Document Detail

Interaction of first- and second-order signals in the extraction of global-motion and optic-flow.
MedLine Citation:
PMID:  22819730     Owner:  NLM     Status:  Publisher    
The intention of this series of experiments was to determine the extent to which the pathways sensitive to first-order and second-order motion are independent of one another at, and above, the level of global motion integration. We used translational, radial and rotational motion stimuli containing luminance-modulated dots, contrast-modulated dots, or a mixture of both. Our results show that the two classes of motion stimuli interact perceptually in a global motion coherence task, and the extent of this interaction is governed by whether the two varieties of local motion signal produce an equivalent response in the pathways that encode each type of motion. This provides strong psychophysical evidence that global motion and optic flow processing are cue-invariant. The fidelity of the first-order motion signal was moderated by either reducing the luminance of the dots or by increasing the displacement of the dots on each positional update. The experiments were carried out with two different types of second-order elements (contrast-modulated dots and flicker-modulated dots) and the results were comparable, suggesting that these findings are generalisable to a variety of second-order stimuli. In addition, the interaction between the two different types of second-order stimuli was investigated and we found that the relative modulation depth was also crucial to whether the two populations interacted. We conclude that the relative output of local motion sensors sensitive to either first-order or second-order motion dictates their weight in subsequent cue-invariant global motion computations.
Craig Aaen-Stockdale; Timothy Ledgeway; Paul McGraw; Robert F Hess
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-18
Journal Detail:
Title:  Vision research     Volume:  -     ISSN:  1878-5646     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012. Published by Elsevier Ltd.
McGill Vision Research Unit, Dept. of Ophthalmology, McGill University, Montreal, Quebec, H3A 1A1, Canada; Currently Visiting Research Fellow at the Institute of Optometry & Visual Science, Buskerud University College, 3603 Kongsberg, Norway.
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