Topographic mapping of electroencephalography coherence in hypnagogic state
Psychiatry and Clinical Neurosciences April 1, 1998 Hideki Tanaka, Mitsuo Hayashi, Tadao Hori
Hypnagogic EEG stages, defined by Hori's nine-stage system, show distinct topographic patterns of brain activity as sleep progresses. Delta and theta power increase prominently in anterior-central areas starting from the vertex sharp-wave stage (stages 6 and 7). Alpha 3 power increases in anterior-central areas from stage 9, and sigma power increases in the central-parietal area from stage 8. These findings suggest that basic sleep processes may begin before the onset of sleep stage 2 or before manually scored sleep spindles appear.