Poster Session E, Monday, March 25, 2:30 – 4:30 pm, Pacific Concourse
The effects of lesions on the modular organization of the brain: A comparison of simulated and real lesions
Yuan Tao1, Brenda Rapp1; 1Johns Hopkins University
Simulation studies directed at understanding the effects of lesions on functional organization have shown that damage to nodes supporting cross-module or within-module integration have opposite effects on whole-brain modular organization (Honey & Sporns, 2008). However, the consequences of actual lesions have been scarcely studied. In this work we examined the consequences of brain lesions in chronic stroke (n=15) and the simulated impact of these lesions in healthy individuals (n=23). A reference modular structure was computed from controls and, on this basis, global (participation coefficient, or PC) and local (within-module density, or WD) integration coefficients were calculated for each node. For each lesion mask, we computed its PC and WD damage scores by averaging the respective integration coefficients. Simulated lesions were created by applying every lesion mask to each control dataset and modularity (Newman’s Q) was calculated for all datasets. Finally, lesion-mask PC and WD damage scores were correlated with modularity. Consistent with previous studies, simulated lesions with larger PC damage resulted in higher modularity (Pearson r=0.43, p<0.05), while WD damage had the reverse effect (r=0.46, p<0.05). However, for actual lesions, PC damage was negatively correlated with modularity (r=-0.48, p<0.05), and WD damage was uncorrelated with modularity (r=0.07, n.s.). The discrepancy between simulated and real lesions indicates that lesion-driven functional re-organization cannot be explained as a simple subtraction of nodes from the healthy brain. Instead, the findings indicate that lesions lead to functional connectivity changes in which global connectors play a pivotal role.
Topic Area: METHODS: Neuroimaging