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Voluntary motor commands reveal awareness and control of involuntary movement

De Havas, J; Ghosh, A; Gomi, H; Haggard, P; (2016) Voluntary motor commands reveal awareness and control of involuntary movement. Cognition , 155 pp. 155-167. 10.1016/j.cognition.2016.06.012. Green open access

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Abstract

The capacity to inhibit actions is central to voluntary motor control. However, the control mechanisms and subjective experience involved in voluntarily stopping an involuntary movement remain poorly understood. Here we examined, in humans, the voluntary inhibition of the Kohnstamm phenomenon, in which sustained voluntary contraction of shoulder abductors is followed by involuntary arm raising. Participants were instructed to stop the involuntary movement, hold the arm in a constant position, and ‘release’ the inhibition after ∼2 s. Participants achieved this by modulating agonist muscle activity, rather than by antagonist contraction. Specifically, agonist muscle activity plateaued during this voluntary inhibition, and resumed its previous increase thereafter. There was no discernible antagonist activation. Thus, some central signal appeared to temporarily counter the involuntary motor drive, without directly affecting the Kohnstamm generator itself. We hypothesise a form of “negative motor command” to account for this novel finding. We next tested the specificity of the negative motor command, by inducing bilateral Kohnstamm movements, and instructing voluntary inhibition for one arm only. The results suggested negative motor commands responsible for inhibition are initially broad, affecting both arms, and then become focused. Finally, a psychophysical investigation found that the perceived force of the aftercontraction was significantly overestimated, relative to voluntary contractions with similar EMG levels. This finding is consistent with the hypothesis that the Kohnstamm generator does not provide an efference copy signal. Our results shed new light on this interesting class of involuntary movement, and provide new information about voluntary inhibition of action.

Type: Article
Title: Voluntary motor commands reveal awareness and control of involuntary movement
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.cognition.2016.06.012
Publisher version: https://doi.org/10.1016/j.cognition.2016.06.012
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Motor control, Involuntary movement, Inhibition, Action awareness, Bilateral movement, Negative motor command
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences > Institute of Cognitive Neuroscience
URI: https://discovery.ucl.ac.uk/id/eprint/10042702
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