Participation of periodontium-sensitive neurons in jaw movements

牙周机械敏感(PM)神经元有助于口腔内对食物的位置、硬度和质地的感觉。它们可以调整下巴的运动，从而有效而流畅地进行咀嚼。为探讨牙周信息对咀嚼下颌运动的影响，研究了麻醉大鼠初级躯体感觉(SI)皮层的反应特性。PM神经元出现在SI皮质的两个区域。吻侧(Rm)区神经元对对侧下颌切牙敏感，吻侧区(RL)区神经元对对侧上颌切牙敏感。他们中的大多数都是快速适应的神经元。在兔中，观察到重复电刺激皮质PM神经元记录部位引起的节律性下颌运动(RJM)。此外，还记录了兔SI皮层的RM和RL区的PM神经元。在RM区，大多数PM单位(85%)对切牙较低敏感。电刺激Rm区产生了断裂型RJM。在RL区，切牙和磨牙敏感的PM单位都被记录到，磨牙敏感的单位比切牙敏感的单位更靠近嘴部内侧。超过一半(66%)的切牙敏感型PM单位是上切牙敏感型。电刺激RL区PM单位记录部位可诱发研磨型RJM。根据这些发现，SI皮层RM区的下部切牙敏感神经元可能主要参与了控制摄食过程中颌骨运动的神经网络。磨牙敏感皮层神经元的反应特性可能有助于区分磨削过程中咬合力的大小和方向。

Periodontal mechanosensitive (PM) neurons contribute to intra-oral sensation of the location, hardness and textures of foods. They modifies jaw movements so that mastication I performed effectively and smoothly. To investigate the effect of periodontal information on masticatory jaw movements, the response properties of the primary somatosensory (SI) cortex were studied in the anesthetized rat. PM neurons were represented in two areas in the SI cortex. The neurons in the rostro-medial (RM) area were sensitive to the contralateral mandibular incisor tooth, and those in the rostro-lateral area (RL) area were sensitive to the contralateral maxillary incisor tooth. The majority of them were rapidly adapting neurons. In the rabbit, rhythmical jaw movements (RJMs) induced by repetitive electrical stimulation of the recording sites of cortical PM neurons were observed. PM neurons of the rabbit were also recorded from the RM and RL areas of the SI cortex. In the RM area, most PM units (85 %) were lower incisor-sensitive. Electrical stimulation of the RM area produced the chopping-type RJMs. In the RL area, both incisor- and molar-sensitive PM units were recorded, and molar-sensitive units were located more rostro-medially than incisor-sensitive units. More than half (66 %) of the incisor-sensitive PM units were upper incisor-sensitive. Electrical stimulation of the PM unit-recording sites in the RL area induced grinding-type RJMs. Based on these findings, the lower incisor-sensitive neurons in the RM area of the SI cortex might mainly contribute to a neural network that controls jaw movements during ingestion. The response properties of molar-sensitive cortical neurons might be useful for discriminating the magnitude and direction of the biting force during grinding.