Characteristic distribution of alpha 2 wave in electroencephalograms of schizophrenic patients during discriminative tasks: support for the hypofrontality hypothesis of schizophrenia.

In a preliminary study, we noticed that alpha 2 activity in the frontal regions was suppressed less in schizophrenic patients than in other patients during the discriminative tasks. This was confirmed with 37 schizophrenic and 16 nonschizophrenic patients under the treatment of neuroleptics, 15 nonmedicated schizophrenic patients and 32 normal controls. The EEGs in eye-closed resting and during the auditory and visual discriminative tasks were recorded. Alpha 2 power values of the frontal, central, parietal, occipital and temporal regions in every subject group were processed by cluster analysis. During the discriminative tasks, the frontal regions were the most isolated cluster in schizophrenic patients and, in the normal and medicated nonschizophrenic groups, the frontal regions were incorporated in a different cluster. The same result was obtained by different statistical analyses of F-alpha 2 power ratio. The relative abundance of alpha 2 power value shifts from the occipital to the frontal regions during the discriminative tasks in schizophrenic patients. The weakened suppression of alpha 2 waves in the frontal regions by the discriminative tasks in schizophrenic patients supports the hypofrontal hypothesis of schizophrenia.