title: Comparison of the magnetically mapped corticomotor representation of a muscle at rest and during low-level voluntary contraction.
abstract: This study has compared the topography of the corticomotor representation of an intrinsic hand muscle in the relaxed state and during a low-level voluntary contraction using transcranial magnetic stimulation. It was found that the optimum cortical stimulus site and the surrounding area of excitable cortex were shifted approximately 6 mm medially as a result of performing a voluntary contraction. This difference may be due to a combination of factors involving the spatial distribution of excitable intracortical fibres, the effects of muscle afferent activity on motor cortex excitability, and task-dependent modifications of corticomotor output.
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001931:Brain Mapping; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D008280:Magnetics; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*