The impact of familiarity on cortical taste coding

Abstract

The role of the gustatory region of the insular cortex in mediating associative taste learning, such as conditioned taste aversion, has been well studied. However, while associative learning plays a role in some taste behaviors, such as avoidance of toxins, taste stimuli are often encountered by animals in their natural environment without explicit consequences. This type of inconsequential experience with sensory stimuli has been studied in other sensory systems, generally with the finding that neuronal responses habituate with repeated sensory exposure. The present study sought to determine the effect of taste familiarity on population taste coding in mouse gustatory cortex (GC). Using microendoscope calcium imaging, we studied the taste responses of visually identifiable neurons over five days of taste experience, during which animals could freely choose to consume taste stimuli. We found that the number of active cells in insular cortex, as well as the number of cells characterized as taste-responsive, significantly decreased as animals became familiar with taste stimuli. Moreover, the magnitude of taste-evoked excited responses increased, and inhibited responses decreased with experience. By tracking individual neurons over time, we focused on taste coding in a subpopulation of "stable" neurons that were present on all days of the taste familiarity paradigm. The population-level response across these stable cells was distinct when taste stimuli were novel but became more intercorrelated among those taste stimuli mice willingly consumed as the stimuli became familiar. Overall, these results highlight the effects of familiarity on taste responses in gustatory cortex.