Human involuntary postural aftercontractions are strongly modulated by limb position

Adamson, Grant; McDonagh, Martin

doi:10.1007/s00421-004-1091-8

Cited by 12 publications

(9 citation statements)

References 23 publications

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“…A single EMG trace from a single participant in an earlier paper shows, but does not quantify, a similar phenomenon (Forbes et al, 1926 ). Later work examined the effect of stopping the Kohnstamm at different arm angles (Adamson and McDonagh, 2004 ), but (a) did not include an unobstructed condition, and (b) focused on the EMG level at each angle of arm abduction, rather than how contacting an obstacle affects EMG in the time domain. By comparing obstruction and no obstruction trials, we showed for the first time that it is the obstruction, and associated afferent input, that causes the change in EMG signal.…”

Section: Methodsmentioning

confidence: 99%

“…The Kohnstamm phenomenon has been interpreted as a result of neural adaptation within a postural control system (Gurfinkel et al, 1989 ; Ghafouri et al, 1998 ; Duclos et al, 2004 , 2007 ; Parkinson and McDonagh, 2006 ). The postural control system is thought to maintain a reference value of motor activity against external perturbation or voluntary movement (Massion, 1992 ; Adamson and McDonagh, 2004 ). This implies an ability to adjust to transient afferent input, before returning to the desired level of motor output.…”

Section: Introductionmentioning

confidence: 99%

“…Forbes et al ( 1926 ) reported that contacting an obstacle does not abolish the aftercontraction. Adamson and McDonagh ( 2004 ) reported that blocking the rising arm resulted in a constant EMG whose amplitude was proportional to the arm angle at the time of the block. However, these studies did not address how this sensory information regarding obstruction might affect the Kohnstamm generator.…”

Section: Introductionmentioning

confidence: 99%

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Sensorimotor organization of a sustained involuntary movement

Havas

Ghosh

Gomi

et al. 2015

Front. Behav. Neurosci.

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Involuntary movements share much of the motor control circuitry used for voluntary movement, yet the two can be easily distinguished. The Kohnstamm phenomenon (where a sustained, hard push produces subsequent involuntary arm raising) is a useful experimental model for exploring differences between voluntary and involuntary movement. Both central and peripheral accounts have been proposed, but little is known regarding how the putative Kohnstamm generator responds to afferent input. We addressed this by obstructing the involuntary upward movement of the arm. Obstruction prevented the rising EMG pattern that characterizes the Kohnstamm. Importantly, once the obstruction was removed, the EMG signal resumed its former increase, suggesting a generator that persists despite peripheral input. When only one arm was obstructed during bilateral involuntary movements, only the EMG signal from the obstructed arm showed the effect. Upon release of the obstacle, the obstructed arm reached the same position and EMG level as the unobstructed arm. Comparison to matched voluntary movements revealed a preserved stretch response when a Kohnstamm movement first contacts an obstacle, and also an overestimation of the perceived contact force. Our findings support a hybrid central and peripheral account of the Kohnstamm phenomenon. The strange subjective experience of this involuntary movement is consistent with the view that movement awareness depends strongly on efference copies, but that the Kohnstamm generator does not produces efference copies.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sensorimotor organization of a sustained involuntary movement

Havas

Ghosh

Gomi

et al. 2015

Front. Behav. Neurosci.

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“…The Kohnstamm phenomenon offers one example. Here, a strong, sustained isometric contraction of a muscle produces, upon relaxation, a slow, involuntary aftercontraction that is associated with a subjective feeling of lightness and a lack of agency (Adamson & McDonagh, 2004;Craske & Craske, 1985;Forbes, Baird, & Hopkins, 1926;Kohnstamm, 1915;Salmon, 1916).…”

Section: Introductionmentioning

confidence: 99%

Voluntary motor commands reveal awareness and control of involuntary movement

et al. 2016

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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 ∼2s. 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.

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“…We found that the strength of the aftercontraction depends on both load and joint angle. Earlier experiments revealed that the size of the response increased with muscle shortening and decreased with muscle lengthening ( Adamson & McDonagh, 2004) .This is very reminiscent of Sherrington's shortening and lengthening reactions and also to the release of muscle cramps by stretching. Perhaps they share a common mechanism?…”

Section: Features Pnmentioning

confidence: 79%

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2009

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Human involuntary postural aftercontractions are strongly modulated by limb position

Cited by 12 publications

References 23 publications

Sensorimotor organization of a sustained involuntary movement

Sensorimotor organization of a sustained involuntary movement

Voluntary motor commands reveal awareness and control of involuntary movement

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