Correction to: Nature Neuroscience https://doi.org/10.1038/nn.2484, published online 31 January 2010.

In the version of this article initially published, errors appeared in the last equation in the Methods section. It should have read:

$$R_{corrected}\left( {c_i,c_j} \right) = \frac{{COV_{corrected}\left( {c_i,c_j} \right)}}{{\sqrt {COV\left( {c_i,c_i} \right) \times COV\left( {c_j,c_j} \right)} }}$$