[Eeglablist] ICA backtranformation

[Dagfinn Matre]

Hi

In the EEGLAB tutorial on artifact rejection http://sccn.ucsd.edu/wiki/Chapter_01:_Rejecting_Artifacts, this list appear at the bottom:

1. Visually reject unsuitable (e.g. paroxysmal) portions of the continuous data.
2. Separate the data into suitable short data epochs.
3. Perform ICA on these epochs to derive their independent components.
4. Perform semi-automated and visual-inspection based rejection on the derived components.*
5. Visually inspect and select data epochs for rejection.
6. Reject the selected components and data epochs.
7. Perform ICA a second time on the pruned collection of short data epochs -- This may improve the quality of the ICA decomposition, revealing more independent components accounting for neural, as opposed to mixed artifactual activity. If desired, the ICA unmixing and sphere matrices may then be applied to (longer) data epochs from the same continuous data. Longer data epochs are useful for time/frequency analysis, and may be desirable for tracking other slow dynamic features. 

Under step 7, it says "... the ICA unmixing and sphere matrices may then be applied to (longer) data epochs from the same continuous data..."

How is this done in practice?

Best,
Dagfinn



Dagfinn Matre, PhD
Forsker/Research scientist
Statens arbeidsmiljøinstitutt/Nat Inst of Occupational Health
P.O. Box 8149 Dep.
N-0033 Oslo, Norway
T: +47 23 19 52 15/F: +47 23 19 52 04/M: +47 47 23 60 47
E: dagfinn at stami.no