Effects of hunger on the responses of neurons in the lateral hypothalamus to the sight and taste of food

Recordings were made from single neurons in the monkey lateral hypothalamus and substantia innominata which had previously been shown to respond with an increase or decrease of their firing rates when the hungry monkey tasted food, and/or when he looked at food. It was found that the responsiveness of these neurons to food decreased over the course of a meal of glucose as satiety increased. When satiety, measured by whether the monkey rejected the glucose, was complete, there was no response of the neurons to the taste and/or to the sight of glucose. The spontaneous firing rates of these cells were not affected by the transitions from hunger to satiety. This modulation of responsiveness to food of hypothalamic cells was specific to them in that it was not seen in cells in the globus pallidus which responded in relation to swallowing and mouth movements, or in cells in the visual inferotemporal cortex which responded when the monkey looked at the glucose-containing syringe. On the basis of this and other evidence it is suggested that the hypothalamic cells described here could be involved in the autonomic, the endocrine, and/or the feeding responses which occur when an animal sees or tastes food.