> Sorry to return to the issue, namely, the meaning of fitted and adjusted
> responses (as derived from the plots of a t-test contrast against the scan
> or time) in the context of VBM.
>
> I searched through the archives in relation to Y (fitted) and y (adjusted)
> values, and I understand that in the context of PET, assuming that the
> proportional scaling has been done, the scale of the plot represents the
> signal change percentage from the global mean of 100 (is that correct?).
>
> In the context of VBM, if between group differences in the grey matter
> volume were examined using proportional scaling, would the plot represent
> the responses as percentage change in the grey matter volume in relation
> to the global mean (of 100?), i.e. the mean total grey matter volume (or
> whole brain volume, if that' s what has been used for global normalisation)
> for each individual scan at this voxel?
The following links may help.
http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0302&L=spm&P=R54629&I=-1
http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0302&L=spm&P=R53220&I=-1
Best regards,
-John
--
Dr John Ashburner.
Functional Imaging Lab., 12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420 http://www.fil.ion.ucl.ac.uk/~john
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