Fig. 3.

iEEG γ peaks (A, B, D, E) and spectral bandwidth distributions (C and F) and in two example patients (patients 7 and 8): panels A, B (patient 7: contacts G5 and F4) D, E (patient 8: contacts G6 and C4) illustrate relative spectra of four different grid contacts. For each panel the blue line denotes the median signal and the purple trace shows the spectral changes between the 25th and 75th percentile of the signal variance. The vertical white line marks the frequency with highest power (maximum power). The vertical dashed green lines enclose the spectral width at full width half max (FWHM) of the spectral peak. A and D illustrate relatively narrow-banded spectral peaks within the SOZ, whereas B and E are relatively broad-banded and outside the SOZ (black arrows panels C and F). Please note that the spectral peak in panel D can be subdivided visually into two distinct maxima. This finding could be reproduced in single trial time-frequency analysis (Fig. Suppl. 1).

iEEG γ peaks (A, B, D, E) and spectral bandwidth distributions (C and F) and in two example patients (patients 7 and 8): panels A, B (patient 7: contacts G5 and F4) D, E (patient 8: contacts G6 and C4) illustrate relative spectra of four different grid contacts. For each panel the blue line denotes the median signal and the purple trace shows the spectral changes between the 25th and 75th percentile of the signal variance. The vertical white line marks the frequency with highest power (maximum power). The vertical dashed green lines enclose the spectral width at full width half max (FWHM) of the spectral peak. A and D illustrate relatively narrow-banded spectral peaks within the SOZ, whereas B and E are relatively broad-banded and outside the SOZ (black arrows panels C and F). Please note that the spectral peak in panel D can be subdivided visually into two distinct maxima. This finding could be reproduced in single trial time-frequency analysis (Fig. Suppl. 1).

C and F show bandwidth changes illustrated on invasive EEG grid contacts co-registered with segmentations of individual cortical surfaces reconstructed from MRIs after surgical resection of the epileptic focus for both patients. Each disk represents one electrode contact. Seizure onset zone (SOZ) contacts are marked with white diamonds. The coloring of the grid contacts denotes bandwidth in log (Hz). White disks represent electrode contacts that were not considered in the comparison, because either no spectral peaks with peak frequencies > 40 Hz could be detected or no significant spectral changes compared to baseline were recorded in the frequency band of the median spectral peak. The resection volume is marked in transparent magenta. The two patients represent two extremes in the range of bandwidth changes: patient 7 exhibits broad-banded spectral maxima in a limited number of contacts, whereas spectral peaks in patient 8 are spatially more distributed and relatively narrow-banded. (panels C and F were created using brainVISA and brainstorm software Mangin et al., 1995, Tadel et al., 2011). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)