Figure 2. Gut–brain signalling related to food intake.

Nutrient-related signals reach the CNS through spinal, vagal and endocrine signalling pathways. Endocrine signalling of gut peptides that are released into the systemic circulation reach the dorsal vagal complex through the area postrema where they modulate the transmission of afferent vagal signals to the dorsal motor nucleus. These gut peptides also reach specialized neurons within the hypothalamus. Paracrine signals activate function-specific vagal afferent fibres that ultimately signal to subregions of the anterior insula (aINS). The sensory aspect of taste is primarily encoded in the aINS, but the multimodal integration of satiety signals with the sensory properties of food (including its flavour, palatability and reward value) as well as the context of food intake (including food related visual and auditory signals) occurs in the orbitofrontal cortex (OFC). Further integration with inputs from the reward system and with interoceptive memories of previous food ingestion generates a multidimensional food-related experience that ultimately determines ingestive behaviour. Prefrontal regions exert cognitive control over ingestive behaviours. Learning about food-related experiences and the formation of interoceptive memories is an important aspect of the cortical circuitry that is involved in this process. ACC, anterior cingulate cortex; AP, area postrema; ARC, arcuate nucleus; cNTS, caudal NTS; HIPP, hippocampus; LH, lateral hypothalamus; NAc, nucleus accumbens; NTS, nucleus tractus solitarius; PeF, pernifornical hypothalamus; OLF, olfaction; PFC, prefrontal cortex; rNTS, rostral NTS; VTA, ventral tegmental area.