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A study on synaptic coupling between single orofacial mechanoreceptors and human masseter muscle
Kemal S Türker1, Skjalg E Johnsen, Paul F Sowman
1Discipline of Physiology, Research Centre for Human Movement Control, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, 5005, SA, Australia. kemal.turker@adelaide.edu.au
Experimental Brain Research
|December 6, 2005
Summary
Single orofacial mechanoreceptive afferents, like those in the skin, mucosa, and tongue, significantly modulate jaw muscle activity. This research clarifies the neural control of mastication and speech.
Area of Science:
- Neuroscience
- Biomechanics
- Sensory Physiology
Background:
- The precise neural pathways linking individual orofacial mechanoreceptors to jaw muscle motoneurons remain unclear.
- Previous studies show bulk stimulation of these afferents elicits responses, but single-unit responses are not well understood.
Purpose of the Study:
- To investigate the functional connections between identified single orofacial mechanoreceptive afferents and jaw muscle motoneurons.
- To determine if single afferent discharges can evoke measurable responses in jaw muscles.
Main Methods:
- Recorded single afferent activity from the inferior alveolar and lingual nerves in human volunteers using microelectrodes.
- Employed spike-triggered averaging and cross-correlation analysis to assess electromyogram (EMG) modulation.
- Utilized coherence analysis to examine frequency-based relationships between nerve activity and EMG.
Main Results:
- Skin and mucosa receptors (lip, gingiva) modulated masseter EMG in 40% of trials.
- Periodontal mechanoreceptors (PMRs) showed higher coupling (70% cross-correlation) but lower coherence (35%).
- Tongue receptors significantly coupled with jaw motoneurons in approximately 40% of trials.
Conclusions:
- Individual orofacial mechanoreceptors play a significant role in controlling jaw muscle activity.
- These neural connections are crucial for the successful execution of complex functions like mastication and speech.