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Quantitative analysis of reflex inhibition in single motor units in human masseter muscle: Effects of stimulus intensity
Author(s) -
GravenNielsen Thomas,
Svensson Peter,
McMillan Anne S.,
ArendtNielsen Lars
Publication year - 2000
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(200002)23:2<259::aid-mus18>3.0.co;2-f
Subject(s) - stimulus (psychology) , h reflex , masseter muscle , stimulation , reflex , inhibitory postsynaptic potential , neuroscience , electromyography , psychology , audiology , medicine , anesthesia , anatomy , psychotherapist
Inhibitory reflex responses to electrical stimulation of the mental nerve were studied in recordings from single motor units (SMU) in the human masseter muscle. A new analytical technique for spike train data was used. Electrical stimuli were delivered to the mental nerve when the SMU fired with two consecutive inter‐spike intervals (ISIs) within the range of 90 ms to 110 ms. Stimuli were delivered with increasing stimulus delays after the preceding SMU action potential (AP). Sham, non‐painful, and painful stimulus intensities were applied. The post‐stimulus firing probability of the SMU was progressively decreased among the three conditions. Analysis of the relation between stimulus delays and ISI for the first post‐stimulus APs revealed a linear relation which was shifted upward, and the slope was increased with increasing stimulus intensity. This may be explained by a differential effect of the increasing stimulus intensity on the duration and amplitude of the inhibitory post‐synaptic potential. The methods used in the present study provide a useful means of quantifying the effects of motoneuron excitability in detail. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 259–266, 2000.