[Eeglablist] Topography

Andres Munguia Barcenas andres.munguiabs at udlap.mx
Thu Apr 3 14:59:21 PDT 2014

Hi Stephen,

I think I'm going to use the information you sent me. But I don't know how I have to add my data. Here is it:

Channels: 72

nsamp: 500

Subjects: 7

The filenames go from 01_CondCong.set to 07_CondCong.set

The filepath is C:\\Users\\137912\\Desktop\\Analisis\\A1\\

I used the function chanedit: EEG=pop_chanedit(EEG, 'load',{'C:\\Users\\137912\\Desktop\\eeglab13_0_1b\\sample_locs\\GSN-HydroCel-257 (72_72).sfp' 'filetype' 'sfp'});

How must I write the code to get the topography?

De: Stephen Politzer-Ahles <politzerahless at gmail.com>
Enviado: lunes, 31 de marzo de 2014 11:36 p. m.
Para: Andres Munguia Barcenas
Asunto: Re: [Eeglablist] Topography

Hi Andres,

There are probably better ways to do this using the STUDY tools, so if you wait a little longer someone else on the list might give you a simpler method. But I have always done this from the command line by manually combining the subjects into a grand average and then using the topoplot() function. Something like this should do it:

% initialize a 3-dimensional matrix that all the subjects' data will go into (these sizes are just samples, yours may be different)
nchan = 32;
nsamp = 1201;
nsubj = 7;
alldata = zeros(32,1201,7);

% loop through all the subjects to load their data and put it in the matrix
for subject = 1:nsubj

% load the data (the specifics may vary depending on how your files are named
EEG = pop_loadset( .... );

% average the data across epochs and put the ERP into the 'alldata' matrix
alldata(:,:,subject) = mean( EEG.data, 3);


% average across subjects to get a grand average
grand_average = mean( alldata, 3 );

% find the samples corresponding to the time window you want to plot
time_window = find( EEG.times >= 410 & EEG.times <= 440 );

% average over the whole time window
voltages = mean( grand_averages( :, time_window ) );

% plot the mean voltages
figure; topoplot( voltages, EEG.chanlocs ); % assuming your chanlocs were already loaded in the EEG structure; if not, they can be read right here with read_locations( 'some_location_file.xyz')


Stephen Politzer-Ahles
New York University, Abu Dhabi
Neuroscience of Language Lab

On Mon, Mar 31, 2014 at 11:07 PM, Andres Munguia Barcenas <andres.munguiabs at udlap.mx<mailto:andres.munguiabs at udlap.mx>> wrote:


I was running an experiment with a group 7 subjects. In the analysis, I want to get a topography which shows the average of the group (right now I can get a topography of each subject). Ideally, I would like to see the average of the activity in a window of 410 to 440 ms post stimulus.

How can I get that topography?

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