Cited research Neuron 67, 49–60 (2010)

Perception of patterns in the eye has long been attributed solely to two types of retinal cell — the rods and cones — but a study suggests that they are not alone in having this ability.

Neuroscientists had thought that intrinsically photosensitive retinal ganglion cells (ipRGCs) could respond only to the presence or absence of light in regulating certain activities, such as circadian rhythms. But Samer Hattar at Johns Hopkins University in Baltimore, Maryland, David Berson at Brown University in Providence, Rhode Island, and their colleagues show that, in mice, these cells are more abundant and diverse than previously thought. In addition, they project into more areas of the brain — including those responsible for visual perception.

Mice engineered to lack the rod and cone biochemical pathways, but with their ipRGC pathways intact, could still distinguish patterns in a visual test. However, it took them double the number of trials to achieve a normal level of performance.