Dear Ian,
the line
matlabbatch{1}.spm.util.voi.expression = 'i1 & i3';
says that the final VOI will be formed of suprathreshold voxels (from
the SPM{.}) within a 6mm radius sphere whose centre was moved to the
largest statistical value within mask image ROI.nii.
If you use 'i1 & i2 & i3', it would mean that the final VOI will be
formed of suprathreshold voxels that are within a 6mm radius sphere
(whose centre...) but also within the mask image ROI.nii. Nothing wrong
with this per se, it's just a different definition of the VOI.
Best regards,
Guillaume.
On 02/04/15 08:02, Ian Lee wrote:
> Dear experts,
>
> I found the link which Guillaume introduced in previous email was very useful!
> However, there is one thing which is still not clear to me, more specifically, in the last line:
>
> matlabbatch{1}.spm.util.voi.spmmat = {'SPM.mat'};
> matlabbatch{1}.spm.util.voi.adjust = 1;
> matlabbatch{1}.spm.util.voi.session = 1;
> matlabbatch{1}.spm.util.voi.name = 'V2';
> matlabbatch{1}.spm.util.voi.roi{1}.spm.spmmat = {''};
> matlabbatch{1}.spm.util.voi.roi{1}.spm.contrast = 3;
> matlabbatch{1}.spm.util.voi.roi{1}.spm.threshdesc = 'none';
> matlabbatch{1}.spm.util.voi.roi{1}.spm.thresh = 0.001;
> matlabbatch{1}.spm.util.voi.roi{1}.spm.extent = 0;
> matlabbatch{1}.spm.util.voi.roi{2}.mask.image = {'ROI.nii'};
> matlabbatch{1}.spm.util.voi.roi{3}.sphere.centre = [0 0 0]; % unused
> matlabbatch{1}.spm.util.voi.roi{3}.sphere.radius = 6;
> matlabbatch{1}.spm.util.voi.roi{3}.sphere.move.global.spm = 1;
> matlabbatch{1}.spm.util.voi.roi{3}.sphere.move.global.mask = 'i2';
> matlabbatch{1}.spm.util.voi.expression = 'i1 & i3';
> matlabbatch{1}.spm.util.voi.expression = 'i1 & i3'; % Here, In this line, why is it only the combination of i1 and i3? Isn't it supposed to be i1&i2&i3?
>
> I am sure that I'm misunderstanding something, but then, would you explain to me what I am missing here?
>
> Thank you in advance.
>
--
Guillaume Flandin, PhD
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
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