Abstract
Brain regions inducing jaw movement and characters of the induced movement were analyzed on the rabbit.
1. The cortical jaw motor area are strictly circumscribed in the region rostral to area insularis and lateral to area postcentralis. The patterns of the jaw movements from here were single contraction of the jaw at low stimulation frequencies and rhythmic jaw movement of 4.5 to 5.75 c/s at higher frequencies. These jaw movements were predominant in the opening direction. The jaw movements from the. internal capsule and subthalamus were almost similar in characters to those from the cortex.
The jaw movement from the lateral amygdaloid nucleus was also a single contraction of the jaw at low frequencies below 4 c/s and at high frequencies a rhythmic jaw movement of 3.5 to 4.0 c/s was evoked. In this case the movement was predominant in the jaw closing direction and its rhythm was similar to that of natural chewing. As compared with the cortex, the amygdala had a lower threshold and longer latency.
2. The cortical and amygdaloid jaw movements could be elicited independently, and the destruction of one of these areas did not affect the jaw movement elicited from the other.
3. The descending neural pathway from the cortical jaw motor area to the trigeminal motor nucleus is assumed to be via the internal capsule, subthalamus and mesencephalic reticular formation, while the pathway from the amygdaloid nucleus may be via the mesencephalic reticular formation, but not through the internal capsule and subthalamus.
