The Time Course of the Integration of Visual Information into the Egocentric Reference Frame
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Date
2020-12-08
Authors
Peterson, Jeffrey
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Publisher
University of Oregon
Abstract
An important function of the visual system is to identify and localize objects within our environment. This task is often facilitated by accounting for the broader visual context in which the object is embedded. However, the modular nature of visual processing and the various neural transmission delays across the visual cortex suggests that the analysis of an object and its context might proceed in an asynchronous fashion.
The experiments presented in this dissertation were designed to assess the time course by which visual context is integrated with the egocentric reference frame. We presented observers with the tilted frame of the rod-and-frame illusion, which, once integrated with the egocentric reference, induces a bias in subjective vertical. To determine the latency between the presentation of the frame and its initial effect on subjective vertical, we assessed participants’ perception of vertical at various times before and after the onset of the tilted frame.
Chapter II describes two experiments in which perceived vertical was assessed with an orientation judgment of a briefly flashed rod. This experiment produced the surprising result that the perceived orientation of a rod presented before frame onset was biased by the direction of the frame’s tilt. We proposed a differential latencies model to account for this result. Specifically, that the latency between the presentation of the rod and the completion of the orientation judgment is longer than the delay between the onset of the frame and its initial effect on perceived vertical. Experiment 2 in this chapter provides a test of this model. Chapter III describes a similar experiment; however, subjective vertical was assessed with a vertically-directed saccadic eye movement. The earliest effect of the tilted frame was observed in saccades initiated 100 ms after frame onset.
The results of our experiments suggest that contextual visual information is rapidly integrated within the egocentric reference frame, where it subsequently shapes our perceptual judgments and guides our actions. The speed of this integration suggests that visual context relevant to global orientation is processed during the initial feedforward sweep of activation ascending the visual hierarchy.
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Keywords
differential latencies, perception and action, reference frame, rod-and-frame, subjective vertical, visual context