title: Focal Changes to Human Electrocorticography With Drowsiness: A Novel Measure of Local Sleep.
abstract: Drowsiness may be defined as the progressive loss of cortical processing efficiency that occurs with time passing while awake. This loss of cortical processing efficiency is reflected in focal changes to the electroencephalogram, including islands of increased delta power concurrent with drop-offs in neuronal activity (i.e., focal cortical inactivity). The authors hypothesized that these focal changes are evidenced at individual electrodes by combination of increased instantaneous amplitude in delta band and decreased instantaneous frequency in theta-alpha band, permitting their categorization as "active" and "inactive." An analysis of records from six patients with refractory epilepsy undergoing video-electrocorticographic monitoring was conducted. Feature extraction and state classification on multiple recordings revealed focal changes consistent with the hypothesis, as well as progressively increased numbers of inactive electrodes with time awake. The implications of these findings on the study of sleep, and particularly local sleep, are discussed.
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Slater
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Mircea I
authors.initials: MI
authors.lastname: Chelaru
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Hansen
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Charles
authors.initials: C
authors.lastname: Beaman
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Giridhar
authors.initials: G
authors.lastname: Kalamangalam
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Nitin
authors.initials: N
authors.lastname: Tandon
authors.affiliation: From the Department of Neurology, University of Texas Medical School at Houston, Houston, Tex. (JDS, GK); the Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Tex. (JDS, MIC, BJH, CB, VD); Department of In Vivo Pharmacology, Merck Research Laboratories, West Point, Penn. (BJH); and the Vivian L. Smith Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Tex. (NT).
authors.forename: Valentin
authors.initials: V
authors.lastname: Dragoi
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology* / Q000503:physiopathology; D058256:Brain Waves; D000069279:Drug Resistant Epilepsy / Q000503:physiopathology; D000069280:Electrocorticography; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D064926:Neurophysiological Monitoring; D057234:Preoperative Period; D012815:Signal Processing, Computer-Assisted; D012894:Sleep Stages / Q000502:physiology*; D014741:Video Recording; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult
keywords: Biological Rhythms; Neurophysiology; Research Design and Methodology; Sleep