Wave coherence in the human EEG.

The investigation is concerned with the phase coherence of human EEG's taken from the median plane of the scalp (N = about 125 male and female undergraduates). Manifestation of coherence was made by using scalp potentials of not less than a fixed value to trigger the sweep of a computer of average transients. Very coherent phase relationships were observed in the occipital region in the form of waves having a period of about 100 msec under a condition of bodily and mental relaxation and eyes closed. With eyes open and under a condition of motivated visual perception, wave coherence disappeared in nearly all S s. Coherence in the alpha frequency diminished as derivation moved toward the frontal region. In some S s, coherence was also noted for waves with a period of 55-60 msec, derived from the occipital region under condition of relaxation. In many individuals, coherent waves of this period were derived from the parietal, central, and frontal areas.