Prions are villains worthy of any comic book. They are infectious misshapen proteins that can convert their normal peers into their own twisted images with a touch. As their numbers grow, they gather in large groups and destroy brain tissue. They cause diseases such as mad cow disease, Creutzfeld-Jacob disease (CJD) and scrapie.

And they’re not alone. It seems that many brain diseases are also caused by clusters of misfolded proteins that can seed fresh groups of themselves. The list includes Alzheimer’s, Parkinson’s and Lou Gehrig’s diseases. None of these are infectious – the proteins behind them can’t spread from one individual to another, but there is mounting evidence that they can trigger waves of corrupted shapes within a single brain.

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