Can light penetrate the human skull and reach the brain? This question often arises among both skeptics and scientists.

The answer is yes but with caveats; this requires an appropriate wavelength (nm) and sufficient irradiance (mW/cm²) In this demonstration with a real human skull, the Vielight Neuro, emitting 810 nm near-infrared light at an industry-leading irradiance of 250 mW/cm², clearly passes through the skullcap.

With the highest irradiance in the brain photobiomodulation field and the most published research in the industry, Vielight has set the benchmark for depth of penetration and the most published brain photobiomodulation studies.

Watch the video here:

Firstly, why deliver light energy through the skull?

The discovery that red to near infrared light energy produces beneficial effects within neurons is groundbreaking. Near-infrared light stimulates a photosensitive enzyme, cytochrome c oxidase, that’s found within mitochondria – which leads to increased cellular energy, leading to a process known as “brain photobiomodulation”. By stimulating cytochrome oxidase activity, transcranial photobiomodulation increases neuronal energy levels – leading to increased gamma brain oscillations, brain plasticity and cognitive flexibility.^[1]

However, this non-invasive, chemical-free brain enhancing stimulation wouldn’t be possible, if near infrared light energy couldn’t reach the brain in the first place.

810nm light energy penetration through a human skull with the Vielight Neuro.

What is near infrared light energy?

Near infrared light (NIR) energy is part of the electromagnetic spectrum – which are waves (or photons) of the electromagnetic field, radiating through space, carrying electromagnetic radiant energy. At this day and age, several existing technologies depend on the ability of electromagnetic energy to penetrate solid objects. Several examples include WiFi, mobile data, radar and navigation satellites.

Figure 1 The electromagnetic spectrum

The depth or the power of penetration by light energy depends on the wavelength in the electromagnetic spectrum. Thus, the longer the wavelength, the greater the ability for photons to penetrate an object. For example, near infrared light is found around the center of the electromagnetic spectrum.

Does 810 nm or 1064 nm (1070nm) penetrate deeper into the brain?

According to a transcranial brain photobiomodulation (PBM) study by Harvard Medical School, Department of Psychiatry, the 810nm wavelength has been found to be superior to other wavelengths, which includes higher wavelengths in the 1070nm range for penetration and dosimetry.

According to this study by Harvard Medical School, the order of penetration and dosimetry effectiveness is:

1. 810 nm – consistently highest across all age groups and regions

2. 850 nm and 1064 nm – next most effective in most cases

3. 670 nm and 980 nm – lesser deposition overall

This Harvard study is also supported by another brain PBM dosimetry study by leading Chinese universities, comparing 660 nm, 810 nm, 880 nm and 1064 nm. They discovered that the distribution of photon fluence at 660 and 810 nm within the brain was much wider and deeper than 980 and 1064 nm.

The distribution of photon fluence at 660 nm, 810 nm, 980 nm and 1064 nm. Wang P, Li T. “Which wavelength is optimal for transcranial low-level laser stimulation?” J. Biophotonics. 2019; 12:e201800173. https://doi.org/10.1002/jbio.201800173

The differences in dosimetry is supported by a well-established biological principle, the body’s first optical window. While, the 1064 and 1070nm wavelengths are longer and scatter less than 810nm, they are more strongly absorbed by water, which is abundant in biological tissues. This increased absorption by water can lead to reduced photonic availability and tissue penetration despite the longer wavelength, which the Harvard Medical study and Peking Medical University study reveal.

The near infrared window or body’s optical window. Image source: Wang, Erica & Kaur, Ramanjot & Fierro, Manuel & Austin, Evan & Jones, Linda & Jagdeo, Jared. (2019). Safety and penetration of light into the brain. 10.1016/B978-0-12-815305-5.00005-1.

• Water Absorption: Light absorption by water increases significantly beyond ~950 nm, and water is abundant in biological tissue. At 1064 nm, absorption by water becomes substantial, which attenuates the light more than at 810 nm. This increased absorption reduces the effective depth of penetration, especially for energy reaching specific chromophores like cytochrome c oxidase (CCO).
• Cytochrome c Oxidase (CCO) Absorption: Mitochondria’s CCO’s absorption spectrum peaks around 810 nm, with a notable decrease in absorption beyond 1000 nm. This means that 810 nm light is more readily absorbed by CCO compared to 1070 nm.

Expanding on the 810nm light penetration study by Harvard Medical School

In order to reach the brain transcranially, NIR light energy must bypass several barriers – skin, blood, water and bone.

In a 2020 study comparing 810nm with 1070nm by researchers from the Harvard Psychiatry Department, they combined similar tissues together to create a simplified head model. This model contains eight different brain tissues: white matter (WM), gray matter (GM), CSF, skull, muscles, skin/muscles, fat, and blood vessels.^[5]

This study involved the simulation of light deposition at five wavelengths commonly used in NIR applications—670, 810, 850, 980, and 1064 (1070) nm. These wavelengths have been widely used in published studies in photobiomodulation, many of which correspond to the absorption spectra of different tissues within the human body.

Figure 3
The average (bars) and peak (dots) energy deposition (penetration) after positioning the LED light source.
The left brain shows the ROIs that receiving the highest (red) and second highest (orange) energy deposition; the right brain shows the energy deposition map on the cortical surface.
(a) fluence at the F3-F4 sites
(b) fluence at the  Fp1–FpZ–Fp2 sites

Figure 4
The average (bars) and peak (dots) energy deposition (penetration) after positioning the intranasal light source in the: (a) nostril, (b) mid-nose, and (c) close to the nose ceiling (in proximity of the cribriform plate)
The left brain shows the ROIs that receiving the highest (red) and second highest (orange) energy deposition; the right brain shows the energy deposition map on the cortical surface.
(a) Nostril position
(b) Mid-nose position
(c) Cribiform plate

Figure 5

Plots of the normalized energy deposition results for (a) the nostril illumination, (b) the mid-nose illumination, and (c) the cribriform plate illumination.
All results are simulated with the optical properties at 810 nm.

Conclusively, they found that the wavelength plays an important role in determining the magnitude of the energy deposition. In general, there was a clear trend showing that 810 nm offered the highest light penetration onto the brain, followed closely by 1064 and 850 nm.

Additionally, a study done in 2012 by the State University of New York, Downstate Medical Center, compared the transmission of NIR LED light (830nm) versus visible red LED light (633nm) through soft tissue, bone, water and blood.

Here were their results from their study on the penetration of NIR light through a human head^[3]:

Figure 3. Percent Penetrance of Light through Coronal Sections of Cadaver Skull, Bone Only.

Figure 4. Percent Penetrance of Light through Sagittal Sections of Cadaver Skull with Intact Soft Tissue.

Figure 5. Percent Penetrance of Light through Various Concentrations of Blood.

Figure 6. Percent Penetrance of Light through Human Cheek in vivo. 

These findings demonstrate that NIR light measurably penetrates skin, bone and brain tissue in a human head model. On the other hand, there isn’t as much transmission of red light in the same conditions.

As mentioned earlier, quite a few technologies depend on the diffusion of light energy through these barriers. For example, brain imaging technology known as near infrared spectroscopy (NIRS). NIRS involves detecting changes in blood hemoglobin concentrations associated with neural activity within cortical brain tissue.  Fundamentally, this technology is based on the penetration of NIR light through the cranium and into the brain, reaching up to 4 cm of depth.

Emphasis on the intranasal channel

The intranasal channel is an important gateway for light energy to reach the ventral prefrontal cortex of the brain. Otherwise, this area is inaccessible through the cranium. Furthermore, the ventral prefrontal cortex plays a role in emotional responses, decision making and self control – which play important roles in performance and mental balance.

Watch how Vielight’s patented intranasal technology can reach deep brain structures through the nasal channel:

MoreMore emphasis on the intranasal channel

Additionally, a study on the intranasal diffusion of NIR light through a human head was done by the Institute of Chemical Sciences and Engineering in Switzerland. This study demonstrated that it is possible to illuminate deep brain tissues transcranially and intranasally.^[4] The measurement of the fluence rate distribution was, once again, carried out on a human cadaveric head.

Figure 7 View on the 3D mesh of the skull

This study quantifies the light distribution within brain tissue when illuminating from the nasal cavity with a controlled energy deposition.

Figure 8 (a) Fluence rate distribution at 671 nm. (b) Fluence rate distribution at 808 nm.

The results obtained from the study suggests that light at 810 nm is the better choice. This is due to less absorption and reduced scattering at 810 nm in all tissue types. The increased light propagation at the 810 nm wavelength improves the penetration and diffusion rate of photons into deeper brain regions.

Figure 9 Transmission of light energy through a human cadaver with the Vielight Neuro.

Conclusion

The penetration of light energy into the brain is highly dependent on the wavelength. In light of this, several studies support the ability of near infrared light (808 – 820nm) to penetrate through the skull and up to 4 cm into brain tissue. Thus, these studies help to answer the question: “Can light penetrate the brain?” with a “Yes.”

Figure 9 The light penetration difference among different wavelengths and the effects on cellular mechanisms.

Only the wavelengths in the near-infrared window of 600–850nm is absorbed by the mitochondrial electron transfer chain and leads to upregulation of the neuronal respiratory capacity. Source : Mol Neurobiol. 2018 Aug; 55(8): 6601–6636.

References

1. Gonzalez-Lima, F; Barrett, Douglas; “Augmentation of cognitive brain functions with transcranial lasers”, Frontiers in Systems Neuroscience : doi:10.3389/fnsys.2014.00036
2. Smith, Andrew M.; Mancini, Michael C.; Nie, Shuming (2009). “Bioimaging: Second window for in vivo imaging”. Nature Nanotechnology. 4(11): 710–711. doi:1038/nnano.2009.326. ISSN 1748-3387. PMC 2862008
3. Jagdeo JR, Adams LE, Brody NI, Siegel DM (2012) Transcranial Red and Near Infrared Light Transmission in a Cadaveric Model. PLoS ONE 7(10): e47460. https://doi.org/10.1371/journal.pone.0047460
4. Pitzschke, Andreas & Lovisa, B & Seydoux, O & Zellweger, M & Pfleiderer, M & Tardy, Y & Wagnières, Georges. (2015). Red and NIR light dosimetry in the human deep brain. Physics in medicine and biology. 60. 2921-2937. 10.1088/0031-9155/60/7/2921.
5. Yuan Y, Cassano P, Pias M, Fang Q. Transcranial photobiomodulation with near-infrared light from childhood to elderliness: simulation of dosimetry. Neurophotonics. 2020 Jan;7(1):015009. doi: 10.1117/1.NPh.7.1.015009. Epub 2020 Feb 24. PMID: 32118086; PMCID: PMC7039173.

1. A growing problem facing the elderly – age-related cognitive decline
2. Several factors of brain aging and age-related cognitive decline
3. Brain photobiomodulation (PBM) and mitochondrial function
4. Brain PBM and metabolic effects
5. Brain PBM and anti-inflammatory effects
6. Brain PBM leads to a reduction in neuronal excitotoxicity
7. Brain PBM increases cerebral vascularity and oxygenation
8. Published research – Brain PBM within elderly demographics

A growing problem facing the elderly – age-related cognitive decline.

Due to advances in medical technology, the elderly demographic is the fastest growing segment of the global population. Consequently, the side effects of natural age-related cognitive decline – such as slowed thinking, memory recall and low mental energy is an increasingly prevalent problem because of the growth of the elderly population and the negative qualitative impacts on their quality of life.

Source: United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019.

On the other hand, advancements in brain stimulation research combined with technological innovation has made longevity (or anti-aging) neurotechnology a promising proposition for  in the 21st century.

The question arises: how can brain photobiomodulation be used as a longevity biohacking tool to partially mitigate the negative side effects from brain aging, by augmenting certain physiological processes?

In this article, we’ll reference published research studies to explore how brain photobiomodulation could be used for longevity and anti-aging by improving neuronal mitochondrial function and overall enhanced holistic brain performance.

Please note that nothing known can reverse genetic aging and its negative effects, but lifestyle and technological interventions have the potential to lessen or mitigate some of aging’s negative effects.

Several factors of brain aging and age-related cognitive decline

Brain aging is a natural biological process that results in a decline in brain physiological functions. Multiple factors contribute to this phenomenon.

One of the notable factors of brain aging is a gradual decline in mitochondrial function within neurons. This leads to a decline in cognitive function and suboptimal brain performance because neurons experience a reduction in mitochondrial energy metabolism.

Additionally, a decrease in cerebral blood flow and oxygenation due to a loss in brain vascularity leads to a decline in cognitive function.^[19]

The aging brain is also characterized by an increase neuroinflammation.^[17] Scientists have linked neuroinflammation with cognitive decline and higher risks for age-related cognitive impairment.^[18]

What are mitochondria and neurons?

• Mitochondria are the batteries of the cell. These membrane-bound cell organelles (mitochondrion, singular) generate most of the chemical energy needed to power the cell’s biochemical reactions. Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP).
• Neurons are information messengers. Neurons, sometimes called nerve cells, make up around 10 percent of the brain; the rest consists of glial cells and astrocytes that support and nourish neurons. They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system.

Focusing on neuronal mitochondria and the aging process

Neuronal mitochondria play key roles in regulating the brain aging process. When their function declines, the production of adenosine triphosphate (ATP) is reduced, leading to a reduction in neuronal metabolism. Additionally, a decline in mitochondrial function leads to reduced activation of signaling pathways and transcription factors that modulate the expression of various proteins.^[1]

Note: Transcription factors regulate the transcription of genes— the process of copying into RNA during protein synthesis (quick fact: at least 10,000 different proteins make you what you are and keep you that way). Proteins are the building blocks of who you are.

Brain photobiomodulation and mitochondrial function

Brain photobiomodulation holds the potential to enhance mitochondrial function, partially mitigating the negative effects of aging.

The mechanism of photobiomodulation (PBM) is due to the ability of cells to absorb photons of red-to-near infrared light (620–1100 nm) by the mitochondria photoacceptor, cytochrome c oxidase (CCO).^[2]

Note: CCO is the fourth enzymatic complex of the mitochondrial respiratory chain and it catalyzes the reaction reducing oxygen into water, which is coupled to the production of metabolic energy in cells.

Figure 1: Activation of mitochondria cytochrome c oxidase through photobiomodulation

The mitochondrial biomechanisms of photobiomodulation

CCO upregulation

The absorption of red to NIR photons by mitochondria CCO triggers a series of cellular and physiological effects occur in the brain, also known as CCO upregulation.

Figure 2: The cascade effects of photobiomodulation

CCO upregulation leads to:

• A small increase in reactive oxygen species (ROS), which activate mitochondrial signaling pathways linked to neuroprotection. ^[3]
• An increase in nitric oxide (NO) which stimulate vasodilation and cerebral blood flow.^[4]
• An increase in ATP production ^[5]

Combined, these effects trigger and improve the activation of signaling pathways and transcription factors that modulate the long-term expression of various proteins and metabolic pathways in the brain.^[6] Additionally, electrophysiological effects on the human brain have also been demonstrated by PBM in older people.^{[7, 8]}

Metabolic effects and brain oxygenation

The metabolic effects of PBM in the elderly have been shown to increase cerebral blood flow (CBF) due to the increase in CCO activity, leading to an increase in brain oxygenation. Photobiomodulation of the prefrontal cortex was able to increase the resting-state EEG alpha, beta and gamma power, and more efficient prefrontal fMRI response, facilitating cognitive processing in the elderly. ^[8] Additionally, photobiomodulation of the Default Mode Network (DMN) has also been shown to increase cerebral perfusion due to an increase in mitochondrial activity. ^[9]

Brain PBM and anti-inflammatory effects

In addition to the above findings, PBM may be a promising strategy for improving aging brains because of its anti-inflammatory effects. ^{[10, 11]}

Brain PBM leads to a reduction in neuronal excitotoxicity

In 2022, researchers from the University of Alberta published a multi-layered study investigating the way that living cells, cellular structures, and components such as microtubules and tubulin respond to near-infrared photobiomodulation (NIR PBM) using the Vielight Neuro Alpha.

Their study showed that PBM balances excitatory stimulation with inhibition, indicating that PBM may reduce excitotoxicity which is relevant to the maintenance of a healthy brain. This study also showed that low-intensity PBM upregulates mitochondrial potential and improves physiological brain functions impaired due to trauma or neurodegeneration. ^[14]

Brain PBM increases cerebral vascularity and oxygenation

Aging is accompanied by changes in tissue structure, often resulting in functional decline. The blood vessels within the brain are no exception. As one ages, a decrease in blood flow to the brain is caused by a loss of cerebral vascularity, leading to cognitive decline when neurons cannot obtain sufficient oxygen.^[21] Brain photobiomodulation has also been shown to increase cerebral blood flow due to the vasodilation that occurs after the release of nitric oxide.^[20]

Figure 3: The beneficial effects of photobiomodulation

Summary

These findings are promising because as one gets older, mitochondrial function decreases, cerebral perfusion and oxygenation decreases^[12] , inflammation increases and brain vascularity decreases.

However, brain photobiomodulation has the potential to partially improve mitochondrial function, cerebral blood flow, brain vascularity and potentially, reduce inflammation.

Published research – Brain PBM within elderly demographics

In 2017, researchers from the Department of Psychology and Institute for Neuroscience, University of Texas at Austin found that brain photobiomodulation increases resting-state EEG alpha, beta and gamma power, promotes more efficient fMRI activity, and facilitates behavioral cognitive processing in middle-aged and older adults at risk for cognitive decline. No adverse effects were reported.

These findings support the potential of brain photobiomodulation to augment neurocognitive function and to combat aging-related and vascular disease-induced cognitive decline ^[13]

In 2019, Dr. Chao from the Center for Imaging of Neurodegenerative Diseases, San Francisco VA Medical Center conducted a study on patients in their 80s diagnosed with dementia. The NIR PBM treatments were administered by a study partner at home three times per week with the Vielight Neuro Gamma device. After 12 weeks, there were improvements in the ADAS-cog and NPI scores, increased cerebral perfusion and increased connectivity between the posterior cingulate cortex and lateral parietal nodes within the default-mode network in the PBM group. ^[15]

In 2021, researchers from the School of Medical Sciences, University of Sydney, discovered that measures of mobility, cognition, dynamic balance and fine motor skill were significantly improved with PBM treatment for 12 weeks and up to one year in a pilot study with 12 participants. Many individual improvements were above the minimal clinically important difference, the threshold judged to be meaningful for participants. Individual improvements varied but many continued for up to one year with sustained home treatment using the Vielight Neuro Gamma. There was a demonstrable Hawthorne Effect that was below the treatment effect. No side effects of the treatment were observed.

References

1. Jang, J. Y., Blum, A., Liu, J., & Finkel, T. (2018). The role of mitochondria in aging. The Journal of clinical investigation, 128(9), 3662–3670. https://doi.org/10.1172/JCI120842
2. Dompe, C., Moncrieff, L., Matys, J., Grzech-Leśniak, K., Kocherova, I., Bryja, A., Bruska, M., Dominiak, M., Mozdziak, P., Skiba, T., Shibli, J. A., Angelova Volponi, A., Kempisty, B., & Dyszkiewicz-Konwińska, M. (2020). Photobiomodulation-Underlying Mechanism and Clinical Applications. Journal of clinical medicine, 9(6), 1724. https://doi.org/10.3390/jcm9061724
3. Suski, J. M., Lebiedzinska, M., Bonora, M., Pinton, P., Duszynski, J., & Wieckowski, M. R. (2012). Relation between mitochondrial membrane potential and ROS formation. In Mitochondrial bioenergetics (pp. 183-205). Humana Press.
4. Wang X., Tian F., Soni S.S., Gonzalez-Lima F., Liu H. Interplay between up-regulation of cytochrome-c-oxidase and hemoglobin oxygenation induced by near-infrared laser. Sci. Rep. 2016;6:30540. doi: 10.1038/srep30540.
5. Hamblin M.R. Photobiomodulation for traumatic brain injury and stroke. J. Neurosci. Res. 2018;96:731–743. doi: 10.1002/jnr.24190.
6. Cardoso FDS, Mansur FCB, Lopes-Martins RÁB, Gonzalez-Lima F, Gomes da Silva S. Transcranial Laser Photobiomodulation Improves Intracellular Signaling Linked to Cell Survival, Memory and Glucose Metabolism in the Aged Brain: A Preliminary Study. Front Cell Neurosci. 2021 Sep 3;15:683127. doi: 10.3389/fncel.2021.683127. PMID: 34539346; PMCID: PMC8446546.
7. Wang, X., Dmochowski, J. P., Zeng, L., Kallioniemi, E., Husain, M., GonzalezLima, F., & Liu, H. (2019). Transcranial photobiomodulation with 1064-nm laser modulates brain electroencephalogram rhythms. Neurophotonics, 6(2), 025013.
8. Vargas E, Barrett DW, Saucedo CL, et al. Beneficial neurocognitive effects of transcranial laser in older adults. Lasers in medical science. 2017;32(5):1153–1162. [PubMed: 28466195]
9. Chao LL. Effects of Home Photobiomodulation Treatments on Cognitive and Behavioral Function, Cerebral Perfusion, and Resting-State Functional Connectivity in Patients with Dementia: A Pilot Trial. Photobiomodul Photomed Laser Surg. 2019 Mar;37(3):133-141. doi: 10.1089/photob.2018.4555. Epub 2019 Feb 13. PMID: 31050950.
10. Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophys. 2017;4(3):337-361. doi: 10.3934/biophy.2017.3.337. Epub 2017 May 19. PMID: 28748217; PMCID: PMC5523874.
11. dos Santos Cardoso, F., Mansur, F.C.B., Araújo, B.H.S. et al.Photobiomodulation Improves the Inflammatory Response and Intracellular Signaling Proteins Linked to Vascular Function and Cell Survival in the Brain of Aged Rats. Mol Neurobiol 59, 420–428 (2022). https://doi.org/10.1007/s12035-021-02606-4
12. Braz, I. D., & Fisher, J. P. (2016). The impact of age on cerebral perfusion, oxygenation and metabolism during exercise in humans. The Journal of physiology, 594(16), 4471–4483. https://doi.org/10.1113/JP271081
13. Vargas E, Barrett DW, Saucedo CL, Huang LD, Abraham JA, Tanaka H, Haley AP, Gonzalez-Lima F. Beneficial neurocognitive effects of transcranial laser in older adults. Lasers Med Sci. 2017 Jul;32(5):1153-1162. doi: 10.1007/s10103-017-2221-y. Epub 2017 May 2. PMID: 28466195; PMCID: PMC6802936.
14. Staelens Michael, Di Gregorio Elisabetta, Kalra Aarat P., Le Hoa T., Hosseinkhah Nazanin, Karimpoor Mahroo, Lim Lew, Tuszyński Jack A. Near-Infrared Photobiomodulation of Living Cells, Tubulin, and Microtubules In Vitro, Frontiers in Medical Technology 4. 2022 May 04, https://doi.org/10.3389/fmedt.2022.871196, ISBN:2673-3129
15. Chao LL. Effects of Home Photobiomodulation Treatments on Cognitive and Behavioral Function, Cerebral Perfusion, and Resting-State Functional Connectivity in Patients with Dementia: A Pilot Trial. Photobiomodul Photomed Laser Surg. 2019 Mar;37(3):133-141. doi: 10.1089/photob.2018.4555. Epub 2019 Feb 13. PMID: 31050950.
16. Liebert A, Bicknell B, Laakso EL, Heller G, Jalilitabaei P, Tilley S, Mitrofanis J, Kiat H. Improvements in clinical signs of Parkinson’s disease using photobiomodulation: a prospective proof-of-concept study. BMC Neurol. 2021 Jul 2;21(1):256. doi: 10.1186/s12883-021-02248-y. PMID: 34215216; PMCID: PMC8249215.
17. Sparkman NL, Johnson RW. Neuroinflammation associated with aging sensitizes the brain to the effects of infection or stress. Neuroimmunomodulation. 2008;15(4-6):323-30. doi: 10.1159/000156474. Epub 2008 Nov 26. PMID: 19047808; PMCID: PMC2704383.
18. Simen AA, Bordner KA, Martin MP, Moy LA, Barry LC. Cognitive dysfunction with aging and the role of inflammation. Ther Adv Chronic Dis. 2011 May;2(3):175-95. doi: 10.1177/2040622311399145. PMID: 23251749; PMCID: PMC3513880.
19. Yang T, Sun Y, Lu Z, Leak RK, Zhang F. The impact of cerebrovascular aging on vascular cognitive impairment and dementia. Ageing Res Rev. 2017 Mar;34:15-29. doi: 10.1016/j.arr.2016.09.007. Epub 2016 Sep 28. PMID: 27693240; PMCID: PMC5250548.
20. Salgado AS, Zângaro RA, Parreira RB, Kerppers II. The effects of transcranial LED therapy (TCLT) on cerebral blood flow in the elderly women. Lasers in medical science. 2015;30(1):339– 346. doi: 10.1007/s10103-014-1669-2 [PubMed: 25277249]
21. Yang T, Sun Y, Lu Z, Leak RK, Zhang F. The impact of cerebrovascular aging on vascular cognitive impairment and dementia. Ageing Res Rev. 2017 Mar;34:15-29. doi: 10.1016/j.arr.2016.09.007. Epub 2016 Sep 28. PMID: 27693240; PMCID: PMC5250548.

“tPBM has become a central element in my protocol design process. I find it to be an excellent complement to the functional support provided by neurofeedback.”
“Helping brains develop new connections which support better function is an important part of neurofeedback training. Based on emerging research, tPBM can potentially support the growth of those new pathways.”
Penijean Gracefire, LMHC, BCN, qEEG-D, Neurofeedback and tPBM provider and Neuro Pro user.

What is the place of photobiomodulation in a neurofeedback practice?

Every neurofeedback practitioner is aware that human brains prioritize resourcing and organization based on what they pay the most attention to. However, not everyone is aware that photobiomodulation can be an effective way to recruit the brain’s attentional networks for better results.

Neurofeedback and photobiomodulation are relatively new fields. For many, they are still somewhat esoteric fields of brain stimulation, training and modulation. Incidentally, both began their development in the late 1950s. The field of neurofeedback originated in California, while the field of PBM started in Hungary by accident. Furthermore, both can help the brain deal with complex issues while complementing each other.

The brain is an adaptive and self-reinforcing system, and neurofeedback, as a form of brain modulation, attempts to retrain neural response patterns. However, even the most effective neurofeedback interventions can encounter less responsive central nervous systems. Luckily, neurofeedback providers can benefit from having multiple ways to supply information to the brain. Thus, some brains will respond better to tPBM or to a combination of tPBM and EEG feedback. Therefore, having access to modern technological tools that offer a variety of viable brain-training options can improve neurofeedback’s outcomes.

Recent Developments in Photobiomodulation

Photobiomodulation has emerged as a promising therapy for ameliorating symptoms associated with both mental health and neurophysiological conditions. Early findings recorded in the literature indicate that photobiomodulation has significant clinical potential in the treatment of a number of brain-based disorders. These include, but not limited to, traumatic brain injury (Henderson, 2016), Alzheimer’s and Parkinson’s (Johnstone, 2015), improving executive function (Barrett, 2013), memory (Rojas, 2012), stroke and developmental disorders (Hamblin, 2016), and depression (Cassano, 2015).

A meta-analysis of articles examining the link between photobiomodulation and biological processes such as metabolism, inflammation, oxidative stress and neurogenesis suggest that these processes are potentially effective targets for photobiomodulation to treat depression and brain injury. There is also preliminary clinical evidence suggesting the efficacy of photobiomodulation in treating major depressive disorder, comorbid anxiety disorders, and suicidal ideation (Cassano, 2016).

Pairing tPBM’s documented enhancement of BDNF (brain-derived neurotrophic factor) and synaptogenesis (Hennessy, 2017) with EEG-based feedback paradigms that focus on supporting neural connectivity (Collura, 2008) potentially offers a novel approach to building better brain infrastructure at any age.

Why is photobiomodulation technology synergetic with neurofeedback? 

Neurofeedback is often based on scalp electroencephalography (EEG), which measures cortical activity, and doesn’t explicitly include activity from subcortical brain regions. However, a specialized transcranial photobiomodulation (tPBM) system, like Vielight Neuro Pro for example, can deliver NIR light to the brain stem. It can offer a more direct impact to lower central nervous system circuitry. This is one way specialized photobiomodulation technology can complement neurofeedback and help to improve its timeline and effects.

As a source of light, tPBM supports the brain energetically, helping it with energy supply to build new connections. Neurofeedback specialists can take advantage of this new optimized state that is supportive of learning. Furthermore, when this happens, neurofeedback training can help the brain to develop better cognitive functions.

Moreover, technically astute neurofeedback practitioners may prefer additional customization options from their tPBM device to further improve outcomes. They may want to directly impact neural network patterns, particularly if they are qEEG users. This group of neurofeedback specialists may prefer to use advanced features of a professional tPBM system. For example, features like phase synchrony/asynchrony of tPBM pulsing, or options to develop a database of specialized tPBM programs that complement neurofeedback.

What are the benefits of combining neurofeedback and brain photobiomodulation? 

Neurofeedback is a form of biofeedback that is based specifically on brain activity. To put it simply, neurofeedback utilizes neuroplasticity to modulate and change the brain’s response to various stimuli. Neuroplasticity refers to the brain’s ability to adapt and change. To attain such change, the brain needs to go through training. Thus, during the training, the brain learns to adopt a new response to a known stimulus.

Interestingly, additional stimulus or stimuli may be introduced to help the brain change its response. For example, light, color, sound, and tactile sensations are some of the primary stimuli that can be used to retrain the brain during neurofeedback sessions.

Brain photobiomodulation is a way to deliver the light to the brain. Therefore, it can be used as an additional stimulus for neurofeedback. A specialized tPBM system can become a very useful and synergetic tool in neurofeedback. For example, it can act as a mechanism for priming the brain prior to a neurofeedback session. It can also open numerous opportunities for creative approaches to improving neurofeedback outcomes.

Furthermore, neurofeedback practitioners are well aware that some individuals have difficulty tolerating initial neurofeedback sessions. This can be either because of anxiety or sensory processing issues. Therefore, having an alternative intervention that is less time-intensive and doesn’t involve pastes or gels can be helpful. It can provide some early alleviation of symptom intensity until the client is more comfortable with the neurofeedback process.

Effects of transcranial PBM on the brain 

Brain PBM, or tPBM, can be helpful for the brain on cellular level. It helps to support the brain by transcranially delivering the energy of the near-infrared (NIR) light directly to the neurons.

Current abundant research shows that NIR has the best penetration rate and is particularly suitable for brain stimulation and modulation. Although the research into tPBM has a long way to go, the science behind tPBM is gaining acceptance

While therapeutic uses of red light across the body are well documented, research into the effects of various light pulsation frequencies on the brain are more limited. The most commonly known tPBM frequencies are 10 Hz (Alpha) and 40 Hz (Gamma). Both correspond to the respective alpha and gamma oscillations in the brain. Most of the tPBM pulse frequency related research is focused on these two frequencies and below. Thus, the effects of the higher frequency pulse rates on the brain need more research. Modern tPBM systems offer more sophisticated options to conduct tPBM-related research.

The importance of specialized tPBM hardware for neurofeedback 

The absence of hardware suitable for extended research utilizing higher pulse frequencies has been somewhat of a hindrance. However, over the last few years, tPBM research has made significant progress opening the doors for deeper knowledge dives. Thus, both the researchers and practitioners utilizing tPBM are showing interest in studying and analyzing the effects of higher pulse frequencies on the brain.

Furthermore, new technologies and growing body of knowledge are helping to improve the capabilities of new tPBM hardware. For example, the recently introduced Vielight Neuro Pro tPBM system allows setting the pulse frequency between 0 and 10,000 Hz. The Neuro Pro’s numerous other variables can also be changed to find the best possible fit for the task at hand.

Why brain photobiomodulation should be of interest for neurofeedback practitioners?

Many neurofeedback practitioners have already discovered the beneficial synergies between neurofeedback and brain photobiomodulation. Thus, some use functional Magnetic Resonance Imaging (fMRI), others use Frequency and Power Neurofeedback, and there are other forms and options. While practitioners can use different tools for and types of neurofeedback in their practice, many principles stay common.

For example, the concepts of brain mapping and brain priming are familiar to many neurofeedback practitioners. While brain mapping requires measuring tools, brain priming requires interventional tools. However, interventions do not have to be invasive.

One form of noninvasive intervention for brain priming can be transcranial photobiomodulation. There are neurofeedback practitioners who have already discovered the important and effective synergies that tPBM can offer in their work.

Photobiomodulation Research References: 

Barrett D.W., Gonzalez-Lima F. Transcranial infrared laser stimulation produces beneficial cognitive and emotional effects in humans. Neuroscience. 2013;230:13–23. [PubMed]

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]

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]

Collura, T.F. (2008) Towards a coherent view of brain connectivity. Journal of Neurotherapy. 12, 2–3, 99–110.

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.

Gonzalez-Lima F., Barrett D.W. Augmentation of cognitive brain functions with transcranial lasers. Front. Syst. Neurosci. 2014;8:36. [PubMed]

Hamblin, M. R. (2016). Shining light on the head: Photobiomodulation for brain disorders. BBA Clinical, 6, 113–124. http://doi.org/10.1016/j.bbacli.2016.09.002

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]

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]

More References: 

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]

Hennessy, M., & Hamblin, M. R. (2017). Photobiomodulation and the brain: a new paradigm. Journal of Optics (2010), 19(1), 013003–. https://doi.org/10.1088/2040-8986/19/1/013003

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]

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]

Rojas, JC., Gonzalez-Lima, F. Neurological and psychological applications of transcranial lasers and LEDs. Biochem Pharmacol. 2013 Aug 15;86(4):447-57. doi: 10.1016/j.bcp.2013.06.012. Epub 2013 Jun 24.

What can be achieved by combining neurofeedback with photobiomodulation?

A creative and curious mind can be a beginning of something new, something important, even something big. This is as true in the field of arts as it is in the field of sciences. This article offers one more testament to these observations.

Penijean Gracefire is a licensed mental health counsellor (LMHC) in the state of Florida. She focuses on the applications of neurofeedback in her work with clients. Like many neurofeedback practitioners, she is excited by technology that can help her in her work. Unlike most, she is a techno geek, when it comes to her tools. Moreover, her interest in and fascination with technology helps her to discover new ways of helping her clients. She also happened to have an affinity for engineering and innovation, and pushes the frontier of her tools to the limits.

Thus, one day Penijean discovered trascranial photobiomodulation (tPBM) and Vielight’s tPBM devices. What happened when a talented neurofeedback practitioner with a curious mind decided on combining neurofeedback with photobiomodulation. Let’s find out the answer directly from Penijean Gracefire, LMHC.

How long have you been working with transcranial photobiomodulation (tPBM)?

Penijean: I’ve been interested in how light affects brains and bodies for as long as I can remember. Sometimes I joke that my interest in the therapeutic applications of light began when I was four years old. That is when I discovered that I could soothe a fussy younger sibling using a prism. Even as a child I noticed that my mood was affected by light and color, and I wanted to know why.

I picked up my first infrared light therapy device in 2005. Then I spent some years using tPBM for peripheral applications, such as relaxation and pain management.

What have brought you to tPBM initially and why did you stay with it?

Penijean: My initial experience using tPBM to stimulate the peripheral nervous system was informative and useful. However, I found that the applications were limited for my interests. Eventually I moved on to interventions that focused more on the central nervous system.

In 2017, I met Dr. Lew Lim at a neurofeedback conference. Our discussion of his Vielight Neuro device reignited my interest in tPBM. At that time I had been sitting on ideas for integrating infrared stim (stimulation) into a closed loop neuromodulation design. Dr. Lim was willing to allow me to use the Vielight platform to start creating new techniques. My design concept incorporated both the tPBM and the neurofeedback protocols.

The early results from the prototype designs were very promising. Thus, tPBM has become a much more central element in my protocol design process. I found it to be an excellent and naturally fitting complement to neurofeedback.

Where do you see synergies between tPBM and neurofeedback?

Penijean: Research indicates that tPBM has potential to support synaptogenesis – the creation of new synapses. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870908/

Neurofeedback relies on brain plasticity (https://en.wikipedia.org/wiki/Neuroplasticity) to help individuals learn new ways to process information and regulate stress responses. Injury or illness can reduce neural capacity to adapt in real time to the changing demands of our environment. Brains need healthy and flexible neural networks to be able to prioritize and shift attention. Furthermore, they need to have the capacity to signal the central nervous system to wind down and relax. For example, this would be useful when a busy day is over.

Helping brains develop new connections, which support better function, is an important part of neurofeedback training. In my view, tPBM can potentially support the growth of those new pathways.

Combining tPBM with Neurofeedback, have you noticed anything new that could have a strong potential for helping your clients?

Penijean: The “feedback” part of neurofeedback means that we are giving the brain information based on its own behavioral changes. Typically, this feedback consists of musical sounds or visual data displays or, perhaps, an object that physically vibrates. For the feedback to work, it needs to be sufficiently novel and stimulating to recruit the brain’s attention.

After experimenting with and designing a number of innovative feedback techniques, I created the first EEG-modulated pEMF designs. While pEMF stands for pulsed electromagnetic field therapy, EEG stands for electroencephalogram. This protocol design has tremendous therapeutic potential. At the same time, these new integrated training protocols were yielding very exciting results. However, I work with many populations that are medically fragile and have compromised systems. Therefore, not all cases were suitable for the information-dense combination of neurofeedback and pEMF.

Combining Neurofeedback and Photobiomodulation

For some individuals, integrated tPBM and neurofeedback offers the perfect balance. Thus, on the one hand, this combination provides not so much feedback that their system feels overwhelmed. On the other hand, it provides not too little feedback that would fail to effectively recruit the brain’s attention.

I adapted my designs and created the first closed loop EEG-modulated pNIR (pulsed near-infrared light) protocols. This means that the individual not only simultaneously receives both the tPBM and the neurofeedback, but the NIR pulses themselves are changing in real time based on live EEG.

The combination of neurofeedback and tPBM is like a conversation with a wise friend while sitting in the afternoon sun. You receive both, the benefits of learning new helpful things about yourself and the benefits of absorbing natural light.

TPBM is the light source that supports your brain energetically, as it builds new connections. When this happens, the neurofeedback takes advantage of this optimized learning state to help your brain develop better cognitive function.

Can you provide some examples of how you employ tPBM in your neurofeedback practice?

Penijean: The practical flexibility of tPBM in a clinical setting is one of its strengths. Whether I use tPBM as a standalone therapeutic approach or combine it with other modalities often depends on individual needs.

Some people are sufficiently responsive. Thus, for them, 5-10 minutes of tPBM by itself is enough to produce a noticeable impact. Other people are a little more resilient. For those, I may do multiple things in a session, but in a sequence instead of simultaneously.

TPBM can be an effective primer at the beginning of a session before introducing sensory grounding techniques, or heart rate variability training. By applying tPBM to the head, we can help stimulate neural activity immediately prior to a neurofeedback session.

When combining tPBM with other modalities, you are only limited by your own creativity. Therefore, I try to be as creative as appropriate. For example, I may have someone wear a pair of violet eye lenses while receiving a 40hz tPBM stimulation. This helps to create a shift in gamma activity. I can also have someone wear a pair of dark amber or orange lenses, when receiving a 10hz stimulation. This can help to support slowing down into a more alpha-wave friendly state.

I noticed that layering other inputs over tPBM can also help with state flexibility and integration. Thus, utilizing inputs like binaural beats, vibrating sensory aids, or progressive relaxation audio can be helpful.

What benefits do you see tPBM on its own and in combination with neurofeedback can provide at this stage?

Penijean: A helpful way to think about these modalities is in terms of how much of a resource demand they place on a nervous system. This can be in terms of demand on attention, arousal, processing and integration. Each technique is a different way of asking the brain to prioritize and learn from specific types of sensory information. Furthermore, different brains may respond differently to the stimuli.

Some brains learn more easily when we present information to them in simpler ways. Those people make quicker, more noticeable progress, if they receive tPBM and neurofeedback separately. This separation can be done either during different sessions, or at different times during a session.

Other brains have more capacity for integrating complex information. They seem to benefit more from the combination of neurofeedback and tPBM. Often such individuals are less medically fragile and have more physical resources to help them process more dense cognitive tasks.

Both of these approaches are beneficial. Usually, we start with the simpler approach and build up over time to more complex feedback designs.

What benefits do your clients report during and following your protocols that include tPBM?

Penijean: Clients report results across a wide spectrum. Some improvements are expected, such as better sleep, more functional attention and cognitive flexibility, and less anxiety. However, I am pleasantly surprised by how frequently clients report unanticipated benefits.

For example, one elderly woman recovered her ability to remember music that she thought she lost years ago. An executive who came to reduce his anxiety around work was very happy to discover his golf game improved significantly. Children, brought in by parents concerned about academic performance, have noticed improved visual integration, better frontal lobe inhibition, and increased social awareness. As you can see, there is a lot to learn.

As you are aware, Vielight has developed and will be launching a unique new tPBM device, the Neuro Pro. What do you think the applications of the Neuro Pro can be for neurofedback practitioners and their patients specifically?

Penijean: Being both a health and wellness practitioner and a designer of innovative ways to interact with the brain, I am limited only by two things. These things are my own creativity, and the capabilities of my tools. I am someone who tends to push devices to their limits. Therefore, I am always looking for user interfaces that allow as much customization and choice as the platform can support.

The Neuro Pro is the type of device, which will allow to design and build tPBM sessions specifically tailored to a specific individual. The capacity for programming a series of pulses based on a person’s unique EEG signatures will be unprecedented.

While not every practitioner will want to design their own protocols, the Neuro Pro will still provide the platform for all practitioners to run the protocols developed by researchers.

New Brain Modulation Techniques

When new effective brain modulation techniques emerge, they can only spread as widely as the availability of the technology. Neuro Pro will support the innovation of new tPBM protocols. At the same time it will provide the devices by which these protocols can be implemented and used.

This means that neurofeedback providers will be able to pair up more precise tPBM protocols with the customized EEG biofeedback. Techniques that have not been possible before, such as cross frequency coupling feedback timed synced with near infrared pulses, to improve neural networks, or ramping frequency delivery protocols that help the brain learn state flexibility, may become much more accessible.

What could be the applications of this device for researchers and health and wellness practitioners dealing with human brains?

Penijean: One of the critical principles of interacting with the brain in effective ways is being able to observe and, to a degree, mimic some of the complex dynamics, which make up flexible neural states. The brain habituates quickly to repetitive stimuli, because so it can prioritize its limited resources.

The Neuro Pro offers the possibility of building more sophisticated and precise tPBM protocols. These protocols could not only capture the brain’s attention better, but also could produce informational sequences, which more closely match neural patterns. Thus, this Vielight device opens potential for advanced stimulation designs that can target network behaviors with more nuance and specificity.

What else would you like to add in conclusion?

Penijean: In an increasingly tech savvy society, as we are suffering from the habitual overexposure to specific light frequencies from heavy screen use, it seems poetic to me that we may be able to help rewire these brains using other types of light. The light is information. Our bodies rely on light sources to help us regulate various systems and functions. Thus, regulating circadian rhythms, affecting our sleep cycles, our immune systems, our metabolism, and our mental health are some possibilities.

Wavelengths of light are a language. The more we learn, the better we can speak to our body in ways, which it recognizes as familiar and healing. Transcranial photobiomodulation could be an invaluable mechanism in our pursuit of improving brain’s function and wellbeing.

How Red Light Therapy Differs from Near Infrared Light Therapy, and What is Low Level Laser Therapy? 

Light therapy terminology could be bewildering. The only way around this is to understand this terminology, the meaning behind the terms and the types of light therapy. If you are new to the light therapy space, you may find this cascade of names overwhelming and confusing. Hopefully, this article will help you to bring some order and clarity on the subject of light therapy related terminology.

Red light therapy and low-level laser therapy (LLL) are terms that describe the use of light in therapeutic applications. These terms are better known, because they have been around longer than other terms denoting light therapy. For example, near infrared light therapy (NIR) and infrared light therapy (ILT) are also two forms of light therapy. Their names are defined by the spectrum of the wavelength used. Each of them, as well as the red light therapy, can be a form of LLL. Another term for light therapy, that is more recent, is photobiomodulation therapy, PBM or PBMT.

Understanding the differences among various forms of light therapy is not as complicated as it might seem at first. The easiest way to start is to understand the related terminology. To do that, you should start from the top of the hierarchy and move down the chain. Along the way you will be able to learn and understand the relevant terms.

The Hierarchy of the Light Therapy Terminology

The term light therapy is the original name. Therefore, it stands at the top of the hierarchy. More modern equivalent of light therapy is photobiomodulation therapy (PBMT). Thus, these two terms are equal in meaning and occupy the top position in the hierarchy. The next level deeper brings about terms that are critical in understanding of the variety of forms of light therapy.

Already mentioned earlier, low-level laser therapy, is one of the earliest modern forms of light therapy. Originally developed in the 60s, this name became equivalent to the name light therapy. They are often used interchangeably. However, this is not a completely correct way to use these terms. While LLL is a form of light therapy, it is not its only form. Furthermore, LLL usually refers to light therapy in the red light thorough to infrared wavelength spectrum. Yet, today, there are numerous other light therapy options from yellow to blue to ultraviolet light spectra.

This article will focus only on the subjects relevant to the light therapy in the red to infrared spectra. This should help to avoid any confusion regarding beneficial effects of light. Thus, unlike the light in red to infrared spectra, light of other spectra could be harmful in some cases. For example, ultraviolet light can cause harm, if it is used improperly. However, that is the subject matter which outside of the scope of this article.

LLL and LED Light Therapy Options

Since the invention of LLL, technological advancements allowed the use of modern light emitting diodes (LED) for light therapy. Thus, LEDs dethroned low level lasers (LLL) as the only option for light therapy. Nonetheless, many are still using the term LLL synonymously with light therapy. Just like the brand name “Hoover” displaced the common name “vacuum cleaner” for many, “LLL” displaced “light therapy” for some. However, regardless of individual preferences for terminology, the reality is that today LLLs and LEDs share the light therapy space. Each one is prominent in its own rights and for numerous applications in general wellness, medicine and beauty related fields.

The Top Levels of Light Therapy Terminology

To sum up, the two top levels of the light therapy hierarchy are:
Level 1: Light Therapy or Photobiomodulation (PBM)
Level 2: Low level laser (LLL) therapy and LED-based light therapy.

The next level down brings about terms that differentiate forms of photobiomodulation by the wavelength of light. Thus, you may encounter terms like red light therapy, near infrared light therapy and infrared light therapy. While these three types of photobiomodulation closely related, they also differ.

Prior to discussing these three wavelength options, it is important to note again that there are others. For example, ultraviolet light, blue light, green light, they all have their uses. They differ in wavelength and the quality of light. However, most importantly, they differ in the effects of these types of light on the body.

As you may recall, the focus of this article is on the light in the red to infrared spectra. Therefore, there will be no discussion of any light in the other spectra. You will be ahead of the game, if you remember that the applications of those forms of light are different.

Photobiomodulation using Light in the Red to Infrared Spectra

The red light waves fall in the range of 600 nm to 700 nm. The near infrared light waves fall into the 700 nm to 1400 nm range. The term “near infrared” alludes to the fact that this is the type of invisible infrared light that is closest to the visible red light range. Last, but not least, is the infrared light, which falls into the 780 nm to 1 mm wavelength spectrum. These three types of light have different depths of penetration and absorption by the life tissue. Therefore, their applications are in accordance with those factors.

Thus, to sum up, the next level in the terminology hierarchy belongs to the wavelengths of the light. The focus of this article is primarily on red to infrared light spectra. Other wavelengths of light, from yellow to blue, are also suitable for various forms of light therapy applications.

Level 3: Photobiomodulation based on the light wavelength, or spectrum:

1. Red light therapy.
2. Near infrared light therapy.
3. Infrared light therapy.

Types of Photobiomodulation by Application

Now you can differentiate three levels in defining light therapy or PBM. Moving forward, the next level in the hierarchy of terminology defines PBM by application type. Thus, red light therapy is suitable for topical and systemic applications. It can be used for wound healing, for various forms of skin therapy, for muscle relaxation and more. Numerous studies provide evidence to support benefits for these applications.

The term systemic photobiomodulation defines applications of red light therapy via the blood. Relatively recent research has shown that blood contains free-floating mitochondria, which absorbs the energy of red light. The term systemic implies that this type of light therapy can produce systemic effects in the body.

Using Light Therapy for Brain Stimulation

Perhaps the most complex and sophisticated application of light therapy is its use for brain stimulation. This form of light therapy is called transcranial photobiomodulation or tPBM. The light is used to penetrate through the skin, muscles and the cranium to reach the brain. Current research shows that the best form of light for tPBM is near infrared light (NIR). NIR has presented best penetration and absorption rates, and these facts have been documented using EEG and MRI scans of the brain.