Intrinsic excitability in layer IV-VI anterior insula to basolateral amygdala projection neurons encodes the confidence of taste valence

Avoiding potentially harmful, and consuming safe food is crucial for the survival of living organisms. However, sensory information can change its valence following conflicting experiences. Novelty and aversiveness are the two crucial parameters defining the currently perceived valence of taste. Importantly, the ability of a given taste to serve as CS in conditioned taste aversion (CTA) is dependent on its valence. Activity in anterior insula (aIC) layer IV-VI pyramidal neurons projecting to the basolateral amygdala (BLA) is correlative and necessary for CTA learning and retrieval, as well as the expression of neophobia towards novel tastants, but not learning taste familiarity. Yet, the cellular mechanisms underlying the updating of taste valence representation in this specific pathway are poorly understood. Here, using retrograde viral tracing and whole cell patch-clamp electrophysiology in trained mice, we demonstrate that the intrinsic properties of deep-lying layer IV-VI, but not superficial layer I-III aIC-BLA neurons, are differentially modulated by both novelty and valence, reflecting the subjective predictability of taste valence arising from prior experience. These correlative changes in the profile of intrinsic properties of LIV-VI aIC-BLA neurons were detectable following both simple taste experiences, as well as following memory retrieval, extinction learning and reinstatement.