Thank you for your suggestions Bruce and Mike. Mike, could you please provide the motivation behind your suggestion of using mean cortical thickness as a covariate ?
Let's consider this is the context of a simple example. Let's say we compare the mean thickness of the pre-central gyrus in patients versus controls. Does the biology suggest that even after one accounts for age and gender, there are natural variations in the gyrus thickness measurements ( that is, some people would just happen to have larger thickness measurements ) ? If this is the case, then one could normalize the thickness of the individual gyrus measurement (pre-central gyrus in this example) with the mean cortical thickness. However, in most of the papers I have only seen age and gender used as co-variates. Thanks Mehul On Sun, Nov 1, 2009 at 4:44 PM, Michael Harms <mha...@conte.wustl.edu>wrote: > > To me, it makes much more sense to use mean cortical thickness as a > covariate for thickness-based analyses. > > cheers, > Mike H. > > > Hi Mehul, > > > > the MNI group had an abstract showing that thickness didn't need eTIV > > correction at HBM a number of years ago, and it has been our experience > > as well. > > > > cheers, > > Bruce > > > > On Sat, 31 Oct 2009, Mehul Sampat wrote: > > > >> Hi Folks, > >> > >> If am comparing the mean thickness for certain gyri (pre-central, > >> post-central) in a controls versus patients. > >> I obtain the thickness measurements from lh.aparc.a2009s.stats and > >> rh.aparc.a2009s.stats > >> I was wondering if I need to normalize these thickness measurement > >> with the estimated > >> total intracranial volume (eTIV) ? > >> > >> Or has anyone reported that the these are independent of eTIV ? If so > >> then > >> as I understand I would only > >> need to account for age and gender in any subsequent analysis using GLM. > >> > >> Thanks > >> Mehul > >> > > _______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > >
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