Fig. 3.

Seizure localization by post-hoc spectral analysis. Selected channels of the subdural recording of seizure 1 from patient F, visualized with 50–300 Hz bandpass/60 Hz notch filter, shows the high frequency oscillations (HFOs) on the left side of the figure. Note that the block E1 enclosed by the square brackets is 2 sec long. A 400-ms epoch (highlighted in yellow) is placed at the beginning of this block. The fast Fourier transform-derived power spectra over this epoch (≥70 Hz in red, <70 Hz in black), the dominant frequencies (Hz) and power (µV²) are shown at the right side of the figure. Although all the depicted channels could be considered as potential ictal HFOs channels because of dominant frequencies ≥70 Hz, the three channels (RG35-36, RG57-58 and AT1-2) would not qualify as ictal HFOs channels because of their power being <median power. The channels with subsequent evolution of the ictal HFOs into slower frequency activity (i.e., HFOs+ev channels) are highlighted. See text for details.