Flavor and the Formation of Category-Specific Processing in Olfaction

The perception of flavor occurs when objects, such as food and drink, are placed in the mouth. Although the sensation that ensues depends upon inputs from multiple sensory modalities, due to a combination of oral referral and common sensory qualities (e.g., odors and tastes can both be sweet), it is experienced as a unitary flavor perception. In this paper, it is proposed that neural processing within the somatomotor mouth area of the Rolandic operculum mediates oral referral and causes the neural binding of multimodal inputs to create a flavor percept. It is further proposed that unimodal taste and unimodal smell neurons alter the selectivity of bimodal taste/smell cells only if the binding mechanism in the somatomotor mouth area is active. The encoded flavor object is thus represented by a bounded pattern of response that includes the sculpted bimodal cells as well as the unimodal responses distributed across the insula, operculum, anterior cingulate cortex, and orbitofrontal cortex. Once an odor is encoded in this way, the odor acquires the ability to reactivate this encoded percept, whether experienced orthonasally or retronasally. Finally, it is proposed that one manifestation of this process is the existence of category-specific processing in olfaction.