Exposure to light can enhance activity in the brain during cognitive tasks, even in some people are completely blind, say researchers at the Université de Montréal and Boston’s Brigham and Women’s Hospital.
The researchers say that the brains of blind people can detect light via unique photoreceptors in a cell layer of the retina, which differ from the rods and cones used for vision. Scientists believe that the specialized photoreceptors contribute to the brain’s visual function even when the cells responsible for image formation are unable to receive or process light.
Researchers asked three blind participants who could not see light whether a blue light was on or off. “We found that the participants did indeed have a non-conscious awareness of the light – they were able to determine correctly when the light was on greater than chance without being able to see it,” Gilles Vandewalle, first author, said.
“Light stimulates day-like brain activity, improving alertness and mood, and enhancing performance on many cognitive tasks,” said Julie Carrier, senior co-author.
In another test, the researchers closely monitored the brain activity when a light was flashed at the participants’ eyes and a sound was made at the same time. The scientists say that the brain patterns related to attentiveness were affected by the light.
“We were stunned to discover that the brain still responds significantly to light in these rare three completely blind patients despite having absolutely no conscious vision at all,” said Steven Lockley, senior co-author of the study. “Light doesn’t just allow us to see, it tells the brain whether it’s night or day which in turn ensures that our physiology, metabolism and behavior are synchronized with environmental time.”
Scientists also ran a functional MRI brain scan as the participants performed a simple sound matching task while lights flashed in their eyes. The fMRI showed that less than a minute of blue light activated brain regions important to perform the task. These areas are involved in cognition regulation and alertness.
“Our results raise the intriguing possibility that light is key to maintaining sustained attention,” said Lockley. “This theory may explain why the brain’s performance is improved when light is present during tasks.”
