The study, published in the journal Nature, found levels of a "cold-shock" chemical called RBM3 soared when young mice were chilled, but not in old mice.
It suggested RBM3 was key to the formation of new connections.
In a further set of tests, the team showed the brain cell deaths from prion disease and Alzheimer's could be prevented by artificially boosting RBM3 levels.
Prof Giovanna Mallucci, from the MRC Toxicology Unit in Leicester, told the BBC News website: "This gives us a target to develop a drug in the same way paracetamol is used for a fever rather than a cold bath."
Memory back
Memories can be restored during hibernation as only the receiving end of the synapse shuts down.
I asked Prof Mallucci if memories could be restored in people if their synapses could be restored: "Absolutely, because a lot of memory decline is correlated with synapse loss, which is the early stage of dementia, so you might get back some of the synapse you've lost."
The discovery comes from the laboratory that was the first to prevent the death of brain tissue in a neurodegenerative disease.
It is still only an interesting concept, but has attracted some praise.
Dr Doug Brown, the director of research and development at the Alzheimer's Society said: "We know that cooling body temperate can protect the brain from some forms of damage and it's interesting to see this protective mechanism now also being studied in neurodegenerative disease.
"Connections between brain cells - called synapses - are lost early on in several neurodegenerative conditions, and this exciting study has shown for the first time that switching on a cold-shock protein called RBM3 can prevent these losses.
"While we don't think body cooling is a feasible treatment for long-term, progressive conditions like Alzheimer's disease, this research opens up the possibility of finding drugs that can have the same effect. We are very much looking forward to seeing this research taken forward to the next stage."
Dr Eric Karran, the director of research at Alzheimer's Research UK, said the study was "promising" and "highlights a natural process nerve cells use to protect themselves".
He added that "a future treatment able to bolster nerve cells against damage could have wide-reaching benefits".