Longitudinal Changes in Resting-State Connectivity after Traumatic Axonal Injury
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Little is known about neural network connectivity immediately after a traumatic axonal injury (TAI). This is the first longitudinal study in TAI to examine functional connectivity in the Default Mode Network (DMN) and Central Executive Network (CEN) within 48 hours after traumatic brain injury with repeat imaging 7 months later. Aims: (a) characterize connectivity in these networks at the sub-acute stage of injury, (b) evaluate longitudinal change in networks with recovery, and (c) explore how this change might be associated with structural connectivity and neurocognitive outcome. Resting-state fMRI and diffusion tensor imaging (DTI) scans were acquired from 21 patients with moderate-severe brain injuries consistent with TAI compared with 8 non-injured controls. Neurocognitive outcome was assessed at 7 months. Results revealed lower resting-state DMN connectivity 48 hours after TAI compared to non-injured controls, and this persisted 7 months after injury. CEN connectivity was comparable between acutely injured patients and controls, though patients demonstrated increased CEN connectivity at 7 months. These patterns of functional connectivity in patients were associated with alterations in structural connectivity, where areas of decreased functional connectivity were associated with decreased integrity of white matter tracts connecting those regions. However, some regions within these networks demonstrated increased functional connectivity despite presence of structural damage. Taken together, results suggest disruptions in functional and structural connectivity are present as early as 48 hours after a TAI. Alterations in functional connectivity during the recovery period may be explained either by structural damage or could suggest the presence of neural compensation in functional connectivity.