Researchers at the University of Montreal and Boston's Brigham and Women's Hospital's findings contribute to scientists' understanding of everyone's brains, as they also revealed how quickly light impacts on cognition.
Senior co-author Steven Lockley said that they 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.
He said that 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.
Senior co-author Julie Carrier said that for diurnal species like ours, light stimulates day-like brain activity, improving alertness and mood, and enhancing performance on many cognitive tasks.
The results indicate that their brains can still "see", or detect, light via a novel photoreceptor in the ganglion cell layer of the retina, different from the rods and cones we use to see.
Scientists believe, however, that these specialized photoreceptors in the retina also contribute to visual function in the brain even when cells in the retina responsible for normal image formation have lost their ability to receive or process light.