Nat. Neurosci. 13, 1225–1232 (2010); published online 12 September 2010; corrected after print 13 April 2011

In the version of this article initially published, the vertical scale bars in Figures 2c and 3a,c,d were labeled with incorrect units (μA). The correct units should be pA. Also, the vertical scale bar label (50 pA) was missing from Figure 7a, and the labels “burst duration” and “mean Po” in Figure 4e were reversed. The errors have been corrected in the HTML and PDF versions of the article.