Hi All,
I have a few questions regarding analysis in SPM (SPM5 in particular).
1) For multi-session single-subject realignment, the process is:
1) realign first image of >1st session to first image of first
session
2) realign images in each session to first image in that session
How is the mean image calculated from here and used for 2-pass
registration?
i.e. Is the mean image just the mean of all realigned images in all
sessions and then
all realigned images in all sessions are realigned to the mean
image or ....
2) For determining the voxels that are "pooled" and enter the ReML
calculation of hyperparameters, the code is somewhat hard to decipher. Is
it correct to assume that the voxel is "significant" and enters "pooled"
data (i.e. Cy) if:
F(voxel) > F(p=0.001)
where: F(p=0.001) is calculated using numerator and denominator d.o.f. as
determined from design matrix (i.e. trace(X) and trace(R) respectively)
Also, is pooling "significant" voxels done for theoretical or computational
reasons and would there be a reason not to just pool all in-mask voxels???
Thank you,
Brian Lenoski
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