Figure 7. Systemic MB prevented the disruption in PCC effective connectivity induced by sodium azide.

Metabolic mapping data was used to construct structural equation models of thalamo-cingulo-hipocampal effective connectivity and determine significant group differences in logical topology. The diagrams represent regions holding direct or indirect anatomical connections (lines). The direction of information flow (effectiveness) is represented by arrowheads and the strength of the effective connection is represented by arrow thickness, which is at the same time, a representation of beta (path) coefficients. Solid lines represent positive and dashed lines negative path coefficients. The control model showed the posterior cingulate/retrosplenial cortex (PCC) having reciprocal connections with the anteromedial thalamic nucleus (AM) and the hippocampus (HC), and receiving negative influences from the secondary visual cortex (V2) and the raphe nuclei (RLi). Azide (AZ) changed the coefficient sign of all PCC inputs and outputs and strengthened the interactions with AM, V2 and RLi. Methylene blue (MB) prevented the changes in PCC effective connectivity, although the strong thalamo-cingular connectivity and the strong recruitment of visual and subcortical regions induced by sodium azide were also observed in the AZ+MB-treated group.