Table 1.
Composite factors and their measures.
Figure 1.
A–D: Structural models testing for the role of lifetime exposures (LE).
The letters labeling each arrow in the figure correspond to the parameters in the equations and column headings in the tables of results. The models testing whether LE: A) decreased the effect of advancing age on neural measures, B) decreased the effect of age-related declines in neural measures on cognitive abilities, C) had both of these effects or D) had no effect.
Figure 2.
Locations where the mediating effect of age group on fluid ability via gray matter volume/thickness is significantly moderated by lifetime exposures. The black underlay is the Freesurfer parcellation of all 84 cortical and subcortical brain regions tested in these analyses. If a brain parcellation is significant at p(FDR) <0.05 it is colored yellow.
Table 2.
Fluid ability, Model B.
Figure 3.
Qualitative illustration of the relationships between brain and cognitive measures for the two age groups at different levels of lifetime exposures.
Lifetime exposures was divided into tertiles and referred to as low, medium and high LE. The lines representing the brain-cognition relationships have length equal to the range of values for each tertile of LE. The size of cross hairs on each line is centered at the mean values and has line lengths equal to the standard error. A significant moderation of brain on cognition by LE is evident by a changing slope in the lines as the level of LE changes.
Figure 4.
Diagram explaining results by comparing brain measures to cognitive measures for both age groups and various levels of lifetime exposures (LE).
This diagram uses results from Model B and the left accumbens volume from Figure 3B as a guide. Parameters refer to those from equations and models in Figure 1. A) Parameter a represents a difference between age groups for the brain measure. Parameter c’ represents a difference between age groups for the cognitive measure. B) The crosses plot the brain and cognitive measures against each other for three levels of LE for both age groups. The parameter q represents the differing relationship between the brain and cognitive measures for the three different LE groups, low middle and high. C) The parameter b represents the overall relationship between the brain and cognitive measures across all levels of LE, i.e. the slope. D) The parameter v represents the differing relationship between the brain and cognitive measures for the three LE groups.