Neurosystems linking corticolimbic and hypothalamic pathways in energy balance: view from the Chair

Abstract

Recent work has advanced our knowledge of the neural pathways interfacing corticolimbic substrates of food motivation and reward with hypothalamic controls of food intake. As a neuroanatomical interface between limbic motivational processes, energy-sensing mechanisms in the mediobasal hypothalamus and motor output pathways, several studies draw attention to the lateral hypothalamus. Reviewed here are some highlights of the first session of the 11th International Symposium of the Merck- Keywords: dopamine; endocannabinoids; nucleus accumbens; orexin; melanin-concentrating hormoneThe central nervous system plays a crucial role in integrating numerous hormonal and metabolic signals derived from the periphery and thereby generating adaptive behavioral responses to changing energy demands. Under normal conditions, there are several mechanisms at the level of the hypothalamus and hindbrain that effectively respond to states of energy deficit or surplus in part by modulating appetite. The significance of key hypothalamic neuronal populations for energy homeostasis is underscored by genetic gain-and loss-function studies. 1 On the other hand, there exist cortical and limbic processes that underlie the cognitive and rewarding aspects of food by assimilating information about taste, texture, smell and post-ingestive consequences. 2,3 Sensory and value representations of food and the cues and properties associated with obtaining food are stored in the memory where they serve an essential function, especially during conditions of low food availability, to orient animals back to (or away from in conditions of aversion) the source of food.The heightened behavioral, emotional and cognitive response to palatable high-fat and -sugar foods that has evolved can be understood in terms of what these foods offer in energy value. Indeed, the rewarding experience that is produced by eating tasty, energy-rich foods can produce a lasting impression that acts to strengthen action-outcome associations and reinforce future behavior directed at obtaining food. Of relevance for the epidemiology of obesity in humans, we must consider that food intake is accompanied by several precipitating factors in modern industrialized societies. Many foods come in catchy packaging, are well advertised, easily obtainable and relatively cheap. Thus, we are frequently bombarded with food-associated cues that remind us about how, where and when we can get access to these foods. As we have become well acquainted with the contribution of rewarding, easily accessible and inexpensive high-fat and -sugar foods to the epidemic of obesity, it is increasingly evident that we need to unravel the neural mechanisms that process not only the hedonic effects of palatable foods, but also those that govern reward-relevant learning, valuation and decision making in the context of modern social and economic climates.Of direct bearing to the discussion here, it is important that we identify which neural pathways and processes interface corticolimbic mechanisms affecting feeding...

IMAGING IN ENDOCRINOLOGY: The use of functional MRI to study the endocrinology of appetite

“…Rodent models confirm a structural and functional connection between the hypothalamus, hippocampus and corticolimbic systems (19). fMRI has allowed us the opportunity to probe this interface between neuroendocrinology and psychology in humans.…”