Representation in the human brain of food texture and oral fat.
Important factors that influence food palatability are its texture and fat content. We investigated their representation in the human brain using event-related functional magnetic resonance imaging. It was shown that the viscosity of oral stimuli is represented in the (primary) taste cortex in the anterior insula, in which activation was proportional to the log of the viscosity of a cellulose stimulus (carboxymethyl cellulose), and was also produced by sucrose. Oral viscosity was also represented in a mid-insular region that was posterior to the taste cortex. Third, it was found that oral delivery of fatty vegetable oil activates both of these insular cortex regions, the hypothalamus, and the dorsal midanterior cingulate cortex. Fourth, it was found that the ventral anterior cingulate cortex, where it borders the medial orbitofrontal cortex, was activated by oral fat independently of its viscosity and was also activated by sucrose taste. This ventral anterior cingulate region thus represents two indicators of the energy content and palatability of foods. These are the first investigations of the oral sensory representation of food texture and fat in the human brain, and they start to reveal brain mechanisms that may be important in texture-related sensory properties of foods that make them palatable and that may accordingly play a role in the hedonic responses to foods, the control of food intake, and obesity.