title: Microstimulation activates a handful of muscle synergies.
abstract: Muscle synergies have been proposed as a mechanism to simplify movement control. Whether these coactivation patterns have any physiological reality within the nervous system remains unknown. Here we applied electrical microstimulation to motor cortical areas of rhesus macaques to evoke hand movements. Movements tended to converge toward particular postures, driven by synchronous bursts of muscle activity. Across stimulation sites, the muscle activations were reducible to linear sums of a few basic patterns-each corresponding to a muscle synergy evident in voluntary reach, grasp, and transport movements made by the animal. These synergies were represented nonuniformly over the cortical surface. We argue that the brain exploits these properties of synergies-postural equivalence, low dimensionality, and topographical representation-to simplify motor planning, even for complex hand movements.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA. overduin@eecs.berkeley.edu
authors.forename: Simon A
authors.initials: SA
authors.lastname: Overduin
authors.forename: Andrea
authors.initials: A
authors.lastname: d'Avella
authors.forename: Jose M
authors.initials: JM
authors.lastname: Carmena
authors.forename: Emilio
authors.initials: E
authors.lastname: Bizzi
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001931:Brain Mapping; D004525:Efferent Pathways / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D006225:Hand; D007699:Kinesthesis / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D046709:Pattern Recognition, Physiological; D011187:Posture