Functional connectivity within posterolateral parietal cortex and its alteration in traumatic brain injury

Restricted (Penn State Only)
Author:
Venkatesan, Umesh Meyyappan
Graduate Program:
Psychology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 18, 2017
Committee Members:
  • Frank Gerard Hillary, Dissertation Advisor
  • Frank Gerard Hillary, Committee Chair
  • Nancy Anne Coulter Dennis, Committee Member
  • Stephen Jeffrey Wilson, Committee Member
  • Charles Geier, Outside Member
Keywords:
  • traumatic brain injury
  • fmri
  • functional connectivity
  • resting state
  • graph theory
  • neuroplasticity
  • parietal
  • default mode
  • neuropsychology
  • TBI
  • frontoparietal
Abstract:
Spatially distributed functional brain networks show multiple points of regional convergence (“hubs”), suggesting that local network architecture supports global systems communication. Traumatic brain injury (TBI) alters global connectivity patterns, but relatively little is known about its effect on interactions within local hub environments and whether this has implications for cognition. The goal of the dissertation was to examine one such environment, the posterolateral parietal cortex (PPC), in relation to distributed network connectivity and cognition in both TBI (n=18) and healthy controls (n=19). Using resting-state functional MRI in conjunction with seed-voxel and graph theoretical connectivity analyses, the study revealed evidence for increased connectivity, or hyperconnectivity, in TBI from portions of left and right PPC to right-lateralized default mode and frontoparietal control network regions, as well as within the local right PPC network itself. Across groups, right versus left PPC showed increased local connection strength and decreased betweenness centrality, a measure of network hubness. In TBI, strength and global efficiency within the right PPC were strongly negatively correlated with auditory attention span and attentional reaction time, respectively. Overall, these findings substantiate hyperconnectivity on both global and local levels after TBI. Importantly, they propose a special role for local network communication within the right hemisphere in facilitating large-scale information transfer after neurologic insult. Local network organization in TBI also appears to have consequences for cognitive functioning, potentially reflecting a need to balance functional resource demand with network efficiency.