Apply Laplacian montage issues

tourette95 · June 16, 2020, 2:46am

Good evening!
I applied laplacian montage on a 32 channel EEG file (using run, standarize, apply montage, scalp current density) but the output has only 18 channels (???)

why?

When I use laplacian montage on continous eeg file just for viewing purpose (without actually apply it) it keeps the 32 channels, but with the standarize function I lost many channels

Thanks in advance!

Update: I check and it did not erase the channels but marked them as Bad (?)

Francois · June 16, 2020, 6:54am

Applying the montage would propagate your bad channels, indeed.

github.com

brainstorm-tools/brainstorm3/blob/master/toolbox/process/functions/process_montage_apply.m#L148


% Cannot have the number of channels that change without writing a new channel file

elseif ~isCreateChan && ((length(iMatrixDisp) ~= length(iMatrixChan)) || ~isequal(sMontage.DispNames(iMatrixDisp), sMontage.ChanNames(iMatrixChan)))

    bst_report('Error', sProcess, sInputs, ['The montage "' sMontage.Name '" changes the names of the channels, it requires the creation of new folders.']);

    return;

end

% Apply montage

if isCreateChan

    DataMat.F = panel_montage('ApplyMontage', sMontage, DataMat.F(iChannels,:), sInputs(iInput).FileName, iMatrixDisp, iMatrixChan);

    % Compute channel flag

    ChannelFlag = ones(size(DataMat.F,1),1);

    isChanBad = (double(sMontage.Matrix(iMatrixDisp,iMatrixChan) ~= 0) * reshape(double(DataMat.ChannelFlag(iChannels) == -1), [], 1) > 0);

    ChannelFlag(isChanBad) = -1;

else

    DataMat.F(iChannels,:) = panel_montage('ApplyMontage', sMontage, DataMat.F(iChannels,:), sInputs(iInput).FileName, iMatrixDisp, iMatrixChan);

    ChannelFlag = DataMat.ChannelFlag;

end



% Get output study

if isCreateChan

    % If the subject has default channel: Create new subject

    if (sSubject.UseDefaultChannel > 0)

If you are unhappy with this, you can try using the process "Standardize > FieldTrip: ft_scalpcurrentdensity"

tourette95 · June 16, 2020, 1:24pm

it works!
Thank you!