Our brains glow. We can’t see it happen with the naked eye, but scientists can measure extremely subtle light passing through the skull – and a recent study has found that this light changes depending on what we’re doing.
All living tissue emits a faint light called ultraweak photon emissions (UPE). This light extinguishes when the tissue dies. However, the human brain produces a significant amount of UPE due to the high energy it consumes (the brain accounts for approximately 20 per cent of the body’s total energy).
“Ultraweak photon emissions, or UPE, are very weak light signals – trillions of times weaker than a light bulb – that are generated by cells of all kinds throughout the body,” senior author Dr Nirosha Murugan, assistant professor of health sciences at Wilfrid Laurier University, in Ontario, Canada, told BBC Science Focus.
“Even though UPEs are very weak signals, the brain’s energy consumption makes it a great generator of light relative to other organs,” she said. “Imagine hundreds of billions of brain cells, each individually generating weak light signals, but with a collective glow that we can measure outside the head.”
Murugan’s team wanted to investigate whether this glow changed depending on what the brain was doing, to see if scientists could use it to measure brain activity.
So, they recruited 20 adults to sit in a dark room while the scientists measured electrical signals – using a cap fitted with electricity sensors – as well as light emitted from their brains.
Participants were instructed to carry out simple instructions, involving opening and closing their eyes, and listening to sound recordings.
The scientists then compared the electrical signals and UPEs that they recorded – and found a correlation.
“We discovered that light signals detected around the head were related to the brain’s electrical activity during cognitive tasks,” said Murugan. “These light emission patterns from the brain are constantly changing. They oscillate, are complex and carry information.”
The brains emitted this light in slow rhythmic patterns, at a frequency slower than once per second, that seemed to steady over the course of each two-minute task.
Murugan said that measuring this brain light could “change the field of neuroscience” by giving scientists and doctors new ways to scan the brain, to potentially find signs of disorders such as epilepsy, dementia or depression.
This light could even be playing a role inside our brains, rather than just being a byproduct of its function. Murugan said that studying it could “reveal a hidden dimension” of the inner workings of our minds.
“We hope the prospect of detecting and deciphering light signals from the brain will inspire new questions that were previously unthinkable,” she said. “For example, because UPEs travel through the skull, could they possibly influence other brains in the environment?”
This was only a small, preliminary study, so there is still a lot for scientists to discover when it comes to UPEs in the brain.
But Murugan said she hoped her team’s findings would “initiate new conversations about the role of light in brain function.”
Read more:
- All humans emit subtle light until they die, study suggests
- Specific neurons in your brain light up when you hear singing
- Unlocking the secrets of the brain
About our expert
Dr Nirosha Murugan is an assistant professor in the Department of Health Sciences at Wilfrid Laurier University in Ontario, Canada. She was recently appointed as a Tier 2 Canada Research Chair in Biophysics from Algoma University, also in Ontario.
