Questions on Dipole fitting

gao zai zaifengg at GMAIL.COM
Wed May 26 10:53:09 CEST 2010

Dear all,

Currently I am trying to do the Dipole fitting on the MEG data. I have 1
problem that puzzled me, in particular,

When I did dipole on individual subject,I used the scripts according to  to
one posted in the Fieldtrip website, it runs ok but I get only null result
(naked MRI picture without any dipole inside.)

I was told that "Local minimum possible. fminunc stopped because the size of
the current step is less than the default value of the step size tolerance."

However, the same data I used SPM8, I get can get dipole. So I wonder is
there anything wrong with my scripts?  I hope I can get your kind help.
Thanks very much in advance.
load s2TL42
plot(1000*s2TL42.time, s2TL42.avg)  % convert time to ms
xlabel('time (ms)')
ylabel('field amplitude (T)')
axis tight
grid on

cfg = [];
cfg.xlim = 0.1:0.025:0.2;
cfg.colorbar = 'no';
cfg.comment = '';
cfg.showxlim = 'no';
cfg.showzlim = 'no';
cfg.layout   = '4D248.lay';
cfg.zlim = [-1.5 1.5] * 1e-13;
ft_topoplotER(cfg, s2TL42);

cfg            = [];
cfg.latency    = [0.15 0.18];  % specify latency window around M165 peak
cfg.numdipoles = 1;
cfg.vol        = vol;   = 'textbar';
cfg.resolution = 2;
dip             = ft_dipolefitting(cfg, s2TL42);

sMRI = read_mri(fullfile(spm('dir'), 'canonical', 'single_subj_T1.nii'));
% the source is expressed in cm
cfg = [];
cfg.location = dip.dip.pos*10;   % convert from cm to mm
figure; ft_sourceplot(cfg, sMRI);


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