Hi Ben and Carles
The PPI.mat file contains a structure. See spm_peb_ppi for the field
specifications. The bottom line is you want to load
PPI.ppi - The interaction term, which is the basis for the PPI inference.
PPI.Y - BOLD signal (will be a regressor of no interest)
PPI.P - "psychological" variable (also a regressor of no interest).
Set up your design to include these 3 regressors and for a PPI your contrast
of interest will be a 1 (or -1) on the PPI.ppi column.
Darren
Darren R. Gitelman, M.D.
Cognitive Neurology and Alzheimer¹s Disease Center
Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
Voice: (312) 908-9023 Fax: (312) 908-8789
>-----Original Message-----
>From: SPM (Statistical Parametric Mapping)
>[mailto:[log in to unmask]] On Behalf Of <Ben> <Harrison>
>Sent: Wednesday, June 21, 2006 7:29 AM
>To: [log in to unmask]
>Subject: [SPM] PPI in SPM5
>
>(Carles's mail doesnt seem to have registered properly, here
>it is again)
>
>
>Hi all,
>
>We are attempting to perform a PPI analysis in SPM5. After
>estimating the PPI, which works well, we cannot load the
>resulting PPI.mat file in a new 1st level analysis (either
>loading it as a multiple regressor or as a design matrix with
>“load”). We suspect that this is because the PPI.mat is saved
>as a structural array instead of double array? Any thoughts?
>
>Thanks in advance
>
>Ben & Carles
>
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