An electromyographic study of mastication in the freely-moving rat.

The EMG patterns of temporalis, masseter and digastric muscles of twenty Wistar white rats were studied as they ate large and small standard food pellets, bread and pudding. Bipolar EMG electrodes were placed in the muscles and led subcutaneously to a connector pedestal on the rat's head. Integrated records of the EMG patterns were used for analysis. The open-close chewing cycle was initiated by digastric activity to open the mouth; temporalis began the closing phase, followed soon thereafter by activity in masseter. A second burst of activity from digastric occurred during this closing phase analogous to the human lateral pterygoid muscle in stabilizing the structures of the mandibular joint.