title: Differential effects of muscle contraction from various body parts on neuromagnetic somatosensory responses.
abstract: We studied eight healthy subjects with a whole-scalp 306-channel neuromagnetometer to explore the effect of motor activity from different body parts on somatosensory responses to left median nerve stimulation. The stimuli produced clear tactile sensation without any motor movement. In the rest condition, the subject had no task. During contraction conditions, the subject had to maintain submaximal isometric contraction in masseter, left deltoid, left thenar, or left tibialis muscles. Short-latency responses from the primary somatosensory cortex did not change during contraction. Responses from both the right (contralateral) and left second somatosensory cortices (SII) were significantly enhanced during contraction of the left thenar muscles. Responses from the left SII were significantly enhanced also during contraction of the left deltoid muscles, but they were decreased during contraction of the masseter and left tibialis anterior muscles. This study implies that SII activation is modulated by motor activity and that the effect depends on the topographical proximity of the stimulated and contracted body parts.
authors.affiliation: Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, FIN-02015 HUT Espoo, Finland.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: Simões
authors.forename: N
authors.initials: N
authors.lastname: Forss
authors.forename: R
authors.initials: R
authors.lastname: Hari
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007537:Isometric Contraction / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*