Table 1.
Multitrait-Multimethod Matrix (MTMM) for candidate biomarkers
| CSD | eLORETA | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Candidate Biomarkers |
MF θ | MF θ normal |
5 Hz Comp. |
9 Hz Comp. |
10.5 Hz Comp. |
rACC θ | rACC θ normal |
6 Hz Comp. |
9 Hz Comp. |
10.5 Hz Comp. |
||
| CSD | MF θ | 0.76 | ||||||||||
| MF θ w/ spatial normalization | 0.22 | 0.42 | ||||||||||
| 5 Hz Comp. | 0.67 | 0.43 | 0.91 | |||||||||
| 9 Hz Comp. | 0.37 | −0.52 | −0.06 | 0.91 | ||||||||
| 10.5 Hz Comp. | 0.41 | 0.21 | 0.28 | −0.14 | 0.91 | |||||||
| eLORETA | rACC θ | 0.45 | −0.33 | 0.20 | 0.48 | 0.01 | 0.87 | |||||
| rACC θ w/ spatial normalization | −0.43 | 0.25 | −0.15 | −0.17 | −0.40 | −0.26 | 0.89 | |||||
| 6 Hz Comp. | 0.58 | 0.41 | 0.82 | 0.04 | 0.15 | 0.11 | −0.15 | 0.89 | ||||
| 9 Hz Comp. | 0.09 | −0.54 | −0.26 | 0.89 | −0.44 | 0.40 | 0.03 | −0.10 | 0.82 | |||
| 10.5 Hz Comp. | 0.48 | −0.08 | 0.22 | 0.24 | 0.69 | −0.07 | −0.48 | 0.16 | −0.10 | 0.90 | ||
Note: A multitrait-multimethod matrix (MTMM) displaying correlations between candidate biomarkers calculated using different methodologies. In particular, averaging of FFT-based amplitude spectra with a priori band limits (i.e., 6.5 to 8.0 Hz; MF θ and rACC θ) versus spectral components identified by frequency PCA (fPCA). Spectral principal components in Table 1 are from separate fPCAs for CSD and eLORETA data so that the effect of EEG transformation method can be directly assessed. Blue cells indicate one-week test-retest reliability (i.e., coefficients on main diagonal); all other cells refer to the first test session only. Green cells indicate validity coefficients: coefficients on the validity diagonal that are larger coefficients than those in red and yellow cells indicate good discriminant and convergent validity. Yellow cells include monomethod-heterotrait coefficients. Red cells include heteromethod-heterotrait coefficients. Alpha and theta principal components demonstrated good convergent validity, good discriminant validity, and good test-retest reliability. Theta metrics calculated using conventional FFT averages of fixed spectral bands generally revealed good test-retest reliability, but had poor convergent and discriminant validity. MTMM correlations are descriptive measures of standardized covariance amongst indices, are not interpreted as inferential statistics, and thus statistical significance for correlations is not reported.