[Eeglablist] Questions about ICA component rejection in EEGLAB

[Arnaud Delorme]

Dear Liu,

(1) yes, the menus are greyed out but to tell the truth, they have always been. This is not the function that is referred to in the paper you mentionned. The function corresponds to the menu "Tools > Reject data epochs > Reject data (all methods)" and "Tools > Reject data using ICA > Reject data (all methods)"

Arno

On 25 Feb 2013, at 18:32, Makoto Miyakoshi wrote:

> Dear Liu,
> 
> (1) I've never noticed them until I confirmed it now. You are right, they are grayed out. They are not available from GUI at least, and I don't know if there are off-GUI functions for them.
> 
> (2) Plot - Component ERPs runs pop_envtopo() where you can evaluate percent variance accounted for (pvaf) and related measures that tell you each IC's contribution to scalp ERPs. ICs with lower numbers have high variance since they are sorted so after ICA. For example your IC90-IC100 would not have even 1/10 of variance of IC1 (could be even 1/100 which is 40dB smaller in FFT plot). This means that discarding 50 out of 100 ICs does not mean discarding 50% of data (variance). If you want to measure how much 'data' are rejected, you may check pvaf as one of measures.
> 
> Makoto  
> 
> 2013/2/25 Liu Pan <pliu261 at gmail.com>
> Dear eeglabbers,
>  
> I have 2 questions about the ICA component rejection function of EEGLAB:
>  
> (1). I read the paper "Automatic artifact rejection for EEG data using high-order statistics and independent component analysis" by Drs. Delorme, Makeig, and Sejnowski. http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&ved=0CEAQFjAB&url=http%3A%2F%2Finc.ucsd.edu%2Fica2001%2F117-delorme.pdf&ei=JakrUbjhCMe30gHevIGoCQ&usg=AFQjCNGwjRtjnTiRvUxguqJNAejvoD6a7g&sig2=9BQuz03YEzUOszEreafYgA
> In section3.3 the authors mentioned that in addition to manually and visually rejecting ICA components based on the component properties, there is a function in EEGLAB software by which one can set an adequate rejction threshold for three high-order statistical measures (the entropy of the activity of the component, the kurtosis of the activity, and the kurtosis of the components' spatial map), then one can automatically detect and reject components (insteady of mannually doing so). In search of this function in EEGLAB, I found that in the Tools--Reject data using ICA--Reject components by map function, there are 3 buttons at the bottom of the popped out window (set threshods, see comp. st..., see projection) which appear to be grey and inactive. I suppose these buttons, especially the on set threshods, are relevant to the automatic ICA component rejection function mentioned in that paper.  However, these buttons are not active and cannot be used. According to the Help file of this function, "if the function POP_REJCOMP is ran prior to this function, some fields of the EEG datasets will be present and the current function will have some more button active to tune up the automatic rejection."  I searched POP_REJCOMP function but failed to get a clue from the tutorial nor the previous discussion list. Could anyone give me any suggestion about this? Are these inactive buttons the ones for automatic ICA component rejection?  If yes, how can I get them to work?
>  
> (2). While doing ICA component rejection, how many of the original components would you reject? I sometimes rejected almost half of them, is it too much or not?
>  
> Thank you very much for any of your input in advance! Pan
> 
> -- 
> Liu Pan, PhD. Candidate
> Neuropragmatics and Emotion Lab (Pell Lab)
> School of Communication Sciences and Disorders
> Faculty of Medicine, McGill University
> Montreal, Canada
> 
> 
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> 
> 
> -- 
> Makoto Miyakoshi
> JSPS Postdoctral Fellow for Research Abroad
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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