Q: As far as I understand, I should calculate the t threshold based on Worsely et al., Human Brain Mapping, 1996. I am really sure that it is very well-written famous paper, but I couldn’t figure out how to calculate the t-threshold in the given conditions. Is there any easy way to calculate t threshold for p<0.05 (corrected)?
And, is it going to be the same even if I consider the whole brain rather than just striatum, e.g., fallypride study?
http://www.bic.mni.mcgill.ca/pipermail/minc-users/2008-May/002025.html
A: > As far as I understand, I should calculate the t threshold based on > Worsely et al., Human Brain Mapping, 1996. > I am really sure that it is very well-written famous paper, but I > couldn’t figure out how to calculate the t-threshold in the given > conditions.
Correct, to calculate this I would suggest that you use Keith Worsleys MATLAB package (called fmristat) to do this.
http://www.math.mcgill.ca/keith/fmristat/
> Is there any easy way to calculate t threshold for p<0.05 (corrected)?
This will depend on the number of subjects, (and thus Degrees of Freedom), the number of voxels you are considering and so forth.
> And, is it going to be the same even if I consider the whole brain rather > than just striatum, e.g., fallypride study?
It will be different, but again this will depend on the method you use to calculate the t-value. Certainly it will change if you calculate pooled variance across you data (or mask).
Again though I would suggest that you spend some time getting acquainted with the fmristat package. Keith has a number of examples on his webpages that should help you get going.