Corticospinal transmission after voluntary contractions.
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.
Taylor
Janet L
JL
Prince of Wales Medical Research Institute, Sydney, NSW, Australia. jl.taylor@unsw.edu.au
Petersen
Nicolas T
NT
Butler
Jane E
JE
Gandevia
Simon
S
D004550:Elbow; D004576:Electromyography; D005071:Evoked Potentials; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*