A presynaptic source drives differing levels of surround suppression in two mouse retinal ganglion cell types

Abstract

In early sensory systems, cell-type diversity generally increases from the periphery into the brain, resulting in a greater heterogeneity of responses to the same stimuli. Surround suppression is a canonical visual computation that begins within the retina and is found at varying levels across retinal ganglion cell types. Our results show that divergence in the level of surround suppression occurs subcellularly, at bipolar cell synapses. Using single-cell electrophysiology and serial block-face scanning electron microscopy, we show that two retinal ganglion cell types exhibit very different levels of surround suppression even though they receive input from the same set of bipolar cell types. This divergence of the bipolar cell signal occurs through synapse-specific regulation by amacrine cells at the scale of tens of microns. These findings indicate that each synapse of a single bipolar cell can carry a unique visual signal, expanding the number of possible functional channels at the earliest stages of visual processing.

Sustained ON alpha retinal ganglion cells in the temporal retina exhibit task-specific regional adaptions in dendritic signal integration

“…The results reported by Swygart et al (43) may also provide another mechanism for the surround suppression in synaptic inputs and postsynaptic Ca 2+ signals we observed. Their data suggest that type 6 BCs have multiplexed out-puts, with ribbon synapses featuring weak and strong surround suppression, mediated by amacrine cells, in individual BCs.…”

“…In another recent study, Swygart et al (43) performed similar experiments to ours, where they also recorded from sONα cells in different regions of the retina. In contrast to our results, they did not find a significant difference in surround suppression between different locations of the retina.…”

“…sONα RGCs have a high base firing rate under steady illumination (20, 21, 41) driven by excitatory synaptic inputs originating mostly in type 6 and type 7 BCs (26, 42, 43). While sONα cells express low levels of melanopsin and are, hence, intrinsically photosensitive (44), their light response is dominated by the synaptic inputs (40).…”

“…While sONα cells express low levels of melanopsin and are, hence, intrinsically photosensitive (44), their light response is dominated by the synaptic inputs (40). The surround receptive field of sONα is antagonistic (20, 40), presumably by suppression of excitatory presynaptic inputs (20, 43).…”

“…A colour-dependency of the surround strength seems plausible given the diverse and location-dependent colour preference of the sONα cell’s surround reported along the dorsal-ventral axis (14). Finally, Swygart et al (43) electrically recorded from sONα somata, whereas we recorded directly from dendrites. It is possible, that the surround suppression we observed on dendritic segments becomes less pronounced in the somatic signal due to the integration of all the dendritic signals.…”