XApEn compared to cross correlation. A, raw data excerpts of 30 s length from channels 1,2 and 7 of the same recording as shown in Figure 1 (control condition). Note the sequence of 'high voltage rhythmic spikes' (HVRS) starting at ~12 s. B, XApEn values calculated from non-overlapping 1 s sequences of all combinations of the three channels shown. C, peak cross correlation values of the same channel combinations and time intervals as shown in B. The peak of each non-overlapping 1 s-segment was determined from the respective cross correlation function in an interval of ± 50 ms relative to zero lag.