Neurodegenerative diseases have been halted by harnessing the regenerative power of hibernation, scientists say.
Bears, hedgehogs and mice destroy brain connections as they enter hibernation, and repair them as they wake up.
A UK team discovered "cold-shock chemicals" that trigger the process. They used these to prevent brain cells dying in animals, and say that restoring lost memories may eventually be possible.
Experts have described the findings as "promising" and "exciting".
In the early stages of Alzheimer's, and other neurodegenerative disorders, synapses are lost. This inevitably progresses to whole brain cells dying.
But during hibernation, 20-30% of the connections in the brain - synapses - are culled as the body preserves precious resources over winter.
And remarkably those connections are reformed in the spring, with no loss of memory.