Brain-mind states: I. Longitudinal field study of sleep/wake factors influencing mentation report length

Study objectives: To collect and analyze reports of mental activity across sleep/wake states. Design: Mentation reports were collected in a longitudinal design by combining our Nightcap sleep monitor with daytime experience sampling techniques. Reports were collected over 14 days and nights from active and quiet wake. after instrumental awakenings at sleep onset, and after both spontaneous and instrumental awakenings from REM and NREM sleep, Setting: All reports were collected in the normal home, work and school environments of the subjects. Participants: Subjects included 8 male and 8 female undergraduate students (19-26 years of age). Interventions: N/A Measurements and Results: A total of 1,748 reports, averaging 109 per subject, were collected from active wake across the day (n=894), from quiet wake in the pre-sleep onset period (n=58), from sleep onset (n=280), and from later REM (n=269) and nonREM (n=247) awakenings. Median report lengths varied more than 2-fold, in the order REM > active wake > quiet wake > NREM approximate to sleep onset. The extended protocol allowed many novel comparisons between conditions. In addition, while spontaneous REM reports were longer than those from forced awakenings, the difference was explained by the time within the REM period at which the awakenings occurred. Finally, intersubject differences in REM report lengths were correlated with similar differences in waking report lengths. Conclusions: The use of the Nightcap sleep monitoring system along with waking experience sampling permits a more complete sampling and analysis of mental activity across the sleep/wake cycle than has been previously possible.