Multimodal Sensory Integration in Orbitofrontal Cortex during Natural Reward Seeking

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PROJECT SUMMARY Perception of rewards is highly dependent on the exact reward seeking context. This suggests that discrete elements of the context may directly influence reward subjective value via multisensory integration, which is important because higher-value rewards can drive increased reward learning and seeking. An understanding of how multimodal stimuli modulate reward subjective value and inform reward learning is incomplete without determining how and where these stimuli are processed in the brain. Ensembles in the orbitofrontal cortex (OFC) have been previously reported to be co-responsive to unique taste/smell pairs, but the stability of this representation over time and direct connection to primary sensory input has not been assessed. The purpose of this project is to determine how multisensory integration of discrete environmental stimuli paired with primary rewards impacts associative learning for reward seeking and to gain a functional understanding of multisensory encoding in the OFC at the single cell level. It is vital to first address this question with natural reward circuitry to gain a full understanding of the basic neurobiology that is maladapted during addiction. As such, this project will utilize a tastant reward and an environmental olfactory stimulus, a combination that has previously been reported to enhance tastant value in human studies. I hypothesize that multisensory integration of environmental stimuli and rewards will increase reward subjective value, expedite the rate of associative learning, and enhance reward seeking. Additionally, I predict that the same OFC ensembles will be consistently activated to multisensory, reward-relevant stimuli and that this activity utilizes direct input from primary sensory cortices. In this project, Aim 1 will address how the multimodal integration of environmental stimuli (odor) with a primary reward (tastant) impacts the rate of learning for reward seeking in a single-day learning task, while assessing reward value using a novel palatability metric. Aim 2 will address the stability and direct connection to primary sensory input of ensembles in the OFC for the multimodal taste/smell stimulus using simultaneous two-photon calcium imaging and optogenetics. Together, these aims will establish the contribution of the integration of discrete environmental stimuli with cued reward to drive learning for reward seeking and provide an understanding of the neural circuitry that may underlie this phenomenon. The results of this project will lay a vital groundwork for future projects to assess how the circuitry that integrates discrete environmental and reward stimuli is coopted during addiction to perpetuate drug seeking during addiction and relapse.