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. 2015 May 20;35(20):7795–7807. doi: 10.1523/JNEUROSCI.3956-14.2015

Table 6.

Simple mediation results for SW amplitude in frontal derivations

Path c (total effect of age): b = −0.08, R2 = 0.46, p < 0.001
Region Lat BA Size Change in variance compared with path c (δF(df), δR2, p value) Parameter estimates
Path a Path b Path c′ Indirect effects (b, 95% CI, K2)
SPL R 7 356 δF(1,60) = 15.6, δR2 = 0.11, p < 0.001 b = −0.22, p < 0.001 b = 0.13, p < 0.001 b = −0.06, p < 0.001 b = −0.03 (−0.05 −0.01) (*) K2 = 0.25
Cuneus L 19 71 δF(1,60) = 11.7, δR2 = 0.09, p = 0.001 b = −0.16, p < 0.001 b = 0.11, p = 0.001 b = −0.07, p < 0.001 b = −0.02 (−0.03 −0.01) (*) K2 = 0.17
MFG R 6 68 δF(1,60) = 11.4, δR2 = 0.09, p = 0.001 b = −0.33, p < 0.001 b = 0.11, p = 0.001 b = −0.05, p = 0.003 b = −0.04 (−0.06 −0.02) (*) K2 = 0.28

Rows illustrate simple mediation models for frontal SW amplitude with mean CT in each region as stand-alone mediators. δF indicates the change in explained variance due to inclusion of the CT cluster as a mediator compared with the total effect model (path c). Coefficients in each path necessary for the computation of indirect effects are shown in designated columns. b-values refer to unstandardized parameters 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 frontal SW amplitude that has been mediated by changes in CT (>0.25 = strong effect; >0.09 = medium effect; >0.001 = small effect). CT in each region is adjusted for ICV.