ELECTROPHYSIOLOGICAL CHANGES DURING THE SLEEP ONSET PERIOD OF PSYCHOPHYSIOLOGICAL INSOMNIACS, PSYCHIATRIC INSOMNIACS, AND NORMAL SLEEPERS

The electroencephalograms (EEGs) of the sleep onset period (SOP) of ps ychophysiological insomniacs, psychiatric insomniacs, and controls wer e compared using power spectral analysis. We predicted that psycho-phy siological insomniacs would show elevated cortical arousal throughout their entry into sleep. Electroencephalograms, electrooculograms (EOGs ), and electromyograms (EMGs) were recorded for two consecutive nights . Power spectral analysis of EEG from the sleep onset period was perfo rmed on all standard frequency bands. Psychophysiological insomniacs h ad less alpha during the first part of the SOP and did not show the dr amatic drop in alpha across the SOP that characterizes normal sleep. T hey showed less delta in the last quartile of the chronological analys is of the SOP. Psychiatric insomniacs showed lower relative beta power values overall, while psychophysiological insomniacs showed higher re lative beta power values during wakefulness. This microanalysis indica tes that the SOP is generally similar for psychiatric insomniacs and n ormal sleepers but that clear differences in the SOP of psychophysiolo gical insomniacs exist. They have higher cortical arousal during the S OP than do psychiatric insomniacs and controls. The dramatic changes i n power values in the latter two groups as sleep begins are not seen i n the psychophysiological insomniacs, which may help explain the diffi culty that psycho-physiological insomniacs have discriminating between wakefulness and sleep.