Fig. 1.

Waveform morphologies. (A and B) Waves exhibiting nearly periodic sequences of peaks are commonly found among θ-oscillations (4 to 12 Hz), but rarely among high frequency waves. The intermittent patterns shown on panels (C) or (D) may be exhibited by γ-waves (30 to 80 Hz), but for the θ-waves, they would be atypical. The temporal clustering shown on panels (D) and (E) are all in all ordinary for γ- or ripples (150 to 250 Hz) but too irregular for the θ-waves. F-pattern could potentially be a θ-wave, a γ-wave, or a ripple. Shown are the peaks exceeding 1/2 of standard deviation from the mean (dashed red line), to exclude the spurious low-amplitude peaks. In actuality, panels A and B are experimental θ-waveforms recorded from the mouse hippocampal CA1 (45, 46), panels C and D are the recorded γ-waves, and panels E and F show ripples.