Quantitative hemispheric EEG differences between normal subjects and temporal epilectics

Verbal function disorders have often been found in left temporal lobe epileptics. but it is not know whether they are due to the brain lesion giving rise to the epileptic seizures or whether the epilepsy itself plays a direct, if partial, role. This study exploited the method of EEG asymmetry during cognitive tasks, considering only patients with normal CT scans to eliminate possible brain lesion interference. The EEG signal from P4-02 and P3-01 derivations during verbal and non-verbal tasks was analyzed in 18 patients with left temporal lobe epilepsy. The R/L log increase during the verbal task observed in a group of normal subjects was not present in the epileptic patients. There were no differences corresponding to seizure frequency among the epileptics, but a longer history of the disease tended to make for greater alterations in task-dependent EEG asymmetry.