Cortical and autonomic responses during staged Taoist meditation: Two distinct meditation strategies

Fig 1. Reduction scheme into 13 major topographic brain regions. Prefrontal—Fp1, Fp2; Left frontal—F7, F3; Right frontal—F4, F8, Frontal–Fz; Central—Cz, Cp1, Cp2, Fc1, Fc2; Parietal–Pz, Left temporal—T7; Right temporal—T8; Left central—C3, Fc5, Cp5; Right central—C4, Fc6, Cp6; Left parietal—P7, P3, Po3; Right parietal—P4, P8, Po4; Occipital—O1, O2, Oz.

Fig 2. Statistical analysis scheme. (A) Comparison of the experienced meditators and the novices groups. (B) Comparison of two subgroups of the experienced meditators.

Fig 3. Changes of ANS activity markers in the experienced meditators (n = 13) and novices (n = 15). Data presented as Median ± IQR. **—significant intergroup difference according to AN-test (p<0.01). The dashed line reflects resting state reference level.

Fig 4. Changes of EEG-derived indices in both groups together. Changes of EEG-derived indices that had the same dynamics in the both groups according to the curve comparison test were analyzed using one-way ANOVA test. The obtained p-values were corrected for multiple comparisons using the FDR B-H procedure. Those that had a significant effect of “meditation stage” factor were analyzed by the post-hoc Tuckey test. Both groups combined (n = 28) were analyzed. Data presented as Median ± IQR. *, **—significant difference from resting state (p<0.05, p<0.01). #, ##- significant difference from the 5th meditation stage (p<0.05, p<0.01).

Fig 5. The index of relaxation (CV* prefrontal alpha to theta ratio) during meditation. (A) in the Experienced meditators and Novices. AN-test revealed a significant difference of curves (p = 0.028). Data presented as Median ± IQR; (B), (C)–in individual Experienced and Novice subjects respectively.

Fig 6. Distribution of habitual meditation styles reported by participants in two subgroups. Please note that most of the subjects reported more than one habitual meditation style.

Fig 7. Changes of ANS activity markers in “relaxed” and “concentrated” experienced meditators and novices. Data presented as Median ± IQR.

Fig 8. Changes of EEG-derived indices in the “relaxed” and “concentrated” experienced meditators. All values were normalized to the individual baseline. Data are presented as a group median value. We have used a common colorbar for all EEG indices and groups to make it easier to compare effects. Dots mark significant (p<0.05) difference between two groups according to the one-way ANOVA test, followed by the post hoc Tuckey’s test. The colors of the dots were chosen to improve visibility and don’t carry any additional information.

Fig 9. Changes of EEG-derived indices in the “relaxed” and “concentrated” experienced meditators and novices. All values were normalized to the individual baseline. Data are presented as a group median value. We have used a common colorbar for all EEG indices and groups to make it easier to compare effects. Dots mark significant (p<0.05) difference between Experienced meditators group and Novices according to the one-way ANOVA test, followed by the post hoc Tuckey’s test. The colors of the dots were chosen to improve visibility and don’t carry any additional information.

Fig 10. Visual summary of the obtained results. Arrows mark direction of changes of markers during meditation.