Editor's key points

Anaesthetic-induced unresponsiveness and non-rapid eye movement (NREM) sleep share common neurophysiological features which might be reflected also at the experiential level.This study compared the prevalence and content of experiences in reports obtained from healthy male volunteers after dexmedetomidine- or propofol-induced unresponsiveness and NREM sleep.Disconnected dream-like experiences and experiences related to research setting were often present in both anaesthesia and sleep interviews, whilst awareness signifying connected consciousness was rarely reported for either.Anaesthetic-induced unresponsiveness and NREM sleep are both characterized by disconnected conscious experiences with similar recall frequencies and content.Anaesthetic-induced unresponsiveness and non-rapid eye movement (NREM) sleep share similarities on mechanistic, neurophysiological, and subjective levels. Relevant for the current study, both the αAt the subjective level, anaesthetic-induced unresponsiveness and NREM sleep are associated with reports of disconnected conscious experiences, that is, both states seem to support purely internally generated experiences that are not induced by external sensory stimuli. In interviews performed immediately after recovery from general anaesthesia conducted with a broad range of agents (excluding ketamine), 21.7–27.7% of patients indicate remembering dreams.In systematic sleep laboratory awakenings from NREM sleep, dream recall averages around 43.0% but has varied significantly between studies depending on how dreaming is defined and the timing of the awakenings.Given the many similarities between anaesthetic-induced unresponsiveness and NREM sleep, we investigated the prevalence and content of subjective experiences in interviews obtained after arousals from dexmedetomidine-induced or propofol-induced unresponsiveness and NREM sleep in the same participants. Direct comparison between the states in a within-subject design was used to account for individual trait differences in recall. We hypothesised that anaesthetic-induced unresponsiveness and NREM sleep are characterised by highly similar rates of recall of subjective experiences and that the contents of the experiences are not systematically different in most respects.