What is the Relation between Chemosensory Perception and Chemosensory Mental Imagery?

The study of chemosensory mental imagery is undoubtedly made more difficult because of the profound individual differences that have been reported in the vividness of (e.g.) olfactory mental imagery. At the same time, the majority of those researchers who have attempted to study people's mental imagery abilities for taste (gustation) have actually mostly been studying flavour mental imagery. Nevertheless, there exists a body of human psychophysical research showing that chemosensory mental imagery exhibits a number of similarities with chemosensory perception. Furthermore, the two systems have frequently been shown to interact with one another, the similarities and differences between chemosensory perception and chemosensory mental imagery at the introspective, behavioural, psychophysical, and cognitive neuroscience levels in humans are considered in this narrative historical review. The latest neuroimaging evidence show that many of the same brain areas are engaged by chemosensory mental imagery as have previously been documented to be involved in chemosensory perception. That said, the pattern of neural connectively is reversed between the 'top-down' control of chemosensory mental imagery and the 'bottom-up' control seen in the case of chemosensory perception. At the same time, however, there remain a number of intriguing questions as to whether it is even possible to distinguish between orthonasal and retronasal olfactory mental imagery, and the extent to which mental imagery for flavour, which most people not only describe as, but also perceive to be, the 'taste' of food and drink, is capable of reactivating the entire flavour network in the human brain.