title: Perturbation-evoked responses in primary motor cortex are modulated by behavioral context.
abstract: 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 ∼20 ms after perturbation onset that does not depend on the intended motor action and a task-dependent response that begins ∼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.
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada;
authors.forename: Mohsen
authors.initials: M
authors.lastname: Omrani
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada; Department of Integrative Medical Biology, Physiology Section, Umeå University, Umeå, Sweden.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Pruszynski
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada;
authors.forename: Chantelle D
authors.initials: CD
authors.lastname: Murnaghan
authors.affiliation: Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada; Department of Biomedical and Molecular Sciences, Kingston, Ontario, Canada; Department of Medicine Queen's University, Kingston, Ontario, Canada; and steve.scott@queensu.ca.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Scott
mesh_terms: D000818:Animals; D001132:Arm / Q000294:innervation / Q000502:physiology; D001696:Biomechanical Phenomena; D019054:Evoked Potentials, Motor; D008253:Macaca mulatta; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D011187:Posture; D011597:Psychomotor Performance; D055698:Touch Perception
keywords: feedback control; neural activity; primary motor cortex; reflex; task dependency; task-independent response; transcortical feedback pathway