Dear Alfonso,
Following your advice, I tested the possible effect of phase shift using my resting state data.  I performed a new first-level analysis using a single region (L Hippocampus) and changed the 'Derivatives order' from o to 1, using multivariate regression analysis (see Fig. 1 in the WORD file). But, it the Results section, I did not find the *_der2 sources, but see the L Hippocampus and L Hippocampus Der 1 scoures (see Fig. 2). Are there any problems for the setting?
Another question is that I am not clear about how to check whether my results are affected by the small phase shift of resting-state data. My understanding is that if there were no significant activations (voxelwise P<0.001, cluster P<0.05 FDR ) for a shifted correlation sign indicated by a sign-shifted -der 1 (see Fig 3), we could conclude that the phase shift effect did not significantly affect our results. Is that right?
Best,
Ivan