Correction to: Nature Neuroscience https://doi.org/10.1038/s41593-018-0276-0, published online 26 November 2018.
In the version of this article initially published, in the PDF, equations (2) and (4) erroneously displayed a curly bracket on the right hand side of the equation. This should not be there. The errors have been corrected in the PDF version of the article. The equations appear correctly in the HTML.
In the supplementary information originally posted, corrupted characters appeared in the Supplementary Figure legends: in Supplementary Figs. 3 and 4, all instances of “ð‘™” should have been l; in Supplementary Fig. 5, the first and second “ð‘™” should have been x, and the “ð” in panel i should have been ‘m’. These errors have been corrected online. The legends appear correctly in the PDF.