Topological association between CT and SW amplitude and related mediation analyses
| Total effect of age at each derivation (path c) (b, p-value) | CT cluster (BAs, peak) | Lat | Cluster size (corrected p value) | Conjunct vertices (age and SW) | Parameter estimates (simple mediation models) | |||
|---|---|---|---|---|---|---|---|---|
| Path a | Path b | Path c′ | Indirect effect (b, 95% CI, K2) | |||||
| Prefrontal b = −0.06, p < 0.001 | Cuneus (BA19) (−14 −89 33) | L | 322 vertices p = 0.009 | 55 | b = −0.17, p < 0.001 | b = 0.12, p < 0.001 | b = −0.04, p < 0.001 | b = −0.02 (−0.04 −0.01) (*) K2 = 0.21 |
| Parietal b = −0.08, p < 0.001 | MPFC (BA9) (−6 48 29) | L | 456 vertices p = 0.02 | 84 | b = −0.23, p < 0.001 | b = 0.11, p < 0.001 | b = −0.05, p < 0.001 | b = −0.02 (−0.05 −0.01) (*) K2 = 0.22 |
Rows illustrate simple mediation models to explain age-related effects on SW amplitude at other derivations (prefrontal, central, parietal, and occipital) with mean CT in each previously identified region as stand-alone mediators. The cluster column depicts the relationship between cluster and SW amplitude at different electrodes when controlling for age. Total effect of age on SW amplitude is shown under each derivation. The conjunction analysis column depicts the number of vertices also significantly associated with age-related thinning. Coefficients in each path necessary for the computation of indirect effects are shown in designated columns. b-values refer to unstandardized parameter estimates of paths shown in Figure 1. Indirect effects are significant at p < 0.05 when 0 is not included in the 95% CI and significance is denoted with an asterisk. K2 is an effect size of mediation and thus represents the proportion of the age-related effect on SW amplitude that has been mediated by changes in cortical thickness (>0.25 = strong effect; >0.09 = medium effect; >0.001 = small effect). CT in each region is adjusted for ICV.