Global organization of functional brain connectivity in methamphetamine abusers

Objective: This study aimed to determine effects of chronic methamphetamine (MA) abuse on global organization of the functional brain connectivity. Methods: Eyes-closed resting-state EEGs of 36 MA abusers and 36 age-matched healthy subjects were recorded using a 32-channel system. The EEGs (1-60 Hz), after removing artifacts, were decomposed into the conventional EEG bands. Using visibility graph similarity (VGS) and coherence methods, the VGS and coherence matrices in each EEG band were constructed. Then the Small-World Network properties, clustering coefficient (C), mean path length (L) and C/L, of the VGS and coherence matrices, were computed in all EEG bands. Then using the Mann-Whitney test and an artificial neural network the differences of C, L and C/L between the two groups were evaluated. Results: The MA abusers showed higher C, lower L and higher C/L at the gamma band (p-value <0.005). An accuracy of 82.8% in discriminating the two groups was obtained by the classifier. Conclusions: The topology of the functional brain connectivity is disrupted in MA abusers, as depicted by deviation from Small-Worldness in the gamma band. Significance: This is the first but quasi-experimental study showing disrupted topology of the functional brain networks in MA abusers. (C) 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.