Document Detail


Movement direction analysers: independence and bandwidth.
MedLine Citation:
PMID:  8351848     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Opponent, or ratio, models of movement direction perception propose that pairs of analysers, sensitive to opposite directions, are linked in an opponent fashion. Alternatively, distribution models posit independence of movement direction analysers. To investigate analyser independence, a direction-selective adaptation experiment was conducted in which motion coherence thresholds for random-dot apparent motion stimuli were measured for upward, downward, leftward and rightward motion with and without prior adaptation to rightward motion. Coherence thresholds for rightward motion were elevated on average by 0.64 log units after adaptation. Thresholds for motion in the other directions remained unchanged. Since opponent models predict enhanced sensitivity after adaptation for the direction opposite that of adaptation, these results suggest that movement direction analysers operate independently. In a second experiment subjects adapted to a bidirectional stimulus containing an equal number of leftward and rightward moving dots. Leftward and rightward coherence thresholds were elevated even though no motion aftereffects were produced. A third experiment in which coherence thresholds for test directions within a narrow range were measured with and without prior adaptation to motion in the direction of the range's mean showed that threshold elevation was maximal when test and adaptation direction were matched and fell off as the difference in adaptation and test direction increased. The resulting functions indicate that the bandwidth of movement direction analysers is between +/- 35 and +/- 40 deg, a value consistent with reported mean directional tuning functions of movement sensitive units in the middle temporal area but smaller than previously reported psychophysical values.
Authors:
J E Raymond
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Vision research     Volume:  33     ISSN:  0042-6989     ISO Abbreviation:  Vision Res.     Publication Date:    1993 Mar-Apr
Date Detail:
Created Date:  1993-09-10     Completed Date:  1993-09-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  767-75     Citation Subset:  IM; S    
Affiliation:
Department of Psychology, University of Calgary, Alberta, Canada.
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Ocular / physiology
Adolescent
Adult
Female
Humans
Male
Models, Psychological
Motion Perception / physiology*
Sensory Thresholds / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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