[Activation-dependent characteristics of the electroencephalogram during visual information processing: II Results of an automatic amplitude analysis based on momentary values of signal voltage (author's transl)].

EEG was recorded in 16 Ss. under conditions of a modified "Konzentrations-Leistung-Test" including four levels of performance (balanced change-over design), and histograms of the momentary values of the signal voltages (derivation F3/01) constructed for frequency bands 4...8 Hz, 8...13 Hz and 13...26 Hz. The type of performance affected significantly standard deviations and the excesses in all frequency bands (multivariate analysis of variance, F-Test). Similar to the results of an interval analysis (Activ. ner. sup. 18, 1976, p. 244), the differences in mean values indicated the preponderant relevance of perceptual factors (NEWMAN-KEULS-Test). Four characteristics showed a significant activation dependence: the standard deviations of the amplitude distributions in the frequency bands 4...8 Hz and 13...26 Hz, corresponding to the root-mean--square values of the signal voltages, as well as the excesses in the frequency bands 8...13 Hz and 13...26 Hz. Only and amplitude of the theta waves were influenced notably by mental arithmetics, significantly though only when this was done under conditions of time stress.