© Flickr user David GoehringA man sleeping in his bed, with a blindfold.
A study reported in the Journal of Cognitive Neuroscience Science says brain imaging shows light activates brain cells even in the blind.
"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 of the study, Steven Lockley.
It is an interesting question with daylight savings approaching this weekend, and some scientists believe it can adversely affect sleeping patterns, even causing accidents at work.
This study examined three blind patients. An earlier one returned similar results but only tested one patient.
One simple test was to put them in a room and turn the light off and on. The subjects could tell when the light was turned on.
"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.
Senior co-author Julie Carrier said the results indicate the brains "see," or detect light via a novel photoreceptor in the ganglion cell layer of the retina. They are separate from the rods and cones used to see.
Researchers at the University of Montreal and Boston's Brigham and Women's Hospital did the study.
Light could be a factor in determining the circadian rhythms that tell the body when to sleep. It has been known for centuries that it is easier to sleep when it is dark.
"Much of our sleep patterns - feeling sleepy at night and awake during the day - are regulated by light and darkness. Light - strong light, like bright outdoor light (which is brighter than indoor light even on cloudy days) - is the most powerful regulator of our biological clock," says The National Sleep Foundation.
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