Physiological mechanism of sequential firing of hippocampal neurons during SW-R

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H07086
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Biological pharmacy
• Research Institution: Keio University
• Principal Investigator: Ishikawa Tomoe 慶應義塾大学, 医学部(信濃町), 助教 (20804587)
• Project Period (FY): 2017-08-25 – 2019-03-31
• Keywords: sharp waves/ripples / シナプス入力 / スパイン / シークエンス入力 / 海馬

Outline of Final Research Achievements

Sequential reactivation of memory-relevant neuron ensembles during hippocampal sharp-wave ripple (SW-R) oscillations reflects cognitive processing. However, how a downstream neuron decodes this spatiotemporally organized activity remains unexplored. Using subcellular calcium imaging from CA1 pyramidal neurons in ex vivo hippocampal networks, we discovered that neighboring spines are activated serially along dendrites toward or away from the cell bodies. The sequential spine activity was engaged repeatedly in different SW-Rs in a complex manner. In a single SW-R event, multiple sequences appeared discretely in dendritic trees, but as a whole, sequences occurred preferentially in some dendritic branches. Thus, sequential replays of multineuronal spikes are distributed across several compartmentalized dendritic foci of a postsynaptic neuron with their spatiotemporal features preserved.

Free Research Field

神経生理学

Academic Significance and Societal Importance of the Research Achievements

本研究では、SW-Rに参加するか否かを明確に分け、シナプス入力の時空間パターンを比較し、SW-Rに参加する細胞は近接したスパインが繰り返しシークエンス入力を受け取ることを見出した。この結果は、記憶再生時の細胞選択的な発火メカニズムに「シークエンス構造をもつシナプス入力」が関与しうること示唆した点で意義深い。また、シークエンス入力の存在を初めて捉えた知見でもあり、今後、樹状突起の演算様式のより詳細な解明につながることが期待される。