Cross-Modal Integration in Olfactory Perception

Abstract

In everyday life, odorous sensations are a multisensory experience. In other words, odors are perceived before, during, or after inputs of other sensory systems like the visual, gustatory, auditory and tactile system. Thus, multisensory processing of olfactory cues should be assumed as a realistic stimulation for the perception of odors. Odors are perceived through two main pathways: orthonasal and retronasal routes and odors are processed in a different manner depending on the pathway. Therefore, before reviewing effects of other sensory cues on olfactory perception, both orthonasal and retronasal olfactory systems are discussed at psychophysical, cortical electrophysiological and neuroanatomical levels. This chapter introduces cross-modal correspondence between olfactory and other sensory cues; it also features the effects of other sensory inputs, such as visual, gustatory, auditory, trigeminal and tactile cues, on olfactory perception, with a focus on key modulators in cross-modal integration. Overall, most of the cross-modal integration between olfactory and other sensory cues appears to occur at a central nervous level. Many studies have emphasized the role of congruency between bimodal cues in cross-modal integration. The modulatory effect of congruency was found to be influenced by many factors such as odor delivery route (orthonasal and retronasal pathways), selective attention, experience (associative learning), cultural background, type of given task (analytical versus synthetic) and characteristics of a given stimulus.