The time-course and magnitude of movement-related gating of tactile
detection in humans. I. Importance of stimulus location.
Stephan R. Williams, Jafar Shenasa, and C. Elaine Chapman.
Centre de recherche en sciences neurologiques, Dpartement de physiologie,
and cole de radaptation, Facult de Mdecine, Universit de Montral,
Montral, Qubec, Canada.
APStracts 4:294N, 1997.
ABSTRACT
The time course and spatial extent of movement-related suppression of the
detection of weak electrical stimuli (intensity, 90% detected at rest) was
determined in 118 experiments carried out in 47 human subjects. Subjects were
trained to perform a rapid abduction of the right index finger (D2) in
response to a visual cue. Stimulus timing was calculated relative to the onset
of movement and the onset of electromyographic (EMG) activity. Electrical
stimulation was delivered to 10 different sites on the body, including sites
on the limb performing the movement (D2, D5, hand, forearm and arm) as well as
several distant sites (contralateral arm, ipsilateral leg). Detection of
stimuli applied to the moving digit diminished significantly and in a time-
dependent manner, with the first significant decrease occurring 120 ms before
movement onset and 70 ms before the onset of EMG activity. Movement-related
and time-dependent effects were obtained at all stimulation sites on the
homolateral arm as well as the adjacent trunk. A pronounced spatiotemporal
gradient was observed: the magnitude of the movement-related decrease in
detectability was greatest and earliest at sites closest to the moving finger
and progressively weaker and later at more proximal sites. When stimuli were
applied to the distant sites, only a small (10%), non time-dependent decrease
was observed during movement trials. A simple model of perceptual performance
adequately described the results, providing insight into the distribution of
movement-related inhibitory controls within the central nervous system.
Received 27 March 1997; accepted in final form 15 October 1997.
APS Manuscript Number J257-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997