EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 1

ICA decomposition and component analysis

Task 1Run ICA

Exercise...Task 2

Plot componentsIdentify components

Task 3Plot component powerPlot component ERP & erpimagesPlot ERSP/Cross coherence

Exercise...

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 2

ICA decomposition and component analysis

Task 1Run ICA

Exercise...Task 2

Plot componentsIdentify components

Task 3Plot component powerPlot component ERP & erpimagesPlot ERSP/Cross coherence

Exercise...

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 3

Reject continuous data

To prepare data for ICA, reject ‘strange‘ artifacts but keep stereotyped artifacts!

Stereotyped

eye blinks

Strange

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 4

Independent Component Analysis

x = scalp EEG W = unmixing matrix

ICA

W-1 (scalp projections)

W*x = u

u = sources

*x = W-1*u

Cha

nnel

s

Time

u = sources

Com

pone

nts

Time

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 5

‘extended’,1

Option Default Comments

‘extended’ 0 1 is recommended to find sub-gaussians

‘stop’ 1e-7 final weight change stop

‘lrate’ determined too small too long…from data too large wts blow up

‘maxsteps’ 512 Should not need more?

‘pca’ 0 or Decompose only a EEG.nbchan principal data subspace

‘stop’,1e-7‘lrate’,1e-3‘maxsteps’,750‘pca’,50

Runica/binica options

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 6

Runica Progress…

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 7

Exercise

• Load dataset 'faces_3.set' from '…/data/' directory

• Reject noise from continuous or epoched data

• Run ICA

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 8

ICA decomposition and component analysis

Task 1Run ICA

Exercise...Task 2

Plot componentsIdentify components

Task 3Plot component powerPlot component ERP & erpimagesPlot ERSP/Cross coherence

Exercise...

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 9

Plot ICA scalp maps

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 10

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 11

Plot ICA scalp maps

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 12

Compare 'good' and 'bad' scalp maps

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 13

Scroll component activities

Note: Activity like this, not separated by ICA, should be removed

and ICA run again for better decomposition

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 14

Com

pone

nts

Cha

nnel

s

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 15

Plot ICA component properties

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 16

Reviewing component properties

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 17

Component scalp maps/properties

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 18

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 19

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 20

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 21

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 22

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 23

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 24

Export ICA weights

How can I apply these weights to other datasets?

Only apply weights to same subject, same session data!!

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 25

Importing ICA weights

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 26

Imported weights

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 27

ICA decomposition and component analysis

Task 1Run ICA

Exercise...Task 2

Plot componentsIdentify components

Task 3Plot component powerPlot component ERP & erpimagesPlot ERSP/Cross coherence

Exercise...

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 28

Plot component power

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 29

Component ERPs

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 30

Data (all channels)

Data Envelope (max min)

Definition: The data envelope

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 31

Component contributions to the dataset ERP

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 32

Component contribution to the dataset ERP

ArtifactComponents!

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 33

ERP Image basics

Trial 1

Trial 2

Trial 3

Trial 4

ERP Image

by default, sorted bytime-on-task

(1st trial, 2nd trial, ...)

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 34

ERP Image basicsTrial 1:Trial 2:

.

.

.

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 35

ERP Images: smoothing across trials

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 36

Component ERP Images

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 37

Plot IC ERSP

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 38

Plot IC cross coherence

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 39

Channel/IC statistics

EEGLAB Workshop III, Nov 15-18, 2006, Singapore: Julie Onton – Data Decomposition with ICA 40

Exercise

• Look at your component maps/activations

• Find components that contribute most to:

• Data power spectrum at 6 Hz

• The ERP between 100 and 500 ms-Remove noise components when plotting

• Plot and study different ERP images for these

components

• Plot ERSP and/or IC cross coherence for selected ICs