Genetic dissection of rod and cone pathways mediating light responses and receptive fields of ganglion cells in the mouse retina.

Retinal ganglion cells (GCs) are important visual neurons which carry complex spatiotemporal information from the retina to higher visual centers in the brain. By taking advantage of pathway-specific knockout/mutant mice and multi-electrode array (MEA) recording techniques, we analyze contributions of rod and cone pathways to responsiveness, kinetics and receptive field profiles of GCs under scotopic and photopic conditions. Our data suggest: (1) Scotopic responses of some GCs require all three rod pathways, some require only the secondary and tertiary rod pathways, and others require only the tertiary rod pathway. (2) There are more responsive GCs in photopic conditions than responsive GCs in scotopic conditions. (3) Gap junctions slow down GCs' scotopic light responses and increase GCs' ratio of antagonistic to center inputs. (4) Cone pathways do not affect the kinetics but alter the ratio of antagonistic to center inputs of scotopic GC responses, and they speed up GCs photopic responses and alter the ratio of GCs' antagonistic to center synaptic inputs and receptive field profiles. (5) Rod bipolar cells shorten response latency of ON GCs and increase the ratio of GCs' antagonistic to center synaptic inputs. (6) Light adaptation speeds up GCs' temporal processing and tunes GC photopic responses to higher frequencies, and the tertiary rod pathway plays a significant role in adaptation-induced TTP changes in some GCs. (7) GC RF center sizes are partially mediated by AIIACs and GC-GC coupling. (8) Connexin36 gap junctions and cone pathways alter synaptic circuits underlying antagonistic surround inputs to GCs in photopic conditions.