Hippocampal Organization of Spatial Map

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03168
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 10040:Experimental psychology-related
• Research Institution: University of Tsukuba
• Principal Investigator: Pavlides C 筑波大学, 人間系, 研究員 (50712808)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: hippocampus / med. entorhinal cortex / lat. entorhinal cortex / immediate early genes / sleep / cluster organization / memory / optogenetics

Outline of Final Research Achievements

We undertook a set of experiments to determine: 1) functional neuronal organization in the hippocampus for the encoding of different types of memories; 2) effects of sleep on functional organization; and 3) possible differential role of medial and lateral entorhinal cortex (MEC, LEC) in spatial and object memory. We found that indeed, there was a formation of clusters in fear conditioned animals, in comparison to non-shocked controls. Further, sleep following conditioning enhanced cluster formation. In a second study, we found a similar cluster-type organization to encode sequential memory, suggesting that cluster-type is a fundamental principle for memory formation in the hippocampus. In a third study, we found that optogenetic suppression of neuronal activity in the MEC disrupted spatial memory while suppression of activity in LEC disrupted object memory. Effects on hippocampal neuronal activity of such suppression on hippocampal clustering are now being tested.

Free Research Field

Neuroscience

Academic Significance and Societal Importance of the Research Achievements

It is known that the hippocampus is involved in memory. Very little is known of how memory is organized in this structure. We had previously shown a cluster-type organization for the encoding of spatial memory. The current studies provide evidence that all types of memories are encoded in clusters.