<p>Cross-correlations in the two species. Below the blue line: cross-correlations during a time window of ±1 s in four units recorded simultaneously in primates. Above the blue line: same in rats. Red lines in every cross-correlogram represent the lower and upper confidence levels (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045421#s2" target="_blank">Methods</a>).</p