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Analysis of oscillatory patterns in the human sleep EEG using a novel detection algorithm
Author(s) -
OLBRICH E.,
ACHERMANN P.
Publication year - 2005
Publication title -
journal of sleep research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 117
eISSN - 1365-2869
pISSN - 0962-1105
DOI - 10.1111/j.1365-2869.2005.00475.x
Subject(s) - electroencephalography , sleep spindle , autoregressive model , superposition principle , sleep (system call) , alpha wave , alpha (finance) , delta rhythm , oscillation (cell signaling) , sigma , audiology , delta wave , physics , k complex , frequency analysis , psychology , slow wave sleep , computer science , mathematics , neuroscience , statistics , alpha rhythm , developmental psychology , acoustics , medicine , biology , psychometrics , construct validity , quantum mechanics , genetics , operating system
Summary The different brain states during sleep are characterized by the occurrence of distinct oscillatory patterns such as spindles or delta waves. Using a new algorithm to detect oscillatory events in the electroencephalogram (EEG), we studied their properties and changes throughout the night. The present approach was based on the idea that the EEG may be described as a superposition of stochastically driven harmonic oscillators with damping and frequency varying in time. This idea was implemented by fitting autoregressive models to the EEG data. Oscillatory events were detected, whenever the damping of one or more frequencies was below a predefined threshold. Sleep EEG data of eight healthy young males were analyzed (four nights per subject). Oscillatory events occurred mainly in three frequency ranges, which correspond roughly to the classically defined delta (0–4.5 Hz), alpha (8–11.5 Hz) and sigma (11.5–16 Hz) bands. Their incidence showed small intra‐ but large inter‐individual differences, in particular with respect to alpha events. The incidence and frequency of the events was characteristic for sleep stages and non‐rapid eye movement (REM)–REM sleep cycles. The mean event frequency of delta and sigma (spindle) events decreased with the deepening of sleep. It was higher in the second half of the night compared with the first one for delta, alpha and sigma oscillations. The algorithm provides a general framework to detect and characterize oscillatory patterns in the EEG and similar signals.