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Comparative Study
. 2013:2013:251638.
doi: 10.1155/2013/251638. Epub 2013 Oct 22.

Spectral asymmetry and Higuchi's fractal dimension measures of depression electroencephalogram

Maie Bachmann  1 , Jaanus Lass, Anna Suhhova, Hiie Hinrikus
Affiliations
Comparative Study

Spectral asymmetry and Higuchi's fractal dimension measures of depression electroencephalogram

Maie Bachmann et al. Comput Math Methods Med. 2013.

Abstract

This study was aimed to compare two electroencephalogram (EEG) analysis methods, spectral asymmetry index (SASI) and Higuchi's fractal dimension (HFD), for detection of depression. Linear SASI method is based on evaluation of the balance of powers in two EEG frequency bands in one channel selected higher and lower than the alpha band spectrum maximum. Nonlinear HFD method calculates fractal dimension directly in the time domain. The resting EEG signals of 17 depressive patients and 17 control subjects were used as a database for calculations. SASI values were positive for depressive and negative for control group (P < 0.05). SASI provided the true detection rate of 88% in the depressive and 82% in the control group. The calculated HFD values detected a small (3%) increase with depression (P < 0.05). HFD provided the true detection rate of 94% in the depressive group and 76% in the control group. The rate of correct indication in the both groups was 85% using SASI or HFD. Statistically significant variations were not revealed between hemispheres (P > 0.05). The results indicated that the linear EEG analysis method SASI and the nonlinear HFD method both demonstrated a good sensitivity for detection of characteristic features of depression in a single-channel EEG.

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Figures

Figure 1
Figure 1
An example of the recorded depression EEG signal in channel P3.
Figure 2
Figure 2
The scheme of SASI method: an EEG spectrum (black line) and a parabolic approximation (green line); f c—the maximum of parabolic approximation; f 1 and f 2—lower and higher boundary frequencies of the lower EEG frequency band; f 3 and f 4—lower and higher boundary frequencies of the higher EEG frequency band.
Figure 3
Figure 3
SASI values averaged over a group of depressive (DEPR) and control (CONT) subjects (n = 17) in various EEG channels. Vertical bars denote standard error.
Figure 4
Figure 4
SASI values in P3 and P4 channels for individual depressive subjects.
Figure 5
Figure 5
SASI values in P3 and P4 channels for individual healthy controls.
Figure 6
Figure 6
HFD values averaged over a group of depressive (DEPR) and control (CONT) subjects (n = 17) in various EEG channels. Vertical bars denote standard error.
Figure 7
Figure 7
HFD values in P3 and P4 channels for individual depressive subjects.
Figure 8
Figure 8
Calculated HFD values in P3 and P4 channels for individual control subjects.
See this image and copyright information in PMC

References

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