Amygdala-hypothalamic control of feeding behavior in monkey: single cell responses before and after reversible blockade of temporal cortex or amygdala projections.

Single unit activity in the monkey amygdala and the lateral hypothalamic area was recorded during an operant feeding task. The task required discrimination of food, non-food, rewarding, aversive, novel, and familiar objects. Correct discriminations were rewarded with food or juice. Some amygdala neurons responded to the sight of objects in a graded manner that depended on the degree of affective significance of the object. Some neurons in the lateral hypothalamus responded to reward predicting objects, such as the sight of some non-food item that had been associated with juice reward. Neuronal responses to the sight of objects were influenced by extinction or reversal tests. Responses in the amygdala depended on extent of the affect or value of the reward and responses in the lateral hypothalamus depended on positive reinforcement. Information processing in the inferotemporal cortex--amygdala--lateral hypothalamus axis was identified by reversible changes induced in the temporal cortex or amygdala by cooling. The results suggest that the amygdala contributes to stimulus--affect associations and that the lateral hypothalamus is related directly to the initiation or termination of feeding through learning of stimulus-reinforcement association and/or maintenance of homeostasis. In addition the results suggest that the amygdala does more sensory processing than the lateral hypothalamus.