Journal article
Increase in flexor but not extensor corticospinal motor outputs following ischemic nerve block
Journal of Neurophysiology, Vol.107(12), pp.3417-3427
2012
Abstract
Human motor cortex is capable of rapid and long-lasting reorganization, evident globally, as shifts in body part representations, and at the level of individual muscles as changes in corticospinal excitability. Representational shifts provide an overview of how various body parts reorganize relative to each other but do not tell us whether all muscles in a given body part reorganize in the same manner and to the same extent. Transcranial magnetic stimulation (TMS) provides information about individual muscles and can therefore inform us about the uniformity of plastic changes within a body part. We used TMS to investigate changes in corticospinal excitability of forearm flexors and extensors after inflation of a tourniquet around the wrist. Motor evoked potential (MEP) amplitudes and input/output (I/O) curves were obtained from wrist flexors and extensors simultaneously before and during block. TMS was delivered to the optimal site for eliciting MEPs in flexors in experiment 1, extensors in experiment 2, and both flexors and extensors in experiment 3. In all experiments flexor MEP amplitude increased during block while extensor MEP amplitude showed no systematic change, and the slope of flexor but not extensor I/O curves increased. Flexor H-reflex amplitude normalized to maximal M wave showed negligible changes during block, suggesting that the increase in corticospinal excitability in the flexors cannot be completely explained by increased excitability at the spinal cord level. These findings show that forearm flexors and extensors differ in their potential for plastic changes, highlight the importance of investigating how experimentally induced plasticity affects anatomically close, but functionally distinct, muscle groups, and suggest that rehabilitation interventions aiming to alter cortical organization should consider the differential sensitivity of various muscle groups to plasticity processes.
Details
- Title
- Increase in flexor but not extensor corticospinal motor outputs following ischemic nerve block
- Authors/Creators
- A.M. Vallence (Author/Creator) - The University of Western AustraliaG.R. Hammond (Author/Creator) - School of Psychological ScienceK.T. Reilly (Author/Creator) - Centre de Recherche en Neurosciences de Lyon
- Publication Details
- Journal of Neurophysiology, Vol.107(12), pp.3417-3427
- Publisher
- American Physiological Society
- Identifiers
- 991005546362707891
- Copyright
- American Physiological Society
- Murdoch Affiliation
- Murdoch University
- Language
- English
- Resource Type
- Journal article
- Note
- Published 15 June 2012
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- Collaboration types
- Domestic collaboration
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- Citation topics
- 1 Clinical & Life Sciences
- 1.82 Gait & Posture
- 1.82.811 Transcranial Magnetic Stimulation
- Web Of Science research areas
- Neurosciences
- Physiology
- ESI research areas
- Neuroscience & Behavior