Tali Bitan wrote:
> Dear DCM experts
>
> In the previous version of DCM (in spm2) it has been shown to be
> insensitive to slight changes in timing and it was indicated that DCM does
> not require slice timing correction. However, in SPM5, slice-timing
> correction is an inherent stage of the DCM specification.
>
> My question is:
> 1) Why is slice-timing correction needed for DCM in SPM5 (when it was not
> necessary in SPM2)?
>
SPM2-DCM is robust to timing misspecifications of up to 1s. Given your
central slice as a reference this means it is suitable for TRs<=2s.
SPM5-DCM is given information about slice acquisition and can handle TRs
up to 5s.
Have a look at Stefan Kiebel's paper:
doi:10.1016/j.neuroimage.2006.10.026
> 2) What should we do during DCM specification if our data is already slice-
> time-corrected during pre-processing?
>
If you have a TR < 3s I would do nothing, otherwise I think SPM5-DCM
will probably be a lot better than the interpolation used in the
'slice-time correction' offered in preprocessing. Stefan has simulated
just this comparison in his paper so its best to have a look at that.
Best,
Will.
> Thanks a lot
> Tali Bitan
> Haifa University
>
>
--
William D. Penny
Wellcome Trust Centre for Neuroimaging
University College London
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London WC1N 3BG
Tel: 020 7833 7475
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URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
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