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<div class="moz-cite-prefix">Dear Marco,<br>
<br>
I once played around with that as well and tried different
approaches. I think the cleanest approach is to define some region
of interest based on anatomy and current literature and take the
neighbouring peak voxel for each subject. In a similar vein as SPM
is doing it, you can first spatially blur your source
reconstructed activity if you like. Of course, instead of taking
the initial ROI from literature, you can also do it as Arjen
suggested take the ROI from some cluster analysis. Anyway, by
making it subject-specific by taking the peak voxel per subject
and blurring it, you will end up with a somewhat consistent region
per subject and will be less sensitive to inter-subject
variability. Unfortunately, you need to write most of this
yourself. <br>
<br>
There are tal2mni and mni2tal functions on the internet for
transforming between these two coordinate systems. Note that this
is only a rough transformation and might not 100% correct.<br>
<br>
For blurring (or smoothing if you want to make it sound fancy) you
can use spm_smooth. Note that this function is does work like the
usual Matlab function in that it does not produce an output
argument but rather changes the input argument inherently (in more
technical terms: call-by-reference rather than call-by-value).<br>
<br>
Good luck! :)<br>
Best,<br>
Jörn<br>
<br>
<br>
On 12/11/2012 9:41 PM, Marco Rotonda wrote:<br>
</div>
<blockquote
cite="mid:CALohiA3t+4NpBF--QRkQ0Sb+OZyNEJfb-n9xE5MvGkoO7Gmo+g@mail.gmail.com"
type="cite">Dear fieldtrip experts,<br>
<div class="gmail_quote">
<div><br>
</div>
<div>I'm sorry to ask again to the list the same question but I
had no answer and I still have not solved my questions.</div>
<div><br>
</div>
<div>I would like to ask you if there is an elegant solution in
the selection/definition of the ROI for a Granger Causality
analysis.</div>
<div><br>
</div>
<div>Just to explain better my doubts.</div>
<div>Let suppose i've the sources reconstructed in the temporal
domain and/or in the frequencies domain.</div>
<div>If now I wish to perform a GC analysis I should know the
ROI or sources on which to perform it.</div>
<div>As far as I've seen most of them are selected with an a
priori knowledge.</div>
<div><br>
</div>
<div>I would like to know if there is a way to define the ROI
from the data, not from my (eventually with bias) knowledge.</div>
<div><br>
</div>
<div>As far as I've searched the only method developed is
the Full-brain auto-regressive modeling (FARM).</div>
<div><a moz-do-not-send="true"
href="http://www.ncbi.nlm.nih.gov/pubmed/21439388"
target="_blank">http://www.ncbi.nlm.nih.gov/pubmed/21439388</a></div>
<div><br>
</div>
<div>
<div>Since there are already ft_mvaranalysis and
ft_connectivityanalysis, do</div>
<div>you think that is possible to integrate the FARM approach
into those</div>
<div>functions?</div>
<div><br>
</div>
<div>
I'm sorry but I know my limitations and I don't know how to
do it.</div>
<div>I hope this could be useful not for me only.</div>
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Marco</div>
</div>
</div>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
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</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group
FieldTrip Development Team
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands
Contact:
E-Mail: <a class="moz-txt-link-abbreviated" href="mailto:jm.horschig@donders.ru.nl">jm.horschig@donders.ru.nl</a>
Tel: +31-(0)24-36-68493
Web: <a class="moz-txt-link-freetext" href="http://www.ru.nl/donders">http://www.ru.nl/donders</a>
Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands</pre>
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