Neural Circuits Underlying Taste Behavior

Survival of all animals critically depend on their ability to incorporate nutrient substances while avoiding poisons. Taste information is detected by epithelial taste receptor cells (TRCs) on the tongue and alate, each one dedicated to a single taste quality, and relayed by neurons in the geniculate/petrosal ganglia to the brain. The ganglia neurons are also tuned to a single taste quality, forming ‘labeled lines’: sweet TRCs signal to sweet neurons, salty to salty, bitter to bitter, etc. Taste information from the periphery is next conveyed to the nucleus of the solitary tract (NTS) in the brainstem. Here, they integrate with other information about the ingesta (odor, texture, temperature, etc..) and the internal state of the animal. Our current understanding of the brainstem circuits is still limited to the gross anatomical ‘nucleus’ level, and specific information about molecules and cells is lacking. Here, I propose studies to uncover the assembly and function of taste-dependent circuits in the brainstem. Aim1. Functional imaging of taste representation in the brainstem. Leveraging my expertise in in vivo calcium imaging, I propose to identify the ‘taste map’ in the NTS. Recent advances in multiphoton microscopy and ‘miniscopes’ have enabled imaging of deep brain regions that were previously inaccessible. I plan to employ these imaging technologies to observe neuronal ensembles as they respond to various taste stimuli using fluorescence from GCaMP calcium reporter as a proxy for neuronal activity. This will provide insights about the tuning properties of these neurons and how they are modulated by other sensory and/or homeostatic cues. Aim2. Identification and functional validation of taste-specific brainstem neuron markers. Molecular markers provide a platform for circuitry mapping and functional manipulations. I propose to identify taste-specific marker genes in the brainstem using a candidate-based approach by analyzing abundant express