Amygdala functions within the alimentary system.

The amygdaloid complex plays an important role in various defensive, sexual and metabolic functions of the organism. Our previous experiments on the defensive functions demonstrated that the amygdala may be divided into dorsomedial excitatory and basolateral inhibitory parts. Our recent experiments showed that this division is true also for alimentary mechanisms. The dorsomedial part of the amygdala acts as a facilitatory "center" and the lateral part as an inhibitory alimentary "center". These functions of the amygdala are parallel to those of the hypothalamic feeding centers. Bilateral damage to either the dorsomedial amygdala or to the lateral hypothalamus produced aphagia with adipsia, decrease of body weight and impairment of both classical and instrumental reactions. These changes were accompanied by low general arousal, atonia, catatonic like positions, negavitism and loss of positive emotional reactions. Damage to the lateral amygdala, on the other hand, produces a syndrome similar to damage to the ventromedial hypothalamus, i.e. hyperphagia and an increase of body weight. Slight increase of both classical and instrumental reactions and disinhibition of responses during intertrial intervals were found in both cases. Combined damage of the dorsomedial amygdala and lateral hypothalamus enhanced the symptoms attributable to each and prolonged the period of aphagia. Damage to the lateral amygdala subsequent to lesions of the dorsomedial amygdala and/or the lateral hypothalamus produced restoration of food intake, instrumental reactions and general arousal.