Dear SPM'ers
I just want to add a comment about including motion parameters in the
designmatrix. This should only be done in batch mode where you can
specify that these covariates are of no interest. Otherwise almost every
voxel in the brain is included in the AR(1) process estimation, and the
estimate becomes too optimistic and the p-values too low.
Torben Lund, Danish Research Centre for MR
Martin Kronbichler wrote:
>Jesper, Rik,
>
>thanks for the fast responses and clarifying this issue, now i see the
>light (a least a little spot of it), too. BTW, since i´m mainly interested
>in the results of the second level analysis (RFX) and therefore within-
>subject varaiance is less a concern than parameter estimates, i will try
>out one analysis that includes rps as a confound and one without to compare
>the results.
>Just another quick question, i recall from one of jesper andersson's mail
>to the list that a distortion correction routine will be implemented in the
>spm2 realign & unwarp routine (and i think there are even now some
>commented lines in spm_realign for using a fieldmap), is there any
>forseeable release date for this feature. Since we're starting some new
>fmri studies this autumn, i´m thinking about acquiring field maps in these
>studies. Is some information available, whether any specific kind of field
>map should be acquired (e.g. gradient echo or spin echo). On the other hand
>i should be able to use rhodri cusack undistortion routine or oxfords fugue
>after realignment and unwarping for undist. correction, correct?
>
>All the best and thanks,
>Martin
>
>
>Martin Kronbichler
>Institute of Psychology
>University of Salzburg
>Hellbrunnerstr. 34
>5020 Salzburg
>Austria
>tel.: 0662/8044-5162
>fax.: 0662/8044-5126
>e-mail: [log in to unmask]
>
>
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