Taste Learning in Insular Cortex: Plasticity Is Influenced by Experience Type

The gustatory cortex (GC) has long been studied as the main cortical area encoding taste stimuli and likely integrates sensory, visceral, and emotional information to guide taste-related behaviors. However, our understanding of cortical taste coding on a single-cell level has only become clear in recent years. The anatomical location of GC on the lateral and ventral surface of the brain makes it difficult to target with traditional imaging methods. Thus, much of what we know about cortical taste coding and cortical taste plasticity has been derived either from multiunit electrode recordings or anesthetized imaging experiments, techniques which lack the ability to reliably track neurons over time. To address this limitation, we use miniaturized microendoscope (miniscope) imaging of the calcium indicator GCaMP6s to investigate how cortical taste coding changes with different types of experience. In a basic taste experience paradigm, in which animals consume taste stimuli based on innate taste preferences, we address the question of how novelty and familiarity of taste stimuli effect cortical coding. Using multiday cell tracking, we find two populations of neurons: a stable population encoding taste quality information, and a transient cell population whose activity correlates with the animal's behavioral state. We use the associative learning paradigm conditioned taste aversion (CTA) to show changes in the transient cell population depend upon experience type. With basic experience, the number of transient cells decreases as animals become familiar with taste stimuli and the behavioral task. After increasing situational salience using CTA, the number of transient cells increases to levels seen during novel taste exposure. This research demonstrates a clear role for novelty and familiarity in population responses to taste stimuli in GC, and suggests an overall implication for these effects in cortical coding of sensory stimuli.