The perception of taste is a complex process that includes the chemosensory detection of a stimulus as well as information regarding its hedonic value, whether a stimulus is pleasant or unpleasant. The gustatory cortex is thought to be a central component of the taste system, and is hypothesized to integrate both of chemosensory and affective dimensions of taste stimuli. However, to date, the neuronal and circuit mechanisms involved in this process remain unclear. In this proposal, we will fill a gap in the current understanding of circuit underpinning for taste by investigating the synaptic mechanisms underlying the integration of thalamocortical and amygdalocortical inputs to the primary gustatory cortex. The thalamocortical projection from the taste thalamus provides the gateway for chemosensory information to the gustatory cortex, while the basolateral nucleus of the amygdala has been identified as a major contributor of hedonic information regarding taste stimuli. Taking advantage of cutting-edge experimental approaches for circuit and synaptic analysis, and of a well-established learning paradigm, conditioned taste aversion, that preserves the chemosensory identity, but alters a stimulus affective dimension, we will determine how sensory and hedonic components of taste are integrated in the gustatory cortical circuit. The approach we propose will begin to bridge the gap between the extensive behavioral/ pharmacological and cellular/molecular work that has significantly advanced the field, but without information about underlying synaptic and circuit mechanisms remains difficult to reconcile in an overarching framework. In addition, our study has important implication for public health. Many neurological and psychiatric disorders are associated with altered sensory perception, or by anhedonia. Taste perception in human and rodents is characterized by sensory and affective dimensions, therefore it provides a unique model for understanding common mechanism of sensory processing, as well as for investigating the circuit underpinning for the integration of sensory stimuli with their hedonic value. Therefore, results from our current study have the potential of identifying novel targets for the development of therapeutic intervention.
We propose to investigate the circuit and synaptic mechanisms involved in enriching sensory stimuli with information regarding their hedonic value: whether a stimulus is pleasant or unpleasant. The primary gustatory cortex provides a unique model for our study, as taste stimuli have a chemosensory identity and can be pleasurable or aversive. By taking advantage of conditioned taste aversion, a learning paradigm that changes the hedonic value of a tastant while preserving its chemosensory identity, and using circuit breaking approaches for the study of synaptic transmission and plasticity, our research plan will provide important missing information regarding the circuit and synaptic mechanisms for taste perception and learning. Results from the proposed work have important implications not only for the taste neuroscience community, but also for public health. Several psychiatric and neurological disorders are co-symptomatic with alterations in sensory perception, ability to process the affective dimensions of a sensory stimulus (anhedonia) or a combination of both. Furthering our understanding of how both components of sensory perception are integrated is a fundamental step toward the development of novel therapeutic approaches.
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