Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States; Department of Anesthesiology and Intensive Care Medicine, University Medical Center Tuebingen, Tuebingen, Germany
Hertie-Institute for Clinical Brain Research, Tuebingen, Germany; Department of Neurology and Epileptology, University Medical Center Tuebingen, Tuebingen, Germany
Bryce A Mander
Department of Psychiatry and Human Behavior, University of California, Irvine, Irvine, United States
Luis Romundstad
Department of Anesthesiology, University of Oslo Medical Center, Oslo, Norway
Jack J Lin
Department of Neurology, University of California, Irvine, Irvine, United States
Matthew P Walker
Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States; Department of Psychology, University of California, Berkeley, Berkeley, United States
Pal G Larsson
Department of Neurosurgery, University of Oslo Medical Center, Oslo, Norway
Robert T Knight
Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States; Department of Psychology, University of California, Berkeley, Berkeley, United States
Deep non-rapid eye movement sleep (NREM) and general anesthesia with propofol are prominent states of reduced arousal linked to the occurrence of synchronized oscillations in the electroencephalogram (EEG). Although rapid eye movement (REM) sleep is also associated with diminished arousal levels, it is characterized by a desynchronized, ‘wake-like’ EEG. This observation implies that reduced arousal states are not necessarily only defined by synchronous oscillatory activity. Using intracranial and surface EEG recordings in four independent data sets, we demonstrate that the 1/f spectral slope of the electrophysiological power spectrum, which reflects the non-oscillatory, scale-free component of neural activity, delineates wakefulness from propofol anesthesia, NREM and REM sleep. Critically, the spectral slope discriminates wakefulness from REM sleep solely based on the neurophysiological brain state. Taken together, our findings describe a common electrophysiological marker that tracks states of reduced arousal, including different sleep stages as well as anesthesia in humans.
