Structural mediation of the default-mode network in children with callosal agenesis.

Agenesis of the corpus callosum is a neurodevelopmental condition characterized by the partial or complete absence of the corpus callosum, the largest white matter bundle connecting the cerebral hemispheres. The default-mode network comprises bilateral frontal, temporal, and parietal regions that exhibit correlated activity at rest. Previous studies show that individuals with agenesis of the corpus callosum show overall preserved default-mode network functional connectivity, suggesting compensatory mechanisms for maintaining bilaterally correlated activity. In this study, we aimed to explore white matter pathways that support default-mode network-related networks in 15 children with agenesis of the corpus callosum and 27 typically developing controls, using combined diffusion and functional magnetic resonance imaging. A seed-based and dynamic functional connectivity approach enabled us to examine default-mode network spatial and temporal properties and their white matter substrates. While spatial default-mode network patterns were similar across groups, we found differences in temporal dynamics of 1 network and in white matter-default-mode network correspondence. These differences were either observed in white matter tracts directly associated with complete or partial absence of the corpus callosum or in white matter tracts such as the fornix and the anterior and posterior commissures, which have been previously implicated in neuroplasticity in agenesis of the corpus callosum. Our findings show that default-mode network dynamics can remain functionally preserved despite significant white matter alterations.