• Figure 3.
    Download figureOpen in new tabFigure 3. True n:m phase-locking leads to significant Rn:m values.

    (A) The left panels show mean Rn:m curves and distributions of R1:5 values for original and surrogate (Random Permutation/Single Run) data obtained from the simulation of two coupled Kuramoto oscillators (n = 300; epoch length = 30 s; *p<0.001, t-test). The right panels show the same, but for uncoupled oscillators. In these simulations, each oscillator has instantaneous peak frequency determined by a Gaussian distribution; the mean natural frequencies of the theta and gamma oscillators were set to 8 Hz and 40 Hz, respectively (coupling does not alter the mean frequencies since they already exhibit a 1:5 ratio; compare with Figure 1). (B) Top panels show results from a simulation of a model network composed of two mutually connected interneurons, O and I cells, which emit spikes at theta and gamma frequency, respectively (Tort et al., 2007; Kopell et al., 2010). Original n:m phase-locking levels are significantly higher than chance (n = 300; epoch length = 30 s; *p<0.001, t-test). The bottom panels show the same, but for unconnected interneurons. In this case, n:m phase-locking levels are not greater than chance.

    DOI: http://dx.doi.org/10.7554/eLife.20515.009

    Figure 6.
    Download figureOpen in new tabFigure 6. Phase-phase plots of hippocampal LFPs display diagonal stripes.

    Phase-phase plot for theta and slow gamma (average over animals; n = 7 rats). Notice diagonal stripes suggesting phase-phase coupling.

    DOI: http://dx.doi.org/10.7554/eLife.20515.022

    Figure 9.
    Download figureOpen in new tabFigure 9. Phase-phase plots of white-noise signals display diagonal stripes.

    (A) Representative phase-phase plots computed for white-noise signals. Notice the presence of diagonal stripes for both 100 s (left) and 1200 s (right) epochs. The colormaps underneath show the p-values of the original bin counts when compared to the mean and standard deviation over bin counts of single time-shifted surrogate runs. Also shown are significance maps after correcting for multiple comparisons (Holm-Bonferroni) using either time-shifted (top) or randomly permutated (bottom) surrogate runs. No bin count was considered statistically significant after the correction. (B) The top panels show original Rn:m curves (green) plotted along with Single Run distributions of Rn:m curves of time-shifted (orange) and randomly permutated (red) surrogates for different epoch lengths (shades denote the 2.5th–97.5th percentile interval; n = 2100 per distribution). The bottom panels show the same in a zoomed scale.

    DOI: http://dx.doi.org/10.7554/eLife.20515.027

  • The following dataset was generated:

    Scheffer-Teixeira R, Tort A, 2016,Multisite LFP recordings from the rat hippocampus during REM sleep, http://dx.doi.org/10.5061/dryad.12t21, Available at Dryad Digital Repository under a CC0 Public Domain Dedication

    The following previously published dataset was used:

    Mizuseki K, Sirota A, Pastalkova E, Diba K, Buzsáki G, 2013,Multiple single unit recordings from different rat hippocampal and entorhinal regions while the animals were performing multiple behavioral tasks, http://dx.doi.org/10.6080/K09G5JRZ, Publicly available at the Collaborative Research in Computational Neuroscience (http://crcns.org/)