title: Sensitivity of cortical movement representations to motor experience: evidence that skill learning but not strength training induces cortical reorganization.
abstract: The topography of forelimb movement representations within the rat motor cortex was examined following forelimb strength training. Adult male rats were allocated to either a Power Reaching, Control Reaching or Non-Reaching Condition. Power Reaching rats were trained to grasp and break progressively larger bundles of dried pasta strands with their preferred forelimb. Control Reaching animals were trained to break a single pasta strand and Non-Reaching animals were not trained. Power Reaching animals exhibited a progressive increase in the maximal size of the pasta bundle that could be retrieved during a 30-day training period. Kinematic analyses showed that this improvement was not due to a change in reaching strategy. Intracortical microelectrode stimulation was used to derive maps of forelimb movement representations within the motor cortex of all animals following training. In comparison to Non-Reaching animals, both Power Reaching and Control Reaching animals exhibited a significant increase in the proportion of motor cortex occupied by distal forelimb movement representations (wrist/digit) and a decrease in the proportion of proximal representations (elbow/shoulder). These results demonstrate that the development of skilled forelimb movements, but not increased forelimb strength, was associated with a reorganization of forelimb movement representations within motor cortex.
authors.affiliation: Department of Psychology and Neuroscience, University of Lethbridge, 4401 University Dr., Lethbridge, Alberta, Canada, T1K 3M4.
authors.forename: M S
authors.initials: MS
authors.lastname: Remple
authors.forename: R M
authors.initials: RM
authors.lastname: Bruneau
authors.forename: P M
authors.initials: PM
authors.lastname: VandenBerg
authors.forename: C
authors.initials: C
authors.lastname: Goertzen
authors.forename: J A
authors.initials: JA
authors.lastname: Kleim
mesh_terms: D000818:Animals; D001931:Brain Mapping; D005552:Forelimb / Q000294:innervation*; D018737:Hand Strength / Q000502:physiology; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans