Pharmacologic alteration of the perception of being awake or asleep.

In order to further explore the effects of triazolam on the subjective experience of sleeping, we awakened chronic insomniacs with an electronic tone at five points across the night after having administered placebo and three doses of triazolam (0.125, 0.25 and 0.375 mg). Triazolam reduced the likelihood of subjects reporting that they had been awake by about half. Drug effects were most evident in the period 5 minutes after "lights out", at which time there was a reduction in the certainty of the subjects' response; the investigator's ratings of mental activity on the dream complexity scale rose from a rating of "awake" following placebo to the borderline of sleep following triazolam. After triazolam administration, subjects reported less certainty about their descriptions of mental imagery. These data are consistent with a hypothesis that during sleep, and particularly at the threshold of electroencephalogram (EEG) defined sleep, triazolam induces cognitive changes in which the subjective distinction between waking and sleep becomes less clear. Several approaches are suggested to determine whether these effects are related to retrospective subjective reports of hypnotic efficacy.