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Hypnodensity graph.
Hypnodensity graph of subject 55 with a temporal resolution of 5 s separately evaluated for the three different EEG channels C4 (a), F4 (b) and O2 (c). The probabilities for all sleep stages at each time point are shown. Each EEG channel is sufficient to perform sleep stage classification, as the hypnodensity graphs are similar.
