Mental fatigue decreases complexity: Evidence from multiscale entropy analysis of instantaneous frequency variation in alpha rhythm

Figures

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  Figure 1. Experimental protocol. (A) Experimental flow diagram of EEG acquisition of spontaneous EEG (SPON) and auditory steady-state response (ASSR) in Sober and MF states. (B) Alpha rhythm extraction from SPON and ASSR with and without instantaneous frequency variation method (IFV), producing preprocessed four types of time series, SPON-α, SPON-α-IFV, ASSR-α, and ASSR-α-IFV, before they were analyzed by multiscale entropy methods (MSE) to compare Sober and MF states. (C) Schematic diagram of the coarse graining process, taking scale 2 and scale 3 as examples. (D) An example of MSE comparison.

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  Figure 2. MSE analysis of SPON-α (A), ASSR-α (B), SPON-α-IFV (C), and ASSR-α-IFV (D) on frontal lobe (channel F3) from four exemplary subjects. The blue and red lines represent the Sober and MF states, respectively. See Section 2.5 for the definitions of terms.

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  Figure 3. MSE analysis of SPON-α (A), ASSR-α (B), SPON-α-IFV (C), and ASSR-α-IFV (D) on parietal lobe (channel P4) from four exemplary subjects. The blue and red lines represent the Sober and MF states, respectively. See Section 2.5 for the definitions of terms.

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  Figure 4. MSE analysis of SPON-α (A), ASSR-α (B), SPON-α-IFV (C), and ASSR-α-IFV (D) on temporal lobe (channel T4) from four exemplary subjects. The blue and red lines represent the Sober and MF states, respectively. See Section 2.5 for the definitions of terms.

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  Figure 5. MSE analysis of SPON-α (A), ASSR-α (B), SPON-α-IFV (C), and ASSR-α-IFV (D) on occipital lobe (channel O1) from four exemplary subjects. The blue and red lines represent the Sober and MF states, respectively. See Section 2.5 for the definitions of terms.

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  Figure 6. Comparison of MSE from frontal lobe (channel F3) on: (A) alpha rhythm from spontaneous EEG (SPON-α), (B) alpha rhythm from ASSR (ASSR-α), (C) IFV in alpha rhythm from spontaneous EEG (SPON-α-IFV), and (D) IFV in alpha rhythm from ASSR (ASSR-α-IFV). The sign * indicates significance at p < 0.05. Shades indicate the standard errors.

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  Figure 7. Comparison of MSE from parietal lobe (channel P4) on: (A) alpha rhythm from spontaneous EEG (SPON-α), (B) alpha rhythm from ASSR (ASSR-α), (C) IFV in alpha rhythm from spontaneous EEG (SPON-α-IFV), and (D) IFV in alpha rhythm from ASSR (ASSR-α-IFV). The sign * indicates significance at p < 0.05. Shades indicate the standard errors.

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  Figure 8. Comparison of MSE from frontal lobe (channel T3) on: (A) alpha rhythm from spontaneous EEG (SPON-α), (B) alpha rhythm from ASSR (ASSR-α), (C) IFV in alpha rhythm from spontaneous EEG (SPON-α-IFV), and (D) IFV in alpha rhythm from ASSR (ASSR-α-IFV). The sign * indicates significance at p < 0.05. Shades indicate the standard errors.

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  Figure 9. Comparison of MSE from occipital lobe (channel O1) on: (A) alpha rhythm from spontaneous EEG (SPON-α), (B) alpha rhythm from ASSR (ASSR-α), (C) IFV in alpha rhythm from spontaneous EEG (SPON-α-IFV), and (D) IFV in alpha rhythm from ASSR (ASSR-α-IFV). The sign * indicates significance at p < 0.05. Shades indicate the standard errors.

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  Figure 10. Complexity loss rates of SPON-α, ASSR-α, SPON-α-IFV, and ASSR-α-IFV from all subjects and channels. See Section 2.5 for the definitions of terms. The sign * indicates significance at p < 0.05.