Bimanual reflexes during shared bimanual tasks are asymmetric

Jacob E Schaffer, Robert L. Sainburg

Research output: Contribution to conferenceAbstract

Abstract

Previous research has shown that during a bilateral task in which both arms carry a single virtual object, perturbation to the dominant arm produces reflexive responses in the non-dominant arm shoulder muscles. However, when the same bilateral motions are performed without a common object, bilateral reflex responses are absent (Mutha and Sainburg, 2009). These findings indicate task dependent modulation of both short and long latency components of the stretch reflex, which is likely mediated by descending influences on spinal circuitry. Given substantial asymmetries in hemispheric control of arm movement, we now ask whether task-dependent bilateral reflexes are symmetric. We tested this question using a virtual object manipulation task. In a virtual reality environment, a cursor representing each hand is used to ‘pick up’ each end of a bar and “drag” it to a target. At the onset of occasional and unpredictable trials, a solenoid engaged for 200 milliseconds, preventing motion along the antero-posterior axis for one of the arms. This prevented ongoing extension of the elbow and resulted in acceleration of the shoulder into horizontal adduction. Thus, the effect of the perturbation was to ‘stretch’ the shortening triceps brachii, as well as the lengthening posterior deltoid (relative to baseline movements). We binned muscle activity into 2 intervals, relative to the initiation of the perturbation: 1) short latency (20-45 ms) and 2) long latency (46-75 ms). We compared muscle activity in these two bins to the corresponding activity in non-perturbed trials. This comparison was done for both the ipsilateral perturbed arm and in the contralateral unperturbed arm. Unilateral responses in the ipsilateral arm: Regardless of which arm was perturbed, ipsilateral responses were similar: Short latency responses were significant in the posterior deltoid, while long latency responses were significant in the triceps brachii. However short latency responses in triceps only reached significance in the dominant (right) arm. Bilateral responses in the contralateral arm: The non-dominant posterior deltoid showed significant short and long latency reflex responses. However, for the dominant arm, short and long latency intervals were not significantly different from that of non-perturbed trials. Thus, bilateral reflex responses to unilateral perturbations are asymmetric, such that the non-dominant arm responds to perturbations of the dominant arm, but not vice versa. Mutha PK, Sainburg RL. Shared bimanual tasks elicit bimanual reflexes during movement. J Neurophys. 2009;102(6):3142-3155.
Original languageEnglish (US)
StatePublished - 2017

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Reflex
Arm
Reaction Time
Muscles
Stretch Reflex
Abnormal Reflexes
Elbow
Hand

Cite this

@conference{7f8d625cca1f4383a5ca25c30c41f1e9,
title = "Bimanual reflexes during shared bimanual tasks are asymmetric",
abstract = "Previous research has shown that during a bilateral task in which both arms carry a single virtual object, perturbation to the dominant arm produces reflexive responses in the non-dominant arm shoulder muscles. However, when the same bilateral motions are performed without a common object, bilateral reflex responses are absent (Mutha and Sainburg, 2009). These findings indicate task dependent modulation of both short and long latency components of the stretch reflex, which is likely mediated by descending influences on spinal circuitry. Given substantial asymmetries in hemispheric control of arm movement, we now ask whether task-dependent bilateral reflexes are symmetric. We tested this question using a virtual object manipulation task. In a virtual reality environment, a cursor representing each hand is used to ‘pick up’ each end of a bar and “drag” it to a target. At the onset of occasional and unpredictable trials, a solenoid engaged for 200 milliseconds, preventing motion along the antero-posterior axis for one of the arms. This prevented ongoing extension of the elbow and resulted in acceleration of the shoulder into horizontal adduction. Thus, the effect of the perturbation was to ‘stretch’ the shortening triceps brachii, as well as the lengthening posterior deltoid (relative to baseline movements). We binned muscle activity into 2 intervals, relative to the initiation of the perturbation: 1) short latency (20-45 ms) and 2) long latency (46-75 ms). We compared muscle activity in these two bins to the corresponding activity in non-perturbed trials. This comparison was done for both the ipsilateral perturbed arm and in the contralateral unperturbed arm. Unilateral responses in the ipsilateral arm: Regardless of which arm was perturbed, ipsilateral responses were similar: Short latency responses were significant in the posterior deltoid, while long latency responses were significant in the triceps brachii. However short latency responses in triceps only reached significance in the dominant (right) arm. Bilateral responses in the contralateral arm: The non-dominant posterior deltoid showed significant short and long latency reflex responses. However, for the dominant arm, short and long latency intervals were not significantly different from that of non-perturbed trials. Thus, bilateral reflex responses to unilateral perturbations are asymmetric, such that the non-dominant arm responds to perturbations of the dominant arm, but not vice versa. Mutha PK, Sainburg RL. Shared bimanual tasks elicit bimanual reflexes during movement. J Neurophys. 2009;102(6):3142-3155.",
author = "Schaffer, {Jacob E} and Sainburg, {Robert L.}",
year = "2017",
language = "English (US)",

}

Bimanual reflexes during shared bimanual tasks are asymmetric. / Schaffer, Jacob E; Sainburg, Robert L.

2017.

Research output: Contribution to conferenceAbstract

TY - CONF

T1 - Bimanual reflexes during shared bimanual tasks are asymmetric

AU - Schaffer, Jacob E

AU - Sainburg, Robert L.

PY - 2017

Y1 - 2017

N2 - Previous research has shown that during a bilateral task in which both arms carry a single virtual object, perturbation to the dominant arm produces reflexive responses in the non-dominant arm shoulder muscles. However, when the same bilateral motions are performed without a common object, bilateral reflex responses are absent (Mutha and Sainburg, 2009). These findings indicate task dependent modulation of both short and long latency components of the stretch reflex, which is likely mediated by descending influences on spinal circuitry. Given substantial asymmetries in hemispheric control of arm movement, we now ask whether task-dependent bilateral reflexes are symmetric. We tested this question using a virtual object manipulation task. In a virtual reality environment, a cursor representing each hand is used to ‘pick up’ each end of a bar and “drag” it to a target. At the onset of occasional and unpredictable trials, a solenoid engaged for 200 milliseconds, preventing motion along the antero-posterior axis for one of the arms. This prevented ongoing extension of the elbow and resulted in acceleration of the shoulder into horizontal adduction. Thus, the effect of the perturbation was to ‘stretch’ the shortening triceps brachii, as well as the lengthening posterior deltoid (relative to baseline movements). We binned muscle activity into 2 intervals, relative to the initiation of the perturbation: 1) short latency (20-45 ms) and 2) long latency (46-75 ms). We compared muscle activity in these two bins to the corresponding activity in non-perturbed trials. This comparison was done for both the ipsilateral perturbed arm and in the contralateral unperturbed arm. Unilateral responses in the ipsilateral arm: Regardless of which arm was perturbed, ipsilateral responses were similar: Short latency responses were significant in the posterior deltoid, while long latency responses were significant in the triceps brachii. However short latency responses in triceps only reached significance in the dominant (right) arm. Bilateral responses in the contralateral arm: The non-dominant posterior deltoid showed significant short and long latency reflex responses. However, for the dominant arm, short and long latency intervals were not significantly different from that of non-perturbed trials. Thus, bilateral reflex responses to unilateral perturbations are asymmetric, such that the non-dominant arm responds to perturbations of the dominant arm, but not vice versa. Mutha PK, Sainburg RL. Shared bimanual tasks elicit bimanual reflexes during movement. J Neurophys. 2009;102(6):3142-3155.

AB - Previous research has shown that during a bilateral task in which both arms carry a single virtual object, perturbation to the dominant arm produces reflexive responses in the non-dominant arm shoulder muscles. However, when the same bilateral motions are performed without a common object, bilateral reflex responses are absent (Mutha and Sainburg, 2009). These findings indicate task dependent modulation of both short and long latency components of the stretch reflex, which is likely mediated by descending influences on spinal circuitry. Given substantial asymmetries in hemispheric control of arm movement, we now ask whether task-dependent bilateral reflexes are symmetric. We tested this question using a virtual object manipulation task. In a virtual reality environment, a cursor representing each hand is used to ‘pick up’ each end of a bar and “drag” it to a target. At the onset of occasional and unpredictable trials, a solenoid engaged for 200 milliseconds, preventing motion along the antero-posterior axis for one of the arms. This prevented ongoing extension of the elbow and resulted in acceleration of the shoulder into horizontal adduction. Thus, the effect of the perturbation was to ‘stretch’ the shortening triceps brachii, as well as the lengthening posterior deltoid (relative to baseline movements). We binned muscle activity into 2 intervals, relative to the initiation of the perturbation: 1) short latency (20-45 ms) and 2) long latency (46-75 ms). We compared muscle activity in these two bins to the corresponding activity in non-perturbed trials. This comparison was done for both the ipsilateral perturbed arm and in the contralateral unperturbed arm. Unilateral responses in the ipsilateral arm: Regardless of which arm was perturbed, ipsilateral responses were similar: Short latency responses were significant in the posterior deltoid, while long latency responses were significant in the triceps brachii. However short latency responses in triceps only reached significance in the dominant (right) arm. Bilateral responses in the contralateral arm: The non-dominant posterior deltoid showed significant short and long latency reflex responses. However, for the dominant arm, short and long latency intervals were not significantly different from that of non-perturbed trials. Thus, bilateral reflex responses to unilateral perturbations are asymmetric, such that the non-dominant arm responds to perturbations of the dominant arm, but not vice versa. Mutha PK, Sainburg RL. Shared bimanual tasks elicit bimanual reflexes during movement. J Neurophys. 2009;102(6):3142-3155.

M3 - Abstract

ER -