| Tremor-related motor unit firing in Parkinson's disease: implications for tremor genesis. | |
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MedLine Citation:
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PMID: 19703960 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Muscle tremors reflect rhythmical motor unit (MU) activities. Therefore, the MU firing patterns and synchrony determine the properties of the parkinsonian force tremor (FT) and the neurogenic components of associated limb tremors. They may also be indicative of the neural mechanisms of tremor genesis which to date remain uncertain. We examined these MU behaviours during isometric contractions of a finger muscle in 19 parkinsonian subjects. Our results reveal that the parkinsonian FT is abnormally large. Like the physiological FT, it is accompanied by in-phase rhythms in all MU activities. However, there exist two important differences. Firstly, the synchrony during the parkinsonian FT is stronger than the normal one and therefore contributes to the FT enhancement. Secondly, the synchronous MU components partly represent rhythmical sequences of spike doublets and triplets whose incidences directly reflect the differences of the MU firing rates to the FT frequency. According to our analyses, the latter frequency coincides with the MU recruitment rate. Consequently, the numerous medium- and small-sized active MUs contribute rhythmical twitch doublets and triplets, i.e. large force pulses, to the parkinsonian FT. The impact of this effect on the FT amplitude is found to predominate over the impact of the augmented synchrony. Importantly, apart from the rule governing the occurrence of doublets/triplets, the mean interspike intervals within such spike events are fairly fixed around 50 ms. Such regularities in MU activities may reflect properties of the neural input underlying the FT, and thus represent a basis for more focused studies of the generator(s) of parkinsonian tremors. |
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Authors:
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C N Christakos; S Erimaki; E Anagnostou; D Anastasopoulos |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2009-08-24 |
Journal Detail:
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Title: The Journal of physiology Volume: 587 ISSN: 1469-7793 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 2009 Oct |
Date Detail:
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Created Date: 2009-10-15 Completed Date: 2010-02-03 Revised Date: 2010-10-18 |
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: 4811-27 Citation Subset: IM |
Affiliation:
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Laboratory of Systems Physiology, Division of Basic Sciences, Medical School, University of Crete, 71003 Heraklion, Greece. ccnncc@med.uoc.gr |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials* Aged Aged, 80 and over Electromyography Female Humans Isometric Contraction Male Middle Aged Motor Activity Motor Neurons / physiology Muscle, Skeletal / physiopathology* Parkinson Disease / physiopathology* Periodicity Recruitment, Neurophysiological Tremor / etiology*, physiopathology |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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