Figure 2—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 2—figure supplement 1.

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Federal University of Rio Grande do Norte, Brazil
Figure 2—figure supplement 1.
Download figureOpen in new tabFigure 2—figure supplement 1. Filtering induces quasi-linear phase shifts in white-noise signals.

(A) Distribution of the phase difference between two consecutive samples for white noise band-pass filtered at theta (4–12 Hz, top) and slow gamma (30–50 Hz, bottom). Epoch length = 100 s; sampling rate = 1000 Hz (dt = 0.001 s). Notice that the top histogram peaks at ~0.05, which corresponds to 2*3.14*8*0.001 (i.e., 2*π*fc*dt, where fc is the center frequency), and the bottom histogram peaks at ~0.25 =2*3.14*40*0.001. (B) Rn:m curves computed for theta- and slow gamma-filtered white-noise signals. The black curve was obtained using continuous 1 s long time series sampled at 1000 Hz. The red curve was obtained by also analyzing 1000 data points, but which were subsampled at 20 Hz (subsampling was performed after filtering). Notice Rn:m peak at n:m = 1:5 only for the former case. See also Figure 5—figure supplement 7 for similar results in hippocampal LFPs.

DOI: http://dx.doi.org/10.7554/eLife.20515.006