If I perform the following calculations:
>> load SPM
>> cB=spm_get_data(SPM.xCon(1).Vcon,[50; 50; 50])

cB =

   -1.4833

>> l=spm_get_data(SPM.VResMS,[50; 50; 50])

l =

    3.1513

>> VcB=SPM.xCon(1).c'*SPM.xX.Bcov*SPM.xCon(1).c

VcB =

   13.5666

>> Z=cB./sqrt(l*VcB)

Z =

   -0.2269

>> Zimage=spm_get_data(SPM.xCon(1).Vspm,[50; 50; 50])

Zimage =

   -1.5833

Why does Zimage not match Z? Am I missing something?

I am trying to get the SE of each beta and was going to use the above calculations by replacing SPM.xCon(1).c with a contrast for each beta (e.g. beta1=[1 0 0 0 0 0]), but if I can't reproduce the Tmap from the formulas, I'm not confident in SE measurement.

The above was derived from:
spm_contrasts lines 173-178

Any thoughts would be appreciated.

--
Best Regards, Donald McLaren
=====================
D.G. McLaren
University of Wisconsin - Madison
Neuroscience Training Program
Office: (608) 265-9672
Lab: (608) 256-1901 ext 12914
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