Brain networks under attack: robustness properties and the impact of lesions

Hannelore Aerts, Wim Fias, Karen Caeyenberghs, Daniele Marinazzo
2016 Brain  
A growing number of studies approach the brain as a complex network, the so-called connectome. Adopting this framework, we examine what types or extent of damage the brain can withstand -referred to as network robustness -and conversely, which kind of distortions can be expected after brain lesions. To this end, we review computational lesion studies and empirical studies investigating network alterations in brain tumor, stroke and TBI patients. Common to these three types of focal injury is
more » ... t the topological properties of a node do not determine its likelihood to be affected by a lesion. Furthermore, large-scale network effects of these focal lesions are compared to those of a widely studied multifocal neurodegenerative disorder, Alzheimer's disease, in which central parts of the connectome are preferentially affected. Results indicate that human brain networks are remarkably resilient to different types of lesions, compared to other types of complex networks such as random or scale-free networks. However, lesion effects have been found to depend critically on the topological position of the lesion. In particular, damage to network hub regions -and especially those connecting different sub-networks -was found to cause the largest disturbances in network organization. Regardless of lesion location, evidence from empirical and computational lesion studies shows that lesions cause significant alterations in global network topology. The direction of these changes though remains to be elucidated. Encouragingly, both empirical and modeling studies have indicated that after focal damage, the connectome carries the potential to recover at least to some extent, with normalization of graph metrics being related to improved behavioral and cognitive functioning. To conclude, we highlight possible clinical 2 implications of these findings, point out several methodological limitations that pertain to the study of brain diseases adopting a network approach, and provide suggestions for future research. Abbreviations: DWI = diffusion-weighted imaging; fMRI = functional MRI; HGG = highgrade glioma; LGG = low-grade glioma; MEG = magnetoencephalography; TBI = traumatic brain injury.
doi:10.1093/brain/aww194 pmid:27497487 fatcat:wybbsc7lcjhildr2t6upgvmyu4