Background and Aims Diffuse white matter injury is the most common form of brain injury following very preterm (VPT) birth. This may reflect altered myelination, which could affect both neurodevelopment and neuronal communication. We investigated whether myelin in the corpus callosum (CC) was associated with functional connectivity; and if these associations differed between young adults born VPT and controls.

Methods 9 VPT-born adults and 13 controls (age 26–28 years) underwent resting state functional MRI (rs-fMRI), diffusion MRI and mcDESPOT, a novel neuroimaging method which provides an in vivo estimate of myelin water fraction (MWF). MWF was calculated along the CC. The default mode network (DMN), which contains brain regions that deactivate when a cognitive task is being performed, was identified in the rs-fMRI data using independent component analysis.

Results The VPT group showed decreased functional connectivity (with the rest of the DMN) in the cingulate gyrus and increased connectivity in the left hippocampus compared to controls. In the whole sample (VPT and controls) MWF in the CC was negatively correlated with functional connectivity in the hippocampus and positively correlated with functional connectivity in the medial prefrontal cortex (mPFC). Moreover, the correlation between MWF and functional connectivity in the mPFC was stronger in controls than in VPT-born individuals. All analyses used a p≤0.05.

Conclusions The degree of myelination of the CC is associated with functional connectivity in the DMN, with altered MWF-functional connectivity relationships displayed in adults born VPT in brain regions underlying important high-order cognitive processes.