Dear all,
I wonder that how to calculate the PPI.P, PPI.Y and PPI.ppi in SPM:
1) Is PPI.P = conv(design, spm_hrf(TR)) correct? (Note: design is a one-dimension array, which means the experimental design for scanning, such as off-on-off-on-off, the most basic form of block-design)
I've plot the two value, finding the shape nearly the same (but actually the values were a little bit different)
2) Is PPI.Y = conv(Y, spm_hrf(TR)) correct? (Note: Y is generated via "eigenvariate" button, which means the mean response in VOI)
It seems that values of PPI.Y ranges from (-2,2), indicating that it has been standardized, whereas values of Y are much larger (e.g. (130, 160))
3) Is PPI.ppi = PPI.P.*PPI.Y correct?
I've also plot the two value, finding the shape nearly the same (but actually the values were a little bit different)
I hope someone can make me understood. Thanks a lot!
Best wishes,
Yang Hu
ICN, ECNU, Shanghai, China
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