Dear SPM,
I have a couple of questions about SPM99.
How does SPM99 fit the AR(1) model to each voxel time series if you
specify this option in the model set-up? Is this a global fit? Are both
the AR coefficient and the innovations variance estimated globally or is
one global and one local? I'd like to know the details and haven't been
able to find them anywhere on the web site.
Also, when using an F-test to test for the significance of a group of
covariates (i.e. a main effect convolved with a basis of functions that
span the space of possible HRF's) why is it that during the cluster
detection the spatial extent threshold is automatically set to zero,
whereas for t-test cluster detection you can choose the threshold?
Thanks
Jonathan Marchini
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