Nature Communications 4: Article number: 1659 (2013); Published: 3 April 2013; Updated: 18 September 2013.

This Article contains errors in Figs 6 and 8 that were introduced during the production process. In Fig. 6, images in panels a and b were inadvertently swapped with those in panels c and d, respectively. In Fig. 8d, double asterisks indicating statistical significance were omitted from the bar labelled ‘55+65’. Corrected versions of both figures appear below.

Figure 6
figure 1

Figure 8
figure 2