The normalizing effect of lateral amygdalar lesions upon the dorsomedial amygdalar syndrome in dogs.

Two types of bilateral amygdalar lesions were performed successively. The first operation, involving the dorsomedial part, produced aphagia and subsequent hypophagia, vomiting and apathy. Consequently the body weight was reduced. After a few weeks partial recovery occurred. The second operation, involving the lateral part of the amygdaloid complex, produced hyperphagia, increase of body weight and restoration of general arousal. These results indicate the existence of two antagonistic systems: excitatory in the dorsomedial amygdala and inhibitory in the lateral amygdala. Damage of the inhibitory system reverses almost completely the syndrome produced by an initial lesion of the excitatory system.