Dear Keith and Toemme
> > as you all know, it is possible to identify early visual areas e.g. with
> > the fmri-analysis tools by Sereno/Dale. However, since this software
> > uses a format different from spm it is quite an effort to
> > convert and superimpose spm-T-maps on the flat maps.
> > Thus, i was wondering if anyone has tried to use spm to identify
> > retinotopic areas ??
> > If so, did you use the same design as the Sereno-group and (most
> > important) were your results promising ?
>
> As far as I can tell, there is no way to extract the phase of the
> activation signal, only the amplitude, using SPM. Therefore it is not
> possible to use such phase-coding methods to map retinotopy. Can someone
> confirm this or correct me?
Well, if you do not have another instrument, you could mimic a phase coding
method using a few cosinus functions shifted in time. However they wouldn't be
a good model and statistical inference may be inacurate because of the
correlation between your regressors. This could be improved by designing more
appropriate regressors, for example convolving a impulse function for each
angle bin with a time limited gaussian. With 4 regressors you should be able to
have t-maps for 8 phases angles (45? resolution). But the big deal is now the
representation of your results to allow a proper map segmentation.
This is just a purely theoretical input, I've never tested that. Did anybody
tried ?
Jack
_________________________________________________________________
| Jack Foucher Universite Louis Pasteur |
| Institut de Physique Biologique UPRES-A 7004 du CNRS |
| 4 rue Kirschleger Tel: 33 (0)3 88 77 89 90 |
| 67085 STRASBOURG Fax: 33 (0)3 88 37 14 97 |
| France |
| Faster E-mail: [log in to unmask] |
| Other [log in to unmask] |
|_______________________________________________________________ |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|