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  Velocity tuned mechanisms in human motion processing

Reisbeck, T., & Gegenfurtner, K. (1999). Velocity tuned mechanisms in human motion processing. Vision Research, 39(19), 3267-3286. doi:10.1016/S0042-6989(99)00017-6.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-E633-1 Version Permalink: http://hdl.handle.net/21.11116/0000-0005-BF7B-B
Genre: Journal Article

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Reisbeck, TE1, 2, Author              
Gegenfurtner, KR1, 2, Author              
Affiliations:
1Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497797              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              

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 Abstract: We determined two-dimensional motion discrimination contours in the spatio-temporal frequency plane to characterize the mechanisms underlying velocity perception. In particular, we wanted to determine whether there exist mechanisms tuned specifically to velocity, rather than separable mechanisms tuned to spatial and temporal frequency. A 4-AFC paradigm was used to determine spatio-temporal frequency discrimination thresholds for moving sinewave gratings defined by luminance contrast. Three of the grating patches used were defined by the same spatial and temporal frequency (standard), the other (test) differed by a fixed proportional change in spatial and temporal frequency. Subjects had to indicate which grating differed most from the others and the thresholds determined for varying proportions of change in spatial and temporal frequency were used to trace out complete threshold contours in the plane spanned by these attributes. Some of the contours, primarily at speeds above 1 deg/s, were noticeably oriented along lines of constant velocity. To further isolate these mechanisms, spatio-temporal noise was added to the standard stimuli either along a line of constant velocity or in the direction orthogonal to it. When spatio-temporal noise of constant velocity was added to the standard stimuli, threshold contours became elongated only along the direction of the noise. The same amount of noise in the orthogonal direction produced an overall increase in thresholds without changing the shape of the contour, presenting clear evidence for velocity tuned mechanisms. In further experiments we discovered that velocity tuned mechanisms interact with separable mechanisms to produce optimal discriminability. Analogous experiments with isoluminant stimuli failed to exhibit evidence for velocity tuning, supporting the notion that the human color vision system is impaired in its coding of stimulus speed, despite excellent sensitivity to direction of motion.

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 Dates: 1999-10
 Publication Status: Published in print
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 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1016/S0042-6989(99)00017-6
BibTex Citekey: 211
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Title: Vision Research
  Other : Vision Res.
Source Genre: Journal
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Publ. Info: Amsterdam : Pergamon
Pages: - Volume / Issue: 39 (19) Sequence Number: - Start / End Page: 3267 - 3286 Identifier: ISSN: 0042-6989
CoNE: https://pure.mpg.de/cone/journals/resource/954925451842