[Eeglablist] ICA data length

[Haresh Sachanandani]

Hi,
 
I have some queries on ICA which I hope you can help with. 
I have 12 channel EEG data and I am working on removing respiration and EKG 
artifacts from my data automatedly. One of the techniques that I'm exploring is 
ICA. I perform ICA on the data in the following manner:
 
1. seperate data into epochs of 5 sec (12 channel data sampling rate: 185 Hz)
2. remove bad epochs i.e transients , pop artifacts etc by time domain analysis
3. perform ICA on remaining epochs individually
4. Determine components containing respiration/EKG artifacts by matching their   
freq with freq of reference respiration/ekg channel
5. project remaining components to get the clean epoch.
 
Do you think this method is correct?. In particular, is the data length (12 x 925 points) sufficient to give 12 components?. I have tried using longer epoch lengths 
but it does not help much in giving cleaner more distinct components, probably 
because the artifacts are fleeting i.e the respiration/EKG artifacts are not 
present throughout the data but they come and go. What do you think?
 
Thanks for you help,
Haresh.



Haresh Sachanandani
Graduate Student 
ECE Department
University of Houston
TX-77204

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