[Eeglablist] SCD transformation

[Hsu, Shen-Mou]

Dear Users,

I am trying to transform my EEG data using delsmap. However, the output looks weird to me. This figure (http://picasaweb.google.com/hsushenmou/EEG#5300683350248874114) represents the original data after averaging across trials. In other words, this shows the ERP results. The Y axis labels the channels and the x axis labels the timepoints. The other figure (http://picasaweb.google.com/hsushenmou/EEG#5300683352942968178) represents the data after laplacian transformation using the del2map. Obviously, there is a discontinuity between 50ms to 1150ms. I was wondering if there is anything wrong during the transformation.

Many thanks in advance.

Shen-Mou Hsu

My script is as below:

fname1 = (['Sub1_ALLCHAN_rj_2_reshaped.set']);

EEG = pop_loadset( 'filename', fname1);
EEG = eeg_checkset( EEG );


[no_channel, no_point, no_epoch] = size(EEG.data);
EEG_data_laplac = EEG.data;

for n = 1:no_epoch
    for m = 80:1262
        
        [ laplac ] = del2map( EEG.data(:,m,n), 'neuroscan.loc');
        EEG_data_laplac(:,m,n) = laplac;

    end
end
    EEG.data = (-1) * EEG_data_laplac;
    fname2 = (['Sub1'_all_rj_2_reshaped_SCD.set']);
 
    EEG = pop_saveset( EEG,  'filename', fname2);
    EEG = eeg_checkset( EEG );