Dear Jorge,
> I have calculated the volume of activation of different brain areas
> using a fixed effects analysis (fMRI data set, SPM99b). How can I
> obtain an estimate of the error of these volumes?
The distributional approximations for spatial extent will be found in:
Friston KJ Worsley KJ Frackowiak RSJ Mazziotta JC & Evans AC Assessing
the significance of focal activations using their spatial extent Human
Brain Mapping 1994;1:214-220
These are used as the basis of inference (i.e. p values) based on
spatial extent. Comparing two clusters however is not so simple, if
that is what you want the error variance for.
I hope this helps - Karl
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