Comparison of fractal and power spectral EEG features: effects of topography and sleep stages.

Fractal nature of the human sleep EEG was revealed recently. In the literature there are some attempts to relate fractal features to spectral properties. However, a comprehensive assessment of the relationship between fractal and power spectral measures is still missing. Therefore, in the present study we investigated the relationship of monofractal and multifractal EEG measures (H and ΔD) with relative band powers and spectral edge frequency across different sleep stages and topographic locations. In addition we tested sleep stage classification capability of these measures according to different channels. We found that cross-correlations between fractal and spectral measures as well as between H and ΔD exhibit specific topographic and sleep stage-related characteristics. Best sleep stage classifications were achieved by estimating measure ΔD in temporal EEG channels both at group and individual levels, suggesting that assessing multifractality might be an adequate approach for compact modeling of brain activities.