Our brains emit a faint light, invisible to the naked eye, but measurable with sensitive equipment. Recent research suggests that this subtle glow fluctuates depending on what the brain is doing. All living tissue produces ultraweak photon emissions (UPE), a type of light that ceases when tissue dies. The human brain, due to its high energy demands – accounting for around 20 per cent of the body’s energy – generates a particularly strong UPE signal.
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“Ultraweak photon emissions are extremely faint light signals – trillions of times weaker than a light bulb – generated by cells throughout the body,” explained Dr Nirosha Murugan, assistant professor of health sciences at Wilfrid Laurier University in Ontario, Canada. “Yet the brain’s energy use makes it a substantial generator of light compared with other organs.”
Murugan’s team aimed to investigate whether this light varies with brain activity. They recruited 20 adults to sit in a dark room while their brain activity was recorded using a cap fitted with electrical sensors, alongside measurements of light emitted from their heads. Participants performed simple tasks, such as opening and closing their eyes and listening to audio recordings.
The researchers discovered a correlation between electrical activity and the brain’s light emissions. “Light signals detected around the head were linked to the brain’s electrical activity during cognitive tasks,” Murugan said. “These light emissions oscillate, are complex, and carry information.”
The emissions followed slow rhythmic patterns, less than one cycle per second, stabilising during each two-minute task. Murugan suggests that measuring this brain light could transform neuroscience, offering new ways to scan for conditions such as epilepsy, dementia, or depression. The light may even play a functional role within the brain itself.
“We hope detecting and interpreting light signals from the brain will spark new research questions,” she added. “For instance, since UPEs pass through the skull, could they influence other brains nearby?”
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Although the study was small and preliminary, it opens intriguing possibilities. Murugan hopes it will “initiate new conversations about the role of light in brain function.”
