Great- thanks for the clarification!
Best,
Sophie
Quoting John Ashburner <[log in to unmask]>:
> On the assumption that Dartel gives more accurate inter-subject
> alignment than other approaches to spatial normalisation using SPM
> (which there is accumulating evidence to support), then I would expect
> the use of Dartel should give more accurate and interpretable findings.
>
> I can not think of any specific issues relating to the registration part
> of the model. The Dartel option to normalise to MNI space will combine
> warping and smoothing in what I believe is a more sensible way than just
> smoothing (although masking at the first level does result in some
> effects that a number of people hadn't expected). I'm not sure how much
> would be optimal, but more accurate alignment generally requires less
> blurring in order to ensure that activations are superimposed. Without
> much evidence to go on, I would probably opt for about 8mm FWHM.
>
> Best regards,
> -John
>
>
> Dear SPMers,
>
> I'm writing to ask your advice on the use of DARTEL in SPM8 for
> normalizing functional images that I am going to be using for
> PPI analysis.
>
> It has been suggested to me to use DARTEL for normalization of
> the contrast images rather than the individual scans for the
> random effects analysis.
>
> Do you think that this has any implications for PPI in terms of
> extracting first eigenvariate of seed region per subject in
> native space?? Do you think that it would be a good idea to
> smooth the images first? Is there anything else that i should be
> thinking about?
>
> A very similar question has been asked before and no one has
> answered as far as I can see- any help would be greatly
> appreciated!!
>
> Best wishes,
> Sophie
>
> --
> John Ashburner <[log in to unmask]>
>
--
Sophie Green
PhD Student
Neuroscience and Aphasia Research Unit (NARU)
Zochonis Building, 3rd Floor
Brunswick Street
University of Manchester
Manchester M13 9PL
Tel: +44 (0)161 306 0451
|