Experience with Odor-Taste Mixtures Reshapes Odor Concentration-Dependent Ingestive Behavior.

Stimulus concentration shapes decisions about what and how much to eat, with numerous studies demonstrating how taste concentration influences consummatory choice. However, eating is inherently multisensory, with gustatory and olfactory signals interacting to shape the perceived intensity and hedonic value of chemosensory stimuli. How odor concentration influences ingestive behavior, either alone or in combination with taste, remains unclear. Here, we used a 2-bottle brief-access task to test whether rats use differences in odor concentration to guide consummatory choice and how experience with odor-taste mixtures influences concentration-dependent ingestive behavior. When presented with low (0.01%) and high (0.1%) nominal concentrations of the same odorant, rats consumed more of the lower concentration for two of four odorants, demonstrating that odor concentration alone can guide consummatory choice in an odorant-specific manner. We next measured ingestive behavior before, during, and after pairing both concentrations of isoamyl acetate with either sucrose or citric acid. After pairing both concentrations with sucrose, rats increased sampling and palatability-related licking of the less-preferred high concentration. In contrast, after pairing with citric acid, rats showed increased sampling and palatability-related licking of the already preferred low concentration. Together, these findings demonstrate that odor concentration contributes to consummatory choice and that experience with odor-taste mixtures reshapes ingestive behavior by altering the behavioral value of different concentrations of the same odorant in a manner that depends on the hedonic value of the paired taste.