> We have an experiment where a subject does one session (run) right after
> another. For us, this leads to 4 sessions.
> SPM creates a single mean image file in preprocessing and a single
> motion text file: this seems logical.
Not really :) If you enter the sessions as single sessions into the
realignment step (which you really should do) then SPM will generate one
rp_*.txt file per session, which is what you want. The realignment is
specifically set up to deal with motion between sessions differently, it
is therefore advisable to let it do that. If you have a good reason to
do otherwise, you could also load in the text file and split it into 4
equal chunks (using spm_load and Matlab's save as text options). This
should be relatively easy to script.
> Moreover, regressing out motion leads to 4 (sessions)
> times 6 (types of motion) = 24 extra columns of the design matrix.
> Can anyone advise?
If you put them all in one big design, which may or may not be what you
want. In any case, the most elegant way to deal with that is the
"multiple regressors" option in the batch editor, where you can load a
text file (for example, the realignment parameters :) specifiying the
covariates you want to include. You only need to select the file and all
regressors specified in there will be added to the design.
Hope this helps,
PD Dr. med. Marko Wilke
Facharzt für Kinder- und Jugendmedizin
Leiter, Experimentelle Pädiatrische Neurobildgebung
Abt. III (Neuropädiatrie)
Marko Wilke, MD, PhD
Head, Experimental Pediatric Neuroimaging
University Children's Hospital
Dept. III (Pediatric Neurology)
D - 72076 Tübingen, Germany
Tel. +49 7071 29-83416
Fax +49 7071 29-5473
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