Melanopsin and rod-cone light-sensing systems explain all main extra visual functions in mice

Mice lacking melanopsin, along with rod and cone systems, exhibit no significant pupil reflex or light/dark cycle entrainment.

• Melanopsin-associated retinal ganglion cells are intrinsically photosensitive, providing crucial photic input.
• Ablation of the melanopsin gene leads to partial impairment in pupil reflex and circadian rhythm phase shifts.
• The action spectrum for phase-shifting locomotor activity matches that of the pupil reflex and melanopsin sensitivity.
• Mice with both melanopsin ablation and disabled rod/cone mechanisms have an intact retina but show no masking response to light.

Simplified