Hi Linda,
for the first part, you can threshold the spmT-maps at the t-value your
chosen threshold corresponds to (see the fine print under the glass
brain :) and then combine them, using ImCalc. It is even easier on the
memory-mapped images, doing something like
image1 = spm_read_vols(spm_vol(spm_select));
image2 = spm_read_vols(spm_vol(spm_select));
thr = 4.0; % your t-value here ;)
temp = (image1>thr)+(image2>thr);
temp(find(temp~=2)) = 0;
overlap = sum(temp(:))
or so. As to the latter, I think this is a bit trickier as you would
need to run simulations as to what your "baseline overlap rate" is,
which I believe to be complicated as you may have to consider shape in
addition to sizes.
Hope this helps,
Marko
Linda Wilbers wrote:
> Hello,
>
> Maybe you can help me with this problem:
>
> In an fmri study we have done two contrasts. Each contrast activates a
> separate area in the prefrontal cortex. Now we would like to prove that
> the two activated areas do not overlap.
>
> The question is how do we prove that the activated areas donot overlap
> more than would be expected by chance given the size of the two clusters
> in the two contrasts?
>
> Thanks a lot,
>
> Linda Wilbers
>
--
____________________________________________________
PD Dr. med. Marko Wilke
Facharzt für Kinder- und Jugendmedizin
Leiter, Experimentelle Pädiatrische Neurobildgebung
Universitäts-Kinderklinik
Abt. III (Neuropädiatrie)
Marko Wilke, MD, PhD
Pediatrician
Head, Experimental Pediatric Neuroimaging
University Children's Hospital
Dept. III (Pediatric Neurology)
Hoppe-Seyler-Str. 1
D - 72076 Tübingen, Germany
Tel. +49 7071 29-83416
Fax +49 7071 29-5473
[log in to unmask]
http://www.medizin.uni-tuebingen.de/kinder/epn
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