Journal
JOURNAL OF NEUROPHYSIOLOGY
Volume 112, Issue 11, Pages 2985-3000Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00270.2014
Keywords
feedback control; task dependency; transcortical feedback pathway; reflex; task-independent response; neural activity; primary motor cortex
Categories
Funding
- Canadian Institutes of Health Research (CIHR)
- CIHR
- Human Frontier Science Program
- GSK-CIHR Chair in Neuroscience
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Corrective responses to external perturbations are sensitive to the behavioral task being performed. It is believed that primary motor cortex (M1) forms part of a transcortical pathway that contributes to this sensitivity. Previous work has identified two distinct phases in the perturbation response of M1 neurons, an initial response starting similar to 20 ms after perturbation onset that does not depend on the intended motor action and a task- dependent response that begins similar to 40 ms after perturbation onset. However, this invariant initial response may reflect ongoing postural control or a task- independent response to the perturbation. The present study tested these two possibilities by examining if being engaged in an ongoing postural task before perturbation onset modulated the initial perturbation response in M1. Specifically, mechanical perturbations were applied to the shoulder and/ or elbow while the monkey maintained its hand at a central target or when it was watching a movie and not required to respond to the perturbation. As expected, corrective movements, muscle stretch responses, and M1 population activity in the late perturbation epoch were all significantly diminished in the movie task. Strikingly, initial perturbation responses (<40 ms postperturbation) remained the same across tasks, suggesting that the initial phase of M1 activity constitutes a task- independent response that is sensitive to the properties of the mechanical perturbation but not the goal of the ongoing motor task.
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