Validity of electrode placement at Fpz to detect alpha wave

The possibility on placing electrodes at Fpz-A2 instead of C3-A2 was investigated to obtain a more stable configuration avoiding obstruction by the hair. Our original system of alpha wave detection by a microcomputer was used, and a total of 22 all-night hypnograms of five healthy young students was recorded. Pearson's moment correlation coefficients of alpha wave % between the two positions were 0.780-0.948. Except for one subject, alpha wave % taken at Fpz-A2 tended to be 3-5% lower than that at C3-A2. The above analysis indicates that using EEG electrode position of Fpz-A2 is valid and useful as a stable electrode configuration for a long-time monitoring.