VISUAL ILLUSIONS AND EEG ALPHA-RHYTHM

During flicker stimulation with the alpha-rhythm frequency through the closed eyes 11 from 12 subjects clearly saw illusory objects (in orde r of descending probability, ring, circle, three-dimensional spiral or spiral spring, funnel, curved crossed bars). The individual optimal s timulation frequency for producing an illusion was always within the a lpha range and was closely correlated with the individual dominant alp ha frequency (r = 0.86). A supposition is discussed that the effect ob tained is based on the quasi-stroboscopic fixation of the spreading co rtical excitation wave of the alpha-rhythm due to its summation with t he isorhythmic afferent diffuse cortical excitation evoked by flashes. This phenomenon enables <<freezing>> of the alpha wave at a certain i nstant of its spreading and makes it <<visible>>.