## 3 Results
### EEG during the 3-Back Task
#### 3.2.5. Comodulogram Variability between Half-Sessions  
The overall appearance of comodulograms for EEG differed considerably both between the half-sessions and between the PAC calculation algorithms (Figure 7), although some of the peaks appeared to be consistent. In some cases, there was one dominant maximum, and in others, the comodulogram contained several peaks of comparable intensity.  
Figure 7: Comodulograms for half-sessions of one subject (selected to have average TGC peak variability as described in the Methods section). The results in figures (**A–I**) were obtained from the same data by the different PAC calculation methods described in Table 2. The red dot in each plot shows the point of maximal PAC. The black dot in each comodulogram for the 2 nd half-session shows the peak from the 1 st half-session for comparison. Note: to provide more detail for coupling in the considered theta-gamma frequency window (shown by the white dashed rectangle), the color scale in each plot was chosen to cover the range of PAC values within this window. Values outside this range are shown by a uniform color (yellow or dark blue).  
The scatter plots between the comodulograms in the half-sessions showed a degree of reproducibility that ranged from moderate to low in the different methods (Figure 8).  
Figure 8: Comparison of PAC measures between the half-sessions for the same subject as in Figure 7. The results in figures (**A**–**I**) were obtained from the same data by the different PAC calculation methods described in Table 2. Each circle corresponds to one point in a comodulogram, i.e., to a pair of frequency bands for phase and amplitude. The orange line “\(y\) = x” corresponds to equal coupling in the two half-sessions (exact reproducibility). The Spearman correlation coefficients (\(\rho\)) of PAC values between the half-sessions are indicated.  
The Spearman correlation coefficients of the comodulograms from the half-sessions were calculated for each subject and method, and their histograms (empirical distributions) are shown in Figure 9. For all methods except the normalized ones, the median correlations were significantly above zero. Thus, for these methods, the comodulograms in the half-sessions on average have some degree of overall similarity.  
To check whether only the comodulograms of the same subject were similar rather than all comodulograms from any subject, we compared the within-subject and between-subject correlations of the half-sessions, which are represented by the diagonal and off-diagonal values in the matrices shown in Figure 10. A possible weak tendency towards larger within-subject than between-subject correlations was observed for the methods 'Butterworth', 'no buffer', 'eegfitlnew', and 'no epochs' (difference in medians 0.05-0.11). For the other methods, the correlations were close (difference in medians 0-0.02), consistent with the unspecific similarity of all comodulograms.  
Figure 9: Distributions of Spearman correlation coefficients between the comodulograms from half-sessions for each PAC calculation method from Table 2 (**A–I**). Medians are indicated, as are the \(p\)-values from [PERSON]’s signed-rank tests. The red lines correspond to no similarity (\(\rho=0\)).