Characteristics of ripples and fast gamma oscillations. A, Normalized distribution of SPW sink magnitudes during fast gamma, ripple oscillatory (90–250 Hz) episodes. B, Correlation between sink (CA1 stratum radiatum) and source (CA1 pyramidal layer) magnitudes during fast gamma and ripple episodes. C, Magnitude of SPW source during fast gamma and ripple oscillations. D, Distribution of SPW sink duration in stratum radiatum for ripple (top) and fast gamma (bottom) oscillations. Sink duration was defined as the time period around the detected oscillation where the normalized CSD signal is <0.5 SDs below the mean. E, Fast oscillation frequency in CA1 and CA3 pyramidal layers as a function of SPW sink magnitude in stratum radiatum. Note the resonant peak in CA1 at 200 Hz (inverted-U relationship). Error bars indicate mean ± SEM (n = 6 animals for CA1; n = 4 for CA3). *indicates statistically significant difference (p < 0.00001).