Samer Hattar, an assistant professor of biology at Johns Hopkins University, has found that the eye uses light in two separate mechanisms, one for the ability to see and a separate one to reset the biological clock.
Hattar’s findings suggests that people with trouble sleeping or seasonal depression could benefit from the development of easier, more available tests to determine if they are able to detect light properly for functions distinct from normal sight.
“It seems that even if individuals have normal sight, they might be having a malfunction that is contributing to their inability to detect light, which can adversely affect their biological clocks,” says Hattar.
In the study, mice were genetically modified so that the cells that receive input from the rods and cones of the animals’ eyes and send information to the brain no longer worked. Researchers found the mice were able to see normally but had problems synchronizing their circadian rhythms to constant lengthening/shortening of daylight hours that occur throughout the year.
“This research illustrates that there are two distinct pathways for the two different aspects of light detection: image-forming and non-image forming,” says Hattar.
The research will appear in the May 1 edition of Nature.