Statistical analysis
SECONDARY
Maps of longitudinal differences in gray matter volume (calculated using the method described in the data processing sub-section above) were modeled voxelwise using a 1-way ANOVA with the total intracranial volume (TIV), age and gender as covariates in SPM12 as recommended by CAT12Follow-up analyses investigating longitudinal gray matter changes within each group considered separately were also performed. Though not able to disentangle treatment effects from potential placebo effects, the more powerful within-subjects design of these secondary analyses permits identification of brain regions that could be used for generating a priori hypotheses in future studies. Currently lacking such a priori anatomical hypotheses, analyses in the present study investigated tDCS induced structural changes at each voxel within the cerebrum since the effects of tDCS can potentially propagate neuronally through brain networksDifferences in clinical and demographic characteristics between the treatment groups were investigated using a 1-way ANOVA (for continuous random variables) and a 