Neuroanatomical correlates of hunger and satiation in humans using positron emission tomography

The central role of the hypothalamus in the origination and/or processing o f feeding-related stimuli may be modulated by the activity of other functio nal areas of the brain including the insular cortex (involved in enterocept ive monitoring) and the prefrontal cortex (involved in the inhibition of in appropriate response tendencies). Regional cerebral blood flow (rCBP), a ma rker of neuronal activity, was measured in 11 healthy, normal-weight men by using positron emission tomography in a state of hunger (after 36-h fast) and a state of satiation (after a liquid meal). Hunger was associated with significantly increased rCBF in the vicinity of the hypothalamus and insula r cortex and in additional paralimbic and limbic areas (orbitofrontal corte x, anterior cingulate cortex, and parahippocampal and hippocampal formation ), thalamus, caudate, precuneus, putamen, and cerebellum. Satiation was ass ociated with increased rCBP in the vicinity of the ventromedial prefrontal cortex, dorsolateral prefrontal cortex, and inferior parietal lobule. Chang es in plasma insulin concentrations in response to the meal were negatively correlated with changes in rCBF in the insular and orbitofrontal cortex. C hanges in plasma free fatty acid concentrations in response to the meal wer e negatively correlated with changes in rCBF in the anterior cingulate and positively correlated with changes in rCBF in the dorsolateral prefrontal c ortex. In conclusion, these findings raise the possibility that several reg ions of the brain participate in the regulation of hunger and satiation and that insulin and free fatty acids may be metabolic modulators of postprand ial brain neuronal events. Although exploratory, the present study provides a foundation for investigating the human brain regions and cognitive opera tions that respond to nutritional stimuli.