Single motor units' study on the role of the human lateral pterygoid muscle in the generation of horizontal mandibular force

目的是验证人翼外肌下头(IH)参与水平等长下颌力的产生和精细控制的假设。在8名受试者中，在对侧(CL)、同侧(IL)、突起(P)方向和两个中间方向(对侧-突起(CL-P)、同侧-突起(IL-P))上，从IHLP记录到单侧运动单位的活动(SMU)。在距牙尖牙位5~8 mm开口处，用固定在下颌水平等长力方向的杆子对传感器施加等长力(用杆子固定在上牙上)。受试者在视频屏幕上跟踪一个目标，该目标需要5-S在400gwt(3.92N)到800gwt(7.84N)之间的每100gwt(0.98N)保持时间。在等长CL收缩过程中，我们可以可靠地区分21个SMU。21个IHLP SMU的平均射击率随着力量的增加而显著增加(p&lt；0.0001)。CL的SMU有三种类型：(A)紧张型(T单位，10/21，48%)，(B)中间型(I单位，4/21，19%)和(C)相期或主相型(P单位，7/21，83%)。21个IHLP SMU的平均放电频率也受到方向的影响，其中CL的活动最高，并且随着方向向IL的移动而逐渐降低。

The aim was to test the hypothesis that the inferior head (IH) of the human lateral pterygoid muscle (LP) is involved in the generation and fine control of horizontal isometric mandibular force. In eight participants, single motor units' activity (SMUs) was recorded from IHLP unilaterally during the generation such forces to a target in contralateral (CL), ipsilateral (IL), protrusive (P) directions and in two intermediate directions (contralateral-protrusive (CL-P), ipsilateral-protrusive (IL-P)). Isometric force at 5-8 mm open from the intercuspul position was exerted on a transducer (attached by a bar to the upper teeth) by a rod attached to the lower teeth of horizontal isometric mandibular force in a direction. Participants tracked a target on a video screen that required 5-s holding periods at each 100 gwt (0.98 N) between 400 gwt (3.92 N) and 800 gwt (7.84 N).We could reliably discriminate 21 SMUs during isometric CL contraction. The mean firing rates of 21 IHLP SMUs significantly increased with force (p<0.0001). Three patterns of SMUs were identified at CL: (a) tonic (t-unit; 10/21, 48%), (b) intermediate (I-unit; 4/21, 19%) and (c) phasic or predominantly phasic (P-unit; 7/21, 83%). The mean firing rates of 21 IHLP SMUs were also affected by direction, with the highest activity being CL, and graded decreases occurring as the direction shifted to IL.The data suggest that the IHLP is involved in the creation and fine control of mandibular forces in different horizontal directions.