Comparison of coherence and phase synchronization of the human sleep electroencephalogram.

Objective: Potential differences between coherence and phase synchronization analyses of human sleep electroencephalogram (EEG) are assessed and occurrences of phase vs. complete synchronization between EEG signals from different locations during different sleep stages are investigated.

Methods: Linear spectral coherence, mean phase coherence (MPC) z-score and Pearson's correlation coefficient of analytic amplitudes were evaluated for different spectral bands of whole-night EEG recordings from 25 healthy subjects.

Automatic sleep scoring: a search for an optimal combination of measures.

Objective: The objective of this study is to find the best set of characteristics of polysomnographic signals for the automatic classification of sleep stages.

Methods: A selection was made from 74 measures, including linear spectral measures, interdependency measures, and nonlinear measures of complexity that were computed for the all-night polysomnographic recordings of 20 healthy subjects. The adopted multidimensional analysis involved quadratic discriminant analysis, forward selection procedure, and selection by the best subset procedure.