Nat. Neurosci. 20, 438–448 (2017); published online 23 January 2017; corrected after print 27 March 2017

In the version of this article initially published, the y-axis scale in Figure 4c was labeled 0–150 instead of 0–300, the gray data points in Figure 6g were duplicates of the black data points in Figure 6f, and the error bars were missing from the green trace in Figure 7e. The errors have been corrected in the HTML and PDF versions of the article.