Document Detail

Two virtual fingers in the control of the tripod grasp.
MedLine Citation:
PMID:  11495936     Owner:  NLM     Status:  MEDLINE    
To investigate the organization of multi-fingered grasping, we asked subjects to grasp an object using three digits: the thumb, the index finger, and the middle or ring finger. The object had three coarse flat contact surfaces, whose locations and orientations were varied systematically. Subjects were asked to grasp and lift the object and then to hold it statically. We analyzed the grasp forces in the horizontal plane that were recorded during the static hold period. Static equilibrium requires that the forces exerted by the three digits intersect at a common point, the force focus. The directions of the forces exerted by the two fingers opposing the thumb depended on the orientation of the contact surfaces of both fingers but not on the orientation of the contact surface of the thumb. The direction of the thumb's force did not depend on the orientation of the contact surfaces of the two fingers and depended only weakly on the orientation of the thumb's contact surface. In general, the thumb's force was directed to a point midway between the two fingers. The results are consistent with a hierarchical model of the control of a tripod grasp. At the first level, an opposition space is created between the thumb and a virtual finger located approximately midway between the two actual fingers. The directions of the forces exerted by the two fingers are constrained to be mirror symmetric about the opposition axis. The actual directions of finger force are elaborated at the next level on the basis of stability considerations.
G Baud-Bovy; J F Soechting
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  86     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2001 Aug 
Date Detail:
Created Date:  2001-08-09     Completed Date:  2001-09-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  604-15     Citation Subset:  IM    
Department of Neuroscience, University of Minnesota, Minneapolis 55455, USA.
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MeSH Terms
Fingers / physiology*
Hand Strength / physiology*
Middle Aged
Thumb / physiology*
User-Computer Interface*
Grant Support

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