Document Detail

Effects of distance and gaze position on postural stability in young and old subjects.
MedLine Citation:
PMID:  16525804     Owner:  NLM     Status:  MEDLINE    
Visual stabilization of posture is known to improve when the distance to target fixation decreases; this is attributed to increased angular size of retinal slip induced by body sway. At near distance, however, the eyes converge and efferent or afferent oculomotor signals could also be involved in posture stabilization. The goal of this study is to test whether the distance effect exists for both young and elderly and to test the role of vergence itself and of gaze position. Eighteen young (25.3 years) and 17 elderly (61.6 years) subjects were asked to fixate a target in quiet stance presented either at close (40 cm) or at far distance (200 cm); the vergence angle was 9 degrees and 2 degrees , respectively. For each distance, three gaze positions were studied straight-ahead (0 degrees ), 15 degrees up or down. We found a decrease in the surface of center of pressure (CoP), of standard deviation of antero-posterior and lateral body sway and of speed variance at near distance that occurs for both young and elderly. At far distance, the surface of CoP is smaller for 15 degrees up or down gaze in comparison with straight-ahead position, but at near distance there is no such gaze position effect. In an additional experiment, subjects fixated a target at far distance (200 cm) but prisms were used to cause the eyes to converge by an amount similar to that required for 40 cm viewing distance. The use of prisms decreased surface of CoP to values similar to those for natural near viewing distance. The effect of gaze position and of convergence (experiment with prisms) leads us to suggest that in addition to retinal slip, the ocular motor signals and perhaps related neck muscle activity are involved in postural stabilization. Finally, the elderly presented higher speed variance of CoP than the young subjects even though the surface itself was similar to adult values. We suggest that increment of speed variance is the first sign of senescence in postural control.
Zoï Kapoula; Thanh-Thuan Lê
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-03-09
Journal Detail:
Title:  Experimental brain research     Volume:  173     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  2006 Aug 
Date Detail:
Created Date:  2006-08-11     Completed Date:  2006-11-14     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  438-45     Citation Subset:  IM    
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MeSH Terms
Adaptation, Physiological / physiology
Aging / physiology*
Distance Perception / physiology*
Fixation, Ocular / physiology*
Middle Aged
Motion Perception / physiology
Neck Muscles / innervation,  physiology
Oculomotor Muscles / innervation,  physiology
Posture / physiology*
Visual Perception / physiology

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