FMRI BOLD activation in response to sweet, sour, and fatty acid oral stimuli in human

Neural responses as measured by functional magnetic resonance imaging (fMRI) to oral exposure to two known primary tastes, sweet (sucrose) and sour (citric acid) were compared with responses to an oral fat stimulus (linoleic acid) to determine whether fat activates areas of the brain involved in taste signal processing similar those activated by known taste primaries. Analysis of responses to deliveries that were correctly identified by participants demonstrated changes blood oxygenation level dependent (BOLD) activation due to all taste stimuli (sucrose, citric acid, and linoleic acid) compared to vehicle in a number of brain areas, including the anterior cingulate cortex, orbitofrontal cortex, insula, and thalamus. However, when responses to individual taste stimuli were analyzed, sucrose was the only stimulus that produced significant changes in activation (in the orbitofrontal cortex and thalamus). The results suggest that changes in BOLD activation during the present task may have reflected the demands of identifying the taste stimulus rather than perceptual responses to oral receipt of the individual taste stimuli.