Changes of amplitude and topographical characteristics of event-related potentials during the hypnagogic period

In the previous study, during the vertex sharp wave period (hypnagogic EEG stage 4), negative components (N300, N550) were dominant at Fz and Ct in contrast to the positive component (P400) being prominent at the other areas, Pt, Oz, T5 and T6. There is no agreement regarding P400 properties during the hypnagogic period. In this study, using topographic mapping. we found that two negative components (N300, N550) and P400 independently increased their amplitude at the different areas of the scalp as arousal level lowered. The anterior negative components may reflect the information processing related to the K-complex. The P400 may reflect other activities different from the K-complex mechanism or P300 attention mechanisms.