Hi all,
I'm studying negative correlations between spontaneous BOLD signal in
different voxels. It is known that substracting a global signal from all
voxel might induce spurious negative correlations in the data. Thus I would
like to know wheter or not the highpass filter in FEAT preprocessing acs
locally (by filtering the BOLD signal in each separately) or globally (by
computing some mean and substracting it from all the voxels). I suspect that
in order to correct the scanner drift FEAT might substract a global signal
from all the voxels.
Does anybody know to some detail the algorithm FEAT uses to do highpass
filtering and wheter or not it is purely local or global?
thanks all!
Enzo.
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