Sorry, I've found an answer to this here: https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg32928.html

Daniel
-- 
Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454
E-mail: yung-jui.yang@yale.edu

On 2/19/14 6:47 PM, "Yang, Daniel" <yung-jui.yang@yale.edu> wrote:

Dear FreeSurfer Experts,

In this webpage (http://surfer.nmr.mgh.harvard.edu/fswiki/FsgdExamples), it says "Two Groups (1 Factor, Two Levels), Two Covariates. DODS only. QDEC-able."

However, I cannot select more than one covariate in qdec. Any suggestion? I'm using qdec in Mac, FreeSurfer 5.3.

Thanks!
Daniel

-- 
Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454