The effect of photobiomodulation on the brain during wakefulness and sleep

" In this review, we consider the potential differential effects of photobiomodulation dependent on the state of arousal. We speculate that the effects of photobiomodulation is on different cells and systems depending on whether it is applied during wakefulness or sleep, that it may follow a circadian rhythm. We speculate further that the arousal-dependent photobiomodulation effects are mediated principally through a biophoton – ultra-weak light emission – network of communication and repair across the brain." {Credits 1}

" Most – if not all – of the reports that have examined the functional activity of neurones in the brain after application of photobiomodulation have been from an external, transcranial device. The light issued from such devices has been shown by many previous studies to penetrate, at the very least as far as the cerebral cortex, approximately ten to fifteen millimeters beneath the cranial surface. Indeed, transcranial photobiomodulation to normal, healthy humans – both young and older – has been reported to improve high-level cognitive functions, in terms of reaction times or performances to a range of learning and memory retrieval tasks." {Credits 1}

" For direct stimulation, photobiomodulation has to fall directly on the neurones (Figure 1). The light is absorbed by photoacceptors found among mitochondria (e.g., cytochrome oxidase c and/or interfacial nanowater) or elsewhere (e.g., transient potential receptor ion channels and/or various types of opsins) within the neurones." {Credits 1}

" In addition to direct stimulation, photobiomodulation has been shown – quite remarkably – to be beneficial to neuronal survival even when it is applied to a distant or remote location; that is, when it is not applied directly to the neurones (Figure 2). The evidence for this indirect stimulation has been accumulated from many previous studies in a range of animal models of disease – from diabetes to Alzheimer’s and Parkinson’s disease – showing that photobiomodulation applied to one body part can induce neuroprotective effects in another, more distant body part." {Credits 1}

" We suggest that ... neurones, in fact all body cells, have light-receptors because they themselves use light to communicate with each other; they also use light to repair themselves, as well as others, during periods of distress and/or damage. In essence, we suggest that photobiomodulation is effective on neuronal function and survival because neurones use the very same wavelengths to communicate and for repair." {Credits 1}

" A most striking feature of biophotons emissions from cells is that they can vary – in terms of intensity and wavelength - depending on the state of homeostasis, whether the cell is healthy or diseased." {Credits 1}

" It is striking that the range of the wavelengths used by biophotons (∼λ = 200–950nm) overlaps with the range of wavelengths effective in photobiomodulation (∼λ = 600–1000), albeit at much lower intensities, and that the same organelles (i.e., mitochondria) and chromophores (e.g., cytochrome oxidase c) have been implicated in both. The idea also offers an explanation as to why neurones located so deep within the near total-darkness of the brain, have receptors to light and benefit from photobiomodulation. That is because they themselves use light to communicate and maintain homeostasis and photobiomodulation engages this network system to produce beneficial outcomes." {Credits 1}

" This speculation, that photobiomodulation works through the biophoton network to achieve beneficial effects, is based on a direct stimulation (Figure 1). The benefits of photobiomodulation using the indirect systemic stimulation (Figure 2) may rely on the biophoton network also. The free-floating mitochondria within the blood plasma are of particular interest here. They too could use biophotons to communicate and repair, as they would as intracellular organelles, so there is every possibility that they may be activated by photobiomodulation – particularly during the state of wakefulness – and swarm to the site of distress, helping neurones survive with their biophoton emissions." {Credits 1}

{Credits 1} 🎪 Moro C, Valverde A, Dole M, Hoh Kam J, Hamilton C, Liebert A, Bicknell B, Benabid A-L, Magistretti P and Mitrofanis J (2022) The effect of photobiomodulation on the brain during wakefulness and sleep. Front. Neurosci. 16:942536. doi: 10.3389/fnins.2022.942536. © 2022 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License.