Dear Amelia,
these are quite different things:
Volumes Toolbox extracts data from image files (with global scaling
applied if you extract from SPM.mat) or from fitted data (X*beta). These
data are extracted voxel by voxel from the specified ROI (sphere, mask
image ...) and optionally averaged by a simple mean.
The extracted eigenvariate contains signal which is adjusted for effects
modelled by the high-pass filter and also for a certain contrast.
Averaging over the ROI is done through eigenvariate analysis.
In general, Volumes Toolbox gives you access to raw time series, while
eigenvariate extracted data are derived from filtered and adjusted data.
Hope this helps,
Volkmar
Am Montag, den 05.05.2008, 15:25 +0100 schrieb versacea:
> Dear SPM experts,
>
> Could anybody explain what the difference between extracted values [ext]
> from VOLUME (SPM toolbox) and the eigenvariate [Y] extracted from VOI???
>
> Any references about this would be appreciated
>
> Thank you very much!!!
> Best Regards
> Amelia
>
--
Volkmar Glauche
-
Department of Neurology [log in to unmask]
Universitaetsklinikum Freiburg Phone 49(0)761-270-5331
Breisacher Str. 64 Fax 49(0)761-270-5416
79106 Freiburg http://fbi.uniklinik-freiburg.de/
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