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Review
. 2016 Oct 1:6:113-124.
doi: 10.1016/j.bbacli.2016.09.002. eCollection 2016 Dec.

Shining light on the head: Photobiomodulation for brain disorders

Michael R Hamblin  1
Affiliations
Review

Shining light on the head: Photobiomodulation for brain disorders

Michael R Hamblin. BBA Clin. .

Abstract

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: Alzheimer's disease; Cognitive enhancement; Ischemic stroke; Low level laser (light) therapy; Major depression; Parkinson's disease; Photobiomodulation; Traumatic brain injury.

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Figures

Image 2
Graphical abstract
Fig. 1
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 B; NO, nitric oxide; ROS, reactive oxygen species; TRPV, transient receptor potential vanilloid.
Fig. 2
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.
Fig. 3
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) . A, 665 nm; B, 730 nm; C, 810 nm; D, 980 nm.
Fig. 4
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) . (B) Mice received 3 daily exposures starting 4 h post-TBI and were sacrificed after 7 or 28 days. BDNF and neurogenesis (BrdU) were increased at 7 days , while synaptogenesis was increased at 28 days .
Fig. 5
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 data).
Fig. 6
Fig. 6
tPBM for major depression and anxiety in humans. (A) Ten patients received a single exposure to the forehead (810 LED, 60 J/cm2 delivered at 250 mW/cm2). (B) Mean Hamilton score for depression at baseline and at two weeks post-treatment .
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