Hi all, Thanks so much for your quick and thoughtful suggestions! I'm still processing all the info, and will most likely try out a few different methods (all of this in tandem with learning the PyMVPA software, itself!). I hadn't previously considered the smoothing effects of interpolation from using a double motion correction procedure. My next step will probably be to try fiddling with the MCFLIRT parameters on the single concatenated file.
Mike On Tue, Jul 12, 2011 at 7:32 PM, Michael Hanke <[email protected]> wrote: > On Tue, Jul 12, 2011 at 04:50:04PM -0500, J.A. Etzel wrote: > > Volume order within a session definitely matters: I had a dataset in > > which the volumes were entered in the wrong order (due to a > > numerical vs. alphabetical file naming mixup) and the motion > > correction was extremely abnormal and poor. Once the file naming was > > fixed the motion correction looked fine. > > According to my experience, most software uses some sort of running > guess on the transformation matrix with heavy constraints on the > translation/rotation magnitude between volume (for speed reasons). > Reverse order of volumes shouldn't have much of an effect, but random > order would. For heavy between session motion (maybe people got out of > the scanner) it might be better to compute a cross-session alignment and > combine that with within session motion correction. But again, that is > nothing MVPA specific. > > Michael > > -- > Michael Hanke > http://mih.voxindeserto.de > > _______________________________________________ > Pkg-ExpPsy-PyMVPA mailing list > [email protected] > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-exppsy-pymvpa >
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