Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/11933
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Type: Journal article
Title: Control of motor units in human flexor digitorum profundus in different hand postures
Author: Garland, S.
Miles, T.
Citation: Journal of Physiology, 1997; 502(3):693-701
Publisher: CAMBRIDGE UNIV PRESS
Issue Date: 1997
ISSN: 0022-3751
1469-7793
Abstract: 1. Changing the posture of the human fingers can functionally 'disengage' the deep finger flexor muscle from its normal action on the terminal phalanx of the fourth (or third) finger. This enables the activity of the muscle to be studied both with and without its normal proprioceptive inputs. 2. Spike trains of long duration from pairs of concurrently active motor units in this muscle were recorded in both the engaged and disengaged hand postures. Subjects voluntarily kept one of the motor units (the 'controlled' unit) discharging at the same target frequency in both postures. The strength of short-term synchrony, the strength of common drive, and the variability of discharge of these pairs of motor units were determined in both postures. 3. All subjects reported that the effort required to activate the motor units in the disengaged hand posture was substantially greater than in the normal engaged posture. 4. Short-term synchrony, which is a function of common corticospinal inputs to pairs of motor units, was similar in both hand postures. However, the strength of common drive was significantly decreased when the muscle was disengaged. Although the neural substrate for common drive is not known, this observation suggests that proprioceptive feedback is involved either directly or indirectly. 5. Although the discharge rate of the 'uncontrolled' motor units increased when the muscle was disengaged, the variability of discharge of these and the 'controlled' motor units increased significantly. This supports the idea that the precision with which fine motor tasks can be performed is improved when proprioceptive feedback is intact.
Keywords: Fingers; Muscle, Skeletal; Motor Neurons; Humans; Electromyography; Proprioception; Action Potentials; Muscle Contraction; Adult; Middle Aged; Female; Male
RMID: 0030004085
DOI: 10.1111/j.1469-7793.1997.693bj.x
Appears in Collections:Physiology publications

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