2.5. Data Preprocessing and VBM Statistical Analysis

Digital Imaging and Communications in Medicine (DICOM) image data were processed with MRIcro software (version 1.40, Chris Rorden's Neuropsychology Laboratory, University of South Carolina, Columbia, SC, USA; http://www.mricro.com). All data were analyzed by using statistical parametric mapping (SPM) 5 (Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK; http://www.fil.ion.ucl.ac.uk/) and voxel-based morphometry (VBM) 5 (Department of Neurology, Department of Psychiatry, Friedrich Schiller University Jena, Thuringia, Germany; http://dbm.neuro.uni-jena.de/vbm/vbm5-for-spm5/) software based on Matlab 7.1 (The MathWorks, Inc., Natick, MA, USA). Each individual image was normalized and transformed into the standardized Montreal Neurological Institute (MNI) template, then resampled in 2 × 2 × 2 mm scale. Normalized images were then segmented into grey matter (GM), white matter (WM), and cerebrospinal fluid (CSF). Modulated GM and WM images were separately smoothened to remove noise using a filter with full width at half maximum (FWHM) of 8 mm.