Document Detail


Influence of handedness on motor unit discharge properties and force tremor.
MedLine Citation:
PMID:  7621929     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Discharge properties of motor units (MUs) in the first dorsal interosseous muscle (FDI) were studied in the dominant and non-dominant hands of six right-handed (RH) and six left-handed (LH) individuals. MU discharge rates and variability were similar in each hand in RH (186 MUs) and LH (160 MUs) subjects. MU synchronization was less prominent in the dominant hand of RH subjects, with 51% (45/88) of cross-correlograms of MU discharge having significant central peaks, compared with 81% (90/111) for the non-dominant hand. The strength of MU synchronization (expressed as the frequency of extra synchronous discharges above chance) was weaker in the dominant hand of right-handers (0.23 +/- 0.03 s-1 vs 0.39 +/- 0.03 s-1), and synchronous peaks from that hand were slightly broader. Four of six RH subjects had significant differences in synchronization between hands (weaker in dominant hand). In contrast, left-handers had similar incidence (80 vs 82%, n = 161) and strength (0.41 +/- 0.03 s-1 vs 0.37 +/- 0.03 s-1) of MU synchrony in dominant and non-dominant hands. No LH subject had a significant difference in synchronization between hands. Force tremor was quantified in each hand in the same subjects during isometric abduction of FDI at 0.5 N and 3.5 N, and directly correlated with the extent of MU synchronization in the muscle. Tremor root mean square amplitude was similar in dominant and non-dominant hands. Power spectral analysis of the tremor force revealed that the peak frequency in the power spectrum was not influenced by handedness, but power at the peak frequency was higher in the non-dominant hand of RH subjects. Correlations between MU discharge variability and synchrony with measures of tremor amplitude were weak. The reduced MU synchronization in the dominant hand of right-handers may reflect a more restricted distribution of direct projections from motor cortical neurons within the FDI motoneuron pool, or reduced excitability of the cortical neurons during the task. These differences in MU synchronization, however, had an insignificant influence on the magnitude of physiological tremor in the FDI.
Authors:
J G Semmler; M A Nordstrom
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental brain research     Volume:  104     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  1995  
Date Detail:
Created Date:  1995-08-31     Completed Date:  1995-08-31     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  115-25     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Adult
Arm / innervation,  physiology
Cortical Synchronization
Electromyography
Functional Laterality / physiology*
Hand / innervation,  physiology
Humans
Isometric Contraction / physiology
Male
Middle Aged
Motor Neurons / physiology*
Muscle, Skeletal / innervation,  physiology*
Tremor / physiopathology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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