The representation of oral fat texture in the human somatosensory cortex

Abstract

How fat is sensed in the mouth and represented in the brain is important in relation to the pleasantness of food, appetite control, and the design of foods that reproduce the mouthfeel of fat yet have low energy content. We show that the human somatosensory cortex (SSC) is involved in oral fat processing via functional coupling to the orbitofrontal cortex (OFC), where the pleasantness of fat texture is represented. Using functional MRI, we found that activity in SSC was more strongly correlated with the OFC during the consumption of a high fat food with a pleasant (vanilla) flavor compared to a low fat food with the same flavor. This effect was not found in control analyses using high fat foods with a less pleasant flavor or pleasant-flavored low fat foods. SSC activity correlated with subjective ratings of fattiness, but not of texture pleasantness or flavor pleasantness, indicating a representation that is not involved in hedonic processing per se. Across subjects, the magnitude of OFC-SSC coupling explained inter-individual variation in texture pleasantness evaluations. These findings extend known SSC functions to a specific role in the processing of pleasant-flavored oral fat, and identify a neural mechanism potentially important in appetite, overeating, and obesity.

Lipids in Eating and Appetite Regulation – A Neuro‐Cognitive Perspective

“…The role of the OFC is hereby primarily discussed with respect to hedonic aspects of fat texture: neural activity in the mid OFC and ACC has been shown to correlate with the pleasantness of oral fat texture, indicating a potentially relevant neural mechanism determining the consumption of fatty foods. In addition, evidence supported an integration of texture as a contextual cue with the chemosensory stimulation indicating the presence of a macronutrient: combined with a pleasant flavor, high fat foods were shown to elicit systematically higher functional coupling between the somatosensory region and the OFC than pleasant‐flavored low fat foods or less pleasant‐flavored high fat foods . These results are consistent with the studies on multisensory integration of food perception described above, showing that activity in reward networks of the OFC and ACC is enhanced when combining, for example, the different sensory cues involved in food perception.…”

Taste, olfactory, and food reward value processing in the brain

“…This provides a foundation for future studies of whether activations in the fat reward system are heightened in people who tend to become obese (Rolls, 2012a). Interestingly, high fat stimuli with a pleasant flavor increase the coupling of activations between the orbitofrontal cortex and somatosensory cortex, suggesting a role for the somatosensory cortex in processing the sensory properties of food in the mouth (Grabenhorst and Rolls, 2014).…”

Functions of the anterior insula in taste, autonomic, and related functions

“…This provides a foundation for future studies of whether activations in the fat reward system are heightened in people who tend to become obese (Rolls, 2012). Interestingly, high fat stimuli with a pleasant flavor increase the coupling of activations between the orbitofrontal cortex and somatosensory cortex, suggesting a role for the somatosensory cortex in processing the sensory properties of food in the mouth (Grabenhorst & Rolls, 2014). On the other hand, activations in a frontal opercular/insular region at Y = 12 and Y = 18 (and in an agranular (far anterior) insular region at Y = 24), are activated in relation to the unpleasantness of fat texture and flavor (Fig.…”