This study was based on the characteristic EEG findings of the 117 cases of the chronic
schizophrenic, who were hospitalized between 1978 to 1979 at The National Mental Hospital. Eighty-five cases of healthy person without discernible neurological and psychiatric
disorders were selected as a control group.
The age of both groups ranged from 18 years to 55 years. All of the EEG records of
the both groups were studied and analyzed according to the incidence of abnormal EEG,
the abnormal patterns, the degree of abnormality, the alpha frequency and o-time, mean
alpha wave voltage on the occipital region, beta %o-time and their predominant site, theta -time and their predominant site, and mean frequency of isolated theta activities. The results were as follows
1. The incidence of EEG abnormality of the chronic schizophrenics was 18.8%, where-as the incidence of the controls was 4.71%. The EEG profiles of both groups were significantly (p<.Ol) different.
2. As to the rate of abnormal EEG in the schizophrenic subtypes, EEG abnormalities were most frequently seen in the catatonics, least in the paranoids.
3. As to the wave patterns of abnormal EEG in the chronic schizophrenics, abnormal
slow waves were 72.73%, paroxysmal patterns were 59.09%, and generalized dysrh-
ythmias were 27.27%. It was revealed that 50.0% of the abnormal EEG seen in the
controls was the borderline abnormality in the degree, whereas 31.82% of the abno-
rmal EEG seen in the chronic schizophrenics was the mild abnormality.
4. As to the alpha frequency, 10.511.4 Hz rhythm, which was dominant in the cont-
rols, was occupied 39.51% of normal EEGs, and their mean frequency of the alpha
activities was 10.75 Hz. In the chronic schizophrenics, 9.510.4 Hz rhythm was occu-
pied 46.32%, and their mean frequency of the alpha activities was 10.34 Hz.
5. In the amount of the %-time of alpha activities, the chronic schizophrenics showed
significantly less the alpha %-time than the controls at the all regions.
6. In the mean voltage of alpha activities, the chronic schizophrenics showed signific-
antly lower amplitude than the controls.
7. In the o-time of beta-1 activities, the chronic schizophrenic showed significantly higher proportion at the frontal and central regions than the controls. In the %o-time of bata-2 activities the chronic schizophrenics showed significantly higher than controls at the all regions.
8. In the %-time of theta activities, the chronic schizophrenics showed significantly higher proportion at the frontal and central regions than the controls, but their mean frequency was not significantly different.
From all of these results, it was demonstrated that the chronic schizophrenics had significantly more fast beta activities (20-3011z) and isolated theta waves than normals, while they had significantly less alpha activities. It was suggested that abnormal EEGs were frequently seen in the chronic schizophrenics compared to the normal controls.
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