A repeated awakening study exploring the capacity of complexity measures to capture dreaming during propofol sedation
Scientific Reports September 24, 2025 Imad J. Bajwa, André Sevenius Nilsen, René Skukies et al. 3 citations
People under general anesthesia are often assumed to be unconscious, but some experience dreams. In 20 healthy participants sedated with propofol, EEG was recorded at rest and with TMS perturbations. Participants were repeatedly awakened from deep sedation and asked if they had an experience just before waking. Of 52 attempted awakenings, 24 yielded reports of an experience, 5 reports of no experience, and 23 were unarousable or gave incoherent reports. Two EEG complexity measures—the state transitions perturbational complexity index and single-channel Lempel-Ziv complexity—decreased from awake to sedated states, but did not differ between periods with and without reported experiences within sedation. The authors discuss interpretations and limitations.