Abstract
Purpose :
Physiological characterizations of ganglion cells in primate retina have been largely restricted to the numerically dominant parasol, midget, and small bistratified types. While some of the more sparsely represented ganglion cell types have been described anatomically, studies of their physiology have been limited. Here, we sought to understand the stimulus selectivities of the lesser-studied ganglion cell types in primates.
Methods :
We used extracellular and whole-cell patch-clamp techniques to record ganglion cell responses from an in vitro preparation of the macaque retina. Retinal tissue was obtained through the Tissue Distribution Program of the National Primate Research Center at the University of Washington. A battery of natural and artificial visual stimuli, designed to probe multiple dimensions of stimulus space, was delivered to the intact retina preparation.
Results :
We characterized the light responses of several lesser-studied ganglion cell types, including smooth monostratified (SM) cells. SM cell light responses showed several atypical properties. First, they spiked preferentially to full-field motion versus motion restricted to the cell’s receptive field center; this is the opposite of the stimulus selectivity exhibited by object-motion sensitive cells in other species. Second, SM cells showed a highly asymmetric distribution of synaptic inputs to their dendritic trees. Excitatory inputs were distributed across the dendritic field, while inhibitory inputs were concentrated within a much smaller region at the center of the receptive field.
Conclusions :
We studied several primate retinal ganglion cells that show non-canonical stimulus selectivity. Due to its unique receptive-field organization and stimulus selectivity, the SM cell exemplifies the rich variety of neural computations performed by the lesser-studied neural pathways in the primate retina. Indeed, the asymmetric distribution of excitatory and inhibitory synaptic inputs contrasts strongly with that of the numerically dominant primate ganglion cell types. Moreover, the preference for wide-field motion further distinguishes SM cells from their better-studied counterparts.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.