All living tissues emit faint light, a phenomenon called ultra-weak photon emission (UPE). It’s so dim that our eyes can’t see it—about a million times fainter than what we can perceive. Scientists have long wondered if the brain, which uses a lot of energy, glows more than other organs because it contains compounds that interact with light.
A recent study aimed to find out if this glow changes with neural activity. Researchers from Algoma University, Tufts University, and Wilfrid Laurier University recruited 20 healthy adults. They placed the participants in a dark chamber and used photomultiplier tubes to measure the light from two parts of the brain while monitoring brain electrical activity with EEG.
The experiment lasted ten minutes and had five phases: eyes open, eyes closed, listening to a tone, eyes closed again, and finally, eyes open. Each phase lasted two minutes, allowing the researchers to observe changes in brain light.
Despite the faintness of the photons, the team, led by Hayley Casey and Nirosha Murugan, successfully distinguished the brain’s light from the background noise. They found that the light fluctuated in a rhythmic pattern, strongest in the area that processes visual information. This finding suggests that the glow isn’t random but could be connected to how the brain is functioning in real-time.
Interestingly, when participants closed their eyes, the photon emissions often increased. This aligns with earlier research showing that closing one’s eyes enhances certain electrical rhythms in the brain. Some participants showed increased emissions with their eyes shut, while others saw a decrease. This variation indicates a personal neural response, but overall patterns persisted across the study.
Auditory stimuli, like a steady tone, also impacted photon emissions, suggesting that processing sound can leave a photonic trace too. UPE measurement is passive, meaning sensors simply wait in the dark without sending energy into the skull. This method could potentially lead to new technologies, like “photoencephalography,” which might aid in diagnosing disorders related to energy use in the brain, such as Alzheimer’s disease or traumatic brain injury.
However, this study only included a small sample size and limited brain areas. Future research will likely involve a larger group with a focus on various age ranges and medical conditions to see if they produce unique light patterns.
The concept that the brain emits light linked to its metabolic state may open new doors in understanding brain health. While photonic signals remain to be fully understood, their presence could offer insights into brain activity and overall functioning without invasive measures.
The study highlights not only the potential of UPE but also reflects a broader trend in neuroscience. Historically, electrical rhythms changed the landscape of our understanding of the brain a century ago. Now, the promise of photo-related technologies may herald a new era in brain research.
For more in-depth information, you can read the study published in the journal iScience here.
