Petra
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping)
> [mailto:[log in to unmask]] On Behalf Of Petra Tomse
> Sent: Wednesday, February 20, 2008 7:09 AM
> To: [log in to unmask]
> Subject: [SPM] cluster signal
>
> Hello List,
>
> I am doing a SPECT analysis (paired t-test) with spm2 and I
> would like to get the value of the activity in the clusters,
> that analysis showed were significant. In my case I would
> expect the activity in the cluster to be higher post-therapy
> (2nd images of Patients), but it seems not to be, or I don't
> understand it...
>
> I understand that Eigenvariate produced by the VOI is
> connected to activity value. The Eigenvariates of my
> significant clusters have values of about 60 or 70.
This should be around the same values as your actual data.
>
> My question is: What is the unit of the Eigenvariate?
I believe they are parameter estimate units (what is called "response" in
the plots). Basically the eigenvariate is just a method for summarizing the
data from all the voxels in your VOI. A more familiar method would be to
take a mean at each data point, across voxels. The eigenvariate is just
another way of summarizing this data that accounts for most of the variance
in the data vector.
> In what order are the values of Eigenvariate given? (is it: from 1st
> image of Patient1; 2nd image of Patient1; 1st image of
> Patient2;... ? )
In whatever order you have entered the scans in your model.
Darren
>
> Thank you in advance,
> Petra
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