Correction to: Nature Neuroscience https://doi.org/10.1038/nn.4598, published online 17 July 2017.

In the version of this article initially published, in Fig. 2a, zeros were omitted from the y-axis labels on the histogram. They should read, from bottom to top: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07. The error has not been corrected in the original article.