Functional consequences of heterotypic retinal ganglion cell coupling

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Neurons communicate using both chemical transmission at traditional synapses and electrical transmission through gap junctions. Electrical transmission is well studied in the mammalian retina, where gap junctions exist between all five major classes of neurons. Retinal ganglion cells (RGCs), the output cells of the retina, comprise ~40 functional types in mammals. Gap junctional coupling among RGCs has always been described as “homotypic,” that is, between RGCs of the same type. We have discovered, for the first time, heterotypic electrical coupling in the mouse retina, between two RGCs of different types, called F-miniON and F-miniOFF RGCs. The existence of heterotypic RGC coupling breaks the rule of functional parallelism between RGC channels and requires new ideas about the role of coupling in retinal computation. This project aims to explore the functional role of heterotypic RGC coupling in the F-mini network through two specific aims. In Aim 1 we will determine whether coupling between F-miniON and F-miniOFF RGCs creates a novel pathway for mixing ON and OFF signals in the inner retina. In Aim 2 we will determine which features of moving stimuli are encoded by synchronized spiking between F-miniON and F-miniOFF RGCs. The proposed studies will advance our understanding of how chemical and electrical synaptic inputs interact to perform neural computations and how sharing of signals between parallel pathways contributes to sensory encoding.