title: Slow-wave activity saturation and thalamocortical isolation during propofol anesthesia in humans.
abstract: The altered state of consciousness produced by general anesthetics is associated with a variety of changes in the brain's electrical activity. Under hyperpolarizing influences such as anesthetic drugs, cortical neurons oscillate at ~1 Hz, which is measurable as slow waves in the electroencephalogram (EEG). We have administered propofol anesthesia to 16 subjects and found that, after they had lost behavioral responsiveness (response to standard sensory stimuli), each individual's EEG slow-wave activity (SWA) rose to saturation and then remained constant despite increasing drug concentrations. We then simultaneously collected functional magnetic resonance imaging and EEG data in 12 of these subjects during propofol administration and sensory stimulation. During the transition to SWA saturation, the thalamocortical system became isolated from sensory stimuli, whereas internal thalamocortical exchange persisted. Rather, an alternative and more fundamental cortical network (which includes the precuneus) responded to all sensory stimulation. We conclude that SWA saturation is a potential individualized indicator of perception loss that could prove useful for monitoring depth of anesthesia and studying altered states of consciousness.
authors.affiliation: Oxford Centre for Functional Magnetic Resonance Imaging of the Brain and Nuffield Division of Anaesthetics, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
authors.forename: Róisín
authors.initials: R
authors.lastname: Ní Mhuircheartaigh
authors.forename: Catherine
authors.initials: C
authors.lastname: Warnaby
authors.forename: Richard
authors.initials: R
authors.lastname: Rogers
authors.forename: Saad
authors.initials: S
authors.lastname: Jbabdi
authors.forename: Irene
authors.initials: I
authors.lastname: Tracey
mesh_terms: D000328:Adult; D000758:Anesthesia; D001519:Behavior / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D003243:Consciousness / Q000187:drug effects / Q000502:physiology; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology; D010812:Physical Stimulation; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*; D012677:Sensation / Q000187:drug effects / Q000502:physiology; D013788:Thalamus / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D015742:Propofol