title: The effect of tonic contraction of the finger muscle on the motor cortical representation of the contracting adjacent muscle.
abstract: This study examined the effect of tonic contraction of the finger muscle on the motor cortical representation of the contracting adjacent muscle. A representation map of the motor evoked potential (MEP) in the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles was obtained with the subject at rest or during tonic contraction of the ADM muscle while the FDI muscle was tonically contracted. The center of gravity (COG) of the MEP map in the FDI muscle shifted medially during contraction of the ADM muscle. Motor cortical excitability in the motor cortical representation of the FDI muscle that did not overlap with the motor cortical representation of the ADM muscle was suppressed, but motor cortical excitability in the motor cortical representation of the FDI muscle overlapping with the motor cortical representation of the ADM muscle was not suppressed during contraction of the ADM muscle. The motor cortical representation of the FDI muscle not overlapping with the motor cortical representation of the ADM muscle was located lateral to that of the FDI muscle that did overlap with the motor cortical representation of the ADM muscle. Medial shift of the COG of the motor cortical representation of the contracting finger muscle induced by tonic contraction of the adjacent finger muscle must be due to suppression of motor cortical excitability in the lateral part of the representation, which is not shared by the adjacent representation.
authors: Graduate School of Comprehensive Rehabilitation, Osaka Prefecture University , Habikino City, Osaka , Japan and.
authors: Yasutomo
authors: Y
authors: Jono
authors: Yuta
authors: Y
authors: Chujo
authors: Yoshifumi
authors: Y
authors: Nomura
authors: Keisuke
authors: K
authors: Tani
authors: Yasutaka
authors: Y
authors: Nikaido
authors: Ryota
authors: R
authors: Hatanaka
authors: Koichi
authors: K
authors: Hiraoka
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005385:Fingers / Q000294:innervation*; D006112:Gravitation; D006801:Humans; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011712:Pyramidal Tracts; D050781:Transcranial Magnetic Stimulation
keywords: Center of gravity; corticospinal excitability; motor cortical representation; primary motor cortex; surround inhibition; transcranial magnetic stimulation