Our ability to recognize previously encountered stimuli is essential for navigating through and interacting with our complex environments. This fact becomes especially apparent when this form of memory, termed recognition memory, is lost or impaired, as is the case with several mental disorders such as schizophrenia, Alzheimer's disease, and epilepsy. Understanding the neural bases for recognition memory has been the topic of a great deal of research, with the studies largely converging on the finding that recognition memory depends upon the hippocampal memory system, which includes the hippocampus proper and adjacent cortices. Nonetheless, the precise contribution to recognition memory made by each component of the hippocampal memory system remains a topic of considerable debate, with the primary issue revolving around whether or not the hippocampus proper contributes to recognition memory for an object without a simultaneous recollection of some contextual detail associated with the object. One issue that may be contributing to the discrepancy is that the majority of experimental approaches employed consider the hippocampus at the level of the structure as a whole, despite evidence indicating that the hippocampus is composed of several functionally and anatomically discrete subregions. Perhaps by employing a more temporo-spatially precise technique capable of assessing interactions between individual subregions, an answer to questions regarding the hippocampal involvement in recognition memory can finally be reached. This project aims to record neuronal activity simultaneously from the four primary subregions of the hippocampus proper (i.e., dentate gyrus, CA1, CA3, and subiculum) in rats during performance of a memory task designed to dissociate memory for items without memory for context (i.e., item-only memory) from memory for items in addition to memory for their context (i.e., item-in-context memory). Analyses will focus on assessing neuronal interactions between subregions during memory encoding, separated based on the type of memory subsequently demonstrated. This project will provide valuable information regarding the coordination of neuronal communication in a normally functioning and intact brain. The short-term goal of the project is to attain a grasp on how physiological interactions within the hippocampus differentially relate to the processing of item-only versus item-in-context memories, while the long term goal will be to understand neural communication more broadly, characterizing normal physiological activity in the intact brain to enhance our capabilities with regards to developing biomarkers for, and improving diagnoses of, neuropsychiatric disorders.
The findings of the proposed research project will lend themselves to our understanding of neuronal communication in a normal, intact brain system. As an increasing amount of research suggests that faulty communication between brain regions may be an underlying cause of several mental disorders (e.g., dementia, schizophrenia, PTSD), the findings from the proposed research will be important and relevant to identifying diagnostic criteria and biomarkers for these disorders while they are in early developmental stages.