Correction to: Nature Neuroscience https://doi.org/10.1038/nn.3761, published online 13 July 2014.

In the version of this article initially published, the catalog numbers for BoNT A and B were given in the Methods section as T0195 and T5644; the correct numbers are B8776 and B6403. The error has been corrected in the HTML and PDF versions of the article.