Abstract
1. Visual evoked potential was obtained by the averaging technique from human occiput. The wave forms had very great individual differences, but it was clear that in the eye-closing state alpha-like waves were observed after the initial response evoked by photic stimulation, while in the eye-opening state such waves were not observed.
2. Even in the averaged EEG without photic stimulation alpha-like waves were observed, especially in the eye-closing state. It could be determined that this was the contamination with alpha waves in original EEG.
3. The amplitude of sine waves summed with random phase differences reached √n fold of original amplitude by increasing the number, n, of times of summation.
4. From the histogram of distribution of frequencies of alpha waves, in the process of summing EEG, the frequencies of ordinary alpha waves were random enough to be treated in the same manner as in the case where sine waves were summed with random phase differences.
5. The degree of the contamination with alpha waves could be determined.
6. The alpha-like waves after the initial response in the averaged response in the eye-closing state were recognized as a real response to photic stimulation.
