Imaging protocol All MRI experiments were performed on a 3.0 T Achieva whole-body MR scanner (Philips Medical Systems, Best, the Netherlands).

Anatomical images were acquired using a high-resolution 3D T1-weighted sequence (MPRAGE) with the following parameters: TR/TE/flip angle of 7.4 ms/3.4 ms/8°, field of view (FOV) of 256 × 256 × 220, voxel size 0.98 × 0.98 × 0.6 mm. After the anatomical imaging, two fMRI images were acquired at resting state, separated by 15 min during which smokers smoked and nonsmokers chewed gum. Each fMRI lasted 7.5 min with the eyes closed Inhibitors,research,lifescience,medical using a single-shot gradient EPI sequence (TR = 1500 ms, TE = 35 ms, FOV = 230 × 230 ×120 mm, flip angle = 80°), 24 contiguous oblique-axial slices (2.7

× 2.7 × 4 mm voxels) parallel to the AC-PC line were obtained. DTI click here volumes were acquired and results are reported elsewhere. (Huang et al. 2013). Data preprocessing Resting-state functional connectivity imaging data were preprocessed using Data Processing Assistant for Resting-State Inhibitors,research,lifescience,medical fMRI (DPARSFA; Chao-Gan and Yu-Feng 2010; http://www.restfmri.net) based on Statistical Parametric Mapping (SPM8) software (http://www.fil.ion.ucl.ac.uk/spm). The fMRI images were corrected for the acquisition delay between slices by shifting the signal measured in each slice relative to the acquisition Inhibitors,research,lifescience,medical of the slice acquired Inhibitors,research,lifescience,medical in the starting time of each TR. The head motion was corrected by estimating the values for translation (Hong et al. 2009;.) and rotation (degree) for each subject. Only subjects with

head motion less than 2 mm in the x, y or z direction and less than 2° rotation about each axis were included. The motion corrected rsFC imaging volumes were spatially normalized to the standard SPM8 EPI template and resampled to 3 × 3 × 3 mm3. The processed Inhibitors,research,lifescience,medical images were then spatially smoothed with a 4 mm full width at half maximum (FWHM) Gaussian kernel. Linear trend removal and temporal band-pass filtering (0.01–0.08 Hz) were performed on the time series of each voxel. The individual T1-weighted MPRAGE images were coregistered to a standard stereotaxic space (MNI space; Brett et al. Edoxaban 2002) to facilitate group analysis. Independent component analysis (Calhoun et al. 2001) was performed to evaluate changes in brain resting-state networks using GIFT toolbox (http://mialab.mrn.org/software/gift/index.html). Number of components was set to 20. The infomax algorithm was used to perform spatial ICA and spatial-temporal regression was chosen for back reconstruction. Independent components were scaled to z-scores (Calhoun et al. 2009). Resulted components were carefully compared to known resting-state networks that have been found consistently co-active during resting state (Damoiseaux et al. 2006; De Luca et al.