Document Detail

Properties of human motoneurones and their synaptic noise deduced from motor unit recordings with the aid of computer modelling.
MedLine Citation:
PMID:  10084717     Owner:  NLM     Status:  MEDLINE    
This paper reviews two new facets of the behaviour of human motoneurones; these were demonstrated by modelling combined with analysis of long periods of low-frequency tonic motor unit firing (sub-primary range). 1) A novel transformation of the interval histogram has shown that the effective part of the membrane's post-spike voltage trajectory is a segment of an exponential (rather than linear), with most spikes being triggered by synaptic noise before the mean potential reaches threshold. The curvature of the motoneurone's trajectory affects virtually all measures of its behaviour and response to stimulation. The 'trajectory' is measured from threshold, and so includes any changes in threshold during the interspike interval. 2) A novel rhythmic stimulus (amplitude-modulated pulsed vibration) has been used to show that the motoneurone produces appreciable phase-advance during sinusoidal excitation. At low frequencies, the advance increases with rising stimulus frequency but then, slightly below the motoneurones mean firing rate, it suddenly becomes smaller. The gain has a maximum for stimuli at the mean firing rate (the 'carrier'). Such behaviour is functionally important since it affects the motoneurone's response to any rhythmic input, whether generated peripherally by the receptors (as in tremor) or by the CNS (as with cortical oscillations). Low mean firing rates favour tremor, since the high gain and reduced phase advance at the 'carrier' reduce the stability of the stretch reflex.
P B Matthews
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of physiology, Paris     Volume:  93     ISSN:  0928-4257     ISO Abbreviation:  J. Physiol. Paris     Publication Date:    1999 Jan-Apr
Date Detail:
Created Date:  1999-05-25     Completed Date:  1999-05-25     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9309351     Medline TA:  J Physiol Paris     Country:  FRANCE    
Other Details:
Languages:  eng     Pagination:  135-45     Citation Subset:  IM    
University Laboratory of Physiology, Oxford, UK.
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MeSH Terms
Computer Simulation*
Membrane Potentials / physiology
Models, Neurological*
Motor Neurons / physiology*
Species Specificity
Synaptic Transmission / physiology*
Tremor / physiopathology

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