[Freesurfer] subcortical volume and qdec

Dear freesurfer experts:

I had processed my data with recon-all, and also ,I had compared the cortical thickness difference between the con and pat with qdec .however,when i I try to compare the sub-cortical volume difference between con and pat ,the results were the same as the thickness,even in Analysis Results window,the option is not changed,as the "Does the average thickness differ between con and pat?" So, I have no idea about it,because I chose the ASEG.VOLUME in the "Stats Data Import" window.

In addition ,I wander whether the volume differ comparison is processed based on ROI or vertex?

Did anyone can help me with any suggestion.

thank you wang