Orientation selectivity in the population of ON-OFF direction-selective ganglion cells in the mouse retina
Date
2023-04-28
Authors
Ravi Chander, Prathyusha
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Abstract
In the mammalian retina, the orientation-selective (OS) and direction-selective (DS) information are generally thought to be relayed to higher visual centers via distinct ganglion cell types. Contrary to this notion, here I report that classic ON-OFF direction-selective ganglion cells (DSGCs) that are known to encode the four cardinal directions, also encode orientation of static stimuli. The DSGC’s preferred orientations was always orthogonal to its preferred-null axis defined by moving stimuli. To evaluate the synaptic mechanisms underlying orientation selectivity a combination of electrophysiological, optogenetic, and gene knock-out techniques were used to assess the functional properties of all four types of ON-OFF DSGCs. Cumulative results from multiple approaches revealed that the glutamate input to all four types of DSGCs was tuned to the vertical axis. This relies on signals from a specific presynaptic source (the bipolar cell type 5A; BC5A), which appear to be electrically coupled to vertically oriented processes of wide-field amacrine cells. By contrast, the GABAergic inhibition mediated largely by starburst amacrine cells was tuned either along the horizontal or vertical axis, consistent with their well-defined asymmetric wiring pattern. Thus, distinct combinations of inhibition and excitation underlie orientation selectivity in the nasal/temporal and dorsal/ventral coding DSGC populations, only the latter critically relying on the starbursts. Together, my work provides novel insights into how feature selectivity emerges in the hierarchical network in the retina.
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Direction-selective, Orientation-selective, Electrophysiology, Optogenetics, Asymmetric inhibition, Vertical excitation, OS is orthogonal to the P-N axis, dv-DSGCs, nt-DSGCs, SACs, BC5As, WACs, Gap-junction coupling, Cx36 gap-junctions, Genetic knockout