<div dir="ltr">Hi,<div><br></div><div style>In MEG normally people use single layer volume conductor and It is believed that three layer is not useful and can deteriorate the results (this is in contrast to EEG). Therefore, you should use a single shell or a single sphere for MEG, which models only the brain (conductivity of the scalp is assumed to be same as the air).</div>
<div style><br></div><div style>Thanks</div><div style><br></div><div style><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On 10 March 2013 17:22, <span dir="ltr"><<a href="mailto:s.rombetto@cib.na.cnr.it" target="_blank">s.rombetto@cib.na.cnr.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi everybody<br>
I'm trying to generate a field for a simulated dipole using the command ft_dipolesimulation, for a MEG study.<br>
<br>
I do the following:<br>
-read the hdr<br>
<br>
-import the sensor structure with the following lines<br>
grad=hdr.grad;<br>
radius = sqrt(sum(grad.chanpos.^2,2));<br>
grad.chanpos = grad.chanpos./ [radius radius radius];<br>
grad.label=hdr.label(1:306)';<br>
<br>
-then I create the vol structure using the following code<br>
vol = [];<br>
vol.r = 12 * [0.88 0.92 1.00]; % radii of spheres, the head radius is 12 cm<br>
vol.c = [1 1/80 1]; % conductivity<br>
vol.o = [0 0 0];<br>
<br>
At this point I have the grad structure, and the vol structure.<br>
Then I give all the options for the dipole simulation with the code<br>
<br>
%% create a dipole simulation with a custom timecourse<br>
cfg = [];<br>
cfg.vol = vol; % see above<br>
cfg.grad = grad; % see above<br>
cfg.dip.pos = [0 0.5 0.3];<br>
cfg.dip.mom = [1 0 0]';<br>
cfg.dip.frequency = 10; %Hz<br>
cfg.ntrials = 10;<br>
cfg.triallength = 20; % seconds<br>
cfg.fsample = 250; % Hz<br>
<br>
but when I try to esecute the line<br>
<br>
raw1 = ft_dipolesimulation(cfg);<br>
<br>
I find this error<br>
<br>
??? Error using ==> ft_compute_leadfield at 301<br>
unsupported volume conductor model for MEG<br>
<br>
Error in ==> ft_dipolesimulation at 198<br>
lf = ft_compute_leadfield(dippos{<u></u>trial}, sens, vol);<br>
<br>
<br>
I really cannot understand why volume conductor model is not supported.<br>
Any suggestion? I'm pretty sure that the mistake is trivial, but I'm not able to see it.<br>
<br>
Thank you!<br>
Dott.ssa Sara Rombetto<br>
<br>
Istituto di Cibernetica<br>
"E. Caianiello"<br>
Via Campi Flegrei, 34<br>
80078 Pozzuoli (NA)<br>
Italy<br>
mob <a href="tel:%2B39%203491530515" value="+393491530515" target="_blank">+39 3491530515</a><br>
tel <a href="tel:%2B39%200818675361" value="+390818675361" target="_blank">+39 0818675361</a><br>
fax <a href="tel:%2B39%200818675128" value="+390818675128" target="_blank">+39 0818675128</a><br>
<br>
<br>
"I disapprove of what you say, but I will defend to the death your right to say<br>
it." [Evelyn Beatrice Hall, The Friends Of Voltaire]<br>
<br>
------------------------------<u></u>------------------------------<u></u>----<br>
This message was sent using IMP, the Internet Messaging Program.<br>
<br>
<br>
<br>
______________________________<u></u>_________________<br>
fieldtrip mailing list<br>
<a href="mailto:fieldtrip@donders.ru.nl" target="_blank">fieldtrip@donders.ru.nl</a><br>
<a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip" target="_blank">http://mailman.science.ru.nl/<u></u>mailman/listinfo/fieldtrip</a><br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>Hamid R. Mohseni, PhD<br>Post-Doctoral Research Assistant<br>Institute of Biomedical Engineering<br>University of Oxford, OX3 7DQ, UK<br>Tel: +44 (0) 1865 2 83826<br>
</div>