Functional connectivity within lateral posterior parietal cortex in moderate to severe traumatic brain injury

Functional brain networks converge on areas of heteromodal processing such as lateral posterior parietal cortex (PPC). Traumatic brain injury (TBI) alters global connectivity patterns secondary to both focal and diffuse damage, but little is known about how it impacts regional environments. We examined local PPC functioning in individuals with moderate-severe TBI and controls during resting-state functional magnetic resonance imaging (rs-fMRI).

Eighteen individuals with moderate-severe TBI and 19 healthy controls underwent rs-fMRI and neurocognitive testing. Seed-based analyses characterized remote connectivity of PPC subregions. Voxelwise graph theoretical approaches were used to probe local PPC connectivity and modularity within and between groups, and to examine relationships between local functioning and cognition.

Seed-based findings included increased connectivity from left and right hemispheric subregions to right-lateralized default mode and frontoparietal control networks in TBI compared to controls. Graph theoretical analyses revealed increased connection strength within right PPC relative to the contralateral region in TBI. Across groups, right PPC also showed decreased betweenness centrality compared with left PPC. Groups did not differ in the extent of modularity within left or right PPC, but there was less interindividual variability in modular structure within the TBI group. Right PPC modularity significantly predicted individual differences in cognitive performance.

Our findings substantiate hyperconnectivity on both local and global levels after TBI and propose a special role for local right hemispheric functioning in supporting cognition independent of neurologic status. Hyperconnectivity does not appear to result from breakdown in local modular organization and may reflect shared responses to neurologic disruption among those with TBI. (PsycINFO Database Record (c) 2019 APA, all rights reserved).