Reading the Brain’s Light Signals

How ultraweak photon emissions may reflect neural health and function

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The human brain isn’t just electric — it’s faintly photonic. Researchers have confirmed that the brain produces ultraweak photon emissions (UPE), a subtle glow of light generated during normal metabolic activity. What began as fringe biophysics is now entering mainstream neuroscience as scientists explore whether this glow could serve as a biological window into cognition and mental health.

A subtle glow tied to metabolism

All living cells emit photons as a result of oxidative chemical reactions, particularly those involving reactive oxygen species. According to researchers publishing in Scientific Reports, this emission arises naturally from normal mitochondrial function rather than from specialized light-producing enzymes.

In laboratory studies, scientists have used high-sensitivity photon-counting cameras to map photon activity across rodent brain tissue, finding direct relationships between UPE intensity, oxidative stress, and mitochondrial health.

In human experiments published in iScience, participants were placed in total darkness while researchers measured scalp photon counts during auditory and visual tasks. The findings revealed modest but consistent correlations between UPE changes and EEG oscillations.

A science journalist at BBC Science Focus summarized it succinctly:

“The brains emitted this light in slow rhythmic patterns … correlated with the brain’s electrical activity during cognitive tasks.”

For context, this glow is a million times fainter than visible light — far below what the human eye can perceive.

Why the brain might emit light

Scientists propose several possible explanations for this mysterious biophotonic emission:

• Indicator of oxidative stress — Because the light originates in redox reactions, it may reflect metabolic distress or mitochondrial dysfunction. This link could be vital in neurodegenerative diseases such as Alzheimer’s.

• Possible optical signaling — Some researchers speculate that neurons might use photons for a form of cell-to-cell optical communication, although the evidence is far from conclusive.

• Waveguiding in neurons — A 2024 University of Rochester study on optical transport in neurons found that axons can theoretically guide light like fiber-optic cables, suggesting the possibility of an internal light-based signaling system.

Meanwhile, an arXiv preprint on astrocytes and glioblastoma cells reported distinct emission signatures between healthy and cancerous tissue — further hinting that biophotons could carry diagnostic information.

A challenging signal to detect

Detecting UPE requires eliminating virtually all background light and thermal noise. Researchers conducting the iScience study recorded in absolute darkness, synchronizing photon sensors with EEG and cross-correlating fluctuations between light and brain wave patterns.

The emissions oscillate at about one cycle every few seconds — far slower than electrical signals — and require ultrasensitive photomultiplier tubes to detect.

Establishing causality remains the biggest hurdle. Are these photons a byproduct of energy metabolism, or do they carry information about neural processes themselves?

Potential medical and scientific uses

If validated, UPE could become a non-invasive biomarker for a range of neurological and metabolic conditions. Potential applications include:

• Monitoring neurodegenerative disease progression (read PMC review on Alzheimer’s biomarkers)

• Mapping brain state changes — Early trials found 5–10% higher photon emission during auditory processing compared to rest (see iScience data set)

• Complementing EEG and fMRI — Because UPE reflects metabolic oxidation, it could add new information beyond electrical or magnetic activity.

• Portable health monitoring — The National Research Council of Canada’s photon-emission technology may eventually enable handheld diagnostic devices.

The state of the science

Despite skepticism, academic attention is growing. Scientific American noted that “the fact that ultraweak photon emission is a real thing is undeniable at this point” (read feature article).

The field is now expanding into photoencephalography — the idea of imaging the brain through its own faint light (Wikipedia overview of photoencephalography). Whether that’s science fiction or the next evolution of neuroimaging remains to be seen.

For a detailed overview, the Frontiers in Physiology 2024 review on biophotonic emissions offers a technical summary of measurement techniques and possible applications.

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