I'm new to Freesurfer; my background is resting-state fMRI using SPM. Years back, left and right cortical thickness measures were calculated for our sample of schizophrenia patients using the Desikan-Killiany atlas and were input to an SPSS spreadsheet. In an exploratory analysis of the data, I found that behavioral performance on a skills assessment was correlated with thickness of lh_rostralmiddlefrontal and lh_parstriangularis regions. 

I'd like to perform a follow-up resting-state fMRI analysis, using these two surface-based parcellations ( lh_rostralmiddlefrontal and lh_parstriangularis) as seed regions and use those behavioral performance scores as a regressor.  Is there a simple way to convert these two 2D-surface-based atlas measurements to masks in nifti format in 3D-volumetric space? I was doing a quick google search and came across the mri_label2vol command. Would this be helpful? Sorry for my naiveté. I appreciate your time.