Light is crucial for vision but its roles in driving non-visual functions are similarly important. Light-dependent regulation of mood is evident from both human and rodent research, however, the biological mechanisms that underlie these non-visual effects are unknown.

The amygdala is a major component of the limbic system, known for emotional processing and mediating stress-induced anxiety. Furthermore, the latest research has identified that medial and central nuclei within the amygdala receive sparse yet direct retinal projections including innervation by melanopsin-expressing ipRGCs (intrinsically photosensitive retinal ganglion cells) that govern non-visual functions, suggesting that the amygdala physiology may be influenced by photic information.

Consequently, we set to investigate what visual input the amygdala receives using in vivo electrophysiology in anesthetized mice while presenting a range of visual stimuli. For this purpose, we utilized red cone mice (Opn1mw^R), a genetically modified strain that expresses human L cone opsin in place of mouse M cone opsin. This enables the use of silent substitution approaches where individual responses from different photoreceptors can be isolated based on their divergent spectral sensitivities using polychromatic light sources. We designed a set of photoreceptor-specific stimuli targeting melanopsin, rods, and individual cone opsins which we tested and validated in the red cone mouse visual thalamus before applying to define photoreceptor contributions to light-responsive neurons within the medial and central nuclei of the amygdala.