Neuronal activity in the putamen and the globus pallidus of rabbit during mastication

The pattern of jaw movements is changed during a masticatory sequence from ingestion of food to its deglutition. The masticatory sequence is divided into three distinct stages in the rabbit. However, the neural mechanism involved in the alteration of the masticatory stages is still unknown. This study was designed to determine whether neuronal activity in the putamen and globus pallidus is related to the alteration of the masticatory stages. Fifty-three percent of the recorded neurons showed significant alterations of activity during mastication. Of these neurons, 16% changed their firing frequency throughout the masticatory sequence (sequence-related neurons) and 84% changed their firing frequency with the transition of the masticatory stages (stage-related neurons). The stage-related neurons were classified into two groups based on their neuronal activity patterns observed during mastication, i.e. simple type and complex type. The former are the neurons that were either facilitated or inhibited once during mastication, and the latter are those showing the facilitation or inhibition twice or more during mastication. Complex-type neurons were observed more frequently in the globus pallidus than in the putamen. These results suggest that the basal ganglia is involved in mastication and may related to the transition between the masticatory stages.