Perfect Vision But Blind To Light (IMAGE) Salk Institute Caption When light activates melanopsin (red), a light receptor found in rare, specialized cells in the retina, they send a signal to different areas in the brain. It allows the body to tell day from night and adjust accordingly. Credit Image: Courtesy of Dr. Megumi Hatori, Salk Institute for Biological Studies Usage Restrictions News media reproduction to illustrate this story permitted with proper attribution as provided above . For one time use only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.