Neurodegenerative networking

Abstract

Comments on the articles, Predicting Regional Neurodegeneration from the Healthy Brain Functional Connectome by J. Zhou et al. (2012) and A Network Diffusion Model of Disease Progression in Dementia by A. Raj et al. (2012). In neurodegenerative diseases, pathology does not spread like a fan from one brain area to neighboring areas. Instead, the spread follows disease-specific patterns that resemble the architecture of brain connectivity networks. What remains unclear is why pathology spreads along such networks and whether the strength of network connectivity predicts the severity of neurodegeneration. Two new studies involving graph theoretical analysis of healthy brain connectivity suggest that in these disorders, neurodegenerative pathology spreads transneuronally through neural networks. Zhou et al. used resting-state functional MRI data from healthy volunteers to determine the functional connectivity of brain regions that are known to undergo atrophy in five different neurodegenerative diseases. They then applied graph theoretical analysis to assess whether the connectivity profile of a region in healthy brains is indicative of regional vulnerability in diseased brains. In the second paper, Raj et al. explicitly modeled the spread of prion-like neurodegenerative pathology by a network diffusive mechanism. They first generated structural connectivity networks from tractography data (obtained using structural MRI) from 14 healthy young individuals and then used graph theoretical analysis to model diffusive progression of pathology along the fibre pathways in these networks. This modeling revealed several spatially distinct patterns-so-called 'eigenmodes'-by which such progression could proceed. Together, the results of these studies provide support for the hypothesis that the spread of neurodegeneration across neural networks occurs via transneuronal propagation. The studies also demonstrate the power of graph theoretical analysis to develop and probe models of neural network breakdown in neurodegenerative disease. (PsycINFO Database Record (c) 2013 APA, all rights reserved)