Frequency analysis of human jaw tremor at rest

doi:10.1016/0003-9969(79)90029-3

Archives of Oral Biology

Volume 24, Issues 10–11, 1979, Pages 709-718

https://doi.org/10.1016/0003-9969(79)90029-3 Get rights and content

Abstract

It is not known whether rest position is controlled actively by a low degree of muscular activity or passively by muscular and tissue visco-elasticity. The frequency analysis of the jaw tremor at rest was studied to determine if it could be useful for the study of rest position. Jaw tremor was recorded in three different head positions of normal subjects by two accelerometers fixed to the upper and lower premolars. The acceleration signals were low-pass filtered, digitized and analysed by computer. A Fast Fourier Transform algorithm was used to determine spectral density. Electromyograms of the right and left anterior temporal and masseter muscles and an electrocardiogram were recorded with surface electrodes, and the data correlated with jaw tremor. The lower jaw oscillated at the same frequency as the head, and the tremor was a low-frequency narrow-band process. Head deflection produced changes in the power spectral density of the tremor. A time correlation between the shape of the acceleration raw data and the heart beat was present in every subject. However, frequency content and power spectral density of the jaw tremor at rest may be determined also by the degree of muscular activity.

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Postural control of the human mandible
2007, Archives of Oral Biology
Citation Excerpt :
Thus, slow, voluntary movements of the mandible are not smooth, but are interspersed with small accelerations and decelerations of 6–7 Hz (i.e., the mandibular tremor frequency), which are the result of alternating activity in antagonistic masticatory muscles superimposed onto the muscle activity that is responsible for the voluntary movements. Clearly, therefore, jaw tremor9,10 is not the result of a reflex because, while the jaw-closing muscles have stretch receptors that can produce reflex closing (e.g.8), jaw-opening muscles do not have comparable stretch reflexes. Furthermore, there are no crossed inhibitory reflexes in the trigeminal system that might account for the alternating activation of the opening and closing muscles.
This article reviews recent experimental evidence explaining the mechanisms that support the mandible in its rest or postural position when the head is stationary and during locomotion. At rest, and during slow jaw movements, there is alternating activation of the jaw-opening and jaw-closing muscles which arises from a central pattern generator. However, this cannot account for the rest position of the mandible even when the head is stationary. Jaw movements and masticatory muscle activity were measured in subjects who stood, walked and ran on a treadmill. Even during walking, there are no bursts of masseter EMG time-locked to heel-landing. However, when subjects ran, the downward movement of the mandible in each step evokes a burst of EMG in the masseters. This is a stretch reflex in the jaw-closing muscles, which acts to limit the downward movement of the mandible relative to the maxilla during locomotion, and to restore the mandibular position towards its rest position. Thus, when the head is stationary, the low-level activity in the jaw-opening and jaw-closing muscles does not contribute to the rest position. Instead, the mandible is supported by passive viscoelastic forces in perioral soft tissues which limit vertical jaw movements even when the head moves gently up and down during walking. When the head moves more vigorously up and down, stretch reflexes in the jaw-closing muscles limit the movement of the mandible. That is, both passive forces and active reflex responses maintain jaw posture within narrow limits during brisk head movements.
Physiological tremor in human jaw-muscle system
1998, Archives of Oral Biology
Small, quasi-rhythmical tremor of the jaw occurs at rest and during voluntary movements. In peripheral limbs, tremor consists of a component due to mechanical resonance properties of the system, and a neurogenic component mediated by a central pacemaker or neural loops. The present study attempted to determine if these components were present in jaw tremor measured with a position transducer held lightly between the incisors. When weights were suspended from the mandible, the tremor frequency was unaltered; sharp taps delivered to the jaw did not elicit any kind of damped oscillations of the system. These findings indicated the absence of mechanical resonance in the system. No correlation of the tremor signal with the electrocardiogram was found. However, a strong correlation was found between the rectified electromyographic signals recorded over the masseter muscles and the tremor signal, where the electromyographic signal preceded jaw movement by 20–30 msec. Frequency-domain analysis also showed positive peaks in a majority of coherence functions between electromyographic and tremor signals. These results suggested a strong neurogenic component of the tremor.
Jaw, head and finger tracking behaviour with delayed visual feedback
1993, Journal of Electromyography and Kinesiology
The contribution of visual feedback to visuomotor tracking of jaw, head and finger was established by delaying the visual feedback display. Fourteen subjects (seven females, seven males; 20–30 years of age) used a movable metal bar to track a pseudorandom waveform on an oscilloscope screen. The tracking signals were recorded by means of a linear variable displacement transducer, amplified and digitized. Two approaches were applied for data analysis: (1) a cross-correlation analysis; (2) a power spectral analysis. On delaying the visual display, response delays for finger tracking increased significantly. A significant spectral shift occurred when a delayed feedback display (0.5-1.0 s) was introduced in both head and finger tracking experiments. A spectral change also occurred after inducing finger fatigue. On the other hand, neither the response delays nor the median frequencies of jaw tracking signals were significantly affected by modifications in the visual feedback display or by maximal voluntary clenching. Another interesting finding was the increase of the median frequency after periodontal anaesthesia. It was concluded that visual information is predominantly involved in finger and head tracking. Interactions between the visual system and the jaw motor system seem unlikely. Jaw tracking control probably relies on well-developed proprioceptive and exteroceptive inputs.
Relationship between amplitude of tremor and reflex response of the human jaw-closing system
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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 forces 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 sunjects, 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 and reflex responses. A correlation coefficient computed between the tremor and reflex measures revealed that subjects with large amplitude tremor tended also to have a large reflex force responses. This correlation is consistent with the suggestion that activity in cutaneous reflex pathways contributes to tremor of the human mandible.
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Frequency analysis of human jaw tremor at rest

Abstract

J. prosth. Dent.

J. prosth. Dent.

J. Dent.

J. prosth. Dent.

Archs oral Biol.

Am. J. Cardiol.

Am. J. Cardiol.

J. Dent.

Electroenceph. clin. Neurophysiol.

J. prosth. Dent.

Archs oral Biol.

The fidelity of digital recordings. A framework for future decisions

Software support for computerized electromyography in clinical dentistry

IEEE Trans. biomed. Engng.

On the nature of normal tremor

Neurology

Cardiovascular factors in limb tremor

Neurology

Motor-unit activity responsible for 8 to 12 Hz component of human physiological finger tremor

J. Neurophysiol.

Computerized data acquisition and analysis for real-time electromyography in clinical dentistry

Numerical analysis and applications software abstracts