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UBC Theses and Dissertations

Visual, vestibular, and proprioceptive contributions to the perception of upright Corbett, Jennifer E.

Abstract

This dissertation examines the integration of visual and bodily inputs for the perception of upright. Normally, we effortlessly integrate external cues from surfaces in the visual environment and internal bodily position signals to accurately determine which way is "up." However, when sensory signals conflict, we base our perceptions of gravitational upright on visual references in the external environment. While tilting the body further decreases the ability to accurately perceive upright in the presence of a tilted visual context, the precise ways in which multisensory inputs to upright are integrated under these circumstances remain undetermined. Chapter 2 examines this question by isolating the effects of tilting the head or the whole body on perceived upright. Findings reveal a hierarchy of sensory contributions to the perception of upright where visual cues are weighted most heavily, followed by vestibular input about head position, and then proprioceptive signals about the position of the body when both visual and vestibular cues are unreliable. Chapter 3 then examines the amount of time necessary to overcome tilt illusions induced by local context in close proximity to a stimulus as compared to spatially remote global context. Results show different time courses for each type of illusion, and suggest the existence of distinct mechanisms involved in each. Chapter 4 follows with an ERP investigation to show that vestibular context influences later, post-perceptual stages of visual processing, as indexed by a modulation of the P3 ERP component. The thesis concludes with a summary of the main findings and outstanding questions, followed by an expanded discussion of how visual, vestibular, and proprioceptive inputs are hierarchically integrated to maintain a stable percept of our dynamic surroundings.

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