Perceiving without seeing: How light resets your internal clock
December 17
Heard on Weekend Edition Saturday
Fred Crittenden has retinitis pigmentosa, an inherited condition that led to the deterioration of his retinas. He lost all his rods (the cells that help us see in dim light) and all his cones (the cells that let us see color in brighter light). Within a single year, in 1985, Crittenden says he went from perfect vision to total blindness.
This brings us to Iggy Provencio, a biologist at the University of Virginia who, in grad school in the '90s, was studying the African clawed frog. "The frog is really a disgusting-looking animal," he chuckles. "It has very slimy skin."
That skin contains cells that darken with pigment when they detect light, which helps the frogs blend in with the streambed below. Provencio discovered the molecule responsible for the light detection, which he called melanopsin. And it wasn't just in the frog's skin. He and his team found it in the retina of the frogs, and of mice too.
"We were looking through the microscope," Provencio recalls, "and I told my colleague who was with me, 'We are the first people in the world to actually view a completely novel sensory system in mammals' " — including humans.
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Story credit NPR Radio, Ari Daniel