Hi folks.

I'm analyzing some fMRI data in FSL using parametric modulation. I have two modulated regressors (call them MR1 and MR2) in addition to an unmodulated regressor (UR).

I know that in SPM the order in which you set your PMs - say (1) UM (2) MR1 (3) MR2 - is important, as MR2 will only account for the variance not explained by MR1, I.E. SPM's default is that subsequent modulators are orthogonalized wrt earlier ones, which makes the regression method hierarchical.

Is this also true for FSL?

Also, assuming that it *is* the case for FSL as well, is there a way to change the FSL code in such a way as to go from a hierarchical to a standard linear regression?

Thanks for your assistance.

Nicolas