Figure 2 | Scientific Reports

Figure 2

From: Difference in spectral power density of sleep electroencephalography between individuals without insomnia and frequent hypnotic users with insomnia complaints

Figure 2

Comparisons of the absolute spectral power density during (a) total, (b) NREM, and (c) REM sleep among the groups. Log-transformed absolute spectral power density (Y-axis) during (a) total, (b) NREM, and (c) REM sleep for each EEG frequency band (X-axis): delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), sigma (12–15 Hz), and beta (15–20 Hz). The mean of absolute spectral power density during total, NREM, and REM sleep among the groups is plotted as the height of the column. Error bars represent the upper standard deviations. We drew the lines between the combinations that differed significantly by ANCOVA and marked them with an asterisk (*). NREM, non-rapid eye movement sleep; REM, rapid eye movement sleep; NI, non-insomnia; INH, insomnia with no hypnotic use; HNI, hypnotic user with no insomnia complaints; HI, hypnotic user with insomnia complaints; SPD, spectral power density; ANCOVA, analysis of covariance.

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