Cellular and circuit mechanisms underlying taste neophobia in the mouse gustatory cortex – NeoTaste

Animals, including humans, primates as well as rodents, often exhibit hesitancy towards consuming new foods due to a lack of information about their safety or toxicity. The initial reluctance is termed taste neophobia, typically a temporary effect that diminishes with repeated exposure as the individual learns the food is harmless. Habituation of neophobia, termed familiarization, continues until the food is accepted as safe and familiar. The highly integrative processes of taste neophobia and familiarization occur within a dedicated cortical area called the gustatory cortex (GC). In rodents, the GC occupies the central portion of the insular cortex and is located on the ventral lateral brain surface, divided by the middle cerebral artery. The GC not only encodes the chemical identity of food but also integrates additional information, such as its hedonic value (e.g., palatability) and novelty, to promptly regulate feeding behaviors. The GC receives chemosensory information from the gustatory thalamus (VPMpc) and palatability input from the amygdala (BLA), with cholinergic projections from the nucleus basalis magnocellularis (NBM) conveying tastant novelty. While the importance of GC and these projecting areas in identifying novel or familiar taste has been previously established, the cellular and circuit mechanisms by which GC neurons dynamically integrate thalamic, amygdalar, and cholinergic inputs remain unknown.
The goal of the NeoTaste project is to investigate how GC integrates gustatory inputs to form neuronal representations of novel and familiar taste. We hypothesize that the unique anatomical and functional properties of dendrites of GC layer 5 pyramidal neurons play a pivotal role in integrating gustatory inputs during neophobia and familiarization. To test our hypothesis, we have created a consortium that enables multi-level analysis leveraging the diverse expertise of the partners. This includes functional synaptic mapping ex vivo, cellular and dendritic physiology, in vivo two-photon imaging in head-fixed behaving mice, fiber-photometry in freely moving mice, and circuit-specific manipulation combined with mouse behaviour. This project represents the first attempt to comprehensively investigate the impact of dendritic active properties in GC processing. With the NeoTaste project, led by M. Carta (IINS, Bordeaux), N. Takahashi (IINS, Bordeaux), and G. Ferreira (NutriNeuro, Bordeaux), we aim to elucidate the mechanisms by which the GC circuit integrates gustatory information to guide behavior. We anticipate that the results of the Neotaste project will yield novel insights into the mechanisms by which taste chemical identity, hedonic value (e.g. palatability), and novelty are integrated within the GC at both the single-neuron and network levels, ultimately guiding behaviour.