artifact processing and erp analysis
DESCRIPTION
Artifact processing and ERP analysis. Task 1 Reject bad channels Task 2 Reject continuous data Task 3 Reject data epochs Task 4 Analysis of channel ERPs Exercise. The example data: faces vs. objects. File ../data/faces_3.set Data - PowerPoint PPT PresentationTRANSCRIPT
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 1
Artifact processing and ERP analysis
Task 1Reject bad channels
Task 2Reject continuous data
Task 3Reject data epochs
Task 4Analysis of channel ERPs
Exercise...
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 2
The example data: faces vs. objects
File../data/faces_3.set
Data33 channel EEG, nose-tip reference, 250 Hz
sampling rate, 0.5-100 Hz, 16 bit, BrainAmpsTask
speeded discrimination between objects and faces, 500 ms presentation duration, ISI 500-1900 ms, 362 trials
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 3
Artifact processing and ERP analysis
Task 1Reject bad channels
Task 2Reject continuous data
Task 3Reject data epochs
Task 4Analysis of channel ERPs
Exercise...
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 4
Reject bad channels
>> EEG = pop_loadset('faces_3.set', '...\data\');>> [ALLEEG EEG CURRENTSET] = eeg_store(ALLEEG, EEG, 0);
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 5
Reject bad channels
>> pop_eegplot(EEG, 1, 1, 1);
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 6
Reject bad channels
EEG = pop_select(EEG, 'nochannel', [19 24]);
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 7
Reject bad channels
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 8
Artifact processing and ERP analysis
Task 1Reject bad channels
Task 2Reject continuous data
Task 3Reject data epochs
Task 4Analysis of channel ERPs
Exercise...
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 9
Reject continuous data
Equivalent!!
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 10
Reject continuous data
TIP: use ICA for eye blink correction
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 11
Reject continuous data
To prepare data for ICA, reject odd artifacts and keep stereotyped artifacts
Eye blinkstrange
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 12
Artifact processing and ERP analysis
Task 1Reject bad channels
Task 2Reject continuous data
Task 3Reject data epochs
Task 4Analysis of channel ERPs
Exercise...
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 13
Extract Epochs (review)
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 14
Extract Epochs (review)
>> EEG = pop_epoch(EEG,{'face' 'object'},[-1 2],...
'newname','faces_3_chans removed epochs',...
'epochinfo','yes');
>> [ALLEEG EEG CURRENTSET] = pop_newset(ALLEEG,EEG,...
CURRENTSET,'setname',' 'faces_3_chans removed epochs ');
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 15
Reject data epochs
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 16
Reject data epochs
visual inspection
probability
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 17
Reject data epochs
Probability (± 5 stds)
Visual inspection
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 18
Reject data epochs
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 19
Reject data epochs
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 20
Reject data epochs
>> EEG = pop_jointprob(EEG,1,[1:31],5,5,0,0);>> EEG = pop_rejepoch(EEG,find(EEG.reject.rejglobal),0);
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 21
Artifact processing and ERP analysis
Task 1Reject bad channels
Task 2Reject continuous data
Task 3Reject data epochs
Task 4Analysis of channel ERPs
Exercise...
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 22
Analysis of ERPs
Create separate data sets for face and object trials
>> EEG=pop_selectevent(EEG,'type',{'face'},'deleteevents', ... 'off','deleteepochs','on');>> [ALLEEG EEG CURRENTSET]=pop_newset(ALLEEG,EEG,4,... 'setname','faces only epochs');
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 23
Analysis of ERPs
Select only 'face' epochs:
create a new dataset
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 24
Analysis of ERPs
>> [EEG,ALLEEG,CURRENTSET]=pop_newset(ALLEEG,EEG,4, ... 'retrieve',3,'study',0);>> EEG=pop_selectevent(EEG,'type',{'object'},'deleteevents', ... 'off','deleteepochs','on');>> [ALLEEG EEG CURRENTSET]=pop_newset(ALLEEG,EEG,5, ... 'setname','object only epochs');
Do the same thing for 'object' epochs
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 25
Analysis of ERPs
>> pop_timtopo(EEG,[-200 796],[165],'ERP data and scalp maps');
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 26
Analysis of ERPs
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 27
Analysis of ERPs
>>pop_topoplot(EEG,1,[0:25:200],'face',[3 3],0,'electrodes','off');
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 28
Analysis of ERPs
>>pop_headplot(EEG,1,[0:25:200],'ERP scalp maps',[3 3],... 'electrodes', 'off');
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 29
Analysis of ERPs
>>pop_comperp(ALLEEG,1,[4 5],[],'addavg','off','addstd','off',... 'addall','on','diffavg','off','diffstd','off','lowpass',20,... 'tplotopt',{'ydir',-1});
4 5
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 30
45
Analysis of ERPs
ERP
difference
between
2 conditions
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EEGLAB Workshop III, Nov. 15-18, 2005, Singapore: Julie Onton – Artifact processing and ERP analysis 31
Analysis of ERPs
>> pop_export(EEG,'D:\tmp\faces.dat','erp','on',... 'transpose','on','time','off');
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Exercise
• Load dataset 'faces_3.set' from '…/data/' directory• Reject noisy channels• (optional: reject continuous data stretches)
• Epoch dataset on all 'face' and 'object' events• Explore 1 or more of the following:
• Reject noisy epochs by hand or use auto-rejection• Compare rejection methods and thresholds
• Select 'face' and 'object' epochs separately• Plot ERPs
• superimposed ERP envelopes• rectangular/scalp array• Compare 'face' vs 'object' ERPs
• Export 'face' ERPs into an ascii file