Cecile Bordier, Carlo Nicolini and the Sybill-AA Consortium
Center for Neuroscience and Cognitive System
Istituto Italiano di Tecnologia
Rovereto (Tn), Italy
Aberrant functional connectivity as measured by resting-state MRI has been observed in subjects addicted to various substances of abuse, including alcohol. The functional implications of these alcohol-induced alterations, and their effects on the large-scale organization of brain connectivity are the subject of active investigation.
Here, we have applied a graph theoretical approach to study the modular structure of resting state functional connectivity networks in the brain of 35 recently detoxified alcoholics vs 34 healthy controls. Disjoint modules in the connectivity networks of healthy subjects are thought to reflect specialized sub-systems within the brain functional organization. Graph theory provides a powerful framework to investigate the mutual interations between these systems, and to identify brain regions that play a pivotal role in the integration of modules into a cohesive structure. We observed an overall reduction in functional connectivity strength in the patients’ group, but we found that the effects on the modular organization were restricted to specific subnetworks, including the temporal/supramarginal and the basal modules. These subnetworks were fragmented into smaller modules in alcoholics, resulting in a profound alteration of the topological role played by specific regions within the functional connectivity network. Specifically, a significant increase in the participation coefficient, a measure of intermodular connectivity, was observed for the anterior, but not the posterior insula. This finding suggests increased centrality for the anterior insula in the functional connectivity networks of alcoholics, consistent with the hipothesis of a bolstered role for this region in the integration of interoception, emotions and decision-making in the addicted brain.