Corticospinal transmission after voluntary contractions.
- PubMed: 12171140
Abstract
Transmastoid stimulation in human subjects evokes a single descending volley in corticospinal axons. Electromyographic (EMG) responses to transmastoid stimuli measured in the relaxed elbow flexor muscles after a maximal voluntary contraction (MVC) are depressed by approximately 50% compared to prior to the MVC. The depression recovers over 2 min. Responses can also be depressed in the relaxed muscle after submaximal contractions and when measured during weak contractions after an MVC. The depression may reflect a decrease in efficacy at the corticospinal-motoneuronal synapse. If so, an activity-dependent decrease in the effectiveness of cortical drive to the motoneurones could affect the control of many voluntary movements.
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