title: Delta rhythm in wakefulness: evidence from intracranial recordings in human beings.
abstract: A widely accepted view is that wakefulness is a state in which the entire cortical mantle is persistently activated, and therefore desynchronized. Consequently, the EEG is dominated by low-amplitude, high-frequency fluctuations. This view is currently under revision because the 1-4 Hz delta rhythm is often evident during "quiet" wakefulness in rodents and nonhuman primates. Here we used intracranial EEG recordings to assess the occurrence of delta rhythm in 18 awake human beings. Our recordings reveal rhythmic delta during wakefulness at 10% of all recording sites. Delta rhythm could be observed in a single cortical lobe or in multiple lobes. Sites with high delta could flip between high and low delta power or could be in a persistently high delta state. Finally, these sites were rarely identified as the sites of seizure onset. Thus rhythmic delta can dominate the background operation and activity of some neocortical circuits in awake human beings.
authors.affiliation: Institute for Biology, Humboldt University of Berlin, Neuroscience Research Center, Berlin, Germany; robert.sachdev@charite.de.
authors.forename: Robert N S
authors.initials: RN
authors.lastname: Sachdev
authors.affiliation: Department of Neurology, Hôpital Erasme-ULB, Cliniques universitaires de Bruxelles, Brussels, Belgium;
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gaspard
authors.affiliation: Department of Neurosurgery, Yale University, New Haven, Connecticut; Department of Neurobiology, Yale University, New Haven, Connecticut; and.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Gerrard
authors.affiliation: Department of Neurology, Yale University, New Haven, Connecticut.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Hirsch
authors.affiliation: Department of Neurosurgery, Yale University, New Haven, Connecticut;
authors.forename: Dennis D
authors.initials: DD
authors.lastname: Spencer
authors.affiliation: Department of Neurology, Yale University, New Haven, Connecticut.
authors.forename: Hitten P
authors.initials: HP
authors.lastname: Zaveri
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology* / Q000503:physiopathology / Q000601:surgery; D003700:Delta Rhythm / Q000502:physiology*; D000069280:Electrocorticography; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000503:physiopathology / Q000601:surgery; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult
keywords: arousal; delta; sleep; wakefulness