Abstract
Mastication is consisted of various jaw movements commencing with ingestion and ending with swallowing. The progress of mastication is dependent on the interaction of the motor mechanism with variable characteristics of chewed food. In the guinea pig, jaw movement patterns with the progress of mastication have not been clarified under freely moving condition. In this study we recorded EMG activities bilaterally from the masseter and the digastric muscles and simultaneously the jaw movements using a magnetic sensor system. The recordings were made for 1-hour ad libitum fed after 5 hours fast. Masticatory behavior was divided into two stages, (1) an intake-stage representing food intake and transport, and (2) a chewing-stage, food chewing. During the intake-stage, vertical jaw movements were associated with synchronous activations of bilateral masseter muscles. The chewing-stage was characterized mostly by alternate lateral jaw excursions with alternate EMG activity in right and left masseter muscles. Within the chewing-stage, jaw movement patterns altered along with the progress of mastication. These data suggests that masticatory stages in guinea pigs can be estimated by the EMGs and jaw movements. [Jpn J Physiol 55 Suppl:S178 (2005)]
