Mechanisms of global visual stability across eye… (F32EY038561) – Project Grant to New York University

Abstract: Current scientific understanding of visual processing relies primarily on experiments that assume passive vision: an observer fixates their gaze, and an experimenter controls what is perceived. However, natural vision is built up across frequent but discrete eye movements (saccades) whose dynamics control the contents of perception just as much as stimulus manipulations. Saccades constantly alter how we view the 3D arrangement of every single visible element in a scene yet, surprisingly, the flow of visual experience is devoid of disorienting jumps or spatial misalignment. This intriguing phenomenon, trans-saccadic stability, is a form of change blindness, whereby changes to sensory input are not consciously noticed. The ubiquity of saccades (2- 3 per second) suggests that the processes governing trans-saccadic change detection and change blindness are fundamental to natural vision. However, despite a wealth of behavioral work, little is known about their neural mechanisms. This GAP is worrying given growing evidence for clinical deficits in perceiving the relational structure of scene elements, particularly in amnesic patients with damage to the medial temporal lobe. This project aims to characterize a physiological system for visual change detection, governed by saccade dynamics, that explains both trans-saccadic stability and these currently unexplained visuospatial perceptual abnormalities in neurological conditions. Detecting or ignoring visual changes requires comparing sensory input to a memory buffer of recent visual experience. This proposal introduces a new approach to trans-saccadic stability that focuses on detecting changes of global spatial structure-the 3D arrangement of all scene landmarks and objects. Namely, IT is unclear a) how saccades configure memory buffers of global structure, b) what neural mechanisms underlie global change detection, and c) whether these mechanisms differ from those for detecting changes to individual object features. We hypothesize that eye movements differently control two spatiotemporally distinct neural systems for local (individual objects) and global (spatial structure) change detection. To test this, we will measure eye movements, gaze position, and whole-brain neural activity while human participants freely view images of natural scenes and report when they notice stimulus changes. We will build computational models of how eye movements influence change detection (aim 1) and characterize the neural representational mechanisms of global and local change detection (aims 2 and 3). This work will contribute to our understanding of natural vision and give insight into clinical deficits in gaze control and visual perception, providing targets for novel oculomotor therapies or neurostimulation treatments. The fellowship plan features training in advanced computational modeling and fmri-MEG representational analyses new to the candidate, naturalistic experiment design, structured professional development and teaching workshops, and intellectual input from a collaborative, interdisciplinary community across NYU.

Mechanisms of global visual stability across eye movements

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