Export of EEG electrode locations from EEGLAB to Cartool

[M Plank]

Dear Cartool community,

I use EEGLAB for EEG data-preprocessing (e.g., ICA-based detection of electromyographic, oculomotoric, or carioballistic artifacts) before exporting the cleaned data to Cartool. However, electrode locations cannot be exported and read in as easily, and you find yourself performing multiple steps from MATLAB to Excel to Word etc. to Cartool.

For those of you who also encounter this problem, the following MATLAB script might be useful:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MPlank - 2011-01-25
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Extract electrode locations from EEG.chanlocs
%<x> <y> <z> <label>

loc = [];
for i = 1:length(EEG.chanlocs)
    loc{i,1} = num2str(EEG.chanlocs(i).X,6);
    loc{i,2} = num2str(EEG.chanlocs(i).Y,6);
    loc{i,3} = num2str(EEG.chanlocs(i).Z,6);
    loc{i,4} = EEG.chanlocs(i).labels;
end;

%save data in EEG_elocs.els;
fid = fopen('EEG_elocs.els','wt');
fprintf(fid,['ES01\n' int2str(size(loc,1)) '\n1\n10-10 System\n' int2str(size(loc,1)) '\n3\n']);
for i = 1 : size(loc,1)
    fprintf(fid,'%s\t %s\t %s\t %s\t\n',loc{i,:});
end;
fclose(fid);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Best regards,
Markus

[Denis]

Thanks Markus!
We can copy this to the Files section, under the Matlab area,
Denis

[Markus Plank]

Thanks, Denis! You guys do great work with Cartool - My colleagues and I appreciate your effort!

M

[Jasna Martinovic]

I am just making a file for my 128 + 4 channels.

The file for exporting the channel structure has the top row which says:
fprintf(fid,['ES01\n' int2str(size(loc,1)) '\n1\n10-10 System\n' int2str(size(loc,1)) '\n3\n']);

I wonder if I should modify this - what should I put for the modified 10-20 system that's used in the 128 electrode system? Should I put 10-20 or GRID or something else? Also, I do not want to use my extra 4 channels in the analysis, so should I have a header that splits it into 2 sections, one of which is titled AUX or somesuch?

I was thinking of a file structured like this, but thought I'd pass it by the experts on the list first as I wouldn't like to make a mistake:

ES01

132

2

GRID

128

3

0

[then i put all the xyzs of the head channels)

AUX

4

0

[then i put the 4 eye channels)

I did search the help files but did not manage to find a sufficiently detailed explanation for electrode file headers in one place.

I look forward to hearing from you.

thanks in advance,
jasna

Dr Jasna Martinovic

School of Psychology

University of Aberdeen

William Guild Building

Aberdeen

AB24 3FX

 tel: 01224 272240

email: j.martinovic @ abdn.ac.uk

web: http://www.abdn.ac.uk/~psy527/dept/

[Fengji Geng]

Hello Jasna,

I used 128 channels EGI net with the CZ added later in my pre-processing. If I understand you rightly, you might want a location file for a 128-channel net. So, I attached the one I am using in the attachment. Hope it helps!  

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