title: Functional Plasticity in Somatosensory Cortex Supports Motor Learning by Observing.
abstract: An influential idea in neuroscience is that the sensory-motor system is activated when observing the actions of others [1, 2]. This idea has recently been extended to motor learning, in which observation results in sensory-motor plasticity and behavioral changes in both motor and somatosensory domains [3-9]. However, it is unclear how the brain maps visual information onto motor circuits for learning. Here we test the idea that the somatosensory system, and specifically primary somatosensory cortex (S1), plays a role in motor learning by observing. In experiment 1, we applied stimulation to the median nerve to occupy the somatosensory system with unrelated inputs while participants observed a tutor learning to reach in a force field. Stimulation disrupted motor learning by observing in a limb-specific manner. Stimulation delivered to the right arm (the same arm used by the tutor) disrupted learning, whereas left arm stimulation did not. This is consistent with the idea that a somatosensory representation of the observed effector must be available during observation for learning to occur. In experiment 2, we assessed S1 cortical processing before and after observation by measuring somatosensory evoked potentials (SEPs) associated with median nerve stimulation. SEP amplitudes increased only for participants who observed learning. Moreover, SEPs increased more for participants who exhibited greater motor learning following observation. Taken together, these findings support the idea that motor learning by observing relies on functional plasticity in S1. We propose that visual signals about the movements of others are mapped onto motor circuits for learning via the somatosensory system.
authors.affiliation: The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada; Department of Psychology, The University of Western Ontario, London, ON N6A 5B7, Canada; Graduate Program in Neuroscience, The University of Western Ontario, London, ON N6A 5B7, Canada.
authors.forename: Heather R
authors.initials: HR
authors.lastname: McGregor
authors.affiliation: The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada; Department of Psychology, The University of Western Ontario, London, ON N6A 5B7, Canada.
authors.forename: Joshua G A
authors.initials: JG
authors.lastname: Cashaback
authors.affiliation: The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada; Department of Psychology, The University of Western Ontario, London, ON N6A 5B7, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5B7, Canada. Electronic address: paul@gribblelab.org.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Gribble
mesh_terms: D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007858:Learning; D008297:Male; D008475:Median Nerve; D009043:Motor Activity; D019370:Observation; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
keywords: action observation; human; median nerve stimulation; motor learning; primary somatosensory cortex; reaching; somatosensory evoked potential