a–e) Daily snapshots of Patient 2’s 8×8 subdural grid, showing day to day variations in local synchrony and identification of LH channel pairs. The location of the grid on the cortical surface is shown in f), with electrode 1 corresponding to the top left corner of the grid maps and electrode 8 to the top right corner. Snapshots were selected from 125 time samples taken over a 5 day monitoring period. Two LH regions are seen, one in the anterior/inferior portion of the grid (frontal and temporal perisylvian region) and one more posteriorly in the parietal lobe. Day to day variations primarily occur at the boundaries of the LH regions, while the core areas are consistently identified as LH in each day’s recording; note that at one point the two regions appear to merge. The boundaries of the presumed epileptogenic zone and resection target area in the grid are indicated with the red tracing in f), while the locally hypersynchronous regions are shown traced in gray.