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Abstract

The body constantly processes information about the outside world and the world inside itself. The mouth serves as a vital sensing gate for the taste, temperature and texture of food. Oral receptors relay sensory information about ingested contents to the insular cortex, which harbors the primary cortical center for gustatory information processing (Small, 2010). The insula receives afferent inputs not only from the mouth but also from the entire body, including the digestive system. The processing of bodily (or interoceptive) information in the insular cortex gives rise to subjective bodily sensations (e.g., taste, hunger, thirst, fullness, warmth) and, in turn, regulates bodily functions (Craig, 2003). Given the importance of these bodily feelings in metabolic wellness and in psychosomatic integration, mapping where each bodily process is represented in the insula is clearly needed. In several 7T fMRI studies with the anesthetized macaque monkey (n=12), we introduced taste and rectal distention paradigms while measuring the sensory information relay to key subcortical and cortical network processing hubs. The insula, in particular, was consistently activated. Analyses of low- and high-intensity sweet, sour and salty taste stimuli disclosed tastant-specific activations across the mid-anterior dorsal insular cortex where other oral sensory afferents are represented, thereby alluding to a potential gustotopic map embedded within a full mouth representation. Rectal distention, on the other hand, activated specifically the ventral anterior insula, suggesting that purely sensory (e.g. taste, temperature and texture of food) and sensory-motor (e.g., distention and contraction of the gut) processing may be represented in two distinct insular territories.