Are there packages that do joint transformation at once? As far as I understand the SPM uses separate steps.
On Tue, May 6, 2014 at 6:16 PM, Yaroslav Halchenko <[email protected]>wrote: > > On Mon, 05 May 2014, J.A. Etzel wrote: > > > On 5/5/2014 2:51 PM, Vadim Axel wrote: > > >I personally use always normalized and I do not think that this > > >should matter too much. I think given that normalization introduces > > >some smoothing, it may probably even increase predictions - as Hans > > >Op De Beeck showed that smoothing might be helpful for prediction > > >rate. > > > Unfortunately, *should* matter doesn't always mean *does* matter, and > > I'm very hesitant to draw too many conclusions from experiences with > > smoothing: some spatial normalization algorithms are far, far > > different than Gaussian smoothing. > > > That doesn't mean to never spatially normalize, but I would > > certainly never assume that it's a neutral procedure. > > moreover, in case of linear "normalization" -- if you "normalize" by > applying a joined transformation (motion correction + normalization) to > each volume, instead of two separate steps (motion correction of entire > 4d series and then normalization of the entire 4d at once), then those > should be nearly identical and theoretically "MVPA" metrics should be > the same if resolution is nearly the same as original and subjects > did move at least a bit since then those volumes would get > interpolated anyway to correct for the motion. > > -- > Yaroslav O. Halchenko, Ph.D. > http://neuro.debian.net http://www.pymvpa.org http://www.fail2ban.org > Research Scientist, Psychological and Brain Sciences Dept. > Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755 > Phone: +1 (603) 646-9834 Fax: +1 (603) 646-1419 > WWW: http://www.linkedin.com/in/yarik > > _______________________________________________ > Pkg-ExpPsy-PyMVPA mailing list > [email protected] > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-exppsy-pymvpa >
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