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Corticospinal transmission after voluntary contractions
Janet L Taylor1, Nicolas T Petersen, Jane E Butler
1Prince of Wales Medical Research Institute, Sydney, NSW, Australia. jl.taylor@unsw.edu.au
Advances in Experimental Medicine and Biology
|August 13, 2002
Summary
Transmastoid stimulation temporarily reduces muscle responses by decreasing corticospinal synapse effectiveness. This activity-dependent depression may impact voluntary movement control.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Transmastoid stimulation elicits a descending volley in corticospinal axons.
- Electromyographic (EMG) responses reflect motoneuronal excitability.
Purpose of the Study:
- To investigate the effect of voluntary muscle contractions on corticospinal excitability.
- To explore the potential synaptic mechanisms underlying changes in motor output.
Main Methods:
- Transmastoid stimulation was applied to human subjects.
- EMG responses were recorded from relaxed elbow flexor muscles.
- Measurements were taken before, during, and after maximal voluntary contractions (MVCs).
Main Results:
- EMG responses were depressed by ~50% after MVC, recovering within 2 minutes.
- Depression was also observed after submaximal contractions and during weak contractions post-MVC.
- Findings suggest a potential decrease in corticospinal-motoneuronal synapse efficacy.
Conclusions:
- Voluntary contractions induce an activity-dependent depression of corticospinal excitability.
- This depression may involve reduced synaptic efficacy, impacting voluntary movement control.