Figure 5—figure supplement 1. | On cross-frequency phase-phase coupling between theta and gamma oscillations in the hippocampus

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On cross-frequency phase-phase coupling between theta and gamma oscillations in the hippocampus

Figure 5—figure supplement 1.

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Federal University of Rio Grande do Norte, Brazil
Figure 5—figure supplement 1.
Download figureOpen in new tabFigure 5—figure supplement 1. Lack of evidence for cross-frequency phase-phase coupling between theta and gamma oscillations using alternative phase-locking metrics.

(A) The left plots show the mean radial distance (R) computed for gamma phases in different theta phase bins, as described in Sauseng et al. (2009). The lines denote the mean ± SD over all channels across animals (n = 16 channels per rat x seven rats); 300 1 s long epochs were analyzed for each channel. Note that original and surrogate R values overlap. The variations of R values within a theta cycle are explained by the different number of theta phase bins (right bar plot), which leads to different number of analyzed samples; the higher the number of analyzed samples, the lower the R (see also Figure 2C). (B) The first column shows the mean pairwise phase consistency (PPC) between gamma and accelerated theta phases as a function of the number of Δφnm samples (dashed lines denote SD over individual PPC estimates; n = 112 channels x 1000 PPC estimates per channel). Since PPC requires independent observations (Vinck et al., 2010), Δφnm was randomly sampled to avoid the statistical dependence among neighboring data points imposed by the filter (Figure 2—figure supplement 1; see also Figure 5—figure supplement 7). The second column shows mean PPC as function of n:m ratio (individual PPC estimates were computed using 1000 Δφnm samples); the boxplot distributions show PPC values at selected n:m ratios, as labeled. PPC values are very low for all analyzed frequency pairs and not statistically different from zero.

DOI: http://dx.doi.org/10.7554/eLife.20515.014