No abstract

The averaged visual evoked responses (AVER), the dispersion pattern (DP) resulting from their variability at each time point locked to the stimulus onset (D=f(t)), were studied in epileptics in comparison with controls of the same age range. In epileptics the AVERs, especially the last components, were higher in amplitude than in controls. The DPs were also generally ampler than in controls; in epileptic patients without mental disorders the pattern of DP was as in normals, except that the third period was higher than the first one, while in epileptics with interictal mental disorders the second period disappeared, and the peak of the DP occurred at the middle third or at the end of the period analysed.

In 20 patients with temporal lobe lesions and 10 controls, the averaged photic-evoked responses (APERs) and their dispersion pattern (DP) were investigated in inion-vertex-lead and bilaterally in inion-parietal leads (I-P₃ and I-P₄). The patients with temporal lobe lesions, regardless of lesion location in temporal areas, displayed either absence of APER (the whole APER or only the initial components) or a latency increase without amplitude changes. The DP was generally abnormal. The role of the temporal lobe in the organization of APER in visual areas is discussed.

In patients with frontal lobe tumours the averaged visual evoked responses (AVER) and their dispersion pattern (DP) in visual areas were investigated before and at different periods after operation. Important changes in AVER (in amplitude and latency) were found in the patients with tumours on the midline or in one of the frontal lobes. The DP was abnormal in all the cases. There was no relation to visual acuity, tumour location and existence of intracranial hypertension. After operation, despite the clinical improvement, the alterations of AVERs or DPs were very marked and in some cases became even more important than before. The role of the frontal lobe in the organization of the responses to peripheral stimuli in the visual areas is discussed.

Studies of the averaged photic-evoked responses (APER) and their dispersion pattern (DP) performed in patients with thalamic lesions (with and without hemianopsia) and in patients with subthalamic lesions showed that the organization of the averaged response and the DP is controlled not by the specific thalamic nuclei only, but by the nonspecific and association nuclei also.