[Eeglablist] Flat lines after epoching in one data set

[Makoto Miyakoshi]

Dear Alexander,

> After following this pipeline, this data set is basically composed of
flat lines except for a few short periods with pikes.

My brute suggestion: check the scale when you see these flat lines. What
does it say?

> When checking the data visually before epoching, I do not notice anything
odd or peculiar, but after epoching all most everything becomes flat.

It's hard to imagine the epoching function misbehaves; however, I know I
tend to noticed something weird after epoching. Let's get more info for
troubleshooting.

Makoto

On Wed, Jun 10, 2015 at 12:01 PM, Alexander Quent <alexander.quent at rub.de>
wrote:

> Dear eeglab users,
> I have encounter a weird problem. I followed Makoto's pipeline for
> pre-processing with a small deviation that I used linked mastoids rather
> than average reference but I cannot imagine this causing my problem.
> I pre-processed 27 data sets and all but one show satisfactory results
> after pre-processing.
> After following this pipeline, this data set is basically composed of
> flat lines except for a few short periods with pikes. I tracked the
> problem down to the function
> pop_epoch. When checking the data visually before epoching, I do not
> notice anything odd or peculiar, but after epoching all most everything
> becomes flat.
>
> Since I am a brute beginner, I indeed have no clue where the problem
> might have hid. Have anybody encountered something similar?
>
> With best regards
> Alexander Quent
>
>
> Appendix:
> % for a = 4:length(population)
> %         EEG         =
> pop_fileio(strcat('C:\Users\Joern\Documents\MATLAB\Daten\BA\eeg\',
> population{i},'.eeg')); % loads data file
> %         if a < 12
> %             EEG       = pop_loadset('filename',
>
> strcat(population{a},'_Cut.set'),'filepath','C:\Users\Joern\Documents\MATLAB\Daten\BA\eeg\wholeData');
>
> %         else
> %             EEG       =
>
> pop_fileio(strcat('C:\Users\Joern\Documents\MATLAB\Daten\BA\eeg\wholeData\',
> population{a},'.eeg')); % loads data file
> %         end
> %         EEG.setname = strcat(population{a},'_Processed.eeg'); % names
> dataset for continuous data
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = pop_cleanline(EEG,
> 'bandwidth',2,'chanlist',[1:32] ,'computepower',1,'linefreqs',[50 100]
>
> ,'normSpectrum',0,'p',0.01,'pad',2,'plotfigures',0,'scanforlines',1,'sigtype','Channels','tau',100,'verb',1,'winsize',4,'winstep',1);
>
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = pop_eegfiltnew(EEG, [], 1, 1650, true, [], 1);
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = pop_editset( EEG, 'chanlocs',
>
> 'C:\\Users\\Joern\\Documents\\MATLAB\\eeglab_current\\eeglab13_4_4b\\sample_locs\\neuroscan_32_EOGincluded.ced');
>
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = eeg_checkset( EEG );
> %         EEG.data    = EEG.data - repmat(EEG.data(17, :) * 0.5,
> [EEG.nbchan 1]); % Re reference to linked mastoid, see also
> http://sccn.ucsd.edu/pipermail/eeglablist/2012/005585.html
> %         EEG         = pop_select( EEG,'nochannel',{'REFlinks'});
> %         EEG         = pop_rejchan(EEG, 'elec',[1:31]
> ,'threshold',5,'norm','on','measure','kurt');
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = pop_epoch( EEG, {  'S 10'  'S 11'  'S 12'  'S
> 13'  'S 14'  'S 15'  }, [-1  2], 'newname',
> strcat(population{a},'_Epochs', 'epochinfo', 'yes');
> %         display('Exclude eye channels from joint')
> %         if length(EEG.chanlocs) < 31
> %             EEG     = pop_jointprob( EEG );
> %         else
> %             EEG     = pop_jointprob( EEG,1,[3:26 28 29:30] ,6,2,1,0);
> %         end
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = eeg_checkset( EEG );
> %         EEG         = pop_runica(EEG, 'extended',1,'interupt','on');
> %         EEG         = eeg_checkset( EEG );
> %         [ALLEEG,EEG,CURRENTSET,com] = pop_ADJUST_interface
> (ALLEEG,EEG,CURRENTSET );
> %         EEG         = eeg_checkset( EEG );
> %         stop        = input('Press 1 to continue: ');
> %         EEG         = pop_subcomp( EEG );
> %         EEG         = pop_eegfiltnew(EEG, [], 45, 148, 0, [], 1);
> %         EEG         = pop_jointprob(EEG,1,[1:length(EEG.chanlocs)]
> ,3,3,1,0);
> %         EEG         = eeg_checkset( EEG );
> %         pop_eegplot( EEG, 1, 1, 1);
> %         stop        = input('Press 1 to continue: ');
> %         EEG         = eeg_checkset( EEG );
> %         for j = 1:length(conditions)
> %             EEG     =
> addEventsBasedCorrectness(EEG,conditions{j},triggerNums(j), responses);
> %             EEG     = eeg_checkset( EEG );
> %         end
> %         EEG         = pop_saveset(EEG, 'filename' ,
> strcat(population{a},'_ProcessedERPEpochs'), 'filepath',
> 'C:\Users\Joern\Documents\MATLAB\Daten\BA\eeg\analyzedERPLAB'); % Saving
> current data to file
> %         EEG         = eeg_checkset( EEG );
> % end
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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