The neurophysiology of feeding

Investigations in non-human primates have provided evidence that the lateral hypothalamus and adjoining substantia innominata are involved in the control of feeding, for there is a population of neurons in these regions which respond to the sight and/or taste of food if the organism is hungry. The responses of these neurons may reflect the rewarding value or pleasantness of food, for stimulation in this region can mimic the reward value of food. It has been found that although after satiation with one food these neurons no longer respond to that food, they may still respond at least partly to other foods which have not been eaten. Following this finding, it has been shown that sensory-specific satiety is an important determinant of human food intake, and that associated with this, variety is an important factor in determining the amount of food eaten. A route for information about which visual stimuli are foods to reach the hypothalamus is provided by temporal lobe structures such as the inferior temporal visual cortex and amygdala, with the amygdala being important for learning which visual stimuli are foods. The orbitofrontal cortex contains a population of neurons which appear to be important in correcting feeding responses as a result of learning. The striatum contains neural systems which are important for the initiation of different types of motor and behavioural responses, including feeding.