Light Helps Activate Brain Activity Even in Totally Blind

Light helps to activate brain activity even in the totally blind, a new study found.

Researchers at the University of Montreal and Boston's Brigham and Women's Hospital said the results, which help to build a clearer picture of brain functioning, surprised them.

"We were stunned to discover that the brain still respond significantly to light in these rare three completely blind patients despite having absolutely no conscious vision at all," said senior co-author Steven Lockley. "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."

A previous study in a single blind patient suggested the possibility that the specialized photoreceptors in the retina detect light separate from the rods and cones used to see. In order to determine whether or not this was the case, the scientists asked three participants whether a blue light was on or off, despite knowing that they could not see it in the traditional sense.

"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," explained first author Gilles Vandewalle.

They then took a closer look at what happened in terms of brain activation when a light was flashed at their eyes while a sound played to measure their attentiveness.

"The objective of this second test was to determine whether the light affected the brain patterns associated with attentiveness - and it did," said first author Olivier Collignon.

Finally, the researchers examined the participants' brain function via a functional MRI (fMRI) brain scan. They did this while the blind individuals performed a sound matching task as lights were flashed in their eyes.

"The fMRI further showed that during an auditory working memory task, less than a minute of blue light activated brain regions important to perform the task," Vandewalle explained. "These regions are involved in alertness and cognition regulation as well being as key areas of the default mode network."

This default network, the researchers hypothesize, allows the brain to use as few resources as possible to monitor the environment when a person is not actively doing something.

"If our understanding of the default network is correct, our results raise the intriguing possibility that light is key to maintaining sustained attention," according to Lockley and co-author Julie Carrier. "This theory may explain why the brain's performance is improved when light is present during tasks."