McMillan A S
Department of Clinical Dental Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
Exp Brain Res. 1993;94(2):336-42. doi: 10.1007/BF00230303.
Muscle activity patterns in some complex human jaw muscles appear to be task sensitive. However, it is presently uncertain how changes in motor task affect motor unit (MU) behaviour in the human temporalis muscle. In this study, activity was recorded from 40 MUs in the anterior region of the muscle. The lowest sustainable firing frequency (LSFF) was reached by slow increases and decreases in firing rate, then firing was maintained at the lowest possible rate without significant pauses. An array of consecutive interspike intervals (ISI) were sampled digitally and used to measure the LSFF for each task associated with the MU. In a controlled paradigm, MU reflex inhibition was measured during the performance of different tasks. Single electrical pulses of non-noxious intensity were delivered to the gingiva near the maxillary canine tooth. During continuous MU firing at a controlled firing frequency of 10 Hz, series of pulses were delivered with increasing delays, after preselected spikes. The MUs fired continuously during the performance of 1-4 postural and tooth-contact tasks. There were significant differences in LSFFs between tasks in those MUs associated with multiple tasks. In the reflex study, all MUs were inhibited, but the magnitude of the inhibition was highly task dependent. Thus, both LSFF and reflex inhibition of temporalis MUs appear to vary with the motor task and are sensitive to the position of the jaw and the direction and location of tooth contact along the tooth row. This behaviour most likely reflects task-related changes in output from orofacial and muscle afferents.
一些复杂的人类颌部肌肉中的肌肉活动模式似乎对任务敏感。然而，目前尚不清楚运动任务的变化如何影响人类颞肌运动单位（MU）的行为。在本研究中，记录了颞肌前部区域40个运动单位的活动。通过缓慢增加和降低放电频率达到最低可持续放电频率（LSFF），然后以尽可能低的速率维持放电，且无明显停顿。对一系列连续的峰间间隔（ISI）进行数字采样，并用于测量与每个运动单位相关的每个任务的最低可持续放电频率。在一个受控范式中，在执行不同任务期间测量运动单位反射抑制。将非有害强度的单个电脉冲施加到上颌尖牙附近的牙龈。在以10Hz的受控放电频率连续运动单位放电期间，在预选的尖峰之后，以增加的延迟施加一系列脉冲。运动单位在执行1-4项姿势和牙齿接触任务期间持续放电。在与多项任务相关的那些运动单位中，不同任务之间的最低可持续放电频率存在显著差异。在反射研究中，所有运动单位均受到抑制，但抑制程度高度依赖于任务。因此，颞肌运动单位的最低可持续放电频率和反射抑制似乎都随运动任务而变化，并且对颌骨位置以及沿牙列的牙齿接触方向和位置敏感。这种行为很可能反映了口面部和肌肉传入神经输出中与任务相关的变化。
