In general, it is difficult to get the critical points for Rx1x2(A). Here, we performed simulations for Rx1x2(A) based on nonreferential signals b1 and b2 having negative and positive correlations. The simulation results show that, first, Rx1x2(A) may monotonically increase as A (> 0) increases when nonreferential signals b1 and b2 have positive correlations [see Fig. 1(D)(b)]. Second, Rx1x2(A) may monotonically decrease to zero and then monotonically increase to one as A (> 0) increases when nonreferential signals b1 and b2 have negative correlations [see Fig. 1(C)]. Third, Rx1x2(A) may monotonically decrease to some positive values and then monotonically increase to one as A (> 0) increases when nonreferential signals b1 and b2 have positive correlations [see Fig. 1(D)(a)]. Similar to the results for correlation, it should be noted that even a small change of coefficient A may lead to significant impact on phase-synchrony values [for example, see the curve corresponding to Cb1b2=−1 in Fig. 1(C)].
