Mouse Study: Memories Persist After Half of Synapses Wiped
SkimNews Take
Memory surviving massive synaptic loss suggests memories aren't locked in individual connections but distributed across network patterns that regenerate intact—implying storage redundancy the brain can rebuild after disruption.
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- Kazumasa Tanaka and colleagues at the Okinawa Institute of Science and Technology conditioned mice to fear an alcohol-scented chamber via foot shocks, then induced two days of artificial hibernation in half the mice using metabolism-slowing drugs.
- Five days later, the hibernated mice still froze when placed in the alcohol-scented chamber, despite brain scans showing more than half of the synapses on engram neurons in their hippocampus had disappeared during hibernation.
- The team found that clustered synapses on engram neurons specifically survived the hibernation while non-clustered synapses were wiped out — suggesting clustered connections preserve memory while others handle recall.
- Non-clustered synapses reappeared within a day after hibernation ended, which Tanaka says indicates those connections may be needed to access stored memories rather than retain them.
- Independent experts including Steve Ramirez of Boston University and George Dragoi of Yale called the findings a "remarkable step forward" in resolving how the brain maintains long-term memories.
- The researchers plan to investigate the molecular pathways that let clustered synapses store information, a line of inquiry Ramirez said could point toward drugs that prevent or slow memory loss in conditions like Alzheimer's disease.
Why it matters: By showing that clustered synapses — not total synaptic count — carry long-term memories, the study reframes memory loss as a problem of access rather than storage. Tanaka's team now has a concrete molecular target, and independent researchers flagged Alzheimer's and amnesia as conditions where dormant memories might still be rescuable.
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