Neurons in the gustatory portion of the insula cortex (gustatory cortex; GC) integrate information related to the sensory and emotional dimensions associated with the experience of eating. Recent experimental evidence led to the proposal that GC achieves this level of integration by processing sensory afferents from the gustatory thalamus (VPMpc) and limbic afferents from the basolateral amygdala (BLA). However other brain areas may contribute to the integrative properties of GC. One of these areas is the mediodorsal nucleus of the thalamus (MD). MD is a higher order thalamic nucleus often studied in relation to its connection with frontal cortices and for its involvement in processing multisensory and reward-related information. From a neuroanatomical point of view, MD is also well suited to process gustatory information: it receives afferents from the parabrachial nucleus (PBN), a key gustatory nucleus in the brainstem and projects axonal efferents to the insula cortex. Despite this information, no data is available on the potential role of MD in taste. The proposed research relies on multiple experimental approaches to test the general hypothesis that MD provides fundamental reward-related information to GC. Neuroanatomical tracers will characterize the neural pathway connecting MD to GC. Multielectrode recordings in behaving mice will unveil how MD neurons represent the different facets of a gustatory stimuli. Chemogenetics silencing combined with electrophysiology in behaving mice will test the causal role of MD in shaping GC taste processing and taste-related behaviors. Altogether, the experiments outlined in this proposal will lay the foundation for an in depth understanding of the interaction between higher order thalamic nuclei and sensory cortical areas. If successful, the proposed research, will unveil the role of MD in affecting taste processing and its involvement in modulating taste-related behaviors.

Public Health Relevance

This proposal aim to understand the role of the mediodorsal thalamus (MD) in taste. Specifically, the experiments aim at understanding how MD modulates neural activity in the gustatory cortex (GC) and consequently shapes taste-related behaviors. In rodents, GC integrates the sensory, affective and cognitive dimensions associated with the experience of eating. This function has been related to inputs from the gustatory thalamus (VPMpc) and from the basolateral amygdala (BLA), while the role and function of GC afferents from MD is completely unknown. With this proposal I intend to study how MD neurons encode gustatory stimuli and their role in shaping GC activity and taste-related behavior. The results of these efforts will provide a comprehensive system-level investigation on the role of MD in taste. If successful, this research will point to MD as a thalamic source of taste-related information and will provide important knowledge on how the brain controls feeding behavior. Knowledge from this grant will be potentially relevant for understanding the circuits involved in eating disorders and for identify new target areas.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Exploratory/Developmental Grants (R21)
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Special Emphasis Panel (ZDC1)
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Sullivan, Susan L
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Florida State University
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