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Proceedings Paper

Transformation of visual direction requires the cognitive visual system
Author(s): Bruce Bridgeman
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Paper Abstract

We differentiate a cognitive branch of the visual system form a sensorimotor branch with the Roelofs effect, a perception that a target's position is biased in the direction opposite the offset of a surrounding fame. When a small fixed target is presented inside a frame that is offset to one side, normal humans perceive the target to be deviated in the direction opposite the frame's offset. They can still jab the target accurately, however, even though it is perceptually mislocalized. This dissociation indicates that motor coordinates are coded in a 'sensorimotor', possibly dorsal, pathway containing visual information that can be inconsistent with perceived information in a 'cognitive', possibly ventral pathway. Lack of a Roelofs effect indicates use of information in the sensorimotor pathway, independent from perception. We ask whether the sensorimotor pathway can handle a transformation of target position, in an anti-jabbing task analogous to anti-saccade tasks: the observer jabs a position symmetrically opposite the target's position, relative to the midline of the head. A 1 deg left or right. Observers were to jab the symmetrically opposite position as soon as the target disappeared. The result was a large and consistent Roelofs effect for an open-loop motor task, indicating that information from the cognitive pathway must be used to perform this task.

Paper Details

Date Published: 8 June 2001
PDF: 6 pages
Proc. SPIE 4299, Human Vision and Electronic Imaging VI, (8 June 2001); doi: 10.1117/12.429512
Show Author Affiliations
Bruce Bridgeman, Univ. of California/Santa Cruz (United States)


Published in SPIE Proceedings Vol. 4299:
Human Vision and Electronic Imaging VI
Bernice E. Rogowitz; Thrasyvoulos N. Pappas, Editor(s)

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