Mandibular physiological tremor is reduced by increasing-force ramp contractions and periodontal anaesthesia

• Published in: Experimental brain research 2008-01, Vol.184 (1), p.71-82
• Main Authors: Sowman, Paul F., Brinkworth, Russell S. A., Türker, Kemal S.
• Format: Article
• Language: English
• Subjects: Adult; Anesthesia; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Bite Force; Brain research; Electromyography; Essential Tremor - physiopathology; Essential Tremor - prevention & control; Feedback; Female; Fundamental and applied biological sciences. Psychology; Humans; Hypotheses; Isometric Contraction - physiology; Male; Mandible - physiopathology; Masseter Muscle - physiopathology; Mechanoreceptors - physiology; Medical sciences; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor Neurons - physiology; Muscle Contraction; Muscle Fatigue; Neurology; Neurosciences; Neurosurgery; Physiology; Research Article; Skull, brain, vascular surgery; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Vertebrates: nervous system and sense organs
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-007-1083-0

We have previously shown that the application of anaesthesia to periodontal mechanoreceptors (PMRs) dramatically reduces the 6–12 Hz physiological tremor (PT) in the human mandible during constant isometric contractions where visual feedback is provided. This current study shows that during a ramp contraction where force is slowly increased, the amplitude of mandibular PT is almost five times smaller on average than when the same force ramp is performed in reverse, i.e. force is slowly decreased. This smaller tremor is associated with a higher mean firing rate of motor units (MUs) as measured by the sub-30 Hz peak in the multi-unit power spectrum. The decrease in the amplitude of PT following PMR anaesthetisation is associated in some instances with a similar increase in the overall firing rate; however this change does not match the diminution of tremor. The authors postulate that the decrease in mandibular PT during increasing force ramps may be due to a change in the mean firing rate of the MUs. The change in tremor seen during PMR anaesthetisation may in part be due to a similar mechanism; however other factors must also contribute to this.