Interaction plots of cost-dependent global efficiencies of fMRI networks with respect to the levels of the -back factor.

<p>We here consider five different costs . The dashed lines represents the cost-specific global efficiencies for each subject, whereas the plain line represents cost-specific global efficiencies averaged over the 43 subjects. The flatness of the lines at each cost levels suggests that the experimental factor has little effect on the topological structure of these networks.</p

Statistical inference for the mixed-effects model described in equation (39).

<p>Testing of the effect of the -back factor on global efficiency. For uniformly cost-integrated () global efficiencies, we have separately tested four different domains of integration, whereas for Beta-binomial () cost-integration, we have considered four different specifications of the parameters of the Beta-binomial distribution.</p

Box plots of cost-integrated global efficiencies.

<p>In panel (a), uniformly cost-integrated and in panel (b), Beta-binomial cost-integrated global efficiencies of fMRI -back networks for four different domains of integration and different choices of parameters are represented. These integrals were estimated using MC approximation over 1,000 samples for each of the 43 subjects in each of the four experimental conditions. Note that different domains of cost-integration do not induce any differences in the effect of the experimental factor, in panel (a). However, the use of the Beta-binomial distribution seems to indicate that a gradual increase in global efficiency follows an increase in cognitive load, in panel (b). However, these relationships did not reach statistical significance (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021570#pone-0021570-t001" target="_blank">Table 1</a>).</p

Running means of Monte Carlo (MC) estimates for uniformly cost-integrated global and local efficiencies in panels (a) and (b), respectively, for the -back network described in example 2.

<p>The grey ribbon represents the variability of these estimators at each , using twice the MC standard error. That is, for both global and local efficiencies. The dashed lines indicate the exact value of . See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021570#s4" target="_blank">Methods</a> A for details.</p

Simulation framework for example 2.

<p>The small-world correlation matrix is transformed into a regular and a hybrid matrix, denoted and , respectively. The regular matrix exhibits a lattice-like topology throughout its cost range, whereas consists of alternating topological layers of random and regular structures. The entries in both matrices have been arranged in decreasing order from the diagonal, to facilitate visualization.</p

Performance Measures for the Sustained Attention Task during 2s, 5s and 8s Delays for 21 Young People Exposed to Childhood Abuse, 19 Psychiatric Controls and 27 Healthy Controls.

<p>Performance Measures for the Sustained Attention Task during 2s, 5s and 8s Delays for 21 Young People Exposed to Childhood Abuse, 19 Psychiatric Controls and 27 Healthy Controls.</p

Group by Delay Interaction Effect on Brain Activation in Healthy Controls, Young People Exposed to Childhood Abuse and Psychiatric Controls.

<p><b>A)</b> Axial sections showing group by delay interaction effect on brain activation during sustained attention in 27 healthy controls, 21 young people exposed to childhood abuse and 19 psychiatric controls as revealed by F test, <i>p</i> < 0.05 FWE-corrected at the cluster-level. Axial slices are marked with the z coordinate as distance in millimetres from the anterior–posterior commissure. The right side of the image corresponds to the right side of the brain. <b>B)</b> fMRI BOLD contrast values in Cluster 1 left IFC/DLPFC and Cluster 2 left temporal/fusiform gyrus for the healthy control group (green), childhood abuse group (blue) and psychiatric control group (red) during the 8s delay condition. The group with a history of childhood abuse had significantly lower activation in the left IFC/DLPFC cluster (p<0.05) and at a trend-level in the left temporal/fusiform cluster (p = 0.09) compared to heathy controls. There were no significant differences between the psychiatric and healthy controls.</p

Group by Delay Interaction Effect on Brain Activation during Sustained Attention in an IQ-matched subsample of Healthy Controls, Young People Exposed to Childhood abuse and Psychiatric Controls.

<p>Axial sections showing group by delay interaction effect on brain activation during sustained attention in a subsample of 18 healthy controls, 19 young people exposed to childhood abuse and 19 psychiatric controls matched on IQ, as revealed by F test, <i>p</i> < 0.05 FWE-corrected at the cluster-level. Axial slices are marked with the z coordinate as distance in millimetres from the anterior–posterior commissure. The right side of the image corresponds to the right side of the brain.</p

Schematic Representation of the Sustained Attention Task.

<p>Subjects are required to press a right-hand button as soon as they see a timer appear on the screen counting seconds. The counter appears after either predictable short delays of 0.5s in blocks of 3–5 stimuli, or after unpredictable long delays of 2s, 5s or 8s, pseudorandomly interspersed into the blocks of 0.5s delays. The long second delays have a progressively higher load on sustained attention than the short 0.5s delays that are typically anticipated and have a higher load on sensorimotor synchronization.</p

Demographic Characteristic of 21 Young People Exposed to Childhood Abuse, 19 Psychiatric Controls and 27 Healthy Controls.

<p>Demographic Characteristic of 21 Young People Exposed to Childhood Abuse, 19 Psychiatric Controls and 27 Healthy Controls.</p