Photobiomodulation: Lighting Up the Brain

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Photobiomodulation: Lighting Up the Brain

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     There are, to date, few methods of non-invasive brain stimulation (NIBS) that show therapeutic potential for neurological dysfunction. The most commonly used forms of NIBS are transcranial magnetic stimulation (TMS), which uses a magnet to generate electrical currents thereby increasing activity in the targeted system of the brain, and transcranial direct current stimulation (tDCS), which uses electrodes to directly translate external electrical currents into the brain. Both of these NIBS techniques require multiple sessions of stimulation administered by a technician which make them, in the long run, relatively costly. However, a significantly cheaper and novel method of NIBS, termed transcranial photobiomodulation (tPBM), is currently undergoing research to determine efficacy. The device itself, branded as Vielight, is commercially available, user friendly, and safe. In this blog we will delve into the potential implications of this technology while analyzing the currently available research on Vielight.

     So what exactly is photobiomodulation? 

     It involves administration of pulsing, low-level red and near-infrared (NIR) light on specific locations in the brain to stimulate neural tissue. The Vielight Neuro Gamma model uses LED lights to deliver 40 Hz pulses of NIR transcranially and intranasally to neural structures associated with the default mode network (DMN), a system associated with introspection when the mind is not actively engaging in actions requiring attention. Activation of the DMN is associated with the brain being in an alpha state meaning that one is in a state of “resting wakefulness”. Previous research suggests that increasing alpha wave activity in the brain aids in inhibition of irrelevant cortical areas and integration of activity in relevant areas, essentially streamlining cognition and creating greater functional connectivity between these areas. This has implications for pathological presentations that involve the DMN such as those associated with Alzheimer’s disease (AD), dementia, schizophrenia, autism, anxiety, and depression. Unfortunately, research has not yet delved into its use for any specific disorders but rather, was used on healthy participants to determine the safety and efficacy for impacting cognition.

     In the study, twenty adults were recruited and attended two study visits each. During one visit they received active tPBM stimulation from the Vielight Neuro Gamma model and during the other they received sham stimulation (placebo), double-blinded to avoid researcher bias and to ensure that any detected changes were not a placebo effect. Participants also received pre- and post-stimulation EEGs to measure neural activity. Interestingly, after both active and sham stimulation sessions, the EEG showed an increase in power for all frequency bands (corresponding to different frequencies of neural firing) in comparison to baseline, but differential increases in the higher frequency bands. Specifically, in the active stimulation condition, participants experienced significant power increases of higher frequency bands (alpha, beta, and gamma) and smaller power increases of lower frequency bands (delta and theta).

     Conditions such as AD present with decreased power of high frequency activity and increased power of low frequency bands. If these abnormal ranges of activity are the cause of cognitive decline, then using tPBM to generate more high frequency activity should, in theory, alleviate some of the symptoms. To confirm this, however, will require pre-clinical and clinical trials on participants with dysfunction of the DMN

     We now know what tPBM is and what it does, but how exactly does it work? The specifics behind the neurophysiology are much less well understood than those associated with tDCS or TMS, but there are certain cellular mechanisms that appear to be impacted by NIR light stimulation. The most well studied are mitochondria, after PBM, ATP production increases as well as transcription of genes for protein synthesis, cell proliferation, anti-inflammatory, and antioxidant responses. In layman’s terms, PBM has the potential to maintain the function of neurons while also promoting growth of new neurites such as dendritic spines for enhanced neuronal communication and, as was seen in a rat model study, even the growth of entirely new neurons after ischemic stroke. This study does mention that there is little evidence that tPBM directly impacts neural activity but through the mechanisms mentioned above it may promote maintenance of functional connectivity through neurite growth as well as maintenance of the activity of individual neurons through transcriptional modulation and ATP production.

     In summation, the therapeutic potential of tPBM through Vielight’s relatively cheap, easily accessible, and portable technology is exciting in terms of possibly enhancing cognition for those with AD or dementia, as well as other disorders of the DMN, in the comfort of your own home. However, it is important to address the fact that this is an extremely new method of NIBS that, as of yet, has not been well studied for disease models in human participants. As such, if purchasing a tPBM system is a financial stretch, it is likely worth waiting for further research to confirm its purported therapeutic effects. On the bright side, for this pilot study none of the participants experienced any adverse effects or even abnormal sensations meaning that further research should be easily approved and, hopefully, within the next year or two we will have concrete proof of any effectiveness of tPBM.

Sources: 
Zomorrodi, R., Loheswaran, G., Pushparaj, A., & Lim, L. Pulsed Near Infrared Transcranial and Intranasal Photobiomodulation Significantly Modulates Neural Oscillations: a pilot exploratory study [Internet]. Nature. 2018. Available from: https://www.nature.com/articles/s41598-019-42693-x
Quiroga, R. Q., & Kreiman, G. Measuring sparseness in the brain: Comment on Bowers (2009) [Internet]. Psychological Review. 2010. Available from:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3154835/