A recent study published in iScience confirms that the human brain emits faint light, and these emissions can be detected through the skull. This phenomenon could pave the way for a novel optical monitoring method called photoencephalography.
What Was Discovered
- Scientists recorded ultraweak photon emissions (UPEs) from 20 healthy adults in complete darkness, using photomultiplier tubes placed near visual and auditory brain regions, while also tracking brain waves via EEG.
- These light emissions are generated as by-products of cellular metabolism—distinct from thermal radiation and far too faint to see with the naked eye.
Correlation with Brain Activity
- Brain-derived photons were statistically distinguishable from background light and fluctuated in rhythmic patterns below 1 Hz, particularly in regions involved in visual and auditory processing.
- Light emissions shifted when participants alternated between tasks (e.g., eyes open vs. closed, listening to sound), suggesting sensitivity to mental state—though correlations with EEG rhythms were modest.
Implications for Neuroscience
- This is the first demonstration that photons emitted by the human brain can be measured non-invasively through the skull—a concept researchers now label “photoencephalography.”
- UPE-based monitoring could one day supplement EEG, offering a passive, light-based method to gauge brain metabolism, functional state, or pathological changes.
Challenges & Limitations
- The study was preliminary: small sample size, limited sensor coverage, and broad detection of varied wavelengths may have obscured finer patterns.
- UPE signals showed individual variability and scanning occurred over short intervals, limiting spatial resolution.
Looking Ahead
Researchers suggest future studies should:
- Use advanced filters and spatially dense sensor arrays to pinpoint signal origins
- Collect data across larger, more diverse populations and mental states
- Investigate whether UPE patterns differ in neurological disorders, aging, or cognitive decline
Key Details at a Glance
| Aspect | Details |
|---|---|
| What Was Detected | Ultraweak photon emissions from the human brain |
| Detection Method | Photomultiplier tubes placed near skull; simultaneous EEG monitoring |
| Emission Sensitivity | Fluctuations observed during cognitive states (e.g., eyes open vs. closed) |
| Signal Characteristics | Below 1 Hz rhythmic pattern; variable among tasks |
| Potential Application | Non-invasive brain monitoring (photoencephalography) |
| Study Limitations | Small size, limited resolution, wavelength variability |
Why It Matters
This discovery challenges the long-held assumption that the brain is optically opaque. Detecting photons emerging from brain activity opens a new frontier in non-invasive neuroscience—revealing potentially new channels of communication or metabolic markers. In the future, light-based brain diagnostics could complement electrical methods (like EEG), offering faster, safer, and more portable tools for tracking health and function.
Final Takeaway
Humans literally glow from within: ultraweak photons are emitted by the brain and can be measured through the skull, with subtle changes reflecting mental activity. While still speculative, this proof-of-concept research lays the groundwork for photoencephalography, a potential new modality for studying brain function and health.
