Nat. Rev. Neurol 11, 308 (2015); published online 5 May 2015; doi:10.1038/nrneurol.2015.78

The version of this Research Highlight initially published online and in print included an erroneous image credit. The image is courtesy of Saif Huda and Angela Vincent (Oxford, UK). The error has been corrected for the PDF and HTML versions of the article.