Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Clark, Damon

Abstract

Animals must infer the three-dimensional structure of their environment from twodimensional retinal images. They use visual cues like motion parallax and binocular disparity to judge distances to objects, and studies across several animal models have foundand characterized neural signals that correlate with visual distance. However, the causal role of these neurons in distance estimation and the range of their possible neural properties remain poorly understood. Here we show that both directional and non-directional feature-selective neurons in the Drosophila visual system are involved in distance estimation during free locomotion. We used a high-throughput behavioral assay to perform a targeted silencing screen of visual neurons, and we subsequently characterized them using in vivo two-photon microscopy, thus linking distance perception behavior directly to neural signals. Silencing the primary motion detectors eliminated distance-dependent behavior, consistent with a reliance on motion parallax. Our screen also identified a visual featuredetecting neuron that encodes motion parallax non-canonically: it is not direction-selective for object or background motion, but it is tuned to the relative speeds of foreground and background, resulting in a signal that can measure relative distance. Our results demonstrate the behavioral role of distance-tuned neurons in the fly and provide a framework for considering broader classes of parallax-encoding neurons across models of vision.

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