Pulsatile motor output in human finger movements is not dependent on the stretch reflex

1. Stretch perturbations were delivered during slow voluntary finger movements with the aim of exploring the role of the stretch reflex in generating the 8-10 Hz discontinuities that characterize these movements. Afferent activity from muscle spindle primary endings in the finger extensor muscles wa...

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Bibliographic Details
Published in:The Journal of physiology 1996-06, Vol.493 (Pt 3), p.895-908
Main Authors: Wessberg, J, Vallbo, A B
Format: Article
Language:English
Subjects:
Adult
Electromyography
Female
Fingers
Fingers - innervation
Fingers - physiology
Fysiologi och anatomi
Humans
innervation
Male
Motor Neurons
Motor Neurons - physiology
Movement
Movement - physiology
physiology
Physiology and Anatomy
Reflex
Reflex, Stretch - physiology
Space life sciences
Stretch
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Summary:1. Stretch perturbations were delivered during slow voluntary finger movements with the aim of exploring the role of the stretch reflex in generating the 8-10 Hz discontinuities that characterize these movements. Afferent activity from muscle spindle primary endings in the finger extensor muscles was recorded from the radial nerve, along with the EMG activity of these muscles, and kinematics of the relevant metacarpo-phalangeal joint. 2. Perturbations elicited a distinct response from the muscle spindles appearing at the recording electrode after 13 ms, and weak reflex responses from the muscle with peak values at 53 and 63 ms during flexion and extension, respectively. 3. The time relations between kinematics, spindle firing and modulations of EMG activity elicited by the perturbations were compared with those of the self-generated discontinuities. These analyses indicate that stretch reflex mechanisms cannot account for the modulations of EMG activity that give rise to successive 8-10 Hz discontinuities. 4. A comparison of the reflex responses to perturbations with the EMG modulations during self-generated movements indicates that the reflex was too weak to account for the pulsatile motor output during voluntary movements. 5. By inference it was concluded that the 8-10 Hz discontinuities during self-generated movements are probably generated by mechanisms within the central nervous system.
ISSN:0022-3751
1469-7793
DOI:10.1113/jphysiol.1996.sp021432