Spontaneous epileptic seizures in Has mutant mice. Representative tracings of electrographic seizures (Ictal) and of interictal abnormal activity (Interictal) observed in three independent Has3^−/− mice are shown. A tracing of baseline EEG activity in a WT mouse is shown at the top. Spike amplitude (in microvolts on y-axis) is plotted as a function of recorded time course (in seconds on x-axis).