Summary: Light exerts a range of powerful biological effects beyond image vision, including effects on mood and learning. While the source of photic information affecting mood and cognitive functions is well established, via intrinsically photosensitive retinal ganglion cells (ipRGCs), the central mediators are unknown. Here, Fernandez and colleagues show that ipRGCs projections to the suprachiasmatic nucleus mediate the effects of light on learning, independently of the suprachiasmatic nucleus pacemaker function. However, mood regulation by light requires a suprachiasmatic nucleus-independent pathway linking ipRGCs to a previously unrecognized thalamic region, termed perihabenular nucleus. The perihabenular nucleus is integrated in a distinct circuitry with mood-regulating centers and is both necessary and sufficient for driving the effects of light on affective behavior. “Together, these results provide new insights into the neural basis required for light to influence mood and learning.”
Fernandez DC, Fogerson PM, Lazzerini Ospri L, Thomsen MB et al: Light Affects Mood and Learning through Distinct Retina-Brain Pathways. Cell 175(1): 71-84 (2018).