The scalp EEG is transformed into the brain by a source montage focusing onto the temporal lobe. The upper 4 traces show the basal, polar, antero- and postero-lateral activities of the left temporal lobe. The next 4 traces show the focal seizure onset lateralized to the homologous right temporal lobe channels with the most prominent signal at the right basal-temporal region.
On the left, the average over 22 seizure cycles, i.e. the first 4 sec after onset is displayed. The 3D whole-head maps show a large negativity over the right infero-temporal scalp that is associated with right temporal-basal discharges. The positive counterpart of the right basal dipole field is seen as a widespread positivity over the upper scalp.
Digital filtering (0.53-30 Hz) and averaging has been used for optimum processing of the seizure onset for source analysis. Localization would not be stable without these important pre-processing steps.