| Unexpected reflex response to transmastoid stimulation in human subjects during near-maximal effort. | |
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MedLine Citation:
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PMID: 11579178 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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1. In human subjects, a high-voltage electrical pulse between electrodes fixed over the mastoid processes activates descending tract axons at the level of the cervico-medullary junction to produce motor responses (cevicomedullary evoked responses; CMEPs) in the biceps brachii and brachioradialis muscles. 2. During isometric maximal voluntary contractions (MVCs) of the elbow flexors, CMEPs in the biceps brachii and brachioradialis muscles are sometimes followed by a second compound muscle action potential. This response can be observed in single trials (amplitude of up to 60 % of the maximal M wave) and follows the CMEP by about 16 ms in both muscles. The response only occurs during very strong voluntary contractions. 3. The second response following transmastoid stimulation appears with stimulation intensities that are at the threshold for evoking a CMEP in the contracting muscles. The response grows with increasing stimulus intensity, but then decreases in amplitude and finally disappears at high stimulation intensities. 4. A single stimulus to the brachial plexus during MVCs can also elicit a second response (following the M wave) in the biceps brachii and brachioradialis muscles. The latency of this response is 3-4 ms longer than that of the second response observed following transmastoid stimulation. This difference in latency is consistent with a reflex response to stimulation of large-diameter afferents. 5. The amplitude of the second response to transmastoid stimulation can be reduced by appropriately timed subthreshold transcranial magnetic stimuli. This result is consistent with intracortical inhibition of the response. 6. We suggest that transmastoid stimulation can elicit a large transcortical reflex response in the biceps brachii and brachioradialis muscles. The response travels via the motor cortex but is only apparent during near-maximal voluntary efforts. |
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Authors:
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J L Taylor; J E Butler; N T Petersen; S C Gandevia |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The Journal of physiology Volume: 536 ISSN: 0022-3751 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 2001 Oct |
Date Detail:
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Created Date: 2001-10-01 Completed Date: 2001-12-31 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: England |
Other Details:
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Languages: eng Pagination: 305-12 Citation Subset: IM |
Affiliation:
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Prince of Wales Medical Research Institute, Randwick, NSW 2031 and the University of New South Wales, Sydney, NSW 2052, Australia. jl.taylor@unsw.edu.au |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials
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physiology Adult Elbow Joint / physiology Electric Stimulation Female Humans Isometric Contraction / physiology* Magnetics Male Mastoid Middle Aged Muscle, Skeletal / innervation, physiology* Reflex / physiology* |
| Comments/Corrections | |
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