2020 Volume 39 Issue 1 Pages 1-7
The “taste” of foods is perceived as a flavor formed from integrating multimodal information such as olfaction, temperature of foods and the sense of touch on the oral mucosa, with gustation. However, the mechanisms for the flavor information processing are still controversial. In this review, it will be described where and how the taste and odor information are integrated into the flavor in the brain on the basis of recent our knowledge. As part of the review, I will also introduce recent our research for this issue. We observed the cortical responses for the taste and/or odor stimulation in the experimental rats and mouse brain under the anesthetized condition using in vivo flavin protein autofluorescence imaging technique. When the animals were stimulated by odor alone, corresponding responses were observed only in the piriform cortex（PC）. Similarly, taste-alone stimulation elicited the responses in the gustatory area（GC）in the insular cortex（IC）. Interestingly, simultaneous stimulation by odor and taste induced the additional response in the agranular insular cortex（AI）. Moreover, in mice trained to learn the association between a taste and an odor, the response area evoked by stimulation with odor or taste alone was altered. In these mice we observed that the odor-alone stimulation evoked the responses not only in the PC but also in the GC, and that taste-alone stimulation evoked the responses in the PC in addition to the GC. These results suggest that the PC, IC including the AI, and surrounding brain region are involved in the formation of associative learning of taste and odor, as “the flavor formation”, and in the representation of the flavor in the brain.
