[Evaluation of blocking and activation response of focal EEG abnormalities by opening and closing the eyes (author's transl)].

Blocking and activation of constant focal EEG abnormalities by opening and closing the eyes were assessed by visual analysis in 173 EEG recordings of 173 patients. Correlations between single variable were weak in general and did not gain statistical significance in any case. The blocking response had similar extent on both hemispheres. There was no sign of direct dependence from extra- or intracerebral localisation of the causal process. However, the biplot method of computing the results discovered several constellations of variables responsible for blocking and activation. Two of them are reported here. 1) Both responses were more prominent at frontal than at occipital areas. 2) A prodominant slowing localized in mainly frontal regions on the left hemisphere and caused by a process extending from extracerebral or cortical to subcortical showed the greatest tendency to be blocked by opening the eyes while the cause of the focus had no influence.