[Eeglablist] Some basic questions about ICA

James Desjardins jdesjardins at brocku.ca
Wed Jan 29 11:16:40 PST 2014


Hi Kris,

1- ICA is blind to channel locations so running ICA without proper locations does not affect the outcome. That being said it is useful to have the proper locations loaded in order to explore the topographical projections of the ICs once they have been derived.

2- From my experience it is best to include as many good (stable low impedance contact with the skin) signals recorded from the head as possible when running ICA (given a montage of about 130 channels). Although I do not have much experience with including bipolar channels it seems that (from previous discussions on this list) they also contain information that is useful for ICA.

This is an interesting topic and comes up regularly in the list. Google searching things like "eeglablist bipolar ica" or "eeglablist eye ica" will return good examples of similar questions such as these:
[Eeglablist] bipolar channels for eyes movement recording<http://sccn.ucsd.edu/pipermail/eeglablist/2006/001452.html>
[Eeglablist] removing eye channels before ICA?<http://sccn.ucsd.edu/pipermail/eeglablist/2011/004047.html>



James Desjardins, MA
Electrophysiology Technologist
Cognitive and Affective Neuroscience Lab, Psychology Department
Jack and Nora Walker Centre for Lifespan Development Research
Brock University
500 Glenridge Ave.
St. Catharines, ON, Canada L2S 3A1
905-688-5550 x4676
--
"'Cause you never can tell What goes on down below!
"This pool might be bigger Than you or I know!"

McElligot's Pool
Dr.Seuss 1947
________________________________
From: eeglablist-bounces at sccn.ucsd.edu [eeglablist-bounces at sccn.ucsd.edu] on behalf of Kristoffer Aberg [kc.aberg at gmail.com]
Sent: January-29-14 4:10 AM
To: eeglablist at sccn.ucsd.edu
Subject: [Eeglablist] Some basic questions about ICA

Hi,
thanks for a wonderful toolbox!

I will try to use ICA to remove blinks / eye-movement / ECG artifacts, but i have some questions i would be very happy if someone could address:

1. For the ICA decomposition, does it matter if the electrode locations are correct? That is, would the decomposition work even if the locations would be completely randomized? I ask because i dont know where to place the eye / ecg electrodes exactly.

2. Is it a good idea to always include the eye / ecg channels in the ICA decomposition? I ask because i thought to decompose data based on scalp electrodes only and then verify blink / pulse components by comparing them to the eye / ecg channels. When should i not include the eye / ecg channels in the ICA decomposition?

Thanks for your time and your responses!

Kris
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