The difference pattern of regulation by muscle spindles during the various cortically-induced rhythmic movements.

为了阐明控制咀嚼力的机制，我们分析了麻醉兔皮质节律性颌骨运动(CRJMs)过程中，三叉神经中脑核(Mesv)的梭形传入放电与咀嚼肌肌电信号和颌骨运动的同步变化。此外，我们还研究了试纸咀嚼前和咀嚼过程中肌电信号差异的开始。制备了5条不同硬度的聚氨酯泡沫塑料试条，并将其插入CRJMS过程中的两对磨牙之间。结果如下：1.咬肌肌电爆发的综合活动和持续时间也随着条带硬度的增加而增加。所有被记录的传入信号都随着颌骨的运动而有节律性地放电，并且闭口期的脉冲数目随着材料硬度的增加而增加。评估咀嚼条状的咬肌肌电反应的起始值，偶尔出现在伸颌反射的最短潜伏期的用力起始点或延时之前。在早期反应中(如文献3所述)，咬肌肌电反应的起始行为如下：(1)咀嚼肌肌电反应不受牙条硬度的影响，(2)不受牙周传入神经支配的影响，(3)肌梭传入传入的去化而延迟，提示肌梭活动参与了咀嚼过程中的前馈机制。

To elucidate mechanisms of controlling masticatory force, we analyzed the discharges of spindle affertents in the mesencephalic trigeminal nucleus (MesV) simultaneously with masticatory muscle EMGs and jaw movements during cortically induced rhythmic jaw movements (CRJMs) in anesthetized rabbits. In addition, we investigated the onset of the difference between the EMG signals of both before and during the chewing of test strip. Five test strips of polyurethane foam of different hardness were prepared and inserted between the opposing molars during CRJMs. Similar recordings were made after deafferentation of periodontal and/or muscle sensations.Results obtaind were as follows :1. The integrated activity and duration of the masseteric EMG bursts also increased with strip hardness.2. All recorded afferents dischrged rhythmically in reration to jaw movements, and the number of impulse during the jaw-closing phase increased with increasing the hardness of the materials.3. The onset of the masseteric EMG response to the chewing of strip was evaluated, and it was occasionaly before the force onset or time lapse of the shortest latency for the jaw-stretch reflex.4. In the early response (as described in 3), the behavior of the onset of the masseteric EMG response was as follows :(1) It was not changed by strip hardness.(2) It was not changed by the denervation of periodontal afferents.(3) It was delayd by the deafferentation of muscle spindle afferents.These results suggest that the muscle spindle activity is involved in the feedforward machanism during chewing.