How Light Wakes Up the Brain

I first learned how our eyes work in a college neuroscience class in the fall of 2002. My textbook showed colorful cartoons of the retina, lined with two types of cells that convert light waves into the electrical currency of the brain. There were rod cells, which are useful in low-light situations, and there were cone cells, which allow us to see colors. Neat and tidy.Unbeknownst to me (because the information hadn’t made it into textbooks yet) neuroscientists had just discovered a third class of light-sensitive eye cells, called, rather uncreatively, ‘intrinsically photosensitive retinal ganglion cells’ (ipRGCs). These cells have nothing to do with vision. They absorb light in order to properly set our circadian clock.In the decade since then, many studies have suggested that ipRGCs do even more than clock-setting. The latest of these reports, out this week in the Proceedings of the National Academy of Sciences, finds that these cells — and the light-sensitive protein they contain, melanopsin — are involved in short-term memory.Read more at...Only Human, March 2014.