The effect of multisensory context and experience on flavor preference decisions in rats

Flavor is perceived through multiple senses, including gustation and olfaction. Previous studies have shown that different sensory qualities that make up flavor are integrated to inform perceptual judgements. Psychophysical work in humans further suggests a prominent role for congruency (i.e., the learnt correspondence between taste and odor components of flavor through eating experience) in shaping multisensory interactions underlying perceptual judgments of flavor. However, eating experience cannot be controlled in humans, and depending on the type of judgement, these studies yielded mixed findings. Here, we used rats to test how experimentally-controlled experience with specific flavor mixtures (Odor_A+Taste_A and Odor_B +Taste_B) from weaning to adulthood affects subsequent flavor preference judgements in a series of two-bottle preference tests. In unisensory conditions, animals made odor or taste preference decisions (i.e., Odor_A versus Odor_B and Taste_A versus Taste_B, respectively). In multisensory conditions, animals made identical decisions, but the addition of the other modality rendered one solution congruent; the other one incongruent (e.g., Odor_A+Taste_A versus Odor_B+Taste_A). The results show that animals effectively learned congruency associations between the taste and smell components of experienced flavor mixtures. Comparing unisensory and multisensory conditions revealed no systematic effect of congruency on the magnitude of flavor preference, but preferences were less variable in multisensory compared to unisensory conditions. Results from a second group of naïve animals further demonstrate that increased reliability of preference judgements in multisensory conditions was independent of experience.