Thanks, Rick.
Yes, demeaning BEFORE the zeros are inserted does not affect the correlation.
However, say I have an errts file, and I extract the time series from certain ROIs. Does this time series also come demeaned before the zeros are inserted (due to scrubbing)?
Additionally, assuming these errts files have a mean of 0, then would the results of dual regression (in FSL) depend on whether certain volumes have 0's in them? Dual regression first does a spatial regression with specified masks (for example, the DMN) on the errts file, which extracts a time course for that mask. The time course is then again regressed onto the errts file, so as to see the spatial extent to which the initial mask or network is represented in the errts file. Would the 0's in the dataset cause dual regression to give different results?
Best,
Avi