Dear Fieldtrip group<br><br>I have got a problem with a very simple program to solve a forward problem. I used the below program to compute leadfield from a source in the origin for two electrodes in different locations. I noticed that when I change the position of one of the electrodes, it affects on the leadfield of the other. I know it should not be like that, since electrodes do not affect each other. Would you please help me?<br>
<br><br>elec.pnt=[4.6*cos(pi/3) 4.6*sin(pi/3) 7.96;4.6*cos(pi/6) 4.6*sin(pi/6) 7.96];<br>for i=1:2<br> elec.label{i} = sprintf('%03d', i);<br>end<br><br>% create a concentric 3-sphere volume conductor, the radius is the same as for the electrodes<br>
vol = [];<br>vol.r = [8 8.1 8.6 9.2]; % radii of spheres<br>vol.c = [1 1 1/80 1]; % conductivity<br>vol.o = [0 0 0]; % center of sphere<br><br>% compute the leadfield for a dipole at position [0 0 0]<br>pos = [0 0 0];<br>
lf = ft_compute_leadfield(pos, elec, vol);<br><br>% compute the potential distribution for a dipole with z-orientation<br>mom = [0 0 1]';<br>pot = lf * mom;<br>end<br><br>Best<br>Ayda<br><br><div class="gmail_quote">On Thu, Mar 1, 2012 at 6:00 AM, <span dir="ltr"><<a href="mailto:fieldtrip-request@donders.ru.nl">fieldtrip-request@donders.ru.nl</a>></span> wrote:<br>
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Today's Topics:<br>
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1. question about MNI alignment (Ali Bahramisharif)<br>
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Message: 1<br>
Date: Wed, 29 Feb 2012 21:10:54 +0100<br>
From: "Ali Bahramisharif" <<a href="mailto:ali@cs.ru.nl">ali@cs.ru.nl</a>><br>
To: <a href="mailto:fieldtrip@donders.ru.nl">fieldtrip@donders.ru.nl</a><br>
Subject: [FieldTrip] question about MNI alignment<br>
Message-ID:<br>
<<a href="mailto:fac73988589583150fc4a6a7a958a215.squirrel@squirrel.science.ru.nl">fac73988589583150fc4a6a7a958a215.squirrel@squirrel.science.ru.nl</a>><br>
Content-Type: text/plain;charset=iso-8859-1<br>
<br>
Dear Fieldtrip users,<br>
<br>
I want to create MNI-aligned grids in individual head-space, and I follow<br>
the guidelines in :<br>
<br>
<a href="http://fieldtrip.fcdonders.nl/example/create_single-subject_grids_in_individual_head_space_that_are_all_aligned_in_mni_space?s[]=template&s[]=grid" target="_blank">http://fieldtrip.fcdonders.nl/example/create_single-subject_grids_in_individual_head_space_that_are_all_aligned_in_mni_space?s[]=template&s[]=grid</a><br>
<br>
<br>
I do not know how old this page is, but I noticed that for example in the<br>
current version "cfg.coordinates" should be "cfg.coordsys". I have the<br>
following problems:<br>
<br>
1- When I run "ft_plot_mesh(template_grid);", I get a cubic grid which is<br>
apparently different from the one shown in the page.<br>
<br>
2- When I run, ft_plot_vol(hdm), it does not seem to be aligned to<br>
"ft_plot_sens(ft_read_sens(dataset{i}));"<br>
<br>
I checked my segmented volumes, and they seem to be fine, and I did not<br>
need to run flipdim. I am wondering whether my segmented data is correct<br>
or it should be flipped somewhere. Please let me know if anybody knows how<br>
to resolve this problem.<br>
<br>
Cheers,<br>
Ali<br>
<br>
<br>
<br>
<br>
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End of fieldtrip Digest, Vol 16, Issue 1<br>
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</blockquote></div><br>