The activations in the ventricles are possibly due to the movement. If
you add the motion regressors AND their derivatives, that should
remove the artifact at the first level. However, this might also
reduce the true activations; especially in the case of task-related
motion.
Is the ventricle effect in all three condition or just when you do a
comparison? Is this between two groups of subjects?
On Mon, May 5, 2008 at 1:45 PM, Gregor Domes <[log in to unmask]> wrote:
> Dear SPMers,
>
> I have a question regarding "activations" in the CSF. I have run a simple
> event-related design with 3 different conditions which were presented in
> random order. Preprocessing, 1st level analyses, and a RFX 2nd level
> analysis were done with SPM5.
>
> Looking at some basic main effects on the 2nd level I noticed activations in
> the ventricles. The first 5 volumes have been discarded for analysis. Thus,
> CSF activations are not likely due to T1 saturation artefacts (if I have
> understood previous comments on the helpline correctly...).
>
> Does anybody have an alternative idea how to explain, or even better, to get
> rid of these unlovely "activations"?
>
> Thanks and all the best
> Gregor
> .......................................
> Gregor Domes
> Clinical Psychology and Psychobiology
> University of Zurich
>
--
Best Regards, Donald McLaren
=====================
D.G. McLaren
University of Wisconsin - Madison
Neuroscience Training Program
Tel: (773) 406 2464
=====================
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