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From following edges to pursuing objectsPrimates can generate accurate, smooth eye-movement responses to moving target objects of arbitrary shape and size, even in the presence of complex backgrounds and/or the extraneous motion of non-target objects. Most previous studies of pursuit have simply used a spot moving over a featureless background as the target and have thus neglected critical issues associated with the general problem of recovering object motion. Visual psychophysicists and theoreticians have shown that, for arbitrary objects with multiple features at multiple orientations, object-motion estimation for perception is a complex, multi-staged, time-consuming process. To examine the temporal evolution of the motion signal driving pursuit, we recorded the tracking eye movements of human observers to moving line-figure diamonds. We found that pursuit is initially biased in the direction of the vector average of the motions of the diamond's line segments and gradually converges to the true object-motion direction with a time constant of approximately 90 ms. Furthermore, transient blanking of the target during steady-state pursuit induces a decrease in tracking speed, which, unlike pursuit initiation, is subsequently corrected without an initial direction bias. These results are inconsistent with current models in which pursuit is driven by retinal-slip error correction. They demonstrate that pursuit models must be revised to include a more complete visual afferent pathway, which computes, and to some extent latches on to, an accurate estimate of object direction over the first hundred milliseconds or so of motion.
Document ID
20040088002
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Masson, Guillaume S.
(Centre National de la Recherche Scientifique F13402 Marseille, France)
Stone, Leland S.
Date Acquired
August 21, 2013
Publication Date
November 1, 2002
Publication Information
Publication: Journal of neurophysiology
Volume: 88
Issue: 5
ISSN: 0022-3077
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Neuroscience
NASA Center ARC
Clinical Trial

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