NSF Award
2434947
In daily life, people experience new events that resemble the past. Processing new information requires the updating of older memories to keep thoughts current. For example, when discussing a shared TV show, a friend may recount details of an older episode and describe how those details are relevant to a new episode. Importantly, the new details must be considered in the context of the older details without overwriting them to later be remembered. This discrimination of new from old events may be supported by brain areas that complete and separate observed patterns. An established view is that pattern completion and pattern separation processes occur primarily in the CA3 and dentate gyrus subfields of the hippocampus. However, mounting evidence suggest that these areas of the hippocampus interact with larger brain regions in the neocortex to keep memories up to date. Understanding how these interactions allow people to keep event details straight may be critical for preserving memory function and reducing interference among memories. The present project aims to use cutting-edge neuroimaging technology to describe the contributions of hippocampal subfields and cortical regions while people discriminate current events from similar memories.<br/><br/>The ability to identify how the present is distinct from the past depends on whether the reinstatement of existing memories supports their comparison with similar experiences. Such mnemonic discrimination may reflect a hippocampal-dependent mechanism called pattern separation. Neural investigations have established contributions of hippocampal subfields to pattern separation enabling mnemonic discrimination. These investigations have emphasized the dentate gyrus (DG), area CA3, and other connected areas. Prior studies have examined separated DG and CA3 brain activity and whole-brain functional connectivity associated with mnemonic discrimination, but no study has been able to adequately assess both using a singular 3T imaging protocol. This gap severely limits conclusions about how hippocampal subfields interact with cortical regions to discriminate new events from memories of similar events. The present project aims to overcome this limitation by introducing an ultra-high resolution functional magnetic resonance sequence that achieves whole-brain coverage, with DG separated from CA3, while minimizing signal dropout in key areas of the prefrontal cortex and anterior temporal lobes. This technology can be used to identify brain activity, representational similarity, and joint whole-brain and hippocampal functional connectivity supporting mnemonic discrimination of everyday objects. Successful completion of this project may provide the proof required to motivate a series of experiments examining the neural mechanisms that enable mnemonic discrimination of both everyday objects and naturalistic ongoing activities.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
