Stupid question on spatial smoothing: does SPM compute a sort of mask
for the brain before smoothing or simply smooth all data? (thus mixing
up non brain and brain tissues on the edges)
Another, maybe less stupid ( :-\ ), question is: if I observe an effect
in a small region (a nucleus) in VBM with a FWHM of 8mm but not at 4mm
nor at 12mm ; Am I right to assume that's because my filter matches the
signal? (at 12mm I may mix the data with non brain hence a drop of the
effect but at 4mm this should not - the observed effect is thus not
related to smoothing mixing up data but related to the spatial size of
Any help will be greatly appreciated.
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.