Contributions of Specific Retinal Circuits and Their Respective Projections to Visual Behaviors
Date of Award
Doctor of Philosophy (PhD)
The survival of a species is inextricably linked to its ability to successfully navigate and interact with its surroundings, whether to seek safety from predators or gain sustenance from prey. Both functions are performed by mice, guided by vision, and rely on intricate processing in the retina and subcortical targets in the brain. This dissertation addresses how specific features of the visual environment and specific retinal ganglion cell circuits that sample a particular space in the visual environment are used to guide efficient predation in mice.Recent studies have begun to link the ability to detect, track, and ultimately capture prey to the retina and its projections to the superficial layers of superior colliculus (sSC). More than 85% of retinal ganglion cells (RGCs) that encode individual features of the visual environment project to SC, resulting in SC neurons that integrate and encode multiple visual features. How a single feature of visual space is utilized to guide complex behaviors and how individual retinal ganglion cells contribute to these computations remain unknown. Here, we show that narrow-field (NF) cells in sSC, which encode object size, speed, and motion direction, are required for accurate approaches toward prey. We show that other visual pathways that encode motion direction are not required for predation and test specifically whether NF cells must encode this feature for mice to accurately target prey. We manipulate the presynaptic retinal circuitry to remove the directional tuning of NF cells, while maintaining retinal excitatory drive through sSC. We show that mice remain able to accurately approach, pursue and capture prey, despite being unable to extract information about how it moves. We then sought to determine which of the RGC types responsible for binocular vision guide predation. Leveraging an intersectional genetic strategy, we silence a subpopulation of 2 ipsilaterally projecting RGCs that can signal prey (ipsi-αRGCs, ~260 total cells) and find that predation is disrupted, consistent with the deficit caused by silencing the NF cells to which they project. Together, these results suggest 3 main findings. First, visual behaviors are guided by specific visual pathways and sSC is required for predation. Second, information about motion direction is not required for efficient predation, despite it being a key feature of prey. This suggests that the ability of cells in sSC to integrate and signal multiple types of visual information is more important than the ability to reliably encode a single feature of interest. Third, 2 subtypes of ipsi-αRGCs can account for the role of binocular vision in predation and might indicate that reliable encoding of a sliver of visual space is most important for efficient predation.
Chair and Committee
Krizan, Jenna Mackenzie, "Contributions of Specific Retinal Circuits and Their Respective Projections to Visual Behaviors" (2022). Arts & Sciences Electronic Theses and Dissertations. 2741.