Document Detail


Prehension of half-full and half-empty glasses: time and history effects on multi-digit coordination.
MedLine Citation:
PMID:  21331525     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We explored how digit forces and indices of digit coordination depend on the history of getting to a particular set of task parameters during static prehension tasks. The participants held in the right hand an instrumented handle with a light-weight container attached on top of the handle. At the beginning of each trial, the container could be empty, filled to the half with water (0.4 l), or filled to the top (0.8 l). The water was pumped in/out of the container at a constant, slow rate over 10 s. At the end of each trial, the participants always held a half-filled container that has just been filled (Empty-Half), emptied (Full-Half) or stayed half-filled throughout the trial (Half-Only). Indices of covariation (synergy indices) of elemental variables (forces and moments of force produced by individual digits) stabilizing such performance variables as total normal force, total tangential force, and total moment of force were computed at two levels of an assumed control hierarchy. At the upper level, the task is shared between the thumb and virtual finger (an imagined digit with the mechanical action equal to that of the four fingers), while at the lower level the action of the virtual finger is shared among the actual four fingers. Filling or emptying the container led to a drop in the safety margin (proportion of grip force over the slipping threshold) below the values observed in the Half-Only condition. Synergy indices at both levels of the hierarchy showed changes over the Full-Half and Empty-Half condition. These changes could be monotonic (typical of moment of force and normal force) or non-monotonic (typical of tangential force). For both normal and tangential forces, higher synergy indices at the higher level of the hierarchy corresponded to lower indices at the lower level. Significant differences in synergy indices across conditions were seen at the final steady state showing that digit coordination during steady holding an object is history dependent. The observations support an earlier hypothesis on a trade-off between synergies at the two levels of a hierarchy. They also suggest that, when a change in task parameters is expected, the neural strategy may involve producing less stable (easier to change) actions. The results suggest that synergy indices may be highly sensitive to changes in a task variable and that effects of such changes persist after the changes are over.
Authors:
Yao Sun; Vladimir M Zatsiorsky; Mark L Latash
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2011-02-18
Journal Detail:
Title:  Experimental brain research     Volume:  209     ISSN:  1432-1106     ISO Abbreviation:  Exp Brain Res     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-03-14     Completed Date:  2011-07-25     Revised Date:  2014-09-20    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  571-85     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Adult
Analysis of Variance
Biomechanical Phenomena / physiology
Female
Hand / physiology
Hand Strength / physiology*
Humans
Male
Psychomotor Performance / physiology*
Grant Support
ID/Acronym/Agency:
AG-018751/AG/NIA NIH HHS; AR-048563/AR/NIAMS NIH HHS; NS-035032/NS/NINDS NIH HHS; R01 NS035032/NS/NINDS NIH HHS; R01 NS035032-15/NS/NINDS NIH HHS
Comments/Corrections

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


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