Quantitative analysis of reflex inhibition in single motor units in human masseter muscle: Effects of stimulus intensity
✍ Scribed by Thomas Graven-Nielsen; Peter Svensson; Anne S. McMillan; Lars Arendt-Nielsen
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 257 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0148-639X
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✦ Synopsis
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.