Jaberzadeh Shapour, Brodin Pål, Flavel Stanley C, O'Dwyer Nicholas J, Nordstrom Michael A, Miles Timothy S
Department of Physiology, The University of Adelaide, Adelaide SA 5005, Australia.
J Physiol. 2003 Mar 1;547(Pt 2):613-20. doi: 10.1113/jphysiol.2003.030221. Epub 2003 Jan 10.
Spectral analysis of jaw acceleration confirmed that the human mandible 'trembles' at a peak frequency around 6 Hz when held in its rest position and at other stationary jaw openings. The 6 Hz tremor increased during very slow movements of the mandible, but other lower-frequency peaks became prominent during more rapid jaw movements. These lower-frequency peaks are likely to be the result of asymmetries in the underlying, voluntarily produced, 'saw-tooth' movements. In comparison, finger tremor at rest and during slow voluntary movements had a mean peak frequency of about 8 Hz: this frequency did not change during rhythmical finger flexion and extension movements, but the power of the tremor increased non-linearly with the speed of the movement. The resting jaw tremor was weakly coherent with the activity of the masseter and digastric muscles at the tremor frequency in about half the subjects, but was more strongly coherent during voluntary movements in all subjects. The masseter activity was at least 150 deg out of phase with the digastric activity at the tremor frequency (and at all frequencies from 2.5-15 Hz). The alternating pattern of activity in antagonistic muscles at rest and during slow voluntary movements supports the idea that the masticatory system is subject to pulsatile control in a manner analogous to that seen in the finger.
下颌加速度的频谱分析证实，当人类下颌处于静止位置以及其他静止的下颌开口状态时，其会以约6Hz的峰值频率“颤抖”。在非常缓慢的下颌运动过程中，6Hz的颤抖会增强，但在更快的下颌运动过程中，其他较低频率的峰值会变得突出。这些较低频率的峰值可能是由潜在的、自主产生的“锯齿状”运动中的不对称性导致的。相比之下，休息时以及缓慢的自主运动过程中的手指颤抖平均峰值频率约为8Hz：在有节奏的手指屈伸运动过程中，该频率不变，但颤抖的功率随运动速度呈非线性增加。在大约一半的受试者中，静止时的下颌颤抖与咬肌和二腹肌在颤抖频率下的活动存在微弱的相关性，但在所有受试者的自主运动过程中，相关性更强。在颤抖频率（以及2.5 - 15Hz的所有频率）下，咬肌活动与二腹肌活动至少有150度的相位差。在休息和缓慢的自主运动过程中，拮抗肌活动的交替模式支持了这样一种观点，即咀嚼系统受到类似于手指中所见的脉动控制。
