Nat. Neurosci. 12, 1524–1533 (2009); published online 1 November 2009; corrected after print 11 December 2009

In the version of this article initially published, the email address of one of the corresponding authors was misspelled. It should be magdalena.goetz@helmholtz-muenchen.de. The error has been corrected in the HTML and PDF versions of the article.