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Thanks! That's very helpful! Esther Chang, Maria wrote: > Including motion parameters should not remove any power from your signal > of interest if movement isn’t correlated with the task. I have always > been advised to check for task-motion correlations before including > motion parameters in the first level analysis. For example, sometimes > kids bob their head a little when they press a response button. In this > case, if you use motion parameters as a regressor you may model out your > task effects. You can calculate task-motion correlations with Sue > Whitfield-Gabrieli’s brain imaging toolbox. > > > > -maria > > > > ------------------------------------------------------------------------ > > *From:* SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] > *On Behalf Of *Michael T Rubens > *Sent:* Thursday, April 30, 2009 5:39 PM > *To:* [log in to unmask] > *Subject:* Re: [SPM] include motion parameters only for some subjects? > > > > I don't really see any drawback to including motion parameters for > everyone. You are not should not be removing any power from your signal > of interest, you are only reducing noise by explaining signal variance > to due to motion. > > -Michael > > On Thu, Apr 30, 2009 at 2:18 PM, Esther Fujiwara <[log in to unmask] > <mailto:[log in to unmask]>> wrote: > > How about dummy motion regressors for those subjects whose motion > parameters I don't want to include (trying to keep down the amount of > data to throw out ...)? > > Michael T Rubens wrote: > > You need to keep the number of covariates constant across subjects. > > -Michael > > On Thu, Apr 30, 2009 at 1:59 PM, Esther Fujiwara <[log in to unmask] > <mailto:[log in to unmask]> <mailto:[log in to unmask] > <mailto:[log in to unmask]>>> wrote: > > Is it possible to include motion parameters in first level analyses > for some > subjects (i.e., those moving around more) but not others if all > subjects are > later combined in a second level analysis? I suppose not, but I am > not sure why. > Thanks for any comments! > Esther > > > > > -- > Research Associate > Gazzaley Lab > Department of Neurology > University of California, San Francisco > > > > > > > -- > Research Associate > Gazzaley Lab > Department of Neurology > University of California, San Francisco > -- Esther Fujiwara, Ph.D. Assistant Professor Department of Psychiatry University of Alberta 3087 Research Transition Facility Edmonton, AB Canada T6G 2V2 Phone: 780 492-6524 Fax: 780 492-6841