This week, rescuing lost memories in mice.

When the memory cells are reactivated, then that means memory is retreat.

And weighing up the impacts of China's immense emissions.

To be honest, the air pollution is a much more priority than the social emissions in China.

Plus the controversial theory of whether Alzheimer's is transmissible. This is the Nature podcast for March the 17th, 2016.

I'm Kerry Smith. And I'm Adam Levy. Researchers in Boston have achieved forgotten memories lost in the brains of mice with Alzheimer's.

Kerry picks up the story with Boston-based interviews by Noah Baker.

Forming a memory is a bit like packing a suitcase.

Right, so I need my recorder.

You put in everything you need for your trip.

I need my phone charger.

You close it.

Oh, passport.

Memory works like this. It can be made and then adjusted as it forms.

Then when you remember something, it's like needing your things at your destination.

You open the case and you recall the information.

But then what's happening when we forget?

Did we just not pack the case properly and the contents are missing, left behind, gone forever?

Or is it more like losing the key to the case or breaking the zip?

The contents are still there, but you just can't access them.

This is an interesting question on its own for memory researchers,

but it's also key to understanding memory loss in conditions like Alzheimer's

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