Tracing pathways in the brain to understand how light affects mood and learning
In 2012, researchers discovered that the effects of light on learning and mood begin in the eye’s retina in a population of cells called intrinsically photosensitive retinal ganglion cells, or ipRGCs. However, nothing was known about the brain pathways through which these effects occur in mice.
IRP researchers, led by Samer Hattar, Ph.D., traced the brain pathways responsible for the effects of light on learning and mood. Their findings revealed that these effects are brought about by two different and distinct pathways from the ipRGCs into the brain that influence mood and learning, respectively. The researchers also successfully alleviated depression-like behaviors in mice by regulating light exposure on a single brain region.
If light travels through two distinct pathways from the eye to the brain in humans as it does in mice, then light-associated problems may require different kinds of therapies depending on whether they affect mood or learning. Furthermore, the study explains why controlling the timing of light exposure shows promise as a potentially effective treatment for depression in humans.
Fernandez DC, Fogerson PM, Ospri LL, Zhao H, Berson DM, Hattar S. (2018). Light affects mood and learning through distinct retina-brain pathways. Cell. 175(1):71-84.