Dear Lars,

it was my fault. After cleaning and deletion of all old scripts related to tapas and physIO, the script went through and created the multiple regressors. There were errors on the pca step but the program did not stop.

Warning: Escaped character '\_' is not valid. See 'doc sprintf' for
supported special characters.

I have now 8 regressors corresponding to the two ROIs (white matter/CSF) with 3 PCA and 1 mean time course respectively.
Thanks again for your support.

Best
Ralf