EEG spectral activity during paradoxical steep: further evidence for cognitive processing

Paradoxical sleep (PS), in which periods with (phasic) and without (tonic) rapid eye movements are intermingled, is hypothesized to be related to cogn itive processing and dreaming. Based on polysomnographic data from 12 healt hy subjects, this study focuses on the spectral differentiation between pha sic and tonic periods. Phasic PS periods exhibited decreased theta and alph a power in the posterior brain areas suggesting the interference of visual processing related to dream imagery. Phasic PS periods were also characteri zed by a shift from beta to gamma activity in frontal, central and occipita l areas reflecting specific phasic related activation. Together, these find ings bring new evidence for the existence of visual imagery and cognitive p rocessing during phasic PS. NeuroReport 11:3667-3671 (C) 2000 Lippincott Wi lliams & Wilkins.