Hi,
Are you doing an FSLVBM analysis? In which case I wouldn't expect you
to be using FEAT for the modelling, but using randomise, as per the
FSLVBM manual. In which case you could either run the different
modellings as completely separate analyses, or just use different
design.mat and design.con models/contrasts at the end - I would expect
that in this scenario it shouldn't make too much difference whether
you've used individualised 'study'-specific templates or not.
Cheers.
On 13 Nov 2008, at 13:13, Ronan Joseph Kelly wrote:
> Dear FSL experts,
>
> I am conducting a VBM analysis involving the comparison of subjects
> at both between-group and within-subject levels of analysis. I have
> created my study-specific template and design files, and have just
> finished my between-group comparisons. So far it has worked well.
>
> However, my question involves my change of analysis technique. I now
> need to compare across subjects in my repeated measures analysis.
> For this, do I need to set up a new design matrix as if I was
> conducting a new study (and as such copy my necessary files to a new
> directory), or simply add new EVs and contrasts to the old design
> matrix used for my between-groups contrasts? One of my problems is
> that not all of my subjects have scans at each time point, so any
> longitudinal analysis design matrix that refers to my origdata
> directory would have to take this into account, and ignore those
> subjects that don't have a 'paired scan' as such. Therefore there is
> more data involved in my between-group analysis than my repeated
> measures.
>
> Intuitively I think I should copy the required images to a new
> folder, and treat it like a new study; create a new study template
> with the paired scans alone (as my old template would be averaged
> from too much data) and run my repeated measures accordingly. Would
> there be any problems with doing this? Is this the correct method in
> this scenario? As far as I can tell it comes down to whether the
> design.fsf script can handle both methods of comparisons. The stat
> examples on the FEAT webpage don't seem to combine any contrast
> types like this.
>
> Any help would be greatly appreciated!
>
> Cheers,
> Ronan
>
> --
> Ronan Kelly
> Neuroinflammatory Research Group
> Trinity College Institute of Neuroscience
> University of Dublin, Trinity College
> Dublin 2
> Ireland
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