PBM. The idea is that this burst of ROS may trigger some mitochondrial signaling pathways leading to cytoprotective, anti-oxidant and anti-apoptotic effects in the cells [12]. The NO that is released by photodissociation acts as a vasodilator as well as a dilator of lymphatic flow. Moreover NO is also a potent signaling molecule and can activate a number of beneficial cellular pathways [13]. Fig. 2 illustrates these mechanisms.

Fig. 2

Tissue specific processes that occur after PBM and benefit a range of brain disorders. BDNF, brain-derived neurotrophic factor; LLLT, low level light therapy; NGF, nerve growth factor; NT-3, neurotrophin 3; PBM, photobiomodulation; SOD, superoxide dismutase.

2.3. Light sensitive ion channels and calcium

It is quite clear that there must be some other type of photoacceptor, in addition to CCO, as is clearly demonstrated by the fact that wavelengths substantially longer than the red/NIR wavelengths discussed above, can also produce beneficial effects is some biological scenarios. Wavelengths such as 980 nm [14], [15], 1064 nm laser [16], and 1072 nm LED [17], and even broad band IR light [18] have all been reported to carry out PBM type effects. Although the photoacceptor for these wavelengths has by no means been conclusively identified, the leading hypothesis is that it is primarily water (perhaps nanostructured water) located in heat or light sensitive ion channels. Clear changes in intracellular calcium can be observed, that could be explained by light-mediated opening of calcium ion channels, such as members of the transient receptor potential (TRP) super-family [19]. TRP describes a large family of ion channels typified by TRPV1, recently identified as the biological receptor for capsaicin (the active ingredient in hot chili peppers) [20]. The biological roles of TRP channels are multifarious, but many TRP channels are involved in heat sensing and thermoregulation [21].

2.4. Signaling mediators and activation of transcription factors

Most authors suggest that the beneficial effects of tPBM on the brain can be explained by increases in cerebral blood flow, greater oxygen availability and oxygen consumption, improved ATP production and mitochondrial activity [22], [23], [24]. However there are many reports that a brief exposure to light (especially in the case of experimental animals that have suffered some kind of acute injury or traumatic insult) can have effects lasting days, weeks or even months [25]. This long-lasting effect of light can only be explained by activation of signaling pathways and transcription factors that cause changes in protein expression that last for some considerable time. The effects of PBM on stimulating mitochondrial activity and blood flow is of itself, unlikely to explain long-lasting effects. A recent review listed no less than fourteen different transcription factors and signaling mediators, that have been reported to be activated after light exposure [10].

Fig. 1 illustrates two of the most important molecular photoreceptors or chromophores (cytochrome c oxidase and heat-gated ion channels) inside neuronal cells that absorb photons that penetrate into the brain. The signaling pathways and activation of transcription factors lead to the eventual effects of PBM in the brain.

Fig. 1

Molecular and intracellular mechanisms of transcranial low level laser (light) or photobiomodulation. AP1, activator protein 1; ATP, adenosine triphosphate; Ca2 +, calcium ions; cAMP, cyclic adenosine monophosphate; NF-kB, nuclear factor kappa

Fig. 2 illustrates some more tissue specific mechanisms that lead on from the initial photon absorption effects explained in Fig. 1. A wide variety of processes can occur that can benefit a correspondingly wide range of brain disorders. These processes can be divided into short-term stimulation (ATP, blood flow, lymphatic flow, cerebral oxygenation, less edema). Another group of processes center around neuroprotection (upregulation of anti-apoptotic proteins, less excitotoxity, more antioxidants, less inflammation). Finally a group of processes that can be grouped under “help the brain to repair itself” (neurotrophins, neurogenesis and synaptogenesis).

2.5. Biphasic dose response and effect of coherence

The biphasic dose response (otherwise known as hormesis, and reviewed extensively by Calabrese et al. [26]) is a fundamental biological law describing how different biological systems can be activated or stimulated by low doses of any physical insult or chemical substance, no matter how toxic or damaging this insult may be in large doses. The most well studied example of hormesis is that of ionizing radiation, where protective mechanisms are induced by very low exposures, that can not only protect against subsequent large doses of ionizing radiation, but can even have beneficial effects against diseases such as cancer using whole body irradiation [27].

There are many reports of PBM following a biphasic dose response (sometimes called obeying the Arndt-Schulz curve [28], [29]. A low dose of light is beneficial, but raising the dose produces progressively less benefit until eventually a damaging effect can be produced at very high light [30]. It is often said in this context that “more does not mean more”.

Another question that arises in the field of PBM is whether the coherent monochromatic lasers that were used in the original discovery of the effect, and whose use continued for many years, are superior to the rather recent introduction of LEDs, that are non-coherent and have a wider band-spread (generally 30 nm full-width half-maximum). Although there are one or two authors who continue to believe that coherent lasers are superior [31], most commentators feel that other parameters such as wavelength, power density, energy density and total energy are the most important determinants of efficacy [8].

3.?Tissue optics, direct versus systemic effects, light sources

3.1. Light penetration into the brain

Due to the growing interest in PBM of the brain, several tissue optics laboratories have investigated the penetration of light of different wavelengths through the scalp and the skull, and to what depths into the brain this light can penetrate. This is an intriguing question to consider, because at present it is unclear exactly what threshold of power density in mW/cm2 is required in the b5rain to have a biological effect. There clearly must be a minimum value below which the light can be delivered for an infinite time without doing anything, but whether this is in the region of ?W/cm2 or mW/cm2 is unknown at present.

Functional near-infrared spectroscopy (fNIRS) using 700–900 nm light has been established as a brain imaging technique that can be compared to functional magnetic resonance imaging (fMRI) [32]. Haeussinger et al. estimated that the mean penetration depth (5% remaining intensity) of NIR light through the scalp and skull was 23:6 + 0:7 mm [33]. Other studies have found comparable results with variations depending on the precise location on the head and wavelength [34], [35].

Jagdeo et al. [36] used human cadaver heads (skull with intact soft tissue) to measure penetration of 830 nm light, and found that penetration depended on the anatomical region of the skull (0.9% at the temporal region, 2.1% at the frontal region, and 11.7% at the occipital region). Red light (633 nm) hardly penetrated at all. Tedord et al. [37] also used human cadaver heads to compare penetration of 660 nm, 808 nm, and 940 nm light. They found that 808 nm light was best and could reach a depth in the brain of 40–50 mm. Lapchak et al. compared the transmission of 810 nm light through the skulls of four different species, and found mouse transmitted 40%, while for rat it was 21%, rabbit it was 11.3 and for human skulls it was only 4.2% [38]. Pitzschke and colleagues compared penetration of 670 nm and 810 nm light into the brain when delivered by a transcranial or a transphenoidal approach, and found that the best combination was 810 nm delivered transphenoidally [39]. In a subsequent study these authors compared the effects of storage and processing (frozen or formalin-fixed) on the tissue optical properties of rabbit heads [40]. Yaroslavsky et al. examined light penetration of different wavelengths through different parts of the brain tissue (white brain matter, gray brain matter, cerebellum, and brainstem tissues, pons, thalamus). Best penetration was found with wavelengths between 1000 and 1100 nm [41].

Henderson and Morries found that between 0.45% and 2.90% of 810 nm or 980 nm light penetrated through 3 cm of scalp, skull and brain tissue in ex vivo lamb heads [42].

3.2. Systemic effects

It is in fact very likely that the beneficial effects of PBM on the brain cannot be entirely explained by penetration of photons through the scalp and skull into the brain itself. There have been some studies that have explicitly addressed this exact issue. In a study of PBM for Parkinson’s disease in a mouse model [43]. Mitrofanis and colleagues compared delivering light to the mouse head, and also covered up the head with aluminum foil so that they delivered light to the remainder of the mouse body. They found that there was a highly beneficial effect on neurocognitive behavior with irradiation to the head, but nevertheless there was also a statistically significant (although less pronounced benefit, referred to by these authors as an ‘abscopal effect”) when the head was shielded from light [44]. Moreover Oron and co-workers [45] have shown that delivering NIR light to the mouse tibia (using either surface illumination or a fiber optic) resulted in improvement in a transgenic mouse model of Alzheimer’s disease (AD). Light was delivered weekly for 2 months, starting at 4 months of age (progressive stage of AD). They showed improved cognitive capacity and spatial learning, as compared to sham-treated AD mice. They proposed that the mechanism of this effect was to stimulate c-kit-positive mesenchymal stem cells (MSCs) in autologous bone marrow (BM) to enhance the capacity of MSCs to infiltrate the brain, and clear ?-amyloid plaques [46]. It should be noted that the calvarial bone marrow of the skull contains substantial numbers of stem cells [47].

3.3. Laser acupuncture

Laser acupuncture is often used as an alternative or as an addition to traditional Chinese acupuncture using needles [48]. Many of the applications of laser acupuncture have been for conditions that affect the brain [49] such as Alzheimer’s disease [50] and autism [51] that have all been investigated in animal models. Moreover laser acupuncture has been tested clinically [52].

3.4. Light sources

A wide array of different light sources (lasers and LEDs) have been employed for tPBM. One of the most controversial questions which remains to be conclusively settled, is whether a coherent monochromatic laser is superior to non-coherent LEDs typically having a 30 nm band-pass (full width half maximum). Although wavelengths in the NIR region (800–1100 nm) have been the most often used, red wavelengths have sometimes been used either alone, or in combination with NIR. Power levels have also varied markedly from Class IV lasers with total power outputs in the region of 10 W [53], to lasers with more modest power levels (circa 1 W). LEDs can also have widely varying total power levels depending on the size of the array and the number and power of the individual diodes. Power densities can also vary quite substantially from the Photothera laser [54] and other class IV lasers , which required active cooling (~ 700 mW/cm2) to LEDs in the region of 10–30 mW/cm2.

3.5. Usefulness of animal models when testing tPBM for brain disorders

One question that is always asked in biomedical research, is how closely do the laboratory models of disease (which are usually mice or rats) mimic the human disease for which new treatments are being sought? This is no less critical a question when the areas being studied include brain disorders and neurology. There now exist a plethora of transgenic mouse models of neurological disease [55], [56]. However in the present case, where the proposed treatment is almost completely free of any safety concerns, or any reported adverse side effects, it can be validly questioned as to why the use of laboratory animal models should be encouraged. Animal models undoubtedly have disadvantages such as failure to replicate all the biological pathways found in human disease, difficulty in accurately measuring varied forms of cognitive performance, small size of mice and rats compared to humans, short lifespan affecting the development of age related diseases, and lack of lifestyle factors that adversely affect human diseases. Nevertheless, small animal models are less expensive, and require much less time and effort to obtain results than human clinical trials, so it is likely they will continue to be used to test tPBM for the foreseeable future.

4.?PBM for stroke

4.1. Animal models

Perhaps the most well-investigated application of PBM to the brain, lies in its possible use as a treatment for acute stroke [57]. Animal models such as rats and rabbits, were first used as laboratory models, and these animals had experimental strokes induced by a variety of methods and were then treated with light (usually 810 nm laser) within 24 h of stroke onset [58]. In these studies intervention by tLLLT within 24 h had meaningful beneficial effects. For the rat models, stroke was induced by middle cerebral artery occlusion (MCAO) via an insertion of a filament into the carotid artery or via craniotomy [59], [60]. Stroke induction in the “rabbit small clot embolic model” (RSCEM) was by injection of a preparation of small blood clots (made from blood taken from a second donor rabbit) into a catheter placed in the right internal carotid artery [61]. These studies and the treatments and results are listed in Table 1.

Table 1

Reports of transcranial LLLT used for stroke in animal models.

CW, continuous wave; LLLT, low level light therapy; MCAO, middle cerebral artery occlusion; NOS, nitric oxide synthase; RSCEM, rabbit small clot embolic model; TGF?1, transforming growth factor ?1.

4.2. Clinical trials for acute stroke

Treatment of acute stroke was addressed in a series of three clinical trials called “Neurothera Effectiveness and Safety Trials” (NEST-1 [65], NEST-2 [66], and NEST-3 [67]) using an 810 nm laser applied to the shaved head within 24 h of patients suffering an ischemic stroke. The first study, NEST-1, enrolled 120 patients between the ages of 40 to 85 years of age with a diagnosis of ischemic stroke involving a neurological deficit that could be measured. The purpose of this first clinical trial was to demonstrate the safety and effectiveness of laser therapy for stroke within 24 h [65]. tPBM significantly improved outcome in human stroke patients, when applied at ~ 18 h post-stroke, over the entire surface of the head (20 points in the 10/20 EEG system) regardless of stroke [65]. Only one laser treatment was administered, and 5 days later, there was significantly greater improvement in the Real- but not in the Sham-treated group (p < 0.05, NIH Stroke Severity Scale). This significantly greater improvement was still present at 90 days post-stroke, where 70% of the patients treated with Real-LLLT had a successful outcome, while only 51% of Sham-controls did. The second clinical trial, NEST-2, enrolled 660 patients, aged 40 to 90, who were randomly assigned to one of two groups (331 to LLLT, 327 to sham) [68]. Beneficial results (p < 0.04) were found for the moderate and moderate-severe (but not for the severe) stroke patients, who received the Real laser protocol [68]. These results suggested that the overall severity of the individual stroke should be taken into consideration in future studies, and very severe patients are unlikely to recover with any kind of treatment. The last clinical trial, NEST-3, was planned for 1000 patients enrolled. Patients in this study were not to receive tissue plasminogen activator, but the study was prematurely terminated by the DSMB for futility (an expected lack of statistical significance) [67]. NEST-1 was considered successful, even though as a phase 1 trial, it was not designed to show efficacy. NEST-2 was partially successful when the patients were stratified, to exclude very severe strokes or strokes deep within the brain [66]. There has been considerable discussion in the scientific literature on precisely why the NEST-3 trial failed [69]. Many commentators have wondered how could tPBM work so well in the first trial, in a sub-group in the second trial, and fail in the third trial. Lapchak’s opinion is that the much thicker skull of humans compared to that of the other animals discussed above (mouse, rat and rabbit), meant that therapeutically effective amounts of light were unlikely to reach the brain [69]. Moreover the time between the occurrence of a stroke and initiation of the PBMT may be an important factor. There are reports in the literature that neuroprotection must be administered as soon as possible after a stroke [70], [71]. Furthermore, stroke trials in particular should adhere to the RIGOR (rigorous research) guidelines and STAIR (stroke therapy academic industry roundtable) criteria [72]. Other contributory causes to the failure of NEST-3 may have been included the decision to use only one single tPBM treatment, instead of a series of treatments. Moreover, the optimum brain areas to be treated in acute stroke remain to be determined. It is possible that certain areas of the brain that have sustained ischemic damage should be preferentially illuminated and not others.

4.3. Chronic stroke

Somewhat surprisingly, there have not as yet been many trials of PBM for rehabilitation of stroke patients with only the occasional report to date. Naeser reported in an abstract the use of tPBM to treat chronic aphasia in post-stroke patients [73]. Boonswang et al. [74] reported a single patient case in which PBM was used in conjunction with physical therapy to rehabilitate chronic stroke damage. However the findings that PBM can stimulate synaptogenesis in mice with TBI, does suggest that tPBM may have particular benefits in rehabilitation of stroke patients. Norman Doidge, in Toronto, Canada has described the use of PBM as a component of a neuroplasticity approach to rehabilitate chronic stroke patients [75].

5. PBM for traumatic brain injury (TBI)

5.1. Mouse and rat models

There have been a number of studies looking at the effects of PBM in animal models of TBI. Oron’s group was the first [76] to demonstrate that a single exposure of the mouse head to a NIR laser (808 nm) a few hours after creation of a TBI lesion could improve neurological performance and reduce the size of the brain lesion. A weight-drop device was used to induce a closed-head injury in the mice. An 808 nm diode laser with two energy densities (1.2–2.4 J/cm2 over 2 min of irradiation with 10 and 20 mW/cm2) was delivered to the head 4 h after TBI was induced. Neurobehavioral function was assessed by the neurological severity score (NSS). There were no significant difference in NSS between the power densities (10 vs 20 mW/cm2) or significant differentiation between the control and laser treated group at early time points (24 and 48 h) post TBI. However, there was a significant improvement (27% lower NSS score) in the PBM group at times of 5 days to 4 weeks. The laser treated group also showed a smaller loss of cortical tissue than the sham group [76].

Hamblin’s laboratory then went on (in a series of papers [76]) to show that 810 nm laser (and 660 nm laser) could benefit experimental TBI both in a closed head weight drop model [77], and also in controlled cortical impact model in mice [25]. Wu et al. [77] explored the effect that varying the laser wavelengths of LLLT had on closed-head TBI in mice. Mice were randomly assigned to LLLT treated group or to sham group as a control. Closed-head injury (CHI) was induced via a weight drop apparatus. To analyze the severity of the TBI, the neurological severity score (NSS) was measured and recorded. The injured mice were then treated with varying wavelengths of laser (665, 730, 810 or 980 nm) at an energy level of 36 J/cm2 at 4 h directed onto the scalp. The 665 nm and 810 nm groups showed significant improvement in NSS when compared to the control group at day 5 to day 28. Results are shown in Fig. 3. Conversely, the 730 and 980 nm groups did not show a significant improvement in NSS and these wavelengths did not produce similar beneficial effects as in the 665 nm and 810 nm LLLT groups [77]. The tissue chromophore cytochrome c oxidase (CCO) is proposed to be responsible for the underlying mechanism that produces the many PBM effects that are the byproduct of LLLT. COO has absorption bands around 665 nm and 810 nm while it has low absorption bands at the wavelength of 730 nm [78]. It should be noted that this particular study found that the 980 nm did not produce the same positive effects as the 665 nm and 810 nm wavelengths did; nevertheless previous studies did find that the 980 nm wavelength was an active one for LLLT. Wu et al. proposed that these dissimilar results may be due to the variance in the energy level, irradiance, etc. between the other studies and this particular study [77].

Fig. 3

tPBM for TBI in a mouse model. Mice received a closed head injury and 4 hours later a single exposure of the head to one of four different lasers (36 J/cm2 delivered at 150 mW/cm2 over 4 min with spot size 1-cm diameter)

Ando et al. [25] used the 810 nm wavelength laser parameters from the previous study and varied the pulse modes of the laser in a mouse model of TBI. These modes consisted of either pulsed wave at 10 Hz or at 100 Hz (50% duty cycle) or continuous wave laser. For the mice, TBI was induced with a controlled cortical impact device via open craniotomy. A single treatment with an 810 nm Ga-Al-As diode laser with a power density of 50 mW/m2 and an energy density of 36 J/cm2 was given via tLLLT to the closed head in mice for a duration of 12 min at 4 h post CCI. At 48 h to 28 days post TBI, all laser treated groups had significant decreases in the measured neurological severity score (NSS) when compared to the control (Fig. 4A). Although all laser treated groups had similar NSS improvement rates up to day 7, the PW 10 Hz group began to show greater improvement beyond this point as seen in Fig. 4. At day 28, the forced swim test for depression and anxiety was used and showed a significant decrease in the immobility time for the PW 10 Hz group. In the tail suspension test which measures depression and anxiety, there was also a significant decrease in the immobility time at day 28, and this time also at day 1, in the PW 10 Hz group.

Fig. 4

tPBM for controlled cortical impact TBI in a mouse model. (A) Mice received a single exposure (810 nm laser, 36 J/cm2 delivered at 50 mW/cm2 over 12 min) [121]. (B) Mice received 3 daily exposures starting 4 h post-TBI

Studies using immunofluorescence of mouse brains showed that tPBM increased neuroprogenitor cells in the dentate gyrus (DG) and subventricular zone at 7 days after the treatment [79]. The neurotrophin called brain derived neurotrophic factor (BDNF) was also increased in the DG and SVZ at 7 days , while the marker (synapsin-1) for synaptogenesis and neuroplasticity was increased in the cortex at 28 days but not in the DG, SVZ or at 7 days [80] (Fig. 4B). Learning and memory as measured by the Morris water maze was also improved by tPBM [81]. Whalen’s laboratory [82] and Whelan’s laboratory [83] also successfully demonstrated therapeutic benefits of tPBM for TBI in mice and rats respectively.

Zhang et al. [84] showed that secondary brain injury occurred to a worse degree in mice that had been genetically engineered to lack “Immediate Early Response” gene X-1 (IEX-1) when exposed to a gentle head impact (this injury is thought to closely resemble mild TBI in humans). Exposing IEX-1 knockout mice to LLLT 4 h post injury, suppressed proinflammatory cytokine expression of interleukin (IL)-I? and IL-6, but upregulated TNF-?. The lack of IEX-1 decreased ATP production, but exposing the injured brain to LLLT elevated ATP production back to near normal levels.

Dong et al. [85] even further improved the beneficial effects of PBM on TBI in mice, by combining the treatment with metabolic substrates such as pyruvate and/or lactate. The goal was to even further improve mitochondrial function. This combinatorial treatment was able to reverse memory and learning deficits in TBI mice back to normal levels, as well as leaving the hippocampal region completely protected from tissue loss; a stark contrast to that found in control TBI mice that exhibited severe tissue loss from secondary brain injury.

5.2. TBI in humans

Margaret Naeser and collaborators have tested PBM in human subjects who had suffered TBI in the past [86]. Many sufferers from severe or even moderate TBI, have very long lasting and even life-changing sequelae (headaches, cognitive impairment, and difficulty sleeping) that prevent them working or living any kind or normal life. These individuals may have been high achievers before the accident that caused damage to their brain [87]. Initially Naeser published a report [88] describing two cases she treated with PBM applied to the forehead twice a week. A 500 mW continuous wave LED source (mixture of 660 nm red and 830 nm NIR LEDs) with a power density of 22.2 mW/cm2 (area of 22.48 cm2), was applied to the forehead for a typical duration of 10 min (13.3 J/cm2). In the first case study the patient reported that she could concentrate on tasks for a longer period of time (the time able to work at a computer increased from 30 min to 3 h). She had a better ability to remember what she read, decreased sensitivity when receiving haircuts in the spots where LLLT was applied, and improved mathematical skills after undergoing LLLT. The second patient had statistically significant improvements compared to prior neuropsychological tests after 9 months of treatment. The patient had a 2 standard deviation (SD) increase on tests of inhibition and inhibition accuracy (9th percentile to 63rd percentile on the Stroop test for executive function and a 1 SD increase on the Wechsler Memory scale test for the logical memory test (83rd percentile to 99th percentile) [89].

Naeser et al. then went on to report a case series of a further eleven patients [90]. This was an open protocol study that examined whether scalp application of red and near infrared (NIR) light could improve cognition in patients with chronic, mild traumatic brain injury (mTBI). This study had 11 participants ranging in age from 26 to 62 (6 males, 5 females) who suffered from persistent cognitive dysfunction after mTBI. The participants’ injuries were caused by motor vehicle accidents, sports related events and for one participant, an improvised explosive device (IED) blast. tLLLT consisted of 18 sessions (Monday, Wednesday, and Friday for 6 weeks) and commenced anywhere from 10 months to 8 years post-TBI. A total of 11 LED clusters (5.25 cm in diameter, 500 mW, 22.2 mW/cm2, 13 J/cm2) were applied for about 10 min per session (5 or 6 LED placements per set, Set A and then Set B, in each session). Neuropsychological testing was performed pre-LED application and 1 week, 1 month and 2 months after the final treatment. Naeser and colleagues found that there was a significant positive linear trend observed for the Stroop Test for executive function, in trial 2 inhibition (p = 0.004); Stroop, trial 4 inhibition switching (p = 0.003); California Verbal Learning Test (CVLT)-II, total trials 1–5 (p = 0.003); CVLT-II, long delay free recall (p = 0.006). Improved sleep and fewer post-traumatic stress disorder (PTSD) symptoms, if present beforehand, were observed after treatment. Participants and family members also reported better social function and a better ability to perform interpersonal and occupational activities. Although these results were significant, further placebo-controlled studies will be needed to ensure the reliability of this these data [90].

Henderson and Morries [91] used a high-power NIR laser (10–15 W at 810 and 980 nm) applied to the head to treat a patient with moderate TBI. The patient received 20 NIR applications over a 2-month period. They carried out anatomical magnetic resonance imaging (MRI) and perfusion single-photon emission computed tomography (SPECT). The patient showed decreased depression, anxiety, headache, and insomnia, whereas cognition and quality of life improved, accompanied by changes in the SPECT imaging.

6. PBM for Alzheimer’s disease (AD)

6.1. Animal models

There was a convincing study [92] carried out in an A?PP transgenic mouse of AD. tPBM (810 nm laser) was administered at different doses 3 times/week for 6 months starting at 3 months of age. The numbers of A? plaques were significantly reduced in the brain with administration of tPBM in a dose-dependent fashion. tPBM mitigated the behavioral effects seen with advanced amyloid deposition and reduced the expression of inflammatory markers in the transgenic mice. In addition, TLT showed an increase in ATP levels, mitochondrial function, and c-fos expression suggesting that there was an overall improvement in neurological function.

6.2. Humans

There has been a group of investigators in Northern England who have used a helmet built with 1072 nm LEDs to treat AD, but somewhat surprisingly no peer-reviewed publications have described this approach [93]. However a small pilot study (19 patients) that took the form of a randomized placebo-controlled trial investigated the effect of the Vielight Neuro system (see Fig. 5A) (a combination of tPBM and intranasal PBM) on patients with dementia and mild cognitive impairment [94]. This was a controlled single blind pilot study in humans to investigate the effects of PBM on memory and cognition. 19 participants with impaired memory/cognition were randomized into active and sham treatments over 12 weeks with a 4-week no-treatment follow-up period. They were assessed with MMSE and ADAS-cog scales. The protocol involved in-clinic use of a combined transcranial-intranasal PBM device; and at-home use of an intranasal-only PBM device and participants/ caregivers noted daily experiences in a journal. Active participants with moderate to severe impairment (MMSE scores 5–24) showed significant improvements (5-points MMSE score) after 12 weeks. There was also a significant improvement in ADAS-cog scores (see Fig. 5B). They also reported better sleep, fewer angry outbursts and decreased anxiety and wandering. Declines were noted during the 4-week no-treatment follow-up period. Participants with mild impairment to normal (MMSE scores of 25 to 30) in both the active and sham sub-groups showed improvements. No related adverse events were reported.

Fig. 5

tPBM for Alzheimer’s disease. (A) Nineteen patients were randomized to receive real or sham tPBM (810 nm LED, 24.6 J/cm2 at 41 mW/cm2). (B) Significant decline in ADAS-cog (improved cognitive performance) in real but not sham (unpublished

An interesting paper from Russia [95] described the use of intravascular PBM to treat 89 patients with AD who received PBM (46 patients) or standard treatment with memantine and rivastigmine (43 patients). The PBM consisted of threading a fiber-optic through a cathéter in the fémoral artery and advancing it to the distal site of the anterior and middle cerebral arteries and delivering 20 mW of red laser for 20–40 min. The PBM group had improvement in cerebral microcirculation leading to permanent (from 1 to 7 years) reduction in dementia and cognitive recovery.

7. Parkinson’s disease

The majority of studies on PBM for Parkinson’s disease have been in animal models and have come from the laboratory of John Mitrofanis in Australia [96]. Two basic models of Parkinson’s disease were used. The first employed administration of the small molecule (MPTP or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) to mice [97]. MPTP was discovered as an impurity in an illegal recreational drug to cause Parkinson’s like symptoms (loss of substantia nigra cells) in young people who had taken this drug [98]. Mice were treated with tPBM (670-nm LED, 40 mW/cm2, 3.6 J/cm2) 15 min after each MPTP injection repeated 4 times over 30 h. There were significantly more (35%–45%) dopaminergic cells in the brains of the tPBM treated mice [97]. A subsequent study showed similar results in a chronic mouse model of MPTP-induced Parkinson’s disease [99]. They repeated their studies in another mouse model of Parkinson’s disease, the tau transgenic mouse strain (K3) that has a progressive degeneration of dopaminergic cells in the substantia nigra pars compacta (SNc) [100]. They went on to test a surgically implanted intracranial fiber designed to deliver either 670 nm LED (0.16 mW) or 670 nm laser (67 mW) into the lateral ventricle of the brain in MPTP-treated mice [101]. Both low power LED and high power laser were effective in preserving SNc cells, but the laser was considered to be unsuitable for long-term use (6 days) due to excessive heat production. As mentioned above, these authors also reported a protective effect of abscopal light exposure (head shielded) in this mouse model [43]. Recently this group has tested their implanted fiber approach in a model of Parkinson’s disease in adult Macaque monkeys treated with MPTP [102]. Clinical evaluation of Parkinson’s symptoms (posture, general activity, bradykinesia, and facial expression) in the monkeys were improved at low doses of light (24 J or 35 J) compared to high doses (125 J) [103].

The only clinical report of PBM for Parkinson’s disease in humans was an abstract presented in 2010 [104]. Eight patients between 18 and 80 years with late stage PD participated in a non-controlled, non-randomized study. Participants received tPBM treatments of the head designed to deliver light to the brain stem, bilateral occipital, parietal, temporal and frontal lobes, and treatment along the sagittal suture. A Visual Analog Scale (VAS), was used to record the severity of their symptoms of balance, gait, freezing, cognitive function, rolling in bed, and difficulties with speech pre-procedure and at study endpoint with 10 being most severe and 0 as no symptom. Compared with baseline, all participants demonstrated a numerical improvement in the VAS from baseline to study endpoint. A statistically significant reduction in VAS rating for gait and cognitive function was observed with average mean change of —1.87 (p < 0.05) for gait and a mean reduction of —2.22 (p < 0.05) for cognitive function. Further, freezing and difficulty with speech ratings were significantly lower (mean reduction of 1.28 (p < 0.05) for freezing and 2.22 (p < 0.05) for difficulty with speech).

8. PBM for psychiatric disorders

8.1. Animal models

A common and well-accepted animal model of depression is called “chronic mild stress” [105]. After exposure to a series of chronic unpredictable mild stressors, animals develop symptoms seen in human depression, such as anhedonia (loss of the capacity to experience pleasure, a core symptom of major depressive disorder), weight loss or slower weight gain, decrease in locomotor activity, and sleep disorders [106]. Wu et al. used Wistar rats to show that after 5 weeks of chronic stress, application of tPBM 3 times a week for 3 weeks (810 nm laser, 100 Hz with 20% duty cycle, 120 J/cm2) gave significant improvement in the forced swimming test (FST) [107]. In a similar study Salehpour et al. [108] compared the effects of two different lasers (630 m nm at 89 mW/cm2, and 810 nm at 562 mW/cm2, both pulsed at 10 Hz, 50% duty cycle). The 810 nm laser proved better than the 630 nm laser in the FST, in the elevated plus maze and also reduced blood cortisol levels.

8.2. Depression and anxiety

The first clinical study in depression and anxiety was published by Schiffer et al. in 2009 [109]. They used a fairly small area 1 W 810 nm LED array (see Fig. 6A) applied to the forehead in patients with major depression and anxiety. They found improvements in the Hamilton depression rating scale (HAM-D) (see Fig. 6B), and the Hamilton anxiety rating scale (HAM-A), 2 weeks after a single treatment. They also found increases in frontal pole regional cerebral blood flow (rCBF) during the light delivery using a commercial NIR spectroscopy device. Cassano and co-workers [110] used tPBM with an 810 nm laser (700 mW/cm2and a fluence of 84  J/cm2 delivered per session for 6 sessions in patients with major depression. Baseline mean HAM-D17 scores decreased from 19.8 ± 4.4 (SD) to 13 ± 5.35 (SD) after treatment (p = 0.004).

Fig. 6

tPBM for major depression and anxiety in humans. (A) Ten patients received a single exposure to the forehead (810 LED, 60 J/cm2delivered at 250 mW/cm2). (B) Mean Hamilton score for depression at baseline and at two weeks post-treatment

9. Cognitive enhancement

From what we have seen above, it need come as no surprise, to learn that there are several reports about cognitive enhancement in normal people or healthy animals using PBM. The first report was in middle aged (12 months) CD1 female mice [111]. Exposure of the mice to 1072 nm LED arrays led to improved performance in a 3D maze compared to sham treated age-matched controls. Francisco Gonzalez-Lima at the University of Texas Austin, has worked in this area for some time [112]. Working in rats they showed that transcranial PBM (9 mW/cm2 with 660 nm LED array) induced a dose-dependent increase in oxygen consumption of 5% after 1 J/cm2 and 16% after 5 J/cm2 [113]. They also found that tPBM reduced fear renewal and prevented the reemergence of extinguished conditioned fear responses [113]. In normal human volunteers they used transcranial PBM (1064 nm laser, 60 J/cm2 at 250 mW/cm2) delivered to the forehead in a placebo-controlled, randomized study, to influence cognitive tasks related to the prefrontal cortex, including a psychomotor vigilance task (PVT), a delayed match-to-sample (DMS) memory task, and the positive and negative affect schedule (PANAS-X) to show improved mood [16]. Subsequent studies in normal humans showed that tPBM with 1064 nm laser could improve performance in the Wisconsin Card Sorting Task (considered the gold standard test for executive function) [114]. They also showed that tPBM to the right forehead (but not the left forehead) had better effects on improving attention bias modification (ABM) in humans with depression [115].

A study by Salgado et al. used transcranial LED PBM on cerebral blood flow in healthy elderly women analyzed by transcranial Doppler ultrasound (TCD) of the right and left middle cerebral artery and basilar artery. Twenty-five non-institutionalized elderly women (mean age 72 years old), with cognitive status > 24, were assessed using TCD before and after transcranial LED therapy. tPBM (627 nm, 70 mW/cm2, 10 J/cm2) was performed at four points of the frontal and parietal region for 30 s each twice a week for 4 weeks. There was a significant increase in the systolic and diastolic velocity of the left middle cerebral artery (25 and 30%, respectively) and the basilar artery (up to 17 and 25%), as well as a decrease in the pulsatility index and resistance index values of the three cerebral arteries analyzed [116].

10. Conclusion

Many investigators believe that PBM for brain disorders will become one of the most important medical applications of light therapy in the coming years and decades. Despite the efforts of “Big Pharma”, prescription drugs for psychiatric disorders are not generally regarded very highly (either by the medical profession or by the public), and many of these drugs perform little better than placebos in different trials, and moreover can also have major side-effects [117]. Moreover it is well accepted that with the overall aging of the general population, together with ever lengthening life spans, that dementia, Alzheimer’s, and Parkinson’s diseases will become a global health problem [118], [119]. Even after many years of research, no drug has yet been developed to benefit these neurodegenerative disorders. A similar state of play exists with drugs for stroke (with the exception of clot-busting enzymes) and TBI. New indications for tPBM such as global ischemia (brain damage after a heart attack), post-operative cognitive dysfunction [120], and neurodevelopmental disorders such as autism spectrum disorder may well emerge. Table 2 shows the wide range of brain disorders and diseases that may eventually be treated by some kind of tPBM, whether that be an office/clinic based procedure or a home-use based device. If inexpensive LED helmets can be developed and successfully marketed as home use devices, then we are potentially in a position to benefit large numbers of patients (to say nothing of healthy individuals). Certainly the advent of the Internet has made it much easier for knowledge about this kind of home treatment to spread (almost by word of mouth so to speak).

Table 2

List of brain disorders that may in principle be treated by tPBM.

Conflict of interest statement

The author declares no conflict of interest.

Transparency document

Transparency document.

Click here to view.(1.1M, pdf)Image 1


MRH was supported by the US NIH grants R01AI050875 and R21AI121700, the Air Force Office of Scientific Research grant FA9550-13-1-0068, the US Army Medical Research Acquisition Activity grant W81XWH-09-1-0514, and by the US Army Medical Research and Materiel Command grant W81XWH-13-2-0067.


The Transparency document associated with this article can be found, in online version.


1. McGuff P.E., Deterling R.A., Jr., Gottlieb L.S. Tumoricidal effect of laser energy on experimental and human malignant tumors. N. Engl. J. Med. 1965;273:490–492. [PubMed]
2. Maiman T.H. Stimulated optical radiation in ruby. Nature. 1960;187:493–494.
3. Mester E., Ludány G., Sellyei M., Szende B., Total G.J. The simulating effect of low power laser rays on biological systems. Laser Rev. 1968;1:3.
4. Mester E., Szende B., Gartner P. The effect of laser beams on the growth of hair in mice. Radiobiol. Radiother. (Berl) 1968;9:621–626. [PubMed]
5. Mester E., Mester A.F., Mester A. The biomedical effects of laser application. Lasers Surg. Med. 1985;5:31–39. [PubMed]
6. Mester E., Nagylucskay S., Doklen A., Tisza S. Laser stimulation of wound healing. Acta Chir. Acad. Sci. Hung. 1976;17:49–55. [PubMed]
7. Mester E., Spiry T., Szende B. Effect of laser rays on wound healing. Bull. Soc. Int. Chir. 1973;32:169–173. [PubMed]
8. Chung H., Dai T., Sharma S.K., Huang Y.Y., Carroll J.D., Hamblin M.R. The nuts and bolts of low-level laser (light) therapy. Ann. Biomed. Eng. 2012;40:516–533. [PubMed]
9. Anders J.J., Lanzafame R.J., Arany P.R. Low-level light/laser therapy versus photobiomodulation therapy. Photomed. Laser Surg. 2015;33:183–184. [PubMed]
10. De Freitas L.F., Hamblin M.R. Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE J. Sel. Top. Quantum Electron. 2016;22:7000417.
11. Lane N. Cell biology: power games. Nature. 2006;443:901–903. [PubMed]
12. Waypa G.B., Smith K.A., Schumacker P.T. O2 sensing, mitochondria and ROS signaling: the fog is lifting. Mol. Asp. Med. 2016;47-48:76–89. [PMC free article] [PubMed]
13. Zhao Y., Vanhoutte P.M., Leung S.W. Vascular nitric oxide: beyond eNOS. J. Pharmacol. Sci. 2015;129:83–94. [PubMed]
14. Ferrante M., Petrini M., Trentini P., Perfetti G., Spoto G. Effect of low-level laser therapy after extraction of impacted lower third molars. Lasers Med. Sci. 2013;28:845–849. [PubMed]
15. Skopin M.D., Molitor S.C. Effects of near-infrared laser exposure in a cellular model of wound healing. Photodermatol. Photoimmunol. Photomed. 2009;25:75–80. [PubMed]
16. Barrett D.W., Gonzalez-Lima F. Transcranial infrared laser stimulation produces beneficial cognitive and emotional effects in humans. Neuroscience. 2013;230:13–23. [PubMed]
17. Dougal G., Lee S.Y. Evaluation of the efficacy of low-level light therapy using 1072 nm infrared light for the treatment of herpes simplex labialis. Clin. Exp. Dermatol. 2013;38:713–718. [PubMed]
18. Vatansever F., Hamblin M.R. Far infrared radiation (FIR): its biological effects and medical applications. Photonics Lasers Med. 2012;4:255–266. [PubMed]
19. Palazzo E., Rossi F., de Novellis V., Maione S. Endogenous modulators of TRP channels. Curr. Top. Med. Chem. 2013;13:398–407. [PubMed]
20. Planells-Cases R., Valente P., Ferrer-Montiel A., Qin F., Szallasi A. Complex regulation of TRPV1 and related thermo-TRPs: implications for therapeutic intervention. Adv. Exp. Med. Biol. 2011;704:491–515.[PubMed]
21. Caterina M.J. Transient receptor potential ion channels as participants in thermosensation and thermoregulation. Am. J. Physiol. Regul. Integr. Comp. Physiol. 2007;292:R64–R76. [PubMed]
22. Cassano P., Petrie S.R., Hamblin M.R., Henderson T.A., Iosifescu D.V. Review of transcranial photobiomodulation for major depressive disorder: targeting brain metabolism, inflammation, oxidative stress, and neurogenesis. Neurophotonics. 2016;3:031404. [PubMed]
23. Morries L.D., Cassano P., Henderson T.A. Treatments for traumatic brain injury with emphasis on transcranial near-infrared laser phototherapy. Neuropsychiatr. Dis. Treat. 2015;11:2159–2175. [PubMed]
24. Tian F., Hase S.N., Gonzalez-Lima F., Liu H. Transcranial laser stimulation improves human cerebral oxygenation. Lasers Surg. Med. 2016;48:343–349. [PubMed]
25. Ando T., Xuan W., Xu T., Dai T., Sharma S.K., Kharkwal G.B., Huang Y.Y., Wu Q., Whalen M.J., Sato S., Obara M., Hamblin M.R. Comparison of therapeutic effects between pulsed and continuous wave 810-nm wavelength laser irradiation for traumatic brain injury in mice. PLoS One. 2011;6 [PMC free article][PubMed]
26. Calabrese E.J. Hormesis and medicine. Br. J. Clin. Pharmacol. 2008;66:594–617. [PubMed]
27. Luckey T.D. Nurture with ionizing radiation: a provocative hypothesis. Nutr. Cancer. 1999;34:1–11.[PubMed]
28. Huang Y.Y., Chen A.C., Carroll J.D., Hamblin M.R. Biphasic dose response in low level light therapy. Dose-Response. 2009;7:358–383. [PubMed]
29. Huang Y.Y., Sharma S.K., Carroll J.D., Hamblin M.R. Biphasic dose response in low level light therapy – an update. Dose-Response. 2011;9:602–618. [PubMed]
30. Wu S., Zhou F., Wei Y., Chen W.R., Chen Q., Xing D. Cancer phototherapy via selective photoinactivation of respiratory chain oxidase to trigger a fatal superoxide anion burst. Antioxid. Redox Signal. 2014;20:733–746. [PubMed]
31. Hode L. The importance of the coherency. Photomed. Laser Surg. 2005;23:431–434. [PubMed]
32. Cui X., Bray S., Bryant D.M., Glover G.H., Reiss A.L. A quantitative comparison of NIRS and fMRI across multiple cognitive tasks. NeuroImage. 2011;54:2808–2821. [PubMed]
33. Haeussinger F.B., Heinzel S., Hahn T., Schecklmann M., Ehlis A.C., Fallgatter A.J. Simulation of near-infrared light absorption considering individual head and prefrontal cortex anatomy: implications for optical neuroimaging. PLoS One. 2011;6 [PMC free article] [PubMed]
34. Strangman G.E., Zhang Q., Li Z. Scalp and skull influence on near infrared photon propagation in the Colin27 brain template. NeuroImage. 2014;85(Pt 1):136–149. [PubMed]
35. Okada E., Delpy D.T. Near-infrared light propagation in an adult head model. II. Effect of superficial tissue thickness on the sensitivity of the near-infrared spectroscopy signal. Appl. Opt. 2003;42:2915–2922.[PubMed]
36. Jagdeo J.R., Adams L.E., Brody N.I., Siegel D.M. Transcranial red and near infrared light transmission in a cadaveric model. PLoS One. 2012;7 [PMC free article] [PubMed]
37. Tedford C.E., DeLapp S., Jacques S., Anders J. Quantitative analysis of transcranial and intraparenchymal light penetration in human cadaver brain tissue. Lasers Surg. Med. 2015;47:312–322.[PubMed]
38. Lapchak P.A., Boitano P.D., Butte P.V., Fisher D.J., Holscher T., Ley E.J., Nuno M., Voie A.H., Rajput P.S. Transcranial near-infrared laser transmission (NILT) profiles (800 nm): systematic comparison in four common research species. PLoS One. 2015;10 [PMC free article] [PubMed]
39. Pitzschke A., Lovisa B., Seydoux O., Zellweger M., Pfleiderer M., Tardy Y., Wagnieres G. Red and NIR light dosimetry in the human deep brain. Phys. Med. Biol. 2015;60:2921–2937. [PubMed]
40. Pitzschke A., Lovisa B., Seydoux O., Haenggi M., Oertel M.F., Zellweger M., Tardy Y., Wagnieres G. Optical properties of rabbit brain in the red and near-infrared: changes observed under in vivo, postmortem, frozen, and formalin-fixated conditions. J. Biomed. Opt. 2015;20:25006. [PubMed]
41. Yaroslavsky A.N., Schulze P.C., Yaroslavsky I.V., Schober R., Ulrich F., Schwarzmaier H.J. Optical properties of selected native and coagulated human brain tissues in vitro in the visible and near infrared spectral range. Phys. Med. Biol. 2002;47:2059–2073. [PubMed]
42. Henderson T.A., Morries L.D. Near-infrared photonic energy penetration: can infrared phototherapy effectively reach the human brain? Neuropsychiatr. Dis. Treat. 2015;11:2191–2208. [PubMed]
43. Johnstone D.M., el Massri N., Moro C., Spana S., Wang X.S., Torres N., Chabrol C., De Jaeger X., Reinhart F., Purushothuman S., Benabid A.L., Stone J., Mitrofanis J. Indirect application of near infrared light induces neuroprotection in a mouse model of parkinsonism – an abscopal neuroprotective effect. Neuroscience. 2014;274:93–101. [PubMed]
44. Johnstone D.M., Mitrofanis J., Stone J. Targeting the body to protect the brain: inducing neuroprotection with remotely-applied near infrared light. Neural Regen. Res. 2015;10:349–351. [PubMed]
45. Farfara D., Tuby H., Trudler D., Doron-Mandel E., Maltz L., Vassar R.J., Frenkel D., Oron U. Low-level laser therapy ameliorates disease progression in a mouse model of Alzheimer’s disease. J. Mol. Neurosci. 2015;55:430–436. [PubMed]
46. Oron A., Oron U. Low-level laser therapy to the bone marrow ameliorates neurodegenerative disease progression in a mouse model of Alzheimer’s disease: a minireview. Photomed. Laser Surg. 2016 [PubMed]
47. Iwashita T., Tada T., Zhan H., Tanaka Y., Hongo K. Harvesting blood stem cells from cranial bone at craniotomy–a preliminary study. J. Neuro-Oncol. 2003;64:265–270. [PubMed]
48. Quah-Smith I., Williams M.A., Lundeberg T., Suo C., Sachdev P. Differential brain effects of laser and needle acupuncture at LR8 using functional MRI. Acupunct. Med. 2013;31:282–289. [PubMed]
49. Quah-Smith I., Sachdev P.S., Wen W., Chen X., Williams M.A. The brain effects of laser acupuncture in healthy individuals: an FMRI investigation. PLoS One. 2010;5 [PMC free article] [PubMed]
50. Sutalangka C., Wattanathorn J., Muchimapura S., Thukham-Mee W., Wannanon P., Tong-un T. Laser acupuncture improves memory impairment in an animal model of Alzheimer’s disease. J. Acupunct. Meridian Stud. 2013;6:247–251. [PubMed]
51. Khongrum J., Wattanathorn J. Laser acupuncture improves behavioral disorders and brain oxidative stress status in the valproic acid rat model of autism. J. Acupunct. Meridian Stud. 2015;8:183–191. [PubMed]
52. Quah-Smith I., Suo C., Williams M.A., Sachdev P.S. The antidepressant effect of laser acupuncture: a comparison of the resting brain’s default mode network in healthy and depressed subjects during functional magnetic resonance imaging. Med. Acupunct. 2013;25:124–133. [PubMed]
53. Henderson T.A. Multi-watt near-infrared light therapy as a neuroregenerative treatment for traumatic brain injury. Neural Regen. Res. 2016;11:563–565. [PubMed]
54. Hacke W., Schellinger P.D., Albers G.W., Bornstein N.M., Dahlof B.L., Fulton R., Kasner S.E., Shuaib A., Richieri S.P., Dilly S.G., Zivin J., Lees K.R., Committees N. Investigators, transcranial laser therapy in acute stroke treatment: results of neurothera effectiveness and safety trial 3, a phase III clinical end point device trial. Stroke. 2014;45:3187–3193. [PubMed]
55. Albin R.L., Miller R.A. Mini-review: retarding aging in murine genetic models of neurodegeneration. Neurobiol. Dis. 2016;85:73–80. [PubMed]
56. Bey A.L., Jiang Y.H. Overview of mouse models of autism spectrum disorders. Curr. Protoc. Pharmacol. 2014;66 (5 66 61–26) [PMC free article] [PubMed]
57. Leung M.C., Lo S.C., Siu F.K., So K.F. Treatment of experimentally induced transient cerebral ischemia with low energy laser inhibits nitric oxide synthase activity and up-regulates the expression of transforming growth factor-beta 1. Lasers Surg. Med. 2002;31:283–288. [PubMed]
58. Peplow P.V. Neuroimmunomodulatory effects of transcranial laser therapy combined with intravenous tPA administration for acute cerebral ischemic injury. Neural Regen. Res. 2015;10:1186–1190. [PubMed]
59. Oron A., Oron U., Chen J., Eilam A., Zhang C., Sadeh M., Lampl Y., Streeter J., DeTaboada L., Chopp M. Low-level laser therapy applied transcranially to rats after induction of stroke significantly reduces long-term neurological deficits. Stroke. 2006;37:2620–2624. [PubMed]
60. Zhang L., Chen J., Li Y., Zhang Z.G., Chopp M. Quantitative measurement of motor and somatosensory impairments after mild (30 min) and severe (2 h) transient middle cerebral artery occlusion in rats. J. Neurol. Sci. 2000;174:141–146. [PubMed]
61. Meyer D.M., Chen Y., Zivin J.A. Dose-finding study of phototherapy on stroke outcome in a rabbit model of ischemic stroke. Neurosci. Lett. 2016;630:254–258. [PubMed]
62. Lapchak P.A., Salgado K.F., Chao C.H., Zivin J.A. Transcranial near-infrared light therapy improves motor function following embolic strokes in rabbits: an extended therapeutic window study using continuous and pulse frequency delivery modes. Neuroscience. 2007;148:907–914. [PubMed]
63. Detaboada L., Ilic S., Leichliter-Martha S., Oron U., Oron A., Streeter J. Transcranial application of low-energy laser irradiation improves neurological deficits in rats following acute stroke. Lasers Surg. Med. 2006;38:70–73. [PubMed]
64. Lapchak P.A., Wei J., Zivin J.A. Transcranial infrared laser therapy improves clinical rating scores after embolic strokes in rabbits. Stroke. 2004;35:1985–1988. [PubMed]
65. Lampl Y., Zivin J.A., Fisher M., Lew R., Welin L., Dahlof B., Borenstein P., Andersson B., Perez J., Caparo C., Ilic S., Oron U. Infrared laser therapy for ischemic stroke: a new treatment strategy: results of the NeuroThera Effectiveness and Safety Trial-1 (NEST-1) Stroke. 2007;38:1843–1849. [PubMed]
66. Huisa B.N., Stemer A.B., Walker M.G., Rapp K., Meyer B.C., Zivin J.A. Nest, investigators, transcranial laser therapy for acute ischemic stroke: a pooled analysis of NEST-1 and NEST-2. Int. J. Stroke. 2013;8:315–320. [PubMed]
67. Zivin J.A., Sehra R., Shoshoo A., Albers G.W., Bornstein N.M., Dahlof B., Kasner S.E., Howard G., Shuaib A., Streeter J., Richieri S.P., Hacke W., N.-. investigators NeuroThera(R) Efficacy and Safety Trial-3 (NEST-3): a double-blind, randomized, sham-controlled, parallel group, multicenter, pivotal study to assess the safety and efficacy of transcranial laser therapy with the NeuroThera(R) laser system for the treatment of acute ischemic stroke within 24 h of stroke onset. Int. J. Stroke. 2014;9:950–955. [PubMed]
68. Zivin J.A., Albers G.W., Bornstein N., Chippendale T., Dahlof B., Devlin T., Fisher M., Hacke W., Holt W., Ilic S., Kasner S., Lew R., Nash M., Perez J., Rymer M., Schellinger P., Schneider D., Schwab S., Veltkamp R., Walker M., Streeter J., NeuroThera E., Safety Trial I. Effectiveness and safety of transcranial laser therapy for acute ischemic stroke. Stroke. 2009;40:1359–1364. [PubMed]
69. Lapchak P.A., Boitano P.D. Transcranial near-infrared laser therapy for stroke: how to recover from futility in the NEST-3 clinical trial. Acta Neurochir. Suppl. 2016;121:7–12. [PubMed]
70. Lapchak P.A. Fast neuroprotection (fast-NPRX) for acute ischemic stroke victims: the time for treatment is now. Transl. Stroke. Res. 2013;4:704–709. [PubMed]
71. Lapchak P.A. Recommendations and practices to optimize stroke therapy: developing effective translational research programs. Stroke. 2013;44:841–843. [PubMed]
72. Lapchak P.A., Zhang J.H., Noble-Haeusslein L.J. RIGOR guidelines: escalating STAIR and STEPS for effective translational research. Transl. Stroke. Res. 2013;4:279–285. [PubMed]
73. Naeser M., Ho M., Martin P.E., Treglia E.M., Krengel M., Hamblin M.R., Baker E.H. Improved language after scalp application of red/near-infrared light-emitting diodes: pilot study supporting a new, noninvasive treatment for chronic aphasia. Procedia. Soc. Behav. Sci. 2012;61:138–139.
74. Boonswang N.A., Chicchi M., Lukachek A., Curtiss D. A new treatment protocol using photobiomodulation and muscle/bone/joint recovery techniques having a dramatic effect on a stroke patient’s recovery: a new weapon for clinicians. BMJ Case Rep. 2012;2012 [PMC free article] [PubMed]
75. Doidge N. Viking Press; New York, NY: 2015. The Brain’s Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity.
76. Oron A., Oron U., Streeter J., de Taboada L., Alexandrovich A., Trembovler V., Shohami E. Low-level laser therapy applied transcranially to mice following traumatic brain injury significantly reduces long-term neurological deficits. J. Neurotrauma. 2007;24:651–656. [PubMed]
77. Wu Q., Xuan W., Ando T., Xu T., Huang L., Huang Y.Y., Dai T., Dhital S., Sharma S.K., Whalen M.J., Hamblin M.R. Low-level laser therapy for closed-head traumatic brain injury in mice: effect of different wavelengths. Lasers Surg. Med. 2012;44:218–226. [PubMed]
78. Karu T.I., Pyatibrat L.V., Afanasyeva N.I. Cellular effects of low power laser therapy can be mediated by nitric oxide. Lasers Surg. Med. 2005;36:307–314. [PubMed]
79. Xuan W., Vatansever F., Huang L., Wu Q., Xuan Y., Dai T., Ando T., Xu T., Huang Y.Y., Hamblin M.R. Transcranial low-level laser therapy improves neurological performance in traumatic brain injury in mice: effect of treatment repetition regimen. PLoS One. 2013;8 [PMC free article] [PubMed]
80. Xuan W., Agrawal T., Huang L., Gupta G.K., Hamblin M.R. Low-level laser therapy for traumatic brain injury in mice increases brain derived neurotrophic factor (BDNF) and synaptogenesis. J. Biophotonics. 2015;8:502–511. [PubMed]
81. Xuan W., Vatansever F., Huang L., Hamblin M.R. Transcranial low-level laser therapy enhances learning, memory, and neuroprogenitor cells after traumatic brain injury in mice. J. Biomed. Opt. 2014;19:108003. [PubMed]
82. Khuman J., Zhang J., Park J., Carroll J.D., Donahue C., Whalen M.J. Low-level laser light therapy improves cognitive deficits and inhibits microglial activation after controlled cortical impact in mice. J. Neurotrauma. 2012;29:408–417. [PubMed]
83. Quirk B.J., Torbey M., Buchmann E., Verma S., Whelan H.T. Near-infrared photobiomodulation in an animal model of traumatic brain injury: improvements at the behavioral and biochemical levels. Photomed. Laser Surg. 2012;30:523–529. [PubMed]
84. Zhang Q., Zhou C., Hamblin M.R., Wu M.X. Low-level laser therapy effectively prevents secondary brain injury induced by immediate early responsive gene X-1 deficiency. J. Cereb. Blood Flow Metab. 2014[PMC free article] [PubMed]
85. Dong T., Zhang Q., Hamblin M.R., Wu M.X. Low-level light in combination with metabolic modulators for effective therapy of injured brain. J. Cereb. Blood Flow Metab. 2015 [PMC free article] [PubMed]
86. Naeser M.A., Hamblin M.R. Traumatic brain injury: a major medical problem that could be treated using transcranial, red/near-infrared LED photobiomodulation. Photomed. Laser Surg. 2015 [PMC free article][PubMed]
87. McClure J. The role of causal attributions in public misconceptions about brain injury. Rehabil. Psychol. 2011;56:85–93. [PubMed]
88. Naeser M.A., Saltmarche A., Krengel M.H., Hamblin M.R., Knight J.A. Improved cognitive function after transcranial, light-emitting diode treatments in chronic, traumatic brain injury: two case reports. Photomed. Laser Surg. 2011;29:351–358. [PubMed]
89. Naeser M.A., Martin P.I., Lundgren K., Klein R., Kaplan J., Treglia E., Ho M., Nicholas M., Alonso M., Pascual-Leone A. Improved language in a chronic nonfluent aphasia patient after treatment with CPAP and TMS. Cogn. Behav. Neurol. 2010;23:29–38. [PubMed]
90. Naeser M.A., Zafonte R., Krengel M.H., Martin P.I., Frazier J., Hamblin M.R., Knight J.A., Meehan W.P., III, Baker E.H. Significant improvements in cognitive performance post-transcranial, red/near-infrared light-emitting diode treatments in chronic, mild traumatic brain injury: open-protocol study. J. Neurotrauma. 2014;31:1008–1017. [PubMed]
91. Henderson T.A., Morries L.D. SPECT perfusion imaging demonstrates improvement of traumatic brain injury with transcranial near-infrared laser phototherapy. Adv. Mind Body Med. 2015;29:27–33. [PubMed]
92. De Taboada L., Yu J., El-Amouri S., Gattoni-Celli S., Richieri S., McCarthy T., Streeter J., Kindy M.S. Transcranial laser therapy attenuates amyloid-beta peptide neuropathology in amyloid-beta protein precursor transgenic mice. J. Alzheimers Dis. 2011;23:521–535. [PubMed]
94. Saltmarche A.E., Naeser M.A., Ho K.F., Hamblin M.R., Lim L. Alzheimer’s Association International Conference, Toronto, Canada. 2016. Significant Improvement in Cognition after Transcranial and Intranasal Photobiomodulation: A Controlled, Single-Blind Pilot Study in Participants with Dementia (Abstract)
95. Maksimovich I.V. Dementia and cognitive impairment reduction after laser transcatheter treatment of Alzheimer’s disease. World J. Neurosci. 2015;5
96. Johnstone D.M., Moro C., Stone J., Benabid A.L., Mitrofanis J. Turning on lights to stop neurodegeneration: the potential of near infrared light therapy in Alzheimer’s and Parkinson’s disease. Front. Neurosci. 2015;9:500. [PubMed]
97. Shaw V.E., Spana S., Ashkan K., Benabid A.L., Stone J., Baker G.E., Mitrofanis J. Neuroprotection of midbrain dopaminergic cells in MPTP-treated mice after near-infrared light treatment. J. Comp. Neurol. 2010;518:25–40. [PubMed]
98. Barcia C. Who else was intoxicated with MPTP in Santa Clara? Parkinsonism Relat. Disord. 2012;18:1005–1006. [PubMed]
99. Peoples C., Spana S., Ashkan K., Benabid A.L., Stone J., Baker G.E., Mitrofanis J. Photobiomodulation enhances nigral dopaminergic cell survival in a chronic MPTP mouse model of Parkinson’s disease. Parkinsonism Relat. Disord. 2012;18:469–476. [PubMed]
100. Purushothuman S., Nandasena C., Johnstone D.M., Stone J., Mitrofanis J. The impact of near-infrared light on dopaminergic cell survival in a transgenic mouse model of parkinsonism. Brain Res. 2013;1535:61–70. [PubMed]
101. Moro C., Massri N.E., Torres N., Ratel D., De Jaeger X., Chabrol C., Perraut F., Bourgerette A., Berger M., Purushothuman S., Johnstone D., Stone J., Mitrofanis J., Benabid A.L. Photobiomodulation inside the brain: a novel method of applying near-infrared light intracranially and its impact on dopaminergic cell survival in MPTP-treated mice. J. Neurosurg. 2014;120:670–683. [PubMed]
102. El Massri N., Moro C., Torres N., Darlot F., Agay D., Chabrol C., Johnstone D.M., Stone J., Benabid A.L., Mitrofanis J. Near-infrared light treatment reduces astrogliosis in MPTP-treated monkeys. Exp. Brain Res. 2016 [PubMed]
103. Moro C., Massri N.E., Darlot F., Torres N., Chabrol C., Agay D., Auboiroux V., Johnstone D.M., Stone J., Mitrofanis J., Benabid A.L. Effects of a higher dose of near-infrared light on clinical signs and neuroprotection in a monkey model of Parkinson’s disease. Brain Res. 2016 [PubMed]
104. Maloney R., Shanks S., Maloney J. The application of low-level laser therapy for the symptomatic care of late stage Parkinson’s disease: a non-controlled, non-randomized study (abstract) Lasers Surg. Med. 2010;185
105. Willner P. Validity, reliability and utility of the chronic mild stress model of depression: a 10-year review and evaluation. Psychopharmacology. 1997;134:319–329. [PubMed]
106. Anisman H., Matheson K. Stress, depression, and anhedonia: caveats concerning animal models. Neurosci. Biobehav. Rev. 2005;29:525–546. [PubMed]
107. Wu X., Alberico S.L., Moges H., De Taboada L., Tedford C.E., Anders J.J. Pulsed light irradiation improves behavioral outcome in a rat model of chronic mild stress. Lasers Surg. Med. 2012;44:227–232.[PubMed]
108. Salehpour F., Rasta S.H., Mohaddes G., Sadigh-Eteghad S., Salarirad S. Therapeutic effects of 10-HzPulsed wave lasers in rat depression model: a comparison between near-infrared and red wavelengths. Lasers Surg. Med. 2016 [PubMed]
109. Schiffer F., Johnston A.L., Ravichandran C., Polcari A., Teicher M.H., Webb R.H., Hamblin M.R. Psychological benefits 2 and 4 weeks after a single treatment with near infrared light to the forehead: a pilot study of 10 patients with major depression and anxiety. Behav. Brain Funct. 2009;5:46. [PubMed]
110. Cassano P., Cusin C., Mischoulon D., Hamblin M.R., De Taboada L., Pisoni A., Chang T., Yeung A., Ionescu D.F., Petrie S.R., Nierenberg A.A., Fava M., Iosifescu D.V. Near-infrared transcranial radiation for major depressive disorder: proof of concept study. Psychiatry J. 2015;2015:352979. [PubMed]
111. Michalikova S., Ennaceur A., van Rensburg R., Chazot P.L. Emotional responses and memory performance of middle-aged CD1 mice in a 3D maze: effects of low infrared light. Neurobiol. Learn. Mem. 2008;89:480–488. [PubMed]
112. Gonzalez-Lima F., Barrett D.W. Augmentation of cognitive brain functions with transcranial lasers. Front. Syst. Neurosci. 2014;8:36. [PubMed]
113. Rojas J.C., Bruchey A.K., Gonzalez-Lima F. Low-level light therapy improves cortical metabolic capacity and memory retention. J. Alzheimers Dis. 2012;32:741–752. [PubMed]
114. Blanco N.J., Maddox W.T., Gonzalez-Lima F. Improving executive function using transcranial infrared laser stimulation. J. Neuropsychol. 2015 [PMC free article] [PubMed]
115. Disner S.G., Beevers C.G., Gonzalez-Lima F. Transcranial laser stimulation as neuroenhancement for attention bias modification in adults with elevated depression symptoms. Brain Stimul. 2016[PMC free article] [PubMed]
116. Salgado A.S., Zangaro R.A., Parreira R.B. Kerppers, II, the effects of transcranial LED therapy (TCLT) on cerebral blood flow in the elderly women. Lasers Med. Sci. 2015;30:339–346. [PubMed]
117. Kalmar S. The importance of neuropsychopharmacology in the development of psychiatry. Neuropsychopharmacol. Hung. 2014;16:149–156. [PubMed]
118. Sindi S., Mangialasche F., Kivipelto M. Advances in the prevention of Alzheimer’s disease. F1000Prime Rep. 2015;7:50. [PubMed]
119. Bellou V., Belbasis L., Tzoulaki I., Evangelou E., Ioannidis J.P. Environmental risk factors and Parkinson’s disease: an umbrella review of meta-analyses. Parkinsonism Relat. Disord. 2016;23:1–9.[PubMed]
120. Liebert A.D., Chow R.T., Bicknell B.T., Varigos E. Neuroprotective effects against POCD by photobiomodulation: evidence from assembly/disassembly of the cytoskeleton. J. Exp. Neurosci. 2016;10:1–19. [PMC free article] [PubMed]
121. Ando T., Xuan W., Xu T., Dai T., Sharma S.K., Kharkwal G.B., Huang Y.Y., Wu Q., Whalen M.J., Sato S., Obara M., Hamblin M.R. Comparison of therapeutic effects between pulsed and continuous wave 810-nm wavelength laser irradiation for traumatic brain injury in mice. PLoS One. 2011;6:e26212–e26220.[PubMed]
Lasers Med Sci. 2016 Aug;31(6):1151-60. doi: 10.1007/s10103-016-1962-3. Epub 2016 May 25.

Cognitive enhancement by transcranial laser stimulation and acute aerobic exercise.

Hwang J1, Castelli DM1, Gonzalez-Lima F2.

Author information

Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Psychology and Institute for Neuroscience, University of Texas at Austin, 108 E. Dean Keeton Stop A8000, Austin, TX, 78712, USA.


This is the first randomized, controlled study comparing the cognitive effects of transcranial laser stimulation and acute aerobic exercise on the same cognitive tasks. We examined whether transcranial infrared laser stimulation of the prefrontal cortex, acute high-intensity aerobic exercise, or the combination may enhance performance in sustained attention and working memory tasks. Sixty healthy young adults were randomly assigned to one of the following four treatments: (1) lowlevel laser therapy (LLLT) with infrared laser to two forehead sites while seated (total 8 min, 1064 nm continuous wave, 250 mW/cm(2), 60 J/cm(2) per site of 13.6 cm(2)); (2) acute exercise (EX) of high-intensity (total 20 min, with 10-min treadmill running at 85-90 % VO2max); (3) combined treatment (LLLT + EX); or (4) sham control (CON). Participants were tested for prefrontal measures of sustained attention with the psychomotor vigilance task (PVT) and working memory with the delayed match-to-sample task (DMS) before and after the treatments. As compared to CON, both LLLT and EX reduced reaction time in the PVT [F(1.56)?=?4.134, p?=?0.01, ? (2) ?=?0.181] and increased the number of correct responses in the DMS [F(1.56)?=?4.690, p?=?0.005, ? (2) ?=?0.201], demonstrating a significant enhancing effect of LLLT and EX on cognitive performance. LLLT + EX effects were similar but showed no significantly greater improvement on PVT and DMS than LLLT or EX alone. The transcranial infrared laser stimulation and acute aerobic exercise treatments were similarly effective for cognitiveenhancement, suggesting that they augment prefrontal cognitive functions similarly.

Curr Alzheimer Res. 2015;12(9):860-9.

Cognitive Improvement by Photic Stimulation in a Mouse Model of Alzheimer’s Disease.

Zhang Y, Wang F, Luo X, Wang L, Sun P, Wang M, Jiang Y, Zou J, Uchiumi O, Yamamoto R, Sugai T, Yamamoto K, Kato N1.

Author information

  • 1Department of Physiology, Kanazawa Medical University, Ishikawa 920-0293, Japan.


We previously reported that activity of the large conductance calcium-activated potassium (big-K, BK) channel is suppressed by intracellular A? in cortical pyramidal cells, and that this suppression was reversed by expression of the scaffold protein Homer1a in 3xTg Alzheimer’s disease model mice. Homer1a is known to be expressed by physiological photic stimulation (PS) as well. The possibility thus arises that PS also reverses A?-induced suppression of BK channels, and thereby improves cognition in 3xTg mice. This possibility was tested here. Chronic application of 6-hour-long PS (frequency, 2 Hz; duty cycle, about 1/10; luminance, 300 lx) daily for 4 weeks improved contextual and tone-dependent fear memory in 3xTg mice and, to a lesser extent, Morris water maze performance as well. Hippocampal long-term potentiation was also enhanced after PS. BK channel activity in cingulate cortex pyramidal cells and lateral amygdalar principal cells, suppressed in 3xTg mice, were facilitated. In parallel, neuronal excitability, elevated in 3xTg mice, was recovered to the control level. Gene expression of BK channel, as well as that of the scaffold protein Homer1a, was found decreased in 3xTg mice and reversed by PS. It is known that Homer1a is an activity-dependently inducible immediate early gene product. Consistently, our previous findings showed that Homer1a induced by electrical stimulation facilitated BK channels. By using Homer1a knockouts, we showed that the present PS-induced BK channel facilitation is mediated by Homer1a expression. We thus propose that PS might be potentially useful as a non-invasive therapeutic measure against Alzheimer’s disease.

BMC Neurosci. 2016 May 18;17(1):21. doi: 10.1186/s12868-016-0259-6.

Comparative assessment of phototherapy protocols for reduction of oxidative stress in partially transected spinal cord slices undergoing secondary degeneration.

Ashworth BE1,2, Stephens E1,2, Bartlett CA1, Serghiou S3, Giacci MK1, Williams A3, Hart NS1,4, Fitzgerald M5.

Author information

  • 1Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, WA, Australia.
  • 2Department of Biology and Biochemistry, The University of Bath, Bath, UK.
  • 3Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, UK.
  • 4Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
  • 5Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, WA, Australia.



Red/near-infrared light therapy (R/NIR-LT) has been developed as a treatment for a range of conditions, including injury to the central nervous system (CNS). However, clinical trials have reported variable or sub-optimal outcomes, possibly because there are few optimized treatment protocols for the different target tissues. Moreover, the low absolute, and wavelength dependent, transmission of light by tissues overlying the target site make accurate dosing problematic.


In order to optimize light therapy treatment parameters, we adapted a mouse spinal cord organotypic culture model to the rat, and characterized myelination and oxidative stress following a partial transection injury. The ex vivo model allows a more accurate assessment of the relative effect of different illumination wavelengths (adjusted for equal quantal intensity) on the target tissue. Using this model, we assessed oxidative stress following treatment with four different wavelengths of light: 450 nm (blue); 510 nm (green); 660 nm (red) or 860 nm (infrared) at three different intensities: 1.93 × 10(16) (low); 3.85 × 10(16) (intermediate) and 7.70 × 10(16) (high) photons/cm(2)/s. We demonstrate that the most effective of the tested wavelengths to reduce immunoreactivity of the oxidative stress indicator 3-nitrotyrosine (3NT) was 660 nm. 860 nm also provided beneficial effects at all tested intensities, significantly reducing oxidative stress levels relative to control (p ? 0.05).


Our results indicate that R/NIR-LT is an effective antioxidant therapy, and indicate that effective wavelengths and ranges of intensities of treatment can be adapted for a variety of CNS injuries and conditions, depending upon the transmission properties of the tissue to be treated.

J Exp Neurosci. 2016 Feb 1;10:1-19. doi: 10.4137/JEN.S33444. eCollection 2016.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton.

Liebert AD1, Chow RT2, Bicknell BT3, Varigos E4.
Author information
1University of Sydney, Sydney, NSW, Australia.
2Brain and Mind Institute, University of Sydney, Sydney, NSW, Australia.
3Australian Catholic University, Sydney, NSW, Australia.
4Olympic Park Clinic, Melbourne, VIC, Australia.
Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer’s disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.
Front Neurosci. 2016 Jan 11;9:500. doi: 10.3389/fnins.2015.00500. eCollection 2015.

Turning On Lights to Stop Neurodegeneration: The Potential of Near Infrared Light Therapy in Alzheimer’s and Parkinson’s Disease.

Johnstone DM1, Moro C2, Stone J1, Benabid AL2, Mitrofanis J2.
Author information
1Department of Physiology, University of Sydney Sydney, NSW, Australia.
2University Grenoble Alpes, CEA, LETI, CLINATEC, MINATEC Campus Grenoble, France.
Alzheimer’s and Parkinson’s disease are the two most common neurodegenerative disorders. They develop after a progressive death of many neurons in the brain. Although therapies are available to treat the signs and symptoms of both diseases, the progression of neuronal death remains relentless, and it has proved difficult to slow or stop. Hence, there is a need to develop neuroprotective or disease-modifying treatments that stabilize this degeneration. Red to infrared light therapy (? = 600-1070 nm), and in particular light in the near infrared (NIr) range, is emerging as a safe and effective therapy that is capable of arresting neuronal death. Previous studies have used NIr to treat tissue stressed by hypoxia, toxic insult, genetic mutation and mitochondrial dysfunction with much success. Here we propose NIr therapy as a neuroprotective or disease-modifying treatment for Alzheimer’s and Parkinson’s patients.
J Mol Neurosci. 2014 Jul 4. [Epub ahead of print]

Low-Level Laser Therapy Ameliorates Disease Progression in a Mouse Model of Alzheimer’s Disease.

Farfara D1, Tuby H, Trudler D, Doron-Mandel E, Maltz L, Vassar RJ, Frenkel D, Oron U.

Author information

  • 1Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.


Low-level laser therapy (LLLT) has been used to treat inflammation, tissue healing, and repair processes. We recently reported that LLLT to the bone marrow (BM) led to proliferation of mesenchymal stem cells (MSCs) and their homing in the ischemic heart suggesting its role in regenerative medicine. The aim of the present study was to investigate the ability of LLLT to stimulate MSCs of autologous BM in order to affect neurological behavior and ?-amyloid burden in progressive stages of Alzheimer’s disease (AD) mouse model. MSCs from wild-type mice stimulated with LLLT showed to increase their ability to maturate towards a monocyte lineage and to increase phagocytosis activity towards soluble amyloid beta (A?). Furthermore, weekly LLLT to BM of AD mice for 2 months, starting at 4 months of age (progressive stage of AD), improved cognitive capacity and spatial learning, as compared to sham-treated AD mice. Histology revealed a significant reduction in A? brain burden. Our results suggest the use of LLLT as a therapeutic application in progressive stages of AD and imply its role in mediating MSC therapy in brain amyloidogenic diseases.

Front Syst Neurosci. 2014; 8: 36.
Published online 2014 Mar 14. doi:  10.3389/fnsys.2014.00036
PMCID: PMC3953713

Augmentation of cognitive brain functions with transcranial lasers

F. Gonzalez-Lima* and Douglas W. Barrett
Department of Psychology and Institute for Neuroscience, University of Texas at Austin, Austin, TX, USA
*Correspondence: ude.saxetu@amilzelaznog
This article was submitted to the journal Frontiers in Systems Neuroscience.
Edited by: Mikhail Lebedev, Duke University, USA
Reviewed by: Julio C. Rojas, University of Texas Southwestern Medical Center, USA; John Mitrofanis, University of Sydney, Australia
Author information ? Article notes ? Copyright and License information ?
Received 2014 Jan 31; Accepted 2014 Feb 27.
Keywords: cognitive enhancement, cytochrome oxidase, low-level light therapy, brain stimulation, photoneuromodulation

Discovering that transcranial infrared laser stimulation produces beneficial effects on frontal cortex functions such as sustained attention, working memory, and affective state has been groundbreaking. Transcranial laser stimulation with low-power density (mW/cm2) and high-energy density (J/cm2) monochromatic light in the near-infrared wavelengths modulates brain functions and may produce neurotherapeutic effects in a nondestructive and non-thermal manner (Lampl, 2007; Hashmi et al., 2010). Barrett and Gonzalez-Lima (2013) provided the first controlled study showing that transcranial laser stimulation improves human cognitive and emotional brain functions. But for the field of low-level light/laser therapy (LLLT), development of a model of how luminous energy from red-to-near-infrared wavelengths modulates bioenergetics began with in vitro and in vivo discoveries in the last 40 years. Previous LLLT reviews have provided extensive background about historical developments, principles and applications (Rojas and Gonzalez-Lima, 2011, 2013; Chung et al., 2012). The purpose of this paper is to provide an update on LLLT’s neurochemical mechanisms supporting transcranial laser stimulation for cognitive-enhancing applications. We will explain first LLLT’s action on brain bioenergetics, briefly describe its bioavailability and dose-response, and finish with its beneficial effects on cognitive functions. Although our focus is on prefrontal-related cognitive functions, in principle LLLT should be able to modulate other brain functions. For example, stimulating different brain regions should affect different functions related to sensory and motor systems.

Brain bioenergetics

The way that near-infrared lasers and light-emitting diodes (LEDs) interact with brain function is based on bioenergetics, a mechanism that is fundamentally different than that of other brain stimulation methods such as electric and magnetic stimulation. LLLT has been found to modulate the function of neurons in cell cultures, brain function in animals, and cognitive and emotional functions in healthy persons and clinical conditions. Photoneuromodulation involves the absorption of photons by specific molecules in neurons that activate bioenergetic signaling pathways after exposure to red-to-near-infrared light. The 600–1150 nm wavelengths allow better tissue penetration by photons because light is scattered at lower wavelengths and absorbed by water at higher wavelengths (Hamblin and Demidova, 2006). Over 25 years ago, it was found that molecules that absorb LLLT wavelengths are part of the mitochondrial respiratory enzyme cytochrome oxidase in different oxidation states (Karu et al., 2005). Thus, for red-to-near-infrared light, the primary molecular photoacceptor of photon energy is cytochrome oxidase (also called cytochrome c oxidase or cytochrome a-a3) (Pastore et al., 2000).

Therefore, photon energy absorption by cytochrome oxidase is well-established as the primary neurochemical mechanism of action of LLLT in neurons (Wong-Riley et al., 2005). The more the enzymatic activity of cytochrome oxidase increases, the more metabolic energy that is produced via mitochondrial oxidative phosphorylation. LLLT supplies the brain with metabolic energy in a way analogous to the conversion of nutrients into metabolic energy, but with light instead of nutrients providing the source for ATP-based metabolic energy (Mochizuki-Oda et al., 2002). If an effective near-infrared light energy dose is supplied, it stimulates brain ATP production (Lapchak and De Taboada, 2010) and blood flow (Uozumi et al., 2010), thereby fueling ATP-dependent membrane ion pumps, leading to greater membrane stability and resistance to depolarization, which has been shown to transiently reduce neuronal excitability (Konstantinovic et al., 2013). On the other hand, electromagnetic stimulation directly changes the electrical excitability of neurons.

A long-lasting effect is achieved by LLLT’s up-regulating the amount of cytochrome oxidase, which enhances neuronal capacity for metabolic energy production that may be used to support cognitive brain functions. In mice and rats, memory has been improved by LLLT (Michalikova et al., 2008; Rojas et al., 2012a) and by methylene blue, a drug that at low doses donates electrons to cytochrome oxidase (Rojas et al., 2012b). Near-infrared light stimulates mitochondrial respiration by donating photons to cytochrome oxidase, because cytochrome oxidase is the main acceptor of photons from red-to-near-infrared light in neurons. By persistently stimulating cytochrome oxidase activity, transcranial LLLT induces post-stimulation up-regulation of the amount of cytochrome oxidase in brain mitochondria (Rojas et al., 2012a). Therefore, LLLT may lead to the conversion of luminous energy into metabolic energy (during light exposure) and to the up-regulation of the mitochondrial enzymatic machinery to produce more energy (after light exposure).

Bioavailability and hormetic dose-response

The most abundant metalloprotein in nerve tissue is cytochrome oxidase, and its absorption wavelengths are well correlated with its enzymatic activity and ATP production (Wong-Riley et al., 2005). High LLLT bioavailability to the brain in vivo has been shown by inducing brain cytochrome oxidase activity transcranially, leading to enhanced extinction memory retention in normal rats (Rojas et al., 2012a) and improved visual discrimination in rats with impaired retinal mitochondrial function (Rojas et al., 2008). Our LLLT studies utilized varied wavelengths (633–1064 nm), daily doses (1–60 J/cm2), fractionation sessions (1–6), and power densities (2–250 mW/cm2) that identified effective LLLT parameters for rats and humans.

For example, we tested in rats the effects of different LLLT doses in vivo on brain cytochrome oxidase activity, at either 10.9, 21.6, 32.9 J/cm2, or no LLLT. Treatments were delivered for 20, 40, and 60 min via four 660-nm LED arrays with a power density of 9 mW/cm2. One day after the LLLT session, brains were extracted, frozen, sectioned, and processed for cytochrome oxidase histochemistry. A 10.9 J/cm2 dose increased cytochrome oxidase activity by 13.6%. A 21.6 J/cm2 dose produced a 10.3% increase. A non-significant cytochrome oxidase increase of 3% was found after the highest 32.9 J/cm2 dose. Responses of brain cytochrome oxidase to LLLT in vivo were characterized by hormesis, with a low dose being stimulatory, while higher doses were less effective.

The first demonstration that LLLT increased oxygen consumption in the rat prefrontal cortex in vivo was provided by Rojas et al. (2012a). Oxygen concentration in the cortex of rats was measured using fluorescence-quenching during LLLT at 9 mW/cm2 and 660 nm. LLLT induced a dose-dependent increase in oxygen consumption of 5% after 1 J/cm2 and 16% after 5 J/cm2. Since oxygen is used to form water within mitochondria in a reaction catalyzed by cytochrome oxidase, more cytochrome oxidase activity should lead to more oxygen consumption.

LLLT may offer some advantages over other types of stimulation, because LLLT non-invasively targets cytochrome oxidase, a key enzyme for energy production, with induced expression linked to energy demand. Hence LLLT is mechanistically specific and non-invasive, while transcranial magnetic stimulation may be non-specific, prolonged forehead electrical stimulation may produce muscle spasms, and deep brain or vagus nerve stimulations are invasive.

Cognitive and emotional functions

LLLT via commercial low-power sources (such as FDA-cleared laser diodes and LEDs) is a highly promising, affordable, non-pharmacological alternative for improving cognitive function. LLLT delivers safe doses of light energy that are sufficiently high to modulate neuronal functions, but low enough to not result in any damage (Wong-Riley et al., 2005). In 2002, the FDA approved LLLT for pain relief in cases of head and neck pain, arthritis and carpal tunnel syndrome (Fulop et al., 2010). LLLT has been used non-invasively in humans after ischemic stroke to improve neurological outcome (Lampl et al., 2007). It also led to improved recovery and reduced fatigue after exercise (Leal Junior et al., 2010). One LLLT stimulation session to the forehead, as reported by Schiffer et al. (2009), produced a significant antidepressant effect in depressed patients. No adverse side effects were found either immediately or at 2 or 4 weeks after LLLT. Thus, these beneficial LLLT treatments have been found to be safe in humans. Even though LLLT has been regarded as safe and received FDA approval for pain treatment, the use of transcranial lasers for cognitive augmentation should be restricted to research until further controlled studies support this application for clinical use.

We used transcranial laser stimulation to the forehead in a placebo-controlled, randomized study, to influence cognitive tasks related to the prefrontal cortex, including a psychomotor vigilance task (PVT) and a delayed match-to-sample (DMS) memory task (Barrett and Gonzalez-Lima, 2013). The PVT assesses sustained attention, with participants remaining vigilant during delay intervals, and pushing a button when a visual stimulus appears on a monitor. Our laser stimulation targeted prefrontal areas which are implicated in the sustained attentional processes of the PVT (Drummond et al., 2005). Similarly, the DMS task engages the prefrontal cortex as part of a network of frontal and parietal brain regions (Nieder and Miller, 2004).

Healthy volunteers received continuous wave near-infrared light intersecting cytochrome oxidase’s absorption spectrum, delivered to the forehead using a 1064 nm low-power laser diode (also known as “cold laser”), which maximizes tissue penetration due to its long wavelength, and has been used in humans for other indications. The power density (or irradiance), 250 mW/cm2, as well as the cumulative energy density (or fluence), 60 J/cm2, were the same that showed beneficial psychological effects in Schiffer et al. (2009). This laser exposure produces negligible heat and no physical damage at the low power level used. This laser apparatus is used safely in a clinical setting by the supplier of the laser (Cell Gen Therapeutics, HD Laser Center, Dallas, TX). Reaction time in the PVT was improved by the laser treatment, as shown by a significant pre-post reaction time change relative to the placebo group. The DMS memory task also revealed significant enhancements in measures of memory retrieval latency and number of correct trials, when comparing the LLLT-treated with the placebo group (Figure (Figure1).1). Self-reported positive and negative affective (emotional) states were also measured using the PANAS-X questionnaire before and 2 weeks after laser treatment. As compared to the placebo, treated subjects reported significantly improved affective states. We suggest that this kind of transcranial laser stimulation may serve as a non-invasive and efficacious method to augment cognitive brain functions related to attention, memory, and emotional functions.

Figure 1

Cognitive performance in the delayed match-to-sample (DMS) memory task was improved after transcranial infrared stimulation to the right forehead. The DMS task involves presentation of a visual stimulus (grid pattern) on a screen. Then the stimulus disappears,

LLLT’s bioenergetics mechanisms leading to cognitive augmentation may also be at play in its neuroprotective effects (Gonzalez-Lima et al., 2013). LLLT’s stimulation of mitochondrial respiration should improve cellular function due to increased metabolic energy, as well as cellular survival after injury, due to the antioxidant effects of increases in cytochrome oxidase and superoxide dismutase (Rojas et al., 2008).

Laser transmittance of the 1064-nm wavelength at the forehead LLLT site was estimated in a post-mortem human specimen, which showed that approximately 2% of the light passed through the frontal bone. This yielded an absorption coefficient of a = 0.24, similar to the reported a = 0.22 transmittance through cranial bone for this wavelength (Bashkatov and Genina, 2006). Thus, we estimated that about 1.2 J/cm2 of the 60 J/cm2 LLLT dose applied reached the surface of the prefrontal cortex. This value is similar to 1 J/cm2, the peak effective LLLT dose in neuron cultures for increasing cytochrome oxidase activity (Rojas and Gonzalez-Lima, 2011).


Transcranial absorption of photon energy by cytochrome oxidase, the terminal enzyme in mitochondrial respiration, is proposed as the bioenergetic mechanism of action of LLLT in the brain. Transcranial LLLT up-regulates cortical cytochrome oxidase and enhances oxidative phosphorylation. LLLT improves prefrontal cortex-related cognitive functions, such as sustained attention, extinction memory, working memory, and affective state. Transcranial infrared stimulation may be used efficaciously to support neuronal mitochondrial respiration as a new non-invasive, cognition-improving intervention in animals and humans. This fascinating new approach should also be able to influence other brain functions depending on the neuroanatomical site stimulated and the stimulation parameters used.


  • Barrett D. W., Gonzalez-Lima F. (2013). Transcranial infrared laser stimulation produces beneficial cognitive and emotional effects in humans. Neuroscience 230, 13–23 10.1016/j.neuroscience.2012.11.016 [PubMed] [Cross Ref]
  • Bashkatov A. N., Genina E. A. (2006). Optical properties of human cranial bone in the spectral range from 800 to 2000 nm. Proc. SPIE 6163, 616310 10.1117/12.697305 [Cross Ref]
  • Chung H., Dai T., Sharma S. K., Huang Y. Y., Carroll J. D., Hamblin M. R. (2012). The nuts and bolts of low-level laser (light) therapy. Ann. Biomed. Eng. 40, 516–533 10.1007/s10439-011-0454-7 [PMC free article] [PubMed] [Cross Ref]
  • Drummond S. P., Bischoff-Grethe A., Dinges D. F., Ayalon L., Mednick S. C., Meloy M. J. (2005). The neural basis of the psychomotor vigilance task. Sleep 28, 1059–1068 [PubMed]
  • Fulop A. M., Dhimmer S., Deluca J. R., Johanson D. D., Lenz R. V., Patel K. B., et al. (2010). A meta-analysis of the efficacy of laser phototherapy on pain relief. Clin. J. Pain 26, 729–736 10.1097/AJP.0b013e3181f09713 [PubMed] [Cross Ref]
  • Gonzalez-Lima F., Barksdale B. R., Rojas J. C. (2013). Mitochondrial respiration as a target for neuroprotection and cognitive enhancement. Biochem. Pharmacol. [Epub ahead of print]. 10.1016/j.bcp.2013.11.010 [PubMed] [Cross Ref]
  • Hamblin M. R., Demidova T. N. (2006). Mechanisms of low level light therapy. Proc. SPIE 6140, 1–12 10.1117/12.646294 [Cross Ref]
  • Hashmi J. T., Huang Y. Y., Osmani B. Z., Sharma S. K., Naeser M. A., Hamblin M. R. (2010). Role of low-level laser therapy in neurorehabilitation. PM R 2, S292–S305 10.1016/j.pmrj.2010.10.013 [PMC free article] [PubMed] [Cross Ref]
  • Karu T. I., Pyatibrat L. V., Kolyakov S. F., Afanasyeva N. I. (2005). Absorption measurements of a cell monolayer relevant to phototherapy: reduction of cytochrome c oxidase under near IR radiation. J. Photochem. Photobiol. B 81, 98–106 10.1016/j.jphotobiol.2005.07.002 [PubMed] [Cross Ref]
  • Konstantinovic L. M., Jelic M. B., Jeremic A., Stevanovic V. B., Milanovic S. D., Filipovic S. R. (2013). Transcranial application of near-infrared low-level laser can modulate cortical excitability. Lasers Surg. Med. 45, 648–653 10.1002/lsm.22190 [PubMed] [Cross Ref]
  • Lampl Y. (2007). Laser treatment for stroke. Expert Rev. Neurother. 7, 961–965 10.1586/14737175.7.8.961 [PubMed] [Cross Ref]
  • Lampl Y., Zivin J. A., Fisher M., Lew R., Welin L., Dahlof B., et al. (2007). Infrared laser therapy for ischemic stroke: a new treatment strategy: results of the neurothera effectiveness and safety trial-1 (NEST-1). Stroke 38, 1843–1849 10.1161/STROKEAHA.106.478230 [PubMed] [Cross Ref]
  • Lapchak P. A., De Taboada L. (2010). Transcranial near infrared laser treatment (NILT) increases cortical adenosine-5′-triphosphate (ATP) content following embolic strokes in rabbits. Brain Res. 1306, 100–105 10.1016/j.brainres.2009.10.022 [PubMed] [Cross Ref]
  • Leal Junior E. C., Lopes-Martins R. A., Frigo L., De Marchi T., Rossi R. P., de Godoi V., et al. (2010). Effects of low-level laser therapy (LLLT) in the development of exercise-induced skeletal muscle fatigue and changes in biochemical markers related to postexercise recovery. J. Orthop. Sports Phys. Ther. 40, 524–532 10.2519/jospt.2010.3294 [PubMed] [Cross Ref]
  • Michalikova S., Ennaceur A., van Rensburg R., Chazot P. L. (2008). Emotional responses and memory performance of middle-aged CD1 mice in a 3D maze: effects of low infrared light. Neurobiol. Learn. Mem. 89, 480–488 10.1016/j.nlm.2007.07.014 [PubMed] [Cross Ref]
  • Mochizuki-Oda N., Kataoka Y., Cui Y., Yamada H., Heya M., Awazu K. (2002). Effects of near-infra-red laser irradiation on adenosine triphosphate and adenosine diphosphate contents of rat brain tissue. Neurosci. Lett. 323, 207–210 10.1016/S0304-3940(02)00159-3 [PubMed] [Cross Ref]
  • Nieder A., Miller E. K. (2004). A parieto-frontal network for visual numerical information in the monkey. Proc. Natl. Acad. Sci. U.S.A. 101, 7457–7462 10.1073/pnas.0402239101 [PMC free article][PubMed] [Cross Ref]
  • Pastore D., Greco M., Passarella S. (2000). Specific helium-neon laser sensitivity of the purified cytochrome c oxidase. Int. J. Radiat. Biol. 76, 863–870 10.1080/09553000050029020 [PubMed][Cross Ref]
  • Rojas J. C., Gonzalez-Lima F. (2011). Low-level light therapy of the eye and brain. Eye Brain 3, 49–67 10.2147/EB.S21391 [Cross Ref]
  • Rojas J. C., Bruchey A. K., Gonzalez-Lima F. (2012a). Low-level light therapy improves cortical metabolic capacity and memory retention. J. Alzheimers Dis. 32, 741–752 10.3233/JAD-2012-120817[PubMed] [Cross Ref]
  • Rojas J. C., Bruchey A. K., Gonzalez-Lima F. (2012b). Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue. Prog. Neurobiol. 96, 32–45 10.1016/j.pneurobio.2011.10.007 [PMC free article] [PubMed] [Cross Ref]
  • Rojas J. C., Gonzalez-Lima F. (2013). Neurological and psychological applications of transcranial lasers and LEDs. Biochem. Pharmacol. 86, 447–457 10.1016/j.bcp.2013.06.012 [PubMed][Cross Ref]
  • Rojas J. C., Lee J., John J. M., Gonzalez-Lima F. (2008). Neuroprotective effects of near-infrared light in an in vivo model of mitochondrial optic neuropathy. J. Neurosci. 28, 13511–13521 10.1523/JNEUROSCI.3457-08.2008 [PMC free article] [PubMed] [Cross Ref]
  • Schiffer F., Johnston A. L., Ravichandran C., Polcari A., Teicher M. H., Webb R. H., et al. (2009). Psychological benefits 2 and 4 weeks after a single treatment with near infrared light to the forehead: a pilot study of 10 patients with major depression and anxiety. Behav. Brain Funct. 5, 46 10.1186/1744-9081-5-46 [PMC free article] [PubMed] [Cross Ref]
  • Uozumi Y., Nawashiro H., Sato S., Kawauchi S., Shima K., Kikuchi M. (2010). Targeted increase in cerebral blood flow by transcranial near-infrared laser irradiation. Lasers Surg. Med. 42, 566–576 10.1002/lsm.20938 [PubMed] [Cross Ref]
  • Wong-Riley M. T., Liang H. L., Eells J. T., Chance B., Henry M. M., Buchmann E., et al. (2005). Photobiomodulation directly benefits primary neurons functionally inactivated by toxins: role of cytochrome c oxidase. J. Biol. Chem. 280, 4761–4771 10.1074/jbc.M409650200 [PubMed][Cross Ref]
Alzheimers Res Ther. 2014; 6(1): 2.
Published online Jan 3, 2014. doi:  10.1186/alzrt232

Photobiomodulation with near infrared light mitigates Alzheimer’s disease- related pathology in cerebral cortex – evidence from two transgenic mouse models.

Sivaraman Purushothuman,1,2 Daniel M Johnstone,corresponding author1,2 Charith Nandasena,1,2 John Mitrofanis,1,3 and Jonathan Stone1,2

Alzheimer’s disease (AD) is a chronic, debilitating neurodegenerative disease with limited therapeutic options; at present there are no treatments that prevent the physical deterioration of the brain and the consequent cognitive deficits. Histopathologically, AD is characterised by neurofibrillary tangles (NFTs) of hyperphosphorylated tau protein and amyloid-beta (A?) plaques [1,2]. The extent of these histopathological features is considered to vary with and to determine clinical disease severity [2]. While the initiating pathogenic events underlying AD are still debated, there is strong evidence to suggest that oxidative stress and mitochondrial dysfunction have important roles in the neurodegenerative cascade [35]. Therefore, it has been proposed that targeting mitochondrial dysfunction could prove valuable for AD therapeutics [6].

One safe, simple yet effective approach to the repair of damaged mitochondria is photobiomodulation with near-infrared light (NIr). This treatment, which involves the irradiation of tissue with low intensity light in the red to near-infrared wavelength range (600 to 1000 nm), was originally pioneered for the healing of superficial wounds [7] but has been recently shown to have efficacy in protecting the central nervous system. While the mechanism of action remains to be elucidated, there is evidence that NIr preserves and restores cellular function by reversing dysfunctional mitochondrial cytochrome c oxidase (COX) activity, thereby mitigating the production of reactive oxygen species and restoring ATP production to normal levels [8,9].

To date, NIr treatment has yielded neuroprotective outcomes in animal models of retinal damage [9,10], traumatic brain injury [11,12], Parkinson’s disease [1315] and AD [16,17]. Furthermore, NIr therapy has yielded beneficial outcomes in clinical trials of human patients with mild to moderate stroke [18] and depression [19]. This treatment represents a promising alternative to drug therapy because it is safe, easy to apply and has no known side-effects at levels even higher than optimal doses [20].

The aim of this study was to assess the efficacy of NIr in mitigating the brain pathology and associated cellular damage that characterise AD. We utilised two mouse models, each manifesting distinct AD-related pathologies: the K3 tau transgenic model, which develops NFTs [21,22]; and the APP/PS1 transgenic model, which develops amyloid plaques [23]. Here, we present histochemical evidence that NIr treatment over a period of 1 month reduces the severity of AD-related pathology and oxidative stress and restores mitochondrial function in brain regions susceptible to neurodegeneration in AD, specifically the neocortex and hippocampus. The findings extend our previous NIr work in models of acute neurodegeneration [13,14] to demonstrate that NIr is also effective in protecting the brain against chronic insults due to AD-related genetic aberrations, a pathogenic mechanism that is likely to more closely model the human neurodegenerative condition.:


Mouse models

The K3 transgenic mouse model, originally generated as a model of frontotemporal dementia [21,22], harbours a human tau gene with the pathogenic K369I mutation; expression is driven by the neuron-specific mThy1.2 promoter. This model manifests high levels of hyperphosphorylated tau and NFTs by 2 to 3 months of age and cognitive deficits by about 4 months of age [21,22]. We commenced our experiments on K3 mice and matched C57BL/6 wildtype (WT) controls at 5 months of age, when significant neuropathology is already present.

The APPswe/PSEN1dE9 (APP/PS1) transgenic mouse model, obtained from the Jackson Laboratory (Stock number 004462; Bar Harbor, ME, USA), harbours two human transgenes: the amyloid beta precursor protein gene (APP) containing the Swedish mutation; and the presenilin-1 gene (PS1) containing a deletion of exon 9 [23]. The APP/PS1 mice exhibit increased A? and amyloid plaques by 4 months of age [24] and cognitive deficits by 6 months of age [25]. We commenced our experiments on APP/PS1 mice and matched C57BL/6 × C3H WT controls at 7 months of age, when numerous amyloid plaques and associated cognitive deficits are present.

Genotyping of mice was achieved by extracting DNA from tail tips through a modified version of the Hot Shot preparation method [26] and amplifying the transgene sequence by polymerase chain reaction. As reported previously, K3 mice were identified using the primers 5-GGGTGTCTCCAATGCCTGCTTCTTCAG-3 (forward) and 5-AAGTCACCCAGCAGGGAGGTGCTCAG-3 (reverse) [21,22] and APP/PS1 mice were genotyped using primers 5-AGGACTGACCACTCGACCAG-3 (forward) and 5-CGGGGGTCTAGTTCTGCAT-3 (reverse) [23].

Experimental design

For each series of experiments on K3 mice (aged 5 months) or APP/PS1 mice (aged 7 months) there were three experimental groups: untreated WT mice, untreated transgenic mice and NIr-treated transgenic mice (n = 5 mice per experimental group for the K3 series, 15 mice in total; n = 6 mice per experimental group for the APP/PS1 series, 18 mice in total). Our design did not include a WT control group exposed to NIr because NIr has no detectable impact on the survival and function of cells in normal healthy brain [1315]. Given the consistency of the previous results, use of animals for this extra control group did not seem justified [27].

Mice in the NIr-treated groups were exposed to one 90-second cycle of NIr (670 nm) from a light-emitting device (LED) (WARP 10; Quantum Devices, Barneveld, WI, USA) for 5 days per week over 4 consecutive weeks. Light energy emitted from the LED during each 90-second treatment equates to 4 Joule/cm2; a total of 80 Joule/cm2 was delivered to the skull over the 4 weeks. Our measurements of NIr penetration across the fur and skull of a C57BL/6 mouse indicate that ~2.5% of transmitted light reaches the cortex.

For each treatment, the mouse was restrained by hand and the LED was held 1 to 2 cm above the head. The LED light generated no heat and reliable delivery of the radiation was achieved [1315]. For the sham-treated WT, K3 and APP/PS1 groups, animals were restrained in the same way and the device was held over the head, but the light was not switched on. This treatment regime is similar to that used in previous studies where beneficial changes to neuropathology and behavioural signs were reported [1315].

Experimental animals were housed two or more to a cage and kept in a 12-hour light (<5 lux)/dark cycle at 22°C; food pellets and water were available ad libitum. All protocols were approved by the Animal Ethics Committee of the University of Sydney.

Histology and immunohistochemistry

At the end of the experimental period, mice were anaesthetised by intraperitoneal injection of sodium pentobarbital (60 mg/kg) and perfused transcardially with 4% buffered paraformaldehyde. Brains were post fixed for 3 hours, washed with phosphate-buffered saline and cryoprotected in 30% sucrose/phosphate-buffered saline. Tissue was embedded in OCT compound (ProSciTech, Thuringowa, QLD, Australia) and coronal sections of the neocortex and the hippocampus (between bregma ?1.8 and ?2.1) were cut at 20 ?m thickness on a Leica cryostat (Nussloch, Germany).


For most antibodies, antigen retrieval was achieved using sodium citrate buffer with 0.1% Triton. Sections were blocked in 10% normal goat serum and then incubated overnight at 4°C with a mouse monoclonal antibody – paired helical filaments-tau AT8, 1:500 (Innogenetics, Ghent, Belgium); 4-hydroxynonenal (4-HNE), 1:200 (JaICA, Fukuroi, Shizuoka, Japan); 8-hydroxy-2?-deoxyguanosine (8-OHDG), 1:200 (JaICA); COX, 1:200 (MitoSciences, Eugene, OR, USA) – and/or a rabbit polyclonal antibody (200 kDa neurofilament, 1:500; Sigma, St. Louis, MO, USA). Sections were then incubated for 3 hours at room temperature in Alexa Fluor-488 (green) and/or Alexa Fluor-594 (red) tagged secondary antibodies specific to host species of the primary antibodies (1:1,000; Molecular Probes, Carlsbad, CA, USA). Sections were then counterstained for nuclear DNA with bisbenzimide (Sigma).

Two different but complementary antibodies were used to label A? peptide: 6E10, which recognises residues 1 to 16; and 4G8, which recognises residues 17 to 24. We have previously used these two antibodies in combination to validate A? labelling, demonstrating identical labelling patterns in the rat neocortex and hippocampus [28]. For double labelling using 6E10 antibodies (1:500; Covance, Princeton, NJ, USA) and anti-glial fibrillary acidic protein antibodies (1:1,000; DAKO, Glostrup, Denmark), antigen retrieval was achieved by incubation in 90% formic acid for 10 minutes, and primary antibody incubation was carried out overnight at room temperature. For labelling using the 4G8 (1:500; Covance) antibody, slides were treated with 3% H2O2 in 50% methanol, incubated in 90% formic acid and then washed several times in dH2O before the blocking step, as described previously [28]. After blocking, sections were incubated overnight at room temperature with 4G8 antibody. Sections were then incubated in biotinylated goat anti-mouse IgG for 1 hour followed by ExtrAvidin peroxidase for 2.5 hours. The sections were then washed and developed with 3,3?-Diaminobenzidine.

Negative control sections were processed in the same fashion as described above except that primary antibodies were omitted. These control sections were immunonegative. Fluorescent images were taken using a Zeiss Apotome 2, Carl Zeiss, Oberkochen, Germany. Brightfield images were taken using a Nikon Eclipse E800, Nikon Instruments, Melville, NY, USA.


NFTs were assessed using the Bielschowsky silver staining method, as described previously [21,22]. Briefly, sections were placed in prewarmed 10% silver nitrate solution for 15 minutes, washed and then placed in ammonium silver nitrate solution at 40°C for a further 30 minutes. Sections were subsequently developed for 1 minute and then transferred to 1% ammonium hydroxide solution for 1 minute to stop the reaction. Sections were then washed in dH2O, placed in 5% sodium thiosulphate solution for 5 minutes, washed, cleared and mounted in dibutyl phathalate xylene.

As described previously [28], A? plaques were studied by staining with Congo red, a histological dye that binds preferentially to compacted amyloid with a ?-sheet secondary structure [29]. Briefly, sections were treated with 2.9 M sodium chloride in 0.01 M NaOH for 20 minutes and were subsequently stained in filtered alkaline 0.2% Congo red solution for 1 hour.

Morphological analysis

Staining intensity and area measurements

To quantify the average intensity and area of antibody labelling within the neocortex and hippocampal regions, an integrated morphology analysis was undertaken using MetaMorph software. For each section, the level of nonspecific staining (using an adjacent region of unstained midbrain) was adjusted to a set level to ensure a standard background across different groups. Next, outlines of retrosplenial cortex area 29 and hippocampal CA1 region were traced and the average intensity and area of immunostaining were calculated by the program. Measurements were conducted on ?4 representative sections per animal and ?3 animals per experimental group. Statistical analyses were performed in Prism 5.0 (Graphpad, La Jolla, CA, USA) using one-way analysis of variance with Tukey’s multiple comparison post test. All values are given as mean ± standard error of mean.

Amyloid-beta plaque measurements

Digital brightfield images of 4G8 staining in the neocortical and hippocampal regions (between bregma ?1.8 and ?2.1) were taken at 4× magnification and analysed with Metamorph, Molecular Devices LLC, Sunnyvale, CA, USA. The software was programmed to measure the number of plaques and the average size of plaques after thresholding for colour. The percentage of area covered by plaques (plaque burden) was calculated by multiplying the number of plaques by the average size of plaques, divided by the area of interest, as described previously [30]. The average number of Congo red-positive plaques in the APP/PS1 brain regions was estimated using the optical fractionator method (StereoInvestigator; MBF Science, Williston, VT, USA), as outlined previously [14]. Briefly, systematic random sampling of sites was undertaken using an unbiased counting frame (100 ?m × 100 ?m). All plaques that came into focus within the frame were counted. Measurements were conducted on ?4 representative sections per animal and ?3 animals per experimental group. Plaque numbers and size were analysed using a two-tailed unpaired t test (when variances were equal) or Welch’s t test (when variances were unequal). All values are given as mean ± standard error of mean. For all analyses, investigators were blinded to the experimental groups.


Evidence of NIr-induced neuroprotection is presented from the neocortex (retrosplenial area) and the hippocampus (CA1 and subiculum), two cortical regions affected in the early stages of human AD [2].

Near-infrared light mitigates the tau pathology of K3 cortex

Hyperphosphorylation of the neuronal microtubule stabilising protein tau and the resulting NFTs are much studied features of dementia pathology [2,31]. The K3 mouse model manifests hyperphosphorylated tau and NFTs by 2 to 3 months of age and cognitive deficits by about 4 months of age [21,22]. We observe strong labelling for hyperphosphorylated tau in the neocortex and the hippocampus at 6 months of age; expression appears to plateau after this age, with similar labelling observed in 12-month-old mice (Figure 1A,B,C,D,E,F).

Figure 1

Time course of the natural development of cortical pathology in K3 and APP/PS1 mice. (A), (B), (C), (D), (E), (F) Micrographs of hyperphosphorylated tau labelling (red), using the AT8 antibody, in the neocortex (A to C) and hippocampus (D toF) of untreated

In the retrosplenial area of the neocortex there was a significant overall difference in AT8 immunolabelling for tau between the experimental groups, both when considering average intensity of labelling (P < 0.01 by analysis of variance; Figure 2A) and labelled area (P < 0.01; Figure 2B). Tukeypost hoc testing revealed significant differences between the untreated K3 group and the other two groups; labelling was much stronger and more widespread in K3 mice than WT controls (17-fold higher intensity, P < 0.01), and this labelling was reduced by over 70% in NIr-treated mice (P < 0.05). Interestingly, there was no significant difference between the WT and K3-NIr groups, suggesting that NIr treatment had reduced hyperphosphorylated tau to control levels in K3 mice. A similar trend was observed when considering the NFT pathology (Figure 2C,D,E). In contrast to WT brain, which showed no NFT-like lesions (Figure 2C), the K3 brain contained many ovoid shaped NFT-like lesions (that is, spheroids; Figure 2D). Such structures were less frequent in the K3-NIr brain (Figure 2E).

Figure 2

Effect of near-infrared light treatment on hyperphosphorylated tau and neurofibrillary tangles in the neocortex of K3 mice. (A), (B) Quantification of tau AT8 immunolabelling, based on average labelling intensity (A) and labelled area (B). All error bars

Similar effects were observed in the hippocampus (Figure 3). There was a significant overall difference between the experimental groups in AT8 immunolabelling of the CA1 pyramidal cells (P < 0.01). As for the neocortex, K3 mice showed far greater labelling than WT mice (17-fold higher intensity, P < 0.01) and this was reduced over 65% by NIr treatment (P < 0.01). Again, there were no significant differences between the WT and K3-NIr groups (P > 0.05). Bielschowsky silver staining of the subiculum (Figure 3C,D,E) revealed axonal swellings and spheroids in the hippocampal region of K3 mice (Figure 3D), which were less pronounced in mice from the K3-NIr group (Figure 3E). No pathology was observed in the hippocampus of WT mice (Figure 3C).

Figure 3

Effect of near-infrared light treatment on hyperphosphorylated tau and neurofibrillary tangles in the hippocampus of K3 mice. (A), (B) Quantification of tau AT8 immunolabelling, based on average labelling intensity (A) and labelled area (B). All error

One should note that the large white matter pathways associated with the hippocampus were labelled intensely by silver staining in all three groups (Figure 3C,D,E). This labelling has been described previously and is not associated with any neuropathology [32].

Near-infrared light reduces oxidative stress in K3 cortex

Oxidative stress and damage are common features of neurodegenerative diseases such as AD, and may be a precursor to neuronal death [35]. We assessed two common markers of oxidative stress: 4-HNE, a toxic end-product of lipid peroxidation that may bind to proteins that then trigger mitochondrial dysfunction and cellular apoptosis in AD [33]; and 8-OHDG, a marker for nuclear and mitochondrial DNA oxidation, which is elevated in AD brains [34].

Overall, 4-HNE immunoreactivity in the neocortex was significantly different between the experimental groups (Figure 4), by both average labelling intensity (P < 0.01) and labelled area (P < 0.001). As with AT8 labelling above, the K3 group showed a much higher average 4-HNE labelling intensity and area than the WT group (fivefold and 20-fold, respectively) and this labelling was significantly reduced (by 50% and 80%, respectively) in the K3-NIr group. Again, these measures showed no significant differences between the WT and K3-NIr groups (P > 0.05).

Figure 4

Effect of near-infrared light treatment on oxidative stress markers in the neocortex of K3 mice. (A), (B), (F), (G)Quantification of immunolabelling of two oxidative stress markers, 4-hydroxynonenal (4-HNE; A, B) and 8-hydroxy-2?-deoxyguanosine

Similar patterns were observed for 8-OHDG immunoreactivity. Overall, there was a significant difference between the groups for 8-OHDG immunolabelling, by both average intensity (P < 0.0001) and labelled area (P < 0.0001). Again the K3 group showed significantly higher 8-OHDG labelling intensity and area than the WT group (sixfold and 17-fold, respectively), and the 8-OHDG labelling intensity and area were significantly reduced in the K3-NIr group relative to untreated K3 (65% and 85% reduction, respectively). The intensity and area of 8-OHDG labelling did not differ significantly between the WT and the K3-NIr groups (P > 0.05), suggesting that NIr treatment reduces markers of oxidative stress to control levels. The representative photomicrographs of 8-OHDG immunoreactivity in the retrosplenial area (Figure 4H,I,J) reflect the quantitative data, with many 8-OHDG+ structures in the K3 group (Figure 4I) but not in the WT and K3-NIr groups (Figure 4H,J).

Near-infrared light mitigates mitochondrial dysfunction in K3 cortex

We assessed expression patterns of the mitochondrial enzyme COX in the neocortex and the hippocampus as a marker of mitochondrial function. Overall, there were statistically significant differences in the patterns of COX immunoreactivity between the different experimental groups, both in the neocortex and the hippocampus (both P < 0.0001; Figure 5). Relative to WT mice, the COX labelling intensity and area were reduced in K3 mice in both the neocortex and the hippocampus (>70% and >75% reductions, respectively). The K3-NIr mice showed a significant recovery of COX immunoreactivity relative to untreated K3 mice in both the neocortex (>1.7-fold increase, P < 0.05) and the hippocampus (>3.4-fold increase, P < 0.001). However, recovery was not complete, with K3-NIr mice having significantly lower COX immunoreactivity than WT mice in the neocortex (~50%, P < 0.001) and significantly lower COX labelling intensity (~20%, P < 0.05) in the hippocampus. These two groups did not differ significantly in COX labelling area in the hippocampus (P > 0.05).

Figure 5

Effect of near-infrared light treatment on cytochrome coxidase labelling in the neocortex and hippocampus of K3 mice. (A), (B), (F), (G) Quantification of immunolabelling of the mitochondrial marker cytochrome c oxidase (COX) in the neocortex retrosplenial

Near-infrared mitigates amyloid pathology in APP/PS1 cortex

Along with NFTs, A? plaques are considered a primary pathological hallmark of AD and A? load is often used as a marker of AD severity [1,35]. We assessed the distribution of A? plaques and more immature forms of the A? peptide in the neocortex and hippocampus of APP/PS1 mice aged 7 months; this age is after the first signs of intracellular A? within cells (at 3 months; Figure 1G) and extracellular A? plaques (at 4.5 and 12 months; Figure 1H and ?and1I,1I, respectively).

Three quantitative measures of plaque pathology were used: percentage plaque burden, average plaque size and number of plaques. Immunohistochemical labelling with the anti-A? antibody 4G8 revealed a significant reduction in percentage plaque burden (Figure 6A,D), average plaque size (Figure 6B,E) and number of plaques (Figure 6C,F) in both the neocortex and the hippocampus of NIr-treated APP/PS1 mice relative to untreated APP/PS1 controls. Percentage plaque burden was reduced by over 40% in the neocortex (Figure 6A; P < 0.001) and over 70% in the hippocampus (Figure 6D; P < 0.01), average plaque size was reduced 25% in the neocortex (Figure 6B) and 30% in the hippocampus (Figure 6E), and the number of plaques was reduced by over 20% in the neocortex (Figure 6C) and by over 55% in the hippocampus (Figure 6F; all P < 0.05).

Figure 6

Effect of near-infrared light on amyloid-beta and plaque pathology in APP/PS1 mice. (A), (B), (C), (D), (E), (F)Quantification of amyloid-beta (A?) 4G8 immunolabelling of amyloid plaques in the neocortex (A, B, C) and hippocampus (D, E, F), based

The photomicrographs of the 4G8 immunoreactivity in Figure 6 reflect the quantitative data described earlier. The WT brain is free of plaques (Figure 6H,K); many 4G8+ plaques (arrows) are present in the neocortex (Figure 6I) and the hippocampus (Figure 6L) of untreated APP/PS1 mice, and fewer plaques are present in NIr-treated APP/PS1 mice (Figure 6J,M). Comparable immunolabelling was achieved using the 6E10 anti-A? antibody (data not shown).

A similar but less pronounced trend was observed when staining with Congo red (Figure 7), which stains only mature plaques. Mean counts of plaques in the neocortex (Figure 7A) and the hippocampus (Figure 7B) of NIr-treated APP/PS1 brains were lower than mean counts in untreated APP/PS1 brains (reductions >30%). However, the differences did not reach statistical significance; given the findings described above with the 4G8 and 6E10 anti-A? antibodies, this suggests that NIr may have greatest effect on recently formed A? deposits. The micrographs in Figure 7 show that mature plaques were absent from the WT brain (Figure 7C,D) but were present in the neocortex (Figure 7E) and hippocampus (Figure 7F) of untreated APP/PS1 brains. There appeared to be fewer plaques in the NIr-treated APP/PS1 brains (Figure 7G,H).

Figure 7

Effect of near-infrared light on Congo red-positive plaque numbers in APP/PS1 mice. (A), (B) Quantification of Congo red-positive plaque counts in the neocortex (A) and hippocampus(B). All error bars indicate standard error of the mean. (C), (D), (E),


Using two mouse models with distinct AD-related pathologies (tau pathology in K3, amyloid pathology in APP/PS1), we report evidence that NIr treatment can mitigate the pathology characteristic of AD as well as reduce oxidative stress and restore mitochondrial function in brain regions affected early in the disease. Further, the extent of mitigation – to levels less than at the start of treatment – suggests that NIr can reverse some elements of AD-related pathology.

The present results add to our previous findings of NIr-induced neuroprotection in models of toxin-induced acute neurodegeneration (that is, MPTP-induced parkinsonism). When incorporated into the growing body of evidence that NIr can also protect against CNS damage in models of stroke, traumatic brain injury and retinal degeneration [912,36], the findings provide a basis for trialling NIr treatment as a strategy for protection against neurodegeneration from a range of causes. Present evidence is based on the use of multiple methods, immunohistochemical and histological, to demonstrate pathological features (for example, 4G8 antibody labelling and Congo red staining for amyloid plaques, AT8 antibody labelling and Bielschowsky silver staining for NFTs).

Relationship to previous studies

The present study focused on pathological features considered characteristic of AD, as well as on signs of cellular damage (for example, oxidative stress, mitochondrial dysfunction) that have been demonstrated in AD and in animal models [24]. Our observations in the K3 strain add to previous studies by providing the first evidence in this strain of extensive oxidative damage and mitochondrial dysfunction [27].

Our findings are consistent with previous reports of the effects of red to infrared light on AD pathology in animal models. De Taboada and colleagues assessed the capacity of 808 nm laser-sourced infrared radiation, delivered three times per week over 6 months, to reduce pathology in an APP transgenic model of A? amyloidosis [17]. Treatment led to a reduction in plaque number, amyloid load and inflammatory markers, an increase in ATP levels and mitochondrial function, and mitigation of behavioural deficits. De Taboada and colleagues commenced treatment at 3 months of age, before the expected onset of amyloid pathology and cognitive effects. Similarly, Grillo and colleagues reported that 1,072 nm infrared light, applied 4 days per week for 5 months, reduces AD-related pathology in another APP/PS1 transgenic mouse model (TASTPM) [16]. These investigators also initiated light treatment before the onset of pathology, at 2 months of age. Both studies thus provide evidence that infrared radiation can slow the progression of cerebral degeneration in these models. The present results confirm these observations, in two distinct transgenic strains; they also confirm that the wound-healing and neuroprotective effects of red-infrared length do not vary qualitatively with wavelength, over a wide range.

Evidence of reversal of pathology

Previous reports have described the natural history of the K3 [21,22] and APP/PS1 transgenic models [24,37]. Based on these previous reports and our own baseline data (Figure 1), significant brain pathology and functional deficits are present in both models at the ages when we commenced treatment. Our results therefore suggest that significant reversal of pathology has been induced by the NIr treatment. This has implications for clinical practice, where most patients are not diagnosed until pathogenic mechanisms have already been initiated and resultant neurologic symptoms manifest [15,27].

This evidence that AD-related neuropathology can be transient – appear then disappear – is not novel. Garcia-Alloza and colleagues described evidence of the transient deposition of A?, including the formation of plaque-like structures, in a transgenic model of A? deposition [24]. Reversal of such pathology, by interventions such as NIr treatment, may therefore be possible. However our results suggest that reversal may also be limited to recently formed, immature plaques, as we observed a significant NIr-induced reduction in immunolabelling with the 4G8 and 6E10 antibodies but no significant difference in Congo red staining. Because the 4G8 and 6E10 antibodies recognise various forms of A?, while Congo red stains only mature, compacted plaques, a reasonable deduction is that NIr treatment reduces only the transient, recently formed A? deposits, with no substantial effect on mature plaques. As there is still no consensus as to the pathogenic roles of different forms of A?, it is unclear how this might impact on the therapeutic potential of NIr in a clinical setting.


The mechanisms underlying the neuroprotective actions of red to infrared light are not completely understood. There is considerable evidence that NIr photobiomodulation enhances mitochondrial function and ATP synthesis by activating photoacceptors such as COX and increasing electron transfer in the respiratory chain, while also reducing harmful reactive oxygen species [3840]. NIr photobiomodulation could also upregulate protective factors such as nerve growth factor and vascular endothelial growth factor [41,42] and mesenchymal stem cells [43] that could target specific areas of degeneration.

The ability of NIr to reduce the expression of hyperphosphorylated tau, which in turn reduces oxidative stress [44], may be key to its neuroprotective effect. Oxidative stress and free radicals increase the severity of cerebrovascular lesions [45,46], mitochondrial dysfunction [4,47], oligomerisation of A? [5,48] and tauopathies and cell death [48,49] in AD. Considering the brain’s high consumption of oxygen and consequent susceptibility to oxidative stress, mitigating such stressors would probably have a pronounced protective effect [50].


Overall, our results in two transgenic mouse models with existing AD-related pathology suggest that low-energy NIr treatment can reduce characteristic pathology, oxidative stress and mitochondrial dysfunction in susceptible regions of the brain. These results, when taken together with those in other models of neurodegeneration, strengthen the notion that NIr is a viable neuroprotective treatment for a range of neurodegenerative conditions. We believe this growing body of work provides the impetus to begin trialling NIr treatment as a broad-based therapy for AD and other neurodegenerations.


A?: Amyloid-beta; AD: Alzheimer’s disease; APP: Amyloid beta precursor protein gene; COX: Cytochrome c oxidase; 4-HNE: 4-hydroxynonenal; LED: Light-emitting diode; NFT: Neurofibrillary tangle; NIr: Near-infrared light; 8-OHDG: 8-hydroxy-2?-deoxyguanosine; PS1: Presenilin 1; WT: Wildtype.

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

SP undertook the bulk of the experimental work and analysis and wrote the manuscript. DMJ and JM were involved with the analysis of the data and the writing of the manuscript. CN was involved with genotyping and treating the animals. JS was involved in conceiving and designing the study and the writing of the manuscript. All authors read and approved the final manuscript.


The authors thank Tenix Corporation, Sir Zelman Cowen Universities Fund and Bluesand Foundation for funding. They are grateful to Prof. Lars Ittner for providing the breeding litter for K369I mice, and to Dr Louise Cole and the Bosch Advanced Microscopy facility for the help with MetaMorph. Sharon Spana was splendid for her technical help. DMJ is supported by a National Health and Medical Research Council of Australia (NHMRC) Early Career Fellowship.


  • Hardy J, Selkoe DJ. The amyloid hypothesis of Alzheimer’s disease: progress and problems on the road to therapeutics. Science. 2002;6:353–356. doi: 10.1126/science.1072994. [PubMed][Cross Ref]
  • Braak H, Braak E. Staging of Alzheimer’s disease-related neurofibrillary changes. Neurobiol Aging. 1995;6:271–278. doi: 10.1016/0197-4580(95)00021-6. [PubMed] [Cross Ref]
  • Nunomura A, Perry G, Aliev G, Hirai K, Takeda A, Balraj EK, Jones PK, Ghanbari H, Wataya T, Shimohama S, Chiba S, Atwood CS, Petersen RB, Smith MA. Oxidative damage is the earliest event in Alzheimer disease. J Neuropathol Exp Neurol. 2001;6:759–767. [PubMed]
  • Yao J, Irwin RW, Zhao L, Nilsen J, Hamilton RT, Brinton RD. Mitochondrial bioenergetic deficit precedes Alzheimer’s pathology in female mouse model of Alzheimer’s disease. Proc Natl Acad Sci USA. 2009;6:14670–14675. doi: 10.1073/pnas.0903563106. [PMC free article][PubMed] [Cross Ref]
  • Stone J. What initiates the formation of senile plaques? The origin of Alzheimer-like dementias in capillary haemorrhages. Med Hypotheses. 2008;6:347–359. doi: 10.1016/j.mehy.2008.04.007. [PubMed] [Cross Ref]
  • Calabrese V, Guagliano E, Sapienza M, Panebianco M, Calafato S, Puleo E, Pennisi G, Mancuso C, Butterfield DA, Stella AG. Redox regulation of cellular stress response in aging and neurodegenerative disorders: role of vitagenes. Neurochem Res. 2007;6:757–773. doi: 10.1007/s11064-006-9203-y. [PubMed] [Cross Ref]
  • Whelan HT, Smits RL Jr, Buchman EV, Whelan NT, Turner SG, Margolis DA, Cevenini V, Stinson H, Ignatius R, Martin T, Martin T, Cwiklinski J, Philippi AF, Graf WR, Hodgson B, Gould L, Kane M, Chen G, Caviness J. Effect of NASA light-emitting diode irradiation on wound healing. J Clin Laser Med Surg. 2001;6:305–314. doi: 10.1089/104454701753342758.[PubMed] [Cross Ref]
  • Desmet KD, Paz DA, Corry JJ, Eells JT, Wong-Riley MT, Henry MM, Buchmann EV, Connelly MP, Dovi JV, Liang HL, Henshel DS, Yeager RL, Millsap DS, Lim J, Gould LJ, Das R, Jett M, Hodgson BD, Margolis D, Whelan HT. Clinical and experimental applications of NIR-LED photobiomodulation. Photomed Laser Surg. 2006;6:121–128. doi: 10.1089/pho.2006.24.121.[PubMed] [Cross Ref]
  • Eells JT, Wong-Riley MT, VerHoeve J, Henry M, Buchman EV, Kane MP, Gould LJ, Das R, Jett M, Hodgson BD, Margolis D, Whelan HT. Mitochondrial signal transduction in accelerated wound and retinal healing by near-infrared light therapy. Mitochondrion. 2004;6:559–567. doi: 10.1016/j.mito.2004.07.033. [PubMed] [Cross Ref]
  • Natoli R, Zhu Y, Valter K, Bisti S, Eells J, Stone J. Gene and noncoding RNA regulation underlying photoreceptor protection: microarray study of dietary antioxidant saffron and photobiomodulation in rat retina. Mol Vis. 2010;6:1801–1822. [PMC free article] [PubMed]
  • Xuan W, Vatansever F, Huang L, Wu Q, Xuan Y, Dai T, Ando T, Xu T, Huang YY, Hamblin MR. Transcranial low-level laser therapy improves neurological performance in traumatic brain injury in mice: effect of treatment repetition regimen. PLoS One. 2013;6:e53454. doi: 10.1371/journal.pone.0053454. [PMC free article] [PubMed] [Cross Ref]
  • Oron A, Oron U, Streeter J, de Taboada L, Alexandrovich A, Trembovler V, Shohami E. Low-level laser therapy applied transcranially to mice following traumatic brain injury significantly reduces long-term neurological deficits. J Neurotrauma. 2007;6:651–656. doi: 10.1089/neu.2006.0198. [PubMed] [Cross Ref]
  • Moro C, Torres N, El Massri N, Ratel D, Johnstone DM, Stone J, Mitrofanis J, Benabid AL. Photobiomodulation preserves behaviour and midbrain dopaminergic cells from MPTP toxicity: evidence from two mouse strains. BMC Neurosci. 2013;6:40. doi: 10.1186/1471-2202-14-40.[PMC free article] [PubMed] [Cross Ref]
  • Shaw VE, Spana S, Ashkan K, Benabid AL, Stone J, Baker GE, Mitrofanis J. Neuroprotection of midbrain dopaminergic cells in MPTP-treated mice after near-infrared light treatment. J Comp Neurol. 2010;6:25–40. doi: 10.1002/cne.22207. [PubMed] [Cross Ref]
  • Peoples C, Spana S, Ashkan K, Benabid AL, Stone J, Baker GE, Mitrofanis J. Photobiomodulation enhances nigral dopaminergic cell survival in a chronic MPTP mouse model of Parkinson’s disease. Parkinsonism Relat Disord. 2012;6:469–476. doi: 10.1016/j.parkreldis.2012.01.005. [PubMed] [Cross Ref]
  • Grillo SL, Duggett NA, Ennaceur A, Chazot PL. Non-invasive infra-red therapy (1072 nm) reduces beta-amyloid protein levels in the brain of an Alzheimer’s disease mouse model, TASTPM. J Photochem Photobiol B. 2013;6:13–22. [PubMed]
  • De Taboada L, Yu J, El-Amouri S, Gattoni-Celli S, Richieri S, McCarthy T, Streeter J, Kindy MS. Transcranial laser therapy attenuates amyloid-beta peptide neuropathology in amyloid-beta protein precursor transgenic mice. J Alzheimers Dis. 2011;6:521–535. [PubMed]
  • Lampl Y, Zivin JA, Fisher M, Lew R, Welin L, Dahlof B, Borenstein P, Andersson B, Perez J, Caparo C, Ilic S, Oron U. Infrared laser therapy for ischemic stroke: a new treatment strategy: results of the NeuroThera Effectiveness and Safety Trial-1 (NEST-1) Stroke. 2007;6:1843–1849. doi: 10.1161/STROKEAHA.106.478230. [PubMed] [Cross Ref]
  • Schiffer F, Johnston AL, Ravichandran C, Polcari A, Teicher MH, Webb RH, Hamblin MR. Psychological benefits 2 and 4 weeks after a single treatment with near infrared light to the forehead: a pilot study of 10 patients with major depression and anxiety. Behav Brain Funct.2009;6:46. doi: 10.1186/1744-9081-5-46. [PMC free article] [PubMed] [Cross Ref]
  • Tuby H, Hertzberg E, Maltz L, Oron U. Long-term safety of low-level laser therapy at different power densities and single or multiple applications to the bone marrow in mice. Photomed Laser Surg. 2013;6:269–273. doi: 10.1089/pho.2012.3395. [PubMed] [Cross Ref]
  • Ittner LM, Fath T, Ke YD, Bi M, van Eersel J, Li KM, Gunning P, Gotz J. Parkinsonism and impaired axonal transport in a mouse model of frontotemporal dementia. Proc Natl Acad Sci USA. 2008;6:15997–16002. doi: 10.1073/pnas.0808084105. [PMC free article] [PubMed][Cross Ref]
  • van Eersel J, Ke YD, Liu X, Delerue F, Kril JJ, Gotz J, Ittner LM. Sodium selenate mitigates tau pathology, neurodegeneration, and functional deficits in Alzheimer’s disease models. Proc Natl Acad Sci USA. 2010;6:13888–13893. doi: 10.1073/pnas.1009038107. [PMC free article][PubMed] [Cross Ref]
  • Jankowsky JL, Fadale DJ, Anderson J, Xu GM, Gonzales V, Jenkins NA, Copeland NG, Lee MK, Younkin LH, Wagner SL, Younkin SG, Borchelt DR. Mutant presenilins specifically elevate the levels of the 42 residue beta-amyloid peptide in vivo: evidence for augmentation of a 42-specific gamma secretase. Hum Mol Genet. 2004;6:159–170. [PubMed]
  • Garcia-Alloza M, Robbins EM, Zhang-Nunes SX, Purcell SM, Betensky RA, Raju S, Prada C, Greenberg SM, Bacskai BJ, Frosch MP. Characterization of amyloid deposition in the APPswe/PS1dE9 mouse model of Alzheimer disease. Neurobiol Dis. 2006;6:516–524. doi: 10.1016/j.nbd.2006.08.017. [PubMed] [Cross Ref]
  • Cao D, Lu H, Lewis TL, Li L. Intake of sucrose-sweetened water induces insulin resistance and exacerbates memory deficits and amyloidosis in a transgenic mouse model of Alzheimer disease.J Biol Chem. 2007;6:36275–36282. doi: 10.1074/jbc.M703561200. [PubMed] [Cross Ref]
  • Truett GE, Heeger P, Mynatt RL, Truett AA, Walker JA, Warman ML. Preparation of PCR-quality mouse genomic DNA with hot sodium hydroxide and tris (HotSHOT) Biotechniques.2000;6:52–54. [PubMed]
  • Purushothuman S, Nandasena C, Johnstone DM, Stone J, Mitrofanis J. The impact of near-infrared light on dopaminergic cell survival in a transgenic mouse model of parkinsonism. Brain Res. 2013;6:61–70. [PubMed]
  • Purushothuman S, Marotte L, Stowe S, Johnstone DM, Stone J. The response of cerebral cortex to haemorrhagic damage: experimental evidence from a penetrating injury model. PLoS One.2013;6:e59740. doi: 10.1371/journal.pone.0059740. [PMC free article] [PubMed] [Cross Ref]
  • Wilcock DM, Gordon MN, Morgan D. Quantification of cerebral amyloid angiopathy and parenchymal amyloid plaques with Congo red histochemical stain. Nat Protoc. 2006;6:1591–1595. doi: 10.1038/nprot.2006.277. [PubMed] [Cross Ref]
  • Yan Q, Zhang J, Liu H, Babu-Khan S, Vassar R, Biere AL, Citron M, Landreth G. Anti-inflammatory drug therapy alters beta-amyloid processing and deposition in an animal model of Alzheimer’s disease. J Neurosci. 2003;6:7504–7509. [PubMed]
  • Augustinack JC, Schneider A, Mandelkow EM, Hyman BT. Specific tau phosphorylation sites correlate with severity of neuronal cytopathology in Alzheimer’s disease. Acta Neuropathol.2002;6:26–35. doi: 10.1007/s004010100423. [PubMed] [Cross Ref]
  • Bruck W, Bitsch A, Kolenda H, Bruck Y, Stiefel M, Lassmann H. Inflammatory central nervous system demyelination: correlation of magnetic resonance imaging findings with lesion pathology. Ann Neurol. 1997;6:783–793. doi: 10.1002/ana.410420515. [PubMed] [Cross Ref]
  • Sayre LM, Zelasko DA, Harris PL, Perry G, Salomon RG, Smith MA. 4-Hydroxynonenal-derived advanced lipid peroxidation end products are increased in Alzheimer’s disease. J Neurochem. 1997;6:2092–2097. [PubMed]
  • Mecocci P, MacGarvey U, Beal MF. Oxidative damage to mitochondrial DNA is increased in Alzheimer’s disease. Ann Neurol. 1994;6:747–751. doi: 10.1002/ana.410360510. [PubMed][Cross Ref]
  • Trinchese F, Liu S, Battaglia F, Walter S, Mathews PM, Arancio O. Progressive age-related development of Alzheimer-like pathology in APP/PS1 mice. Ann Neurol. 2004;6:801–814. doi: 10.1002/ana.20101. [PubMed] [Cross Ref]
  • Oron A, Oron U, Chen J, Eilam A, Zhang C, Sadeh M, Lampl Y, Streeter J, DeTaboada L, Chopp M. Low-level laser therapy applied transcranially to rats after induction of stroke significantly reduces long-term neurological deficits. Stroke. 2006;6:2620–2624. doi: 10.1161/01.STR.0000242775.14642.b8. [PubMed] [Cross Ref]
  • Blanchard V, Moussaoui S, Czech C, Touchet N, Bonici B, Planche M, Canton T, Jedidi I, Gohin M, Wirths O, Bayer TA, Langui D, Duyckaerts C, Tremp G, Pradier L. Time sequence of maturation of dystrophic neurites associated with A? deposits in APP/PS1 transgenic mice. Exp Neurol. 2003;6:247–263. doi: 10.1016/S0014-4886(03)00252-8. [PubMed] [Cross Ref]
  • Karu T. Mitochondrial mechanisms of photobiomodulation in context of new data about multiple roles of ATP. Photomed Laser Surg. 2010;6:159–160. doi: 10.1089/pho.2010.2789.[PubMed] [Cross Ref]
  • Wilden L, Karthein R. Import of radiation phenomena of electrons and therapeutic low-level laser in regard to the mitochondrial energy transfer. J Clin Laser Med Surg. 1998;6:159–165.[PubMed]
  • Wong-Riley MT, Bai X, Buchmann E, Whelan HT. Light-emitting diode treatment reverses the effect of TTX on cytochrome oxidase in neurons. Neuroreport. 2001;6:3033–3037. doi: 10.1097/00001756-200110080-00011. [PubMed] [Cross Ref]
  • Hou JF, Zhang H, Yuan X, Li J, Wei YJ, Hu SS. In vitro effects of low-level laser irradiation for bone marrow mesenchymal stem cells: proliferation, growth factors secretion and myogenic differentiation. Lasers Surg Med. 2008;6:726–733. doi: 10.1002/lsm.20709. [PubMed][Cross Ref]
  • Tuby H, Maltz L, Oron U. Modulations of VEGF and iNOS in the rat heart by low level laser therapy are associated with cardioprotection and enhanced angiogenesis. Lasers Surg Med.2006;6:682–688. doi: 10.1002/lsm.20377. [PubMed] [Cross Ref]
  • Tuby H, Maltz L, Oron U. Induction of autologous mesenchymal stem cells in the bone marrow by low-level laser therapy has profound beneficial effects on the infarcted rat heart. Lasers Surg Med. 2011;6:401–409. doi: 10.1002/lsm.21063. [PubMed] [Cross Ref]
  • Stamer K, Vogel R, Thies E, Mandelkow E, Mandelkow EM. Tau blocks traffic of organelles, neurofilaments, and APP vesicles in neurons and enhances oxidative stress. J Cell Biol.2002;6:1051–1063. doi: 10.1083/jcb.200108057. [PMC free article] [PubMed] [Cross Ref]
  • Aliev G, Smith MA, Seyidov D, Neal ML, Lamb BT, Nunomura A, Gasimov EK, Vinters HV, Perry G, LaManna JC, Friedland RP. The role of oxidative stress in the pathophysiology of cerebrovascular lesions in Alzheimer’s disease. Brain Pathol. 2002;6:21–35. [PubMed]
  • Hamel E, Nicolakakis N, Aboulkassim T, Ongali B, Tong XK. Oxidative stress and cerebrovascular dysfunction in mouse models of Alzheimer’s disease. Exp Physiol. 2008;6:116–120. [PubMed]
  • Zhu X, Perry G, Moreira PI, Aliev G, Cash AD, Hirai K, Smith MA. Mitochondrial abnormalities and oxidative imbalance in Alzheimer disease. J Alzheimers Dis. 2006;6:147–153. [PubMed]
  • Zhang X, Le W. Pathological role of hypoxia in Alzheimer’s disease. Exp Neurol. 2010;6:299–303. doi: 10.1016/j.expneurol.2009.07.033. [PubMed] [Cross Ref]
  • Wen Y, Yang S, Liu R, Brun-Zinkernagel AM, Koulen P, Simpkins JW. Transient cerebral ischemia induces aberrant neuronal cell cycle re-entry and Alzheimer’s disease-like tauopathy in female rats. J Biol Chem. 2004;6:22684–22692. doi: 10.1074/jbc.M311768200. [PubMed][Cross Ref]
  • Uttara B, Singh AV, Zamboni P, Mahajan RT. Oxidative stress and neurodegenerative diseases: a review of upstream and downstream antioxidant therapeutic options. Curr Neuropharmacol.2009;6:65–74. doi: 10.2174/157015909787602823. [PMC free article] [PubMed] [Cross Ref]


J Neuroinflammation.  2012 Sep 18;9(1):219. [Epub ahead of print]

Low-level laser therapy regulates microglial function through Src-mediated signaling pathways: implications for neurodegenerative diseases.

Song S, Zhou F, Chen WR, Xing D.




Activated microglial cells are an important pathological component in brains of patients with neurodegenerative diseases. The purpose of this study was to investigate the effect of He-Ne (632.8 nm, 64.6 mW/cm2) low-level laser therapy (LLLT), a non-damaging physical therapy, on activated microglia, and the subsequent signaling events of LLLT-induced neuroprotective effects and phagocytic responses.


To model microglial activation, we treated the microglial BV2 cells with lipopolysaccharide (LPS). For the LLLT-induced neuroprotective study, neuronal cells with activated microglial cells in a Transwell[trade mark sign] cell-culture system were used. For the phagocytosis study, fluorescence-labeled microspheres were added into the treated microglial cells to confirm the role of LLLT.


Our results showed that LLLT (20 J/cm2) could attenuate toll-like receptor (TLR)-mediated proinflammatory responses in microglia, characterized by down-regulation of proinflammatory cytokine expression and nitric oxide (NO) production. LLLT-triggered TLR signaling inhibition was achieved by activating tyrosine kinases Src and Syk, which led to MyD88 tyrosine phosphorylation, thus impairing MyD88-dependent proinflammatory signaling cascade. In addition, we found that Src activation could enhance Rac1 activity and F-actin accumulation that typify microglial phagocytic activity. We also found that Src/PI3K/Akt inhibitors prevented LLLT-stimulated Akt (Ser473 and Thr308) phosphorylation and blocked Rac1 activity and actin-based microglial phagocytosis, indicating the activation of Src/PI3K/Akt/Rac1 signaling pathway.


The present study underlines the importance of Src in suppressing inflammation and enhancing microglial phagocytic function in activated microglia during LLLT stimulation. We have identified a new and important neuroprotective signaling pathway that consists of regulation of microglial phagocytosis and inflammation under LLLT treatment. Our research may provide a feasible therapeutic approach to control the progression of neurodegenerative diseases.

Postepy High Med Dosw (Online).  2011 Feb 17;65:73-92.

The role of biological sciences in understanding the genesis and a new therapeutic approach to Alzheimer’s disease.

Tegowska E, Wosinska A.

Zaklad Toksykologii Zwierz?a, Wydzial Biologii i Nauk o Ziemi, Uniwersytet Mikolaja Kopernika w Toruniu.


The paper contrasts the historical view on causal factors in Alzheimer’s disease (AD) with the modern concept of the symptoms’ origin. Biological sciences dealing with cell structure and physiology enabled comprehension of the role of mitochondrial defects in the processes of formation of neurofibrillary tangles and ?-amyloid, which in turn gives hope for developing a new, more effective therapeutic strategy for AD. It has been established that although mitochondria constantly generate free radicals, from which they are protected by their own defensive systems, in some situations these systems become deregulated, which leads to free radical-based mitochondrial defects. This causes an energetic deficit in neurons and a further increase in the free radical pool. As a result, due to compensation processes, formation of tangles and/or acceleration of ?-amyloid production takes place. The nature of these processes is initially a protective one, due to their anti-oxidative action, but as the amount of the formations increases, their beneficial effect wanes. They become a storage place for substances enhancing free radical processes, which makes them toxic themselves. It is such an approach to the primary causal factor for AD which lies at the roots of the new view on AD therapy, suggesting the use of methylene blue-based drugs, laser or intranasally applied insulin. A necessary condition, however, for these methods’ effectiveness is definitely an earlier diagnosis of the disease. Although there are numerous diagnostic methods for AD, their low specificity and high price, often accompanied by a considerable level of patient discomfort, make them unsuitable for early, prodromal screening. In this matter a promising method may be provided using an olfactory test, which is an inexpensive and non-invasive method and thus suitable for screening, although as a test of low specificity, it should be combined with other methods. Introducing new methods of AD treatment does not mean abandoning the traditional ones, based on enhancing cholinergic transmission. They are valuable as long as the therapy starts when abundant brain inclusions disturb the transmissions.<br />

Photomed Laser Surg.  2010 Oct;28(5):663-7.

Long-term safety of single and multiple infrared transcranial laser treatments in Sprague-Dawley rats.

McCarthy TJ, De Taboada L, Hildebrandt PK, Ziemer EL, Richieri SP, Streeter J.


PhotoThera, Inc., 5925 Priestly Drive, Suite 120, Carlsbad, California, USA.



Growing interest exists in the use of near-infrared laser therapies for the treatment of numerous neurologic conditions, including acute ischemic stroke, traumatic brain injury, Parkinson’s disease, and Alzheimer’s disease. In consideration of these trends, the objective of this study was to evaluate the long-term safety of transcranial laser therapy with continuous-wave (CW) near-infrared laser light (wavelength, 808?±?10?nm, 2-mm diameter) with a nominal radiant power of 70?mW; power density, 2,230?mW/cm(2), and energy density, 268?J/cm(2) at the scalp (10?mW/cm(2) and 1.2?J/cm(2) at the cerebral cortical surface) in healthy Sprague-Dawley rats.


In this study, 120 anesthetized rats received sequential transcranial laser treatments to the right and left parietal areas of the head on the same day (minimum of 5?min between irradiation of each side), on either Day 1 or on each of Days 1, 3, and 5. Sixty anesthetized rats served as sham controls. Rats were evaluated 1 year after treatment for abnormalities in clinical hematology and brain and pituitary gland histopathology.


No toxicologically important differences were found in the clinical hematology results between sham-control and laser-treated rats for any hematologic parameters examined. All values fell within historic control reference ranges for aged Sprague-Dawley rats. Similarly, brain and pituitary gland histopathology showed no treatment-related abnormalities or induced neoplasia.


Single and multiple applications of transcranial laser therapy with 808-nm CW laser light at a nominal power density of 10?mW/cm(2) at the surface of the cerebral cortex appears to be safe in Sprague-Dawley rats 1 year after treatment.

The Efficacy of 904 nm Laser Therapy for Alzheimer’s Diseases

Kazuyoshi Zenba, Vice president of Kanagawa Acupuncture Massage Association

Prof. Masayuki Inoue, Secretary of JLPLTPA


Although we had reported about the possible efficacy of low power laser therapy (LPLT) for Senile Dementia(S D) 3 times from 1993 at the annual meetings of Japan Society for Laser Medicine, there was no practically useful treatment found for Alzheimer’s disease(AD) and Parkinson disease and other Senile Dementia even after the start of elderly-care-insurance system in Japan. As we have continued above said laser therapy for SD at home care visit of elderly persons and felt very useful and effective, we would like to report about recent situation of laser therapy for AD patients.

Especially recently, the number of Alzheimer’s disease patients is increasing by the arrival of super-aged world in Japan. However the cause of this disease is not known and there is no effective treatment established at present. As to the mechanism of LPLT, its main mechanism is mostly elucidated by the progress in the field of Molecular biology and widely used for the removal of pain, decrease of swelling and treatment of wound. However its application for the treatment of Brain diseases is hardly practiced.

We have continued the treatment of Senile Dementia patients by LPL considering it as to be one of practical and effective treatment of this disease

LPLT is very useful for the medical treatment of the senile dementia patients at home for the expansion of ADL, pain relief, mitigation of inflammation, prevention of bed sore, the treatment of hemiplegia in a brain blood vessel obstacle and the braking of aggravation of Alzheimer’s disease without any fear of side effects by the irradiation of LPL to the head of patients.

It will be not to exaggerate to say LPLT can be one of main treatments of senior patients at home in near future.

(Object of study)

To study the practical usefulness of LPLT for the treatment of Alzheimer’s disease patients at home in terms of improvement of ADL and QOL and also for the reduction of burden of families of the care of patients.

(Method of treatment)

15 Alzheimer’s disease patients, 5 male and 10 female, received irradiation of LPL for 2 minutes at each points, 2-3 times a week for one year. Laser irradiation points were as follows. Acupuncture points established as effective based on long history of Oriental medicine .

(1) Acupuncture point to improve blood circulation (2) Acupuncture point for the treatment of stroke (3) Acupuncture point for adjustment of blood pressure (4) Acupuncture point for adjustment of balance of autonomous nerve.( the forehead, the right and left temple, occiput)

In addition, the method (based on papers in Russia and Armenia that intravenous LPL irradiation  improved the viscosity of blood) of irradiating LPL to the place which touches the pulse of an artery under collarbone was used as an additional medical treatment point.

(LPL instrument)


Among evaluation items, cooperativeness and the lack of composure were observed as useful as an effect, the effect appeared half a year after and continued after one year and later on.

It was suggested that LPLT was useful for the improvement of orientation disturbance, normalization of clothing and the dress. Because, many families and the care workers talked us LPL was very helpful since the present condition could be maintained, without getting worse.

After the start of LPL treatment, It was reported that the coldness of hands and legs of patients vanished and joints and muscular stiffness were also mitigated. Therefore, the joint movable region was also secured comparatively.

Also in excretion care, it became very easy to carry out the care of patients.

It was able to say about all patients that their expression became quiet and came to show understanding to directions of a care worker. It is suggested by this that LPLT as one of practical treatment of patients at home by the improvement of care power at home.


Since the senile-dementia-of-Alzheimer-type has a feature of advance of condition and it was said that condition became gradually critical, we tried this treatment expecting the maintenance of condition, and examination whether there was any delay effect. It is considered to have been suggested at least there was an effect of maintaining present condition in a certain field.

About the effect over the brain of laser irradiation, it was reported at the annual meeting of Japan Society for Laser Surgery and Medicine meeting in 1991 by Jun-Ichi Nishimura et al., of  Department of Physiology, Yokohama City University School of Medicine. The 780 nm wavelength and 1mW laser irradiation to the inner core of rats made the increase of cerebral blood flows at hippocampus by the amount of about 20% in average (control:15, laser:15). Although after 30 minute it was confirmed having maintained the increase of 10%.

In 1992 at the same medical conference, Takayuki Obata et. al., of the same University reported that laser irradiation of 780nm wavelength10mW to the head surface of rats activated cranial nerves activities (control:16, laser:15).

These reports suggested the possible usefulness of LPL treatment to Senile Dementia and other brain diseases patients. Unfortunately these findings did not much attention of medical world In Japan.

However, recently a possibility that ATP and cellmembrane potential of brain neuron could be controlled specifically by the irradiation of near infrared lasers (830nm wavelength) on the surface of heads of rats was reported by Oda-Mochizuki University, Synchrotron Light Life Science Center.

It was suggested by this research center that the condition of Epilepsy could be stabilized by Irradiating infrared laser from out side of heads of patients and decreasing the unusual excitement of cerebral neurons and in case of cerebral infarction, the aggravation of progress of Necrosis and Apotosis of cerebral neurons could be stopped by making stabilize the electric potential of cell membrane of cerebral neurons.

Development of future research in this field is expected as what supports scientifically the medical treatment of LPL and the result of condition improvements, such as Senile Dementia, brain blood vessel obstacles, hemiplegia and Parkinson patients.

Although the wavelength of LPL used for “Examination of the validity of LPL to Senile Dementia Patients” which we announced at the annual meetings of Japan Society for Laser Surgery and Medicine meeting over three years from 1993, was 780nm and out put was10mW, and 1mw.  The LPL used for this examination was of the wavelength of 904nm and the peak value of a pulse was 5W and the average output was 5mW. However, the same medical treatment effect was confirmed. Although it is thought that there was no wavelength dependability of laser to the efficacy over the Alzheimer’s diseases of LPL(780,830,904nm lasers are equally effective for pain removal and wound healing), how is it sure enough? A question remains.

By this examination, at least following effects were confirmed. Namely (1) the advance of condition of Alzheimer’s diseases has been blocked (2) and the expression of patients changed to smiling from disinterestedness, cooperativeness came out , an understanding came to be shown to a partner (3) We received comments from many families that the care of patients became much easier than before. It is considered that the head irradiation of near infrared laser light makes the cerebral blood flow improve, activates nerve activities and have applied brakes to the advance of the apotosis of brain cells as animal experiments are proving. Since the medical treatment efficacy is seldom acknowledged to middle degree class and a serious  patient, although it is hard to call it the fundamental cure for Alzheimer’s disease by the present method, if medical a treatment is started in early stage and continued, it may be possible to call it one of practical cures which can stop subsequent advance of disease.

Based on this experience, collecting newest information overseas, research results in the biology field, we will continue to study the possible LPL method for the dramatic cure of Alzheimer’s diseases by changing the wavelength of laser, the output and the irradiation method and also combination with other therapies