Nat. Neurosci. 12, 1364–1366 (2009); published online 27 September 2009; corrected after print 9 June 2010

In the version of this article initially published, a citation was inadvertently omitted. To correct this, “Attempts to measure the negatively reinforcing actions of MK-801, an NMDA receptor inhibitor, on chronic pain using CPP in a rat model of inflammation have been made, but the data were not conclusive16” has been inserted following the first sentence in the fourth paragraph. A reference was also added to the reference list as follows:

The error has been corrected in the HTML and PDF versions of the article.