Artifact processing and ERP analysis

Transcription

1 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... EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 1

2 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... EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 2

3 The example data: faces vs. objects File Data Task../data/faces_3.set 33 channel EEG, nose-tip reference, 250 Hz sampling rate, Hz, 16 bit, BrainAmps speeded discrimination between objects and faces, 500 ms presentation duration, ISI ms, 362 trials EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 3

4 Load/scroll data >> EEG = pop_loadset('faces_3.set', '...\data\'); >> [ALLEEG EEG CURRENTSET] = eeg_store(alleeg, EEG, 0); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 4

5 Reject bad channels >> pop_eegplot(eeg, 1, 1, 1); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 5

6 Reject bad channels EEG = pop_select(eeg, 'nochannel', [19 24]); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 6

7 Reject bad channels EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 7

8 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... EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 8

9 Reject continuous data Equivalent!! EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 9

10 Reject continuous data TIP: use ICA for eye blink correction EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 10

11 Reject continuous data To prepare data for ICA, reject odd artifacts and keep stereotyped artifacts Eye blink strange EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 11

12 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... EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 12

13 Extract Epochs (review) EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 13

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 '); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 14

15 Reject data epochs EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 15

16 Reject data epochs visual inspection probability EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 16

17 Reject data epochs Probability (± 5 stds) Visual inspection EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 17

18 Plot channel measures over time EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 18

19 Reject data epochs EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 19

20 Reject data epochs EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 20

21 Reject data epochs >> EEG = pop_jointprob(eeg,1,[1:31],5,5,0,0); >> EEG = pop_rejepoch(eeg,find(eeg.reject.rejglobal),0); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 21

22 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... EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 22

23 Select epochs (review) 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'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 23

24 Select epochs (review) Create a new dataset EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 24

25 Select epochs (review) Do the same thing for 'object' epochs >> [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'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 25

26 Analysis of ERPs >> pop_timtopo(eeg,[ ],[165],'ERP data and scalp maps'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 26

27 Analysis of ERPs EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 27

28 Analysis of ERPs >>pop_topoplot(eeg,1,[0:25:200],'face',[3 3],0,'electrodes','off'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 28

29 Analysis of ERPs >>pop_headplot(eeg,1,[0:25:200],'erp scalp maps',[3 3],... 'electrodes', 'off'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 29

30 Analysis of ERPs 4 5 >>pop_comperp(alleeg,1,[4 5],[],'addavg','off','addstd','off',... 'addall','on','diffavg','off','diffstd','off','lowpass',20,... 'tplotopt',{'ydir',-1}); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 30

31 Analysis of ERPs EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 31

32 Analysis of ERP differences 4 5 EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 32

33 Analysis of ERP differences ERP difference between 2 conditions EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 33

34 Export EEG data >> pop_export(eeg,'d:\tmp\faces.dat','erp','on',... 'transpose','on','time','off'); EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 34

35 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 EEGLAB Workshop III, Nov , 2005, Singapore: Julie Onton Artifact processing and ERP analysis 35