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Speed tuning of motion segmentation and discriminationMotion transparency requires that the visual system distinguish different motion vectors and selectively integrate similar motion vectors over space into the perception of multiple surfaces moving through or over each other. Using large-field (7 degrees x 7 degrees) displays containing two populations of random-dots moving in the same (horizontal) direction but at different speeds, we examined speed-based segmentation by measuring the speed difference above which observers can perceive two moving surfaces. We systematically investigated this 'speed-segmentation' threshold as a function of speed and stimulus duration, and found that it increases sharply for speeds above approximately 8 degrees/s. In addition, speed-segmentation thresholds decrease with stimulus duration out to approximately 200 ms. In contrast, under matched conditions, speed-discrimination thresholds stay low at least out to 16 degrees/s and decrease with increasing stimulus duration at a faster rate than for speed segmentation. Thus, motion segmentation and motion discrimination exhibit different speed selectivity and different temporal integration characteristics. Results are discussed in terms of the speed preferences of different neuronal populations within the primate visual cortex.
Document ID
20040141583
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Masson, G. S.
(Centre de Recherche en Neurosciences Cognitives Marseille, France)
Mestre, D. R.
Stone, L. S.
Date Acquired
August 22, 2013
Publication Date
October 1, 1999
Publication Information
Publication: Vision research
Volume: 39
Issue: 26
ISSN: 0042-6989
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center ARC
NASA Discipline Neuroscience

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