Hi Karl

differences in surface area are a bit harder to interpret. There are also some technical issues that perhaps Doug and/or Anderson Winkler can comment on. Anderson had a recent article on this that you might want to look at:

http://www.ncbi.nlm.nih.gov/pubmed/22446492

cheers Bruce

On Mon, 14 Mar 2016, Karl Liu wrote:

Dear FS team:

I want to ask for some advice on how to extract the values of pial surface area. I use QDEC to perform a surface-based F-test. The measurement is area.pial and the smoothing is 10 in QDEC. After correction, there is one significant cluster  with size of ~760 mm^2. The problem comes when I want to extract the measure from each participant, so that I can plot the group means. Currently I used the values from the "cache.th20.neg.y.ocn.dat" file, but all the group means varies between 0.7-1.0 in magnitude. I believe the unit is mm^2, because this is pial surface area. But is 0.7-1.0 mm^2 too small? What is the correct way to extract surface area from this signficant cluster, so I can plot the pattern of group differences in a bar graph?

Another question is  the validity of  surface-based analysis on pial or WM surface area. I found most FS publications focus on the thickness, but not the surface area. From your perspective, is  the surface area as valid as the thickness measure?

Many thanks in advance

Karl