Abstract
In this experiment, the physiological function of the neocortical jaw motor area and amygdaloid nucleus in relation to jaw movement were studied in the rabbits.
1. By single unilateral shock to either of the cortical jaw motor areas, internal capsule, subthalamus or deeper part of mesencephalic reticular formation, the digastric muscles showed marked bilateral electromyographic responses. However, the masseter did not respond at all.
2. The corticofugal pathway for jaw movement was found to have an intercalary center in the subthalamic region after passing through the internal capsule. This pathway may have a decussation at the level of mesencephalic reticular formation.
3. Following stimulation of either the lateral amygdaloid nucleus or dorsal part of the mesencephalic reticular formation only the ipsilateral masseter responded electromyographically.
4. The descending pathway from the amygdala is considered to play a predominant part in closing the jaw and that from the cortex is assumed to be the one for opening the jaw.
