Influence of movement speed on accuracy and coordination of reaching movements to memorized targets in three-dimensional space in a deafferented subject |
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Authors: | Julie?Messier Sergei?Adamovich Michail?Berkinblit Eugene?Tunik Email author" target="_blank">Howard?PoiznerEmail author |
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Institution: | (1) Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Ave, Newark, NJ 07102, USA,;(2) Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow, Russia,;(3) Département de Kinésiolgie, Université de Montréal, Montreal, Québec, Canada, |
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Abstract: | Multiarticular reaching movements at different speeds produce differential demands for the on-line control of ongoing movements
and for the predictive control of intersegmental dynamics. The aim of this study was to assess the ability of a proprioceptively
deafferented patient and aged-matched control subjects to make precise and coordinated three-dimensional reaching movements
at different speeds without vision during the movement. A patient with a complete loss of proprioception below the neck (C.F.)
and five control subjects made reaching movements to four remembered visual targets at slow, natural, and fast speeds. All
movements were performed without vision of the arm during the movements. The spatial accuracy, the movement kinematics and
the interjoint coordination of these movements were analyzed. Results showed that control subjects made larger spatial errors
at both slow and fast speeds than at natural speed. However, they synchronized motions at the shoulder and elbow joints and
kept most movement kinematic features invariant across speed conditions. In contrast, C.F. failed to produce smooth and simultaneous
motions at the shoulder and elbow joints at all speeds. Surprisingly, however, he made much larger errors than control subjects
at slow and natural speeds, but not at fast speed. Analysis of patterns of interjoint coordination revealed that, when instructed
to move fast, C.F. initiated arm movements by fixing the elbow while moving the shoulder joint to damp interaction torques
exerted on the elbow joint from motion of the upper arm. The results demonstrated that, although proprioceptive loss disrupted
normal control of multijoint movements at all speeds, when performing relatively fast three-dimensional movements, C.F. could
control intersegmental dynamics by reducing the number of active joints. More importantly, the results highlight the dual
role of proprioception in controlling multijoint movements; that is, to provide important cues both for the predictive control
of interaction torques and for the synchronization of adjacent joints even when interactive torques are very small. These
findings support the idea that proprioceptive input is used by the CNS to update an internal model of limb dynamics that adapts
the motor plan according to biomechanical contexts.
Electronic Publication |
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Keywords: | Humans Three-dimensional reaching movements Movement speed Interjoint coordination Deafferentation |
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