Abstract
We found the projection from the cortical masticatory area (CMA),which induced chewing-like jaw movement by repetitive electrical stimulation, to the primary motor cortex of the orofacial area (face-MI) using histologicall methods. However, the functional role of this neural connection is still unknown. The aim of this study is to understand the influence of this intracortical connection on elicitation of the rhythmic jaw movements induced by repetitive electrical stimulation to the CMA. Unanesthetized guinea pigs fixed on a stereotaxic apparatus were used. Jaw movements and masticatory muscles EMG activities were recorded. The stimulation electrode was fixed into the CMA where rhythmical jaw movements were evoked. We examined changes of elicitation of jaw movements before and after muscimol injection that inactivated neurons in the face-MI. After inactivation of the face-MI, the latency of cortically-induced jaw movement was prolonged with the same stimulus intensity. In some cases, rhythmic jaw movements were not evoked. On the next day, cortically-induced rhythmic jaw movements from the same site were the same as before muscimol injection. From these results, it is suggested that the intracortical neural connection from the CMA to the face-MI plays an important role on elicitation of rhythmical jaw movements evoked by repetitive electrical stimulation to the CMA. [J Physiol Sci. 2008;58 Suppl:S197]
