[FieldTrip] automatic IC rejection

[Jason Taylor]

Hi Aitor,

If you have an 'objective' measure of the artefact you're trying to remove (e.g., VEOG for blinks), a relatively straightforward method is to run a temporal correlation between each IC's activation time-course and the artefact channel's time-course. You can then reject any IC with a correlation higher than some threshold, or with a Z-score (r value relative to the distribution of IC r values) above some threshold. This tends to work very well for identifying blinks, and fairly well for eye-movements (*EOG), and can work for pulse artefact if you have recorded ECG. To avoid spurious correlations due to high-frequency noise, you can filter (e.g., 1 to 30 Hz) the component and artefact signals before correlating them (but obviously go back to the original unfiltered signals to continue with your analysis). 

Best wishes,
Jason 


-----Original Message-----
From: fieldtrip [mailto:fieldtrip-bounces at science.ru.nl] On Behalf Of David Schubring
Sent: 28 November 2018 12:47
To: fieldtrip at science.ru.nl; aitor.martinezegurcegui at uzh.ch
Subject: Re: [FieldTrip] automatic IC rejection

Dear Aitor,

the closest thing I know of for a data-driven approach of selecting 
independent components is COMPASS, quote:

"COMPASS is a MATLAB and EEGLAB based algorithm with the purpose of 
providing the user with a convenient technique for automatic Independent 
Component (IC) selection with respect to the contributions of the ICs to 
a certain ERP."

Link to the toolbox:

http://53450283.de.strato-hosting.eu/jrw/lab/e_compass.htm

Paper:

Wessel, J. R., & Ullsperger, M. (2011). Selection of independent 
components representing event-related brain potentials: a data-driven 
approach for greater objectivity. Neuroimage, 54(3), 2105-2115. 
https://doi.org/10.1016/j.neuroimage.2010.10.033

I have only theoretical experience with the toolbox as I only learned 
about it in a workshop and did not yet have the time to test and 
implement it in my personal FieldTrip workflow (even though it is on my 
ever growing to-do list). So far it looked like a useful thing to try 
out to me, especially as code can better be reproduced than "personal 
judgement".

Best,
David

Am 28.11.2018 um 10:49 schrieb Aitor Egurtzegi:
> Dear researchers at Fieldtrip,
> 
> 
> In order to make my work more reproducible, I would like to 
> automatically reject ICs instead of doing visual inspection and 
> rejection of the components. Unfortunately, I haven't found any 
> documentation for such thing. Is there a way to do it in Fieldtrip?
> 
> Best,
> Aitor
> 
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> https://doi.org/10.1371/journal.pcbi.1002202

-- 
Dr. David Schubring

General & Biological Psychology
University of Konstanz
Room C524
P.O. Box 36
78457 Konstanz

Phone: +49-(0)7531-88-5350
Homepage: https://gpbp.uni-konstanz.de/people-page/david-schubring
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