Document Detail

Effect of visual surrounding motion on body sway in a three-dimensional environment.
MedLine Citation:
PMID:  11304016     Owner:  NLM     Status:  MEDLINE    
Unidirectional motion of a uniplanar background induces a codirectional postural sway. It has been shown recently that fixation of a stationary foreground object induces a sway response in the opposite direction (Bronstein & Buckwell, 1997) when the background moves transiently. The present study investigated factors determining this contradirectional postural response. In the experiments presented, center of foot pressure and head displacements were recorded from normal subjects. The subjects faced a visual background of 2 x 3 m, at a distance of 1.5 m, which could be moved parallel to the interaural axis. Results showed that when the visual scene consisted solely of a moving background, the conventional codirectional postural response was elicited. When subjects were asked to fixate an earth-fixed foreground (window frame) placed between them and the moving background, a consistent postural response in the opposite direction to background motion was observed. In addition, we showed that this contradirectional postural response was not transient but was sustained for the 11 sec of background motion. We investigated whether this contradirectional postural response was the consequence of the induced movement of the foreground by background motion. Although induced movement was verbally reported by subjects when viewing an earth-fixed target projected onto the moving background, the contradirectional sway did not occur. These results indicate that foreground-background separation in depth was necessary for the contradirectional postural response to occur rather than induced movement. Another experiment showed that, when the fixated foreground was attached to the head of the observer, the contradirectional sway was not observed and was therefore unrelated to vergence. Finally, results showed that the contradirectional postural response was, in the main, monocularly mediated. We conclude that the direction of the postural sway produced by a moving background in a three-dimensional environment is determined primarily by motion parallax.
M Guerraz; C C Gianna; P M Burchill; M A Gresty; A M Bronstein
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Perception & psychophysics     Volume:  63     ISSN:  0031-5117     ISO Abbreviation:  Percept Psychophys     Publication Date:  2001 Jan 
Date Detail:
Created Date:  2001-04-16     Completed Date:  2001-06-21     Revised Date:  2014-02-19    
Medline Journal Info:
Nlm Unique ID:  0200445     Medline TA:  Percept Psychophys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  47-58     Citation Subset:  IM    
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MeSH Terms
Fixation, Ocular
Middle Aged
Motion Perception*
Grant Support
MC_U950770497//Medical Research Council

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

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