Abstract
Mounting evidence suggests that understanding how the brain encodes information and performs computations will require studying the correlations between neurons. The recent advent of recording techniques such as multielectrode arrays and two-photon imaging has made it easier to measure correlations, opening the door for detailed exploration of their properties and contributions to cortical processing. However, studies have reported discrepant findings, providing a confusing picture. Here we briefly review these studies and conduct simulations to explore the influence of several experimental and physiological factors on correlation measurements. Differences in response strength, the time window over which spikes are counted, spike sorting conventions and internal states can all markedly affect measured correlations and systematically bias estimates. Given these complicating factors, we offer guidelines for interpreting correlation data and a discussion of how best to evaluate the effect of correlations on cortical processing.
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Change history
07 November 2011
In the version of this article initially published, the firing rate and mean correlation value given in Table 1 for ref. 26 were incorrect. The correct values are 3.4 Hz and 0.18, respectively. This change affects the corresponding data point in Figure 6 and a value derived from this figure that was stated in the figure legend and main text, which should read "differences in mean rate can account for 33% of the across-study variance in reported values of rSC." The errors have been corrected in the PDF and HTML versions of this article.
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Acknowledgements
We are grateful to P. Latham for analytical descriptions for our simulations and for the derivation of the relationship between measurement window and correlations that are not based on common spikes and to R. Coen-Cagli for the derivation relating correlation to the proportion of spikes discarded during spike sorting. We thank R. Coen-Cagli, B. Cumming, M. Histed, X. Jia, K. Josic, J. Maunsell, A. Ni, H. Nienborg, A. Pouget, O. Schwartz, S. Tanabe, and J.A. Movshon and E. Simoncelli and members of their laboratories for helpful discussions and comments on an earlier version of the manuscript. This work was supported by US National Institutes of Health grants R01 EY016774 (A.K.) and K99 EY020844-01 (M.R.C.).
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Cohen, M., Kohn, A. Measuring and interpreting neuronal correlations. Nat Neurosci 14, 811–819 (2011). https://doi.org/10.1038/nn.2842
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DOI: https://doi.org/10.1038/nn.2842