Example time courses and their relationship with the task.

<p>A) Example time courses from independent components 7 and 23 from a single participant. The correlation between these two time courses is <i>r</i> = 0.65. B) A zoom in on the first 120 seconds of the two time courses. The gray underlying bars represent the three task phases. C) A zoom in on one trial shows the three task phases: stimulus, maintenance and probe.</p

Within and between age group comparisons of the individual time-course of each component and the load dependent contrasts for each task phase.

<p>Notes:</p>**<p><i>p</i><0.01 corrected for 300 multiple comparisons. All measures represent <i>t</i>-values when testing for differences from 0 for within group measures and differences between groups for those comparisons.</p

Mediation analyses for the relationships of age group on the strength of functional network connectivity between independent components via global brain volume.

<p>Notes: c = total effect of age group on outcome measure of functional network connectivity; a = effect of age group on normalized whole brain volume mediator; b = relationship between normalized whole brain volume mediator and outcome measure of functional network connectivity; c′ = direct effect of age group on outcome measure of functional network connectivity; CI = 95% bootstrap confidence interval for the indirect effect (10,000 stratified resamples);</p>*<p><i>p</i><0.05; all tests corrected for gender.</p

The functional network connectivity between 15 spatially independent task-related components.

<p>A) The lines represent the between age group <i>t</i>-values of functional network connectivity. The mean functional network connectivity for the young B) and old C) age groups is presented for descriptive purposes showing the functional network connections that significantly differ between age groups. The placement of the nodes around the circles is related to the order in which the components were extracted with ICA. Therefore, the placement is arbitrary and the reader should not make any inference on the length of the edges in the graphs, only on the fact that the functional network connections are for the most part stronger in the young than the elder age groups.</p

Within and between age group comparisons of the individual time-course of each component and the load independent contrasts for each task phase.

<p>Notes:</p>**<p><i>p</i><0.01 corrected for 300 multiple comparisons. All measures represent <i>t</i>-values when testing for differences from 0 for within group measures and differences between groups for those comparisons.</p

The eighteen spatially independent task-related components.

<p>The components are numbered using the arbitrary ordering resulting from the ICA which extracted 36 total components.</p

Mean (standard deviation) response times and accuracies (d_L).

<p>Mean (standard deviation) response times and accuracies (d_L).</p

Mediation analyses for the relationships of age group on task performance via the strength of functional network connectivity between independent components.

<p>Notes: c = total effect of age group on speeded task performance; a = effect of age group on mediator; b = relationship between mediator and speeded task performance; c′ = direct effect of age group on speeded task performance; CI = 95% bootstrap confidence interval for the indirect effect (10,000 stratified resamples);</p>*<p><i>p</i><0.05; all tests corrected for gender.</p

The mediation models.

<p>A) Model testing whether functional network connectivity is in the causal pathway between age-group and task performance. B) Model testing whether global brain volume is in the causal pathway between age-group and functional network connectivity.</p

Diagram explaining results by comparing brain measures to cognitive measures for both age groups and various levels of lifetime exposures (LE).

<p>This diagram uses results from Model B and the left accumbens volume from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091196#pone-0091196-g003" target="_blank">Figure 3B</a> as a guide. Parameters refer to those from equations and models in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091196#pone-0091196-g001" target="_blank">Figure 1</a>. A) Parameter <i>a</i> 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 <i>q</i> represents the differing relationship between the brain and cognitive measures for the three different LE groups, low middle and high. C) The parameter <i>b</i> represents the overall relationship between the brain and cognitive measures across all levels of LE, i.e. the slope. D) The parameter <i>v</i> represents the differing relationship between the brain and cognitive measures for the three LE groups.</p