An organism's olfactory system must create sensory representations of odors in its environment and use these to drive appropriate behaviors. To do so, the olfactory system must learn to associate odor identities and their behavioral consequences. Recent experimental advances have implicated the piriform cortex and the amygdala as sites of odor learning. Distributed ensembles of neurons in piriform cortex form representations of odors, while ensembles in amygdala mediate behavior. To learn to perform appropriate behaviors given an odor stimulus, the olfactory system must reorganize connections in the piriform cortex-amygdala pathway so that odor presentation leads to activation of the appropriate amygdalar ensemble. Interplay of experimental observations and biologically constrained models is needed to guide future experiments and develop a theoretical understanding of associative learning in this system. With data from experimental collaborators, we will develop a model of piriform cortex responses to determine how randomness and structure in its connectivity leads to reliable representations of odor stimuli. We will then exten this model to include projections to amygdala and identify how plasticity in these projections can lead to associations between odor and appetitive or aversive behavioral responses. Experimental paradigms will be developed to test and verify model predictions. This theoretical/experimental approach will lead to a mechanistic understanding of associative learning in this system. This is an exciting prospect, as most models of sensory systems focus on the structure of their re- sponses to inputs, without extension to how these responses guide learned behavior. The results will be broadly relevant as a link between systems and behavioral neuroscience. They will also advance our understanding of the relationship between sensory perception and emotional behavior, with relevance for disorders involving emotion and substance abuse.
The proposed research involves understanding the mechanisms behind learned associations between stimulus and reward or punishment in the olfactory system. Elucidating these mechanisms will shed light on how the brain processes aversive or appetitive stimuli, with particular relevance for understanding disorders involving emotion and substance abuse.
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