Relationship between amplitude of tremor and reflex responses of the human jaw-closing system.

Jaw-closing force was transduced while subjects maintained a biting force of 9.8 N. To estimate the amplitude of tremor in each subject's force record, the average spectrum of the force was computed, and the definite integral of the averaged spectrum in the frequency range from 3.5 to 10 Hz was calculated. For the same subjects, the amplitude of reflex responses to innocuous mechanical stimuli delivered to intraoral and perioral sites was measured as the peak-to-peak change in jaw-closing force following application of the stimulus. Force responses produced by stimulation at each site were used to compute an average reflex response measure for each subject. Large intersubject variability was observed in the amplitudes of jaw tremor and reflex responses. A correlation coefficient computed between the tremor and reflex measures revealed that subjects with large amplitude tremor tended also to have large reflex force responses. This correlation is consistent with the suggestion that activity in cutaneous reflex pathways contributes to tremor of the human mandible.