Hi.
First of all: why would you want to do this? ICA is constructed such
that the need for the selection of a (potentially biased) seed voxel
is unnecessary. In terms of "seed" and "target", the ICA equals the
seed, and the DR output basically equals the target. What is your aim
doing the same on a seed based method? I am not sure that you aren't
following circular logic here!
Admittedly, before the advent of DR, one could have chosen (and still
can choose) an interesting ICA component and define a ROI based on
that for, e.g., a PPI analysis. Doing a seed based resting state (is
that so?) analysis would include not only defining your ROI of
interest, but also ROIs of NO interest, such as CSF and white matter,
to correct for their (noisy) contributions, which basically means a
full segmentation of your brains with all what that conveys. Ideally,
you would also have other biosignals such as heartbeat and respiration
as regressors of no interest -something you (ideally) do not need in
Melodic/DR, as those signals get their own components. Seed based
analyses are tricky!
But to answer at least one of your questions: yes, there are tools for
signal extraction from a ROI, such as featquery. There have been
several posts on that. As this is a little laborious, I'd suggest you
search the archives on that if you are willing to go that way. Search
for "define ROI from activation" and "featquery" and so forth.
Good luck,
Cornelius (from not-so-far Aachen)
On Tue, Feb 22, 2011 at 7:50 PM, Perri Carol (di) (PSYCHOLOGY)
<[log in to unmask]> wrote:
> Dear FSL group, I have 2 questions for you, I will try to be as clear as possible.
>
> I have run melodic and dual regression on a group of patients and controls.
> I got 25 components, some of them differing spacially on dual regression between the two groups.
>
> At this point I would like to study this components better with a seed-based analysis.
>
> Here come my questions.
>
> 1) Is there an easy way that I can select the voxel / ROI with the highest peak of activation both on the ICA components and on the dual regression output (dr_stage3_ic.._tfce_corrp_tstat..)?
>
>
> 2)how do I do a seed based study? to be more clear how can I select a roi and extract time courses (means of ROI etc.) for post processing ?
>
> Thanks in advance for your help!
>
> Carol
--
Dr. med. Cornelius J. Werner
Department of Neurology
RWTH Aachen University
Pauwelsstr. 30
52074 Aachen
Germany
Institute of Neuroscience and Medicine
MR Physics - INM4
Research Centre Juelich
52425 Juelich
Germany
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