Flavor is an integrative sensation comprised of taste, odor, and mouthfeel. The interaction between olfactory cues and taste is particularly important for flavor formation. Because odor information is conveyed to the insular cortex (IC), the
integration of olfactory and gustatory chemosignals may be performed in the IC. However, little is known about how these chemosignals converge in the IC. In this review, we explore the mechanisms underlying signal
integration in the IC, and we summarize several studies relevant to this issue. Some
morphological findings have indicated the presence of bidirectional connections between the piriform cortex (PC) and IC. Clarifying the functional interactions between these cortices, some groups, including ours, have demonstrated the spatiotemporal dynamics of excitatory propagation induced by simultaneously stimulating olfactory and gustatory pathways, using an
in vivo optical imaging technique with a voltage sensitive dye.
Highlights
In our study, simultaneous stimulation of olfactory and gustatory pathways showed spatially additive responding regions within the PC and IC. Responses of the agranular IC (AI) to simultaneous stimulation showed a synergistic increase in amplitudes, whereas the responses in other areas were of the same order of magnitude as the responses to the single stimulation of either olfactory or gustatory pathway.
Conclusion
Several studies, including fMRI analyses in human and animal studies, suggest that the IC directly integrates olfactory and gustatory chemical signals. In particular, our study raises the possibility that the AI plays an important role in integrating olfactory and gustatory signals.
