Application of EEG-interval-spectrum-analysis (EISA) to the study of photic driving responses. A preliminary report.

Photic driving responses were analyzed by means of Tönnies' EISA method in 65 normal subjects, 20 patients with brain tumor and 4 cases of severe head injury. The response patterns were classified into 5 types, incidence of which in normals were 1. all band-responsive type (38%), 2. Theta-alpha type (8%), 3. Alpha-beta type (32%), 4. Beta type (8%) and 5. non-responsive type (14%). Each response pattern was compared with the resting EEG activities, however, no significant relationship was found between them. The responses of patients with brain tumor or severe head injury were considerably reduced. The reduction of the photic driving responses in brain tumor cases was not specific to the localization of the tumor. It seems to represent the diminution of the general cerebral reactivity corresponding to the severity of the brain damage. Our results have confirmed that EISA is a simple and practical method for the frequency analysis of long duration and suitable for routine clinical examination.