Spontaneous synaptic depression induced by hippocampal ripples

• Project/Area Number: 16H07453
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Biological pharmacy
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Norimoto Hiroaki 国立研究開発法人理化学研究所, 脳科学総合研究センター, 基礎科学特別研究員 (40779568)
• Research Collaborator: Fujisawa Shigeyoshi 理化学研究所, 脳科学総合研究センター, チームリーダー
• Project Period (FY): 2016-08-26 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000); Fiscal Year 2016: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
• Keywords: 海馬 / シナプス可塑性 / sharp wave ripple / sharp wave-ripple / 記憶再生

Outline of Final Research Achievements

The hippocampus is continuously bombarded with a barrage of stimuli and generate an almost unlimited number of memories throughout lifetime. Why can the hippocampus create a series of memories without memory confusion, using a limited number of synapses? We hypothesize that the hippocampus is intrinsically provided with an active neuronal process that eliminates engrams of unnecessary memories while the hippocampus collects new memories. Here we report that hippocampal sharp wave ripples (SWRs) during slow-wave sleep contribute not only to offline reactivation of a recently acquired memory, but also to erasing of the unnecessary memories by inducing synaptic depression. The depression was selectively induced in immature synapses. Furthermore, continuous closed-loop inhibition of SWRs disrupted subsequent spatial learning. These results provide substantial insights into the machinery underlying how the brain consolidate a series of memories using a limited number of synapses.