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In addition to John's feedback I would alsomsuggest looking at the data as a movie with something like fslview. This helps see when motion is "bad." What I meN by bad is that sometimes motion causes big MR artifacts where full slices will be black or at least dark. In my opinion this helps decide whether motion is too big. Jason On Mar 28, 2014 6:22 AM, "Ella" <[log in to unmask]> wrote: > Dear Michael and others, > > > > It seems, that there is no simple "rule-of-thumb" to deal with this > problem. > > > > For block designs, inclusion of motion covariates has a deleterious impact > on GLM sensitivity when activity of interest is correlated with motion, > e.g., in tasks required manual action, speech-production or sudden sound > resentation (Bullmore et al., 1999; Johnstone et al., 2006). Analysis using > movement corrections and regressors should increase the significance and > extent of activations detected before correcting for movement only if they > are orthogonal to movement effects. If any component of activation or > task-related changes are correlated with an estimated movement effect, any > manipulation to minimize motion artifacts might lead to loss of > sensitivity and removal of this component (Bullmore et al., 1999; Freire & > Mangin, 2001; Friston et al., 1996; Hajnal et al., 1994). > > > > Some recent papers dealing with this problem: > > Churchill et al. - 2012 - Optimizing preprocessing and analysis pipelines > for single-subject fMRI. I. Standard temporal motion and physiological > noise correction methods. > > Hutton et al. - 2013 - Phase informed model for motion and susceptibility > > Power et al. - 2014 - Methods to detect, characterize, and remove motion > artifact in resting state fMRI > > > > As far as I understand, this is still unresolved issue and the answer is > "It depends..." > > > > Best, > > > > Ella > > > > > On Fri, Mar 28, 2014 at 12:01 PM, Mouthon Michaël < > [log in to unmask]> wrote: > >> Dear John, thank you for your last post. >> But I have a question regarding including motion parameter of realignment >> as covariate in the GLM. The paper of Johnstone et al 2006 ( >> http://www.ncbi.nlm.nih.gov/pubmed/16456818) shows that the inclusion of >> motion parameter as covariate had a deleterious impact on the GLM >> sensitivity for a fMRI block design and increase of sensitivity for an >> event-related design. >> >> Do you think that it's a bad idea to include these motion parameters as >> covariate in any case for a block design ? Or it could help in the case of >> a population with a lot of movement like older people or patients even if >> it a block design? >> >> >> Thank you in advance >> >> Michaël >> > > > > -- > Ella Gabitov > Ph.D. student > The E.J. Safra Brain Research Center for Learning Disabilities > The Laboratory of Human Brain and Learning > University of Haifa > Israel > Phone: +972-52-6722700 > E-mail: [log in to unmask] >