Ictal and peri-ictal oscillations in the human basal ganglia in temporal lobe epilepsy

Preictal, ictal, and postictal oscillations in the basal ganglia were analyzed. Five persons with temporal lobe epilepsy who were candidates for surgery had diagonal depth electrodes implanted in the basal ganglia: four of them in the putamen, and one in the pallidum and caudate. Time-frequency and power spectral analyses were used to analyze the EEG. Significant frequency components of 2-10 Hz were consistently observed in the basal ganglia. The frequency of this component slowed during seizures. There was a significant ictal increase in power spectral density in all frequency ranges. The changes in the basal ganglia were consistent while seizure activity spread over the cortex, and partially persisted after the clinical seizure ended. They were inconsistent in the period after seizure onset. Seizures originating in the mesiotemporal structures can affect physiological rhythms in the basal ganglia. The basal ganglia did not generate epileptiform EEG activity. An inhibitory role for the basal ganglia during temporal lobe seizures is suggested.