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Stimulus configuration determines the detectability of motion signals in noiseWe measured the detectability of moving signal dots in dynamic noise to determine whether local motion signals are preferentially combined along an axis parallel to the direction of motion. Observers were asked to detect a signal composed of three dots moving in a linear trajectory among dynamic noise dots. The signal dots were collinear and equally spaced in a configuration that was either parallel to or perpendicular to their trajectory. The probability of detecting the signal was measured as a function of noise density, over a range of signal dot spacings from 0.5 degrees to 5.0 degrees. At any given noise density, the signal in the parallel configuration was more detectable than that in the perpendicular configuration. Our four observers could tolerate 1.5-2.5 times more noise in the parallel configuration. This improvement is not due merely to temporal summation between consecutive dots in the parallel trajectory. Temporal summation functions measured on our observers indicate that the benefit from spatial coincidence of the dots lasts for no more than 50 ms, whereas the increased detectability of the parallel configuration is observed up to the largest temporal separations tested (210 ms). These results demonstrate that dots arranged parallel to the signal trajectory are more easily detected than those arranged perpendicularly. Moreover, this enhancement points to the existence of visual mechanisms that preferentially organize motion information parallel to the direction of motion.
Document ID
20040141412
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Verghese, P.
(Smith Kettlewell Eye Research Institute San Francisco, California 94115, United States)
McKee, S. P.
Grzywacz, N. M.
Date Acquired
August 22, 2013
Publication Date
September 1, 2000
Publication Information
Publication: Journal of the Optical Society of America. A, Optics, image science, and vision
Volume: 17
Issue: 9
ISSN: 1084-7529
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Space Human Factors

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