PARAHIPPOCAMPAL REGION /ORBITOFRONTAL CORTEX /MEMORY -
DESCRIPTION (provided by applicant): The proposed project is a part of a larger research program in my laboratory aimed at improving our understanding of the separate roles in memory of the various parts of the hippocampal memory system, including the hippocampus itself, parahippocampal region (PHR), and the neocortical association cortices that ultimately store the memory representation. This project will focus on the interactions between the PHR and the OF (olfactory association neocortex in the rat). Current theory suggests that the storage of long-term, declarative memories is dependent on interactions between the hippocampal memory system and neocortex. By this view, the association neocortex initially processes sensory and behavioral information and can maintain this information for at least a few seconds. The information is propagated via convergent projections to the PHR. The PHR, in turn, appears to sustain these otherwise relatively short-lived representations of single items, such as those needed for familiarity judgments in the delayed nonmatching to sample task (DNMS). The DNMS is a benchmark task of recognition memory, and the odor-version of this task is dependent on both the PHR and the OF in rats. Furthermore, neurons in the OF and the PHR both encode the identity of odor stimuli (sensory responses) and reflect mnemonic information (memory responses) crucial to performance of the DNMS task. While these studies suggest that the sensory signals may be passing through the OF to the PHR, and that the mnemonic signals recorded in OF depend on the PHR, this model has not yet been conclusively demonstrated. Specific Aim 1: To explore the direction and temporal dynamics of the interactions between PHR and OF in DNMS. I, and my students, will simultaneously record from the PHR and OF of individual rats performing a long-term memory task (DNMS). Specific Aim 2: Demonstrate the PHR-dependence of OF memory representations. We will record from the OF of rats with lesions of the PHR performing DNMS. Relevance: This project will provide support for the model of long-term memory storage outlined above, and therefore contribute to our understanding of how long-term memories are ultimately stored in the brain. Further, this project will help prepare gifted undergraduates for graduate school and for careers in science.
