Role of intracortical inhibition in selective hand muscle activation.

Full Abstract

Previous studies have shown that intracortical inhibition (ICI) plays an important role in shaping the output from primary motor cortex (M1). This study explored the muscle specificity and temporal modulation of ICI during the performance of a phasic index finger flexion task. Fifteen subjects were asked to rest their dominant hand on a computer mouse and depress the mouse button using their index finger in time with a 1-Hz auditory metronome, while keeping the rest of their hand as relaxed as possible. Responses to single- and paired-pulse transcranial magnetic stimulation were recorded from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles while subjects were at rest and during "on" and "off" phases of the task. For FDI during the on phase, motor evoked potential (MEP) amplitude and pretrigger EMG increased and ICI decreased, as expected. This pattern of modulation was also observed for APB in seven subjects. The remaining eight subjects demonstrated a decrease in MEP amplitude and increase in ICI for APB during the on phase. This was associated with significantly less APB activation during the on phase. These findings suggest that an increase in ICI and decrease in corticospinal excitability can prevent unwanted muscle activation in a muscle-specific, temporally modulated manner.

Author information

Author/s: Stinear, Cathy M (CM); Byblow, Winston D (WD);

Affiliation: Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand 1005, USA. c.stinear(-atsign-)auckland.ac.nz

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Journal of neurophysiology (J Neurophysiol), published in United States. (Language: eng)

Reference: 2003-Apr; vol 89 (issue 4) : pp 2014-20

Dates: Created 2003/04/10; Completed 2003/05/29; Revised 2006/11/15;

PMID: 12611950, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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