Scientists have detected Biophotons, Light Emitted by Brain Cells - Outside the Skull that needs to be Studied in Neuroscience
Scientists have detected faint, natural light emitted by brain cells - known as biophotons or ultra-weak photon emissions (UPEs) - outside the human skull. This discovery, which confirms a longstanding hypothesis, reveals that the brain emits a subtle glow generated by metabolic activity and chemical reactions, rather than electrical activity alone. Measuring this light opens a new, untapped frontier in neuroscience.
What are Biophotons
Biophotons are faint flashes of light within the visible and near-infrared range, typically produced during cellular metabolism. Every living cell emits these tiny light particles, which are thousands of times weaker than the light from a firefly and invisible to the naked eye. When cells are under metabolic stress or damaged, they actually produce higher intensities of these photons.
A Brain Glow Detected Outside the Skull
A 2025 study published in iScience provided direct evidence that this light can be measured from outside a living human brain. Using exceptionally sensitive cameras and detectors (photomultiplier tubes) in absolute darkness, researchers observed that this "brain glow" is not constant; rather, it changes in variability and rhythm depending on the individual's cognitive tasks.
Remarkably, the intensity of this light appears to relate more to metabolic processes and cellular health rather than traditional action potentials. For instance, certain brain regions showed different biophoton levels when participants rested with their eyes closed, compared to when they performed auditory tasks.
Implications for Neuroscience and Future Study
The detection of biophotons from outside the skull, sometimes referred to as photoencephalography, has profound implications for understanding neural processes:
Non-Invasive Diagnostic Tools: Because biophoton levels change based on the brain's metabolic state, this technique could be used to non-invasively monitor for tumors, injuries, and neurodegenerative illnesses like Alzheimer’s, which are often accompanied by mitochondrial dysfunction and high oxidative stress.
A New Form of Neural Communication: Some researchers propose that biophotons may act as a secondary, rapid communication network between neurons, complimenting chemical and electrical signaling.
Unlocking Consciousness: The synchronization of these emissions during different cognitive tasks suggests they are deeply linked to higher brain functions.
Controversies and Challenges
Despite the excitement, the field is not without controversy. Some scientists argue that properly isolating the head from ambient, background light is difficult, and that what is detected might be from the skin rather than the brain. Others argue that even if detected, the low intensity makes it hard to confirm if these photons have a functional, signaling role or are merely accidental byproducts.
The ability to detect biophotons outside the skull suggests that neurons are not only electric transmitters but also emit and perhaps perceive light. This "code of light" needs intensive study to move beyond background noise and decode the message it may hold. This advancement promises a potential new method for imaging the living brain, and exploring what is happening in human interactions that underpin cognitive responses.