Cortical excitability and motor task in man: an investigation of the wrist extensor motor area

Experimental Brain Research
Jean-Marc Aimonetti, Jens Bo Nielsen

Abstract

Task-related changes in the corticospinal excitation of the right extensor carpi radialis (ECR) muscle were investigated in 16 healthy human subjects. The subjects were asked to perform a tonic isometric wrist extension or to clench their hand around a manipulandum, thereby coactivating the antagonistic wrist muscles. At matched levels of background EMG in the ECR muscle, transcranial magnetic stimulation (TMS) was applied through a figure-of-eight coil at 20-30 sites spaced 1 cm apart over the hand area of the left motor cortex. The cortical maps of the representation of the ECR muscle constructed in this way did not change between the two motor tasks. Nevertheless, for all investigated cortical sites TMS evoked a smaller motor evoked potential (MEP) in the ECR muscles during hand clenching than during wrist extension. A similar decrease in the short-latency peak in the poststimulus time histogram (PSTH) of single ECR motor units to TMS during hand clenching was found in seven subjects (number of motor units = 35). In contrast, short-latency peaks in the PSTH evoked by electrical stimulation of the motor cortex had a similar size during the two tasks (number of motor units = 9; two subjects). Already the initial 0.5-1.0 ms of ...Continue Reading

Citations

Jan 8, 2004·Journal of Cognitive Neuroscience·Mireille BonnardJean Pailhous
Dec 7, 2007·Journal of Child Neurology·Richard E FryeAlvaro Pascual-Leone
Mar 1, 2008·Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology·Michael LeeTimothy J Carroll
Jul 1, 2021·The Journal of Physiology·Toshiki Tazoe, Monica A Perez

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