perhaps an alternative is to use the surface area measure of an ROI, namely the aparc regions, to conduct a group analysis, as the vertex distribution problem is averaged-out over the region.
n. On Wed, 2010-09-29 at 21:02 -0700, Don Hagler wrote: > The area maps do contain the actual surface area of each vertex with > units of mm^2. The problem is that the area at a given vertex depends > on how many vertices a given patch of cortex was divided into, which > is initially uniform but then varies arbitrarily due to topology > correction, rendering it useless for making statistical maps. > > If you are interested in making statistical maps of between-group > differences in surface area, the best way to do that is by calculating > the areal expansion measure. This is not a normally used feature of > freesurfer, but is possible by using make_average_subject separately > for each subject. > > If you use the area values in the aparc stats files, those are the sum > of area for all vertices in each parcellation, and they have units of > surface area (unlike measures of areal expansion). > > > > From: jsadino.que...@gmail.com > > Date: Wed, 29 Sep 2010 15:57:38 -1000 > > To: freesurfer@nmr.mgh.harvard.edu > > Subject: [Freesurfer] Surface Area and Cortical Volume > > > > Hello, > > > > As I understand it, the surface area measure is not a real surface > > area measure. It is more a measure of how much the brain has to be > > stretched in order to get into a common space. My question is that > if > > the cortical volume is calculated by multiplying the thickness and > the > > surface area (right?), then is it a real volume that can be compared > > between subjects? > > > > Also, is it is more accurate to use the cortical volume measures > from > > the aparc files rather than the aseg files, since the aseg files > > overestimate the white matter due to the manual tracing it is based > > on? > > > > Thank you, > > Jeff > > _______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > > > The information in this e-mail is intended only for the person to > whom it is > > addressed. If you believe this e-mail was sent to you in error and > the e-mail > > contains patient information, please contact the Partners Compliance > HelpLine at > > http://www.partners.org/complianceline . If the e-mail was sent to > you in error > > but does not contain patient information, please contact the sender > and properly > > dispose of the e-mail. > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
