Document Detail

Load compensation in targeted limb movements of an insect.
MedLine Citation:
PMID:  12909699     Owner:  NLM     Status:  MEDLINE    
The task of a multi-jointed limb making an aimed movement towards a target requires that the movement is regulated against external perturbations such as changing load. In particular, loading one part of a limb leads to altered static forces on all proximal segments, and to additional dynamic joint interaction forces when the limb moves. We have addressed the question of load compensation in an insect preparation in which a locust makes aimed scratching movements with a hind leg in response to tactile stimulation of a wing. We show that loading the femur or tibia with the equivalent of 8.5 times the mass of the tibia (corresponding to an increase of up to 11.6 times the rotational moment of inertia at the femur-tibia joint) does not impair the animal's ability to make well-coordinated, aimed movements of that leg towards different targets. The kinematics of the movements are the same, and animals aim the same part of their distal tibia at the target, regardless of loading. The movements are carried out with equal accuracy and at the same initial velocity under all load conditions. Because loading of the leg does not change the behavioural performance, there is no indication of a change in aiming strategy. This implies high leg joint stiffness and/or the existence of high gain proprioceptive control loops. We have previously shown that in the unloaded condition, movements elicited by stimuli to different places on the wing are driven by a single underlying movement pattern that shifts depending on stimulus location along the wing surface. Our present data show that leg proprioceptive inputs are also integrated into the leg motor networks, rendering hind limb targeting robust against large changes in moment of inertia.
Tom Matheson; Volker Dürr
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  206     ISSN:  0022-0949     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-08-11     Completed Date:  2004-05-24     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3175-86     Citation Subset:  IM    
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
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MeSH Terms
Extremities / physiology*
Motor Activity / physiology*
Orthoptera / physiology*
Physical Stimulation
Proprioception / physiology*

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