Date of Award

Fall 2024

Document Type

Thesis (Ph.D.)

Department or Program

Cognitive Neuroscience

First Advisor

Peter U. Tse

Abstract

Extensive neuroscientific research has advanced our knowledge of the mechanisms involved in the detection and recognition of visual stimuli. However, to guide flexible behavior in a changing world, the brain must also construct stable and coherent perceptual representations from retinal images that are often ambiguous. To resolve ambiguities and uncertainties, the visual system combines its input with other sources of information such as context and prior knowledge to infer the most likely interpretation of a scene. Thus, perception is inherently an inferential process that goes beyond simple detection or recognition of stimuli. Although inference has been studied in many areas of perception, relatively less is known about the neural mechanisms involved in the perception of position and its role in guiding goal-directed behavior. In this dissertation, we used visual illusions to investigate the critical factors that affect the perceptual inference of position, the coordinates used by perception vs. eye movements, and the modulation of these processes by reward-based learning. First, we explored the role of motion signals in the inference of position using the double-drift stimulus. We found that position inference from motion combination in this stimulus occurs more strongly under positional uncertainty. Next, we explored how reference frames can result in relative position encoding in perception and whether these relativistic representations are used by the brain to guide saccadic eye movements. We demonstrated that the perceptual and oculomotor systems are both affected by a moving frame, but to different extents. This presents one of the few findings of dissociable coordinate systems used by these two systems. Lastly, we utilized computational methods to investigate the effects of learning strategies on position inference from motion. Our results showed evidence for encoding of action-based learning strategy in population activity of neurons in the parietal cortex. Furthermore, we found that individual differences in learning strategies were related to the magnitude of saccadic bias toward illusory position. In conclusion, the findings of this Dissertation shed light on the various mechanisms involved in position inference, their role in guiding behavior, and their modulation by high-level processes.

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