Figure 1.

Low and high frequency ripples in human entorhinal cortex. A, Power spectrum of electrical activity recorded from microelectrode 2. Recording bandwidth: 0.1–10,000 Hz.; peaks at 96 and 284 Hz. B–D, Examples of the unit activity, ripples and fast ripples recorded from the same file with 2 electrodes within entorhinal cortex. E–G, Averages of events (the number is indicated in parentheses). Due to similarities of amplitudes, the events were selected into different files by visual estimation. Single unit activity was recorded only from microelectrode 2; note that ripples are in phase on both electrodes and the fast ripples are out of phase. From Bragin et al7, with permission.