Current density and source activity during reward processing were examined using sLORETA to identify brain regions involved and also to localize the brain deficits in alcoholics. The sLORETA is considered to be a successful solution to the inverse problem, i.e. the problem of localization of brain activity in the EEG and EMG data (Pascual-Marqui, 2002; Pascual-Marqui, 1999). Detailed description and technical information on sLORETA have been provided by its author, R.D. Pascual-Marqui, at: http://www.unizh.ch/keyinst/NewLORETA/LORETA01.htm. In the present study, the current density maps were created for the grand mean data of each condition in alcoholics and controls separately. Then, the time frames that represented the peak ORN and ORP activity were compared across groups and across conditions using the independent and paired t-tests respectively. Statistical analyses involved a voxel-wise Statistical non-Parametric Mapping (SnPM) with 5000 permutations. The t-values in all 2394 voxels were plotted and the t-values above the critical threshold (i.e. significance level) were highlighted (based on the color scale) to show the areas of significance. These values are calculated via a randomization method (Nichols and Holmes, 2002), and the SnPM approach controls for Type I error (Flor-Henry et al., 2004).
