Fig. 1.

Sites with high delta in intracranial EEG (icEEG) recordings. A–C: recording sites in 3 patients before (left) and after (right) antiepileptic drugs (AEDs) had been tapered off. Subdural grid electrodes were positioned over temporal lobe primarily, and subdural strip electrodes were positioned over temporal, frontal, parietal and occipital cortices. Sites of seizures are marked with yellow dots; sites with high delta in excess of 3 SDs from the mean are marked with blue dots. Note that contacts with high delta can be clustered together (B) or separated into multiple cortical sites (A and C), even bilaterally. Furthermore, the sites with high delta can overlap the seizure onset area, but this is atypical. Finally, sites with high delta can show high delta power over 2 recording sessions separated by 3–4 days (before and after AEDs had been tapered off), though this is not necessarily the rule.