Use of an Immediate Swallow Protocol to Assess Taste and Aroma Integration in fMRI Studies

Perception of flavor is a complex process involving the integration of taste and aroma. Few functional magnetic resonance imaging (fMRI) studies have assessed the crossmodal interactions which result in flavor perception, and all previous studies have used a retro-nasal aroma delivery with a delayed swallow, which delays retro-nasal aroma release, and thus, alters taste and aroma integration. In this paper, we assess crossmodal interactions in flavor processing using an immediate swallow fMRI paradigm in 13 healthy volunteers. We compare unimodal taste (sucrose) and unimodal retro-nasal aroma stimuli, with a congruent taste and aroma combination (flavor), to assess crossmodal flavor interactions using an immediate swallow paradigm. Subtraction and conjunction analysis methods are described, and the use of a control stimulus is addressed. Subtraction analysis was found to reveal areas of anterior insula, frontal operculum, anterior cingulate, and orbitofrontal cortex, whilst the conjunction analysis revealed additional active areas in oral somatosensory areas (SI), rolandic operculum and posterior cingulate, supporting the hypothesis that taste, olfactory, and tactile sensations are integrated to produce a flavor percept.