I am trying to use SurfStat to create figures based on my qdec results. However, I cannot figure out what outputs form qdec are what, or what their iunits are. I cannot find a description of qdec's outputs on the Freesurfer Wiki.

1) I want to find the statistic overlay for my contrast of interest. Qdec creates a folder for each possible test I could make based on the design. For exasmple, I would like to overlay the results from the folder lh-Avg-thickness-TESSF-Cor. I think I want to use the gamma.mgh file as my overlay. Is that the true? I have some questions about the units of the gamma.mgh files though. When I use SurfStat, it automatically scales this at -0.2 - 0.2. I assumed this was the Anti-Long P scale used by qdec, so I tried to rescale my display to match the colorscale I use to display results in qdec. However, when I tried to change the scale to -3 - > 3, I get nothing. In qdec, I do see effects using this exact scale( min 1.3, max 3, min -1.3, max -3). So This suggests to me that the gamma.mgh is not in the same units (not anti-log(-p)). What are the units?

2) I was told that qdec saves a mean thickness file. I was also told it was one of the gamma.mgh files. Qdec creates a folder for each hemisphere called, for example, lh-Avg-Intercept-thickness. I assumed this was the correct overlay, but it looked to be demeaned as it had both negative a positive values. Is it demeaned? Is there a file that qdec saves that is just thickness? Or is there a way to manipulate the files so that they are not demeaned?

Best regards,

Jennifer Bramen, Ph.D.
Assistant Research Neuroscientist
David Geffen School of Medicine at UCLA
Developmental Cognitive Neuroimaging 635 Charles Young Drive South
Los Angeles, CA 90095-7332
Phone: (310)267-5116
Fax: (310)206-5518
Email: jbramen@mednet.ucla.edu
Campus Mail Code 176919