[Eeglablist] ICA for eye movement rejection

[赵远方]

Hi Mary-Jane,

As my understanding on the tutorial about ICA-based eye-movement artifact
rejection,it advises that we should first reject polluted epochs by naked
eyes or by several artifact reject criteria(although this practice is not
encouraged in our lab,for every subject's waveform can be quite
different).After this,perform ICA for the first time,and then reject the
waveform epochs based on every IC,just as in the beginning we treat for the
normal epochs.In the last,run ICA again,and directly reject the ICs
representing artifacts.Thus we can get the data we have clearest.

Best

在 2012年3月16日 上午3:41，Stephen Politzer-Ahles <politzerahless at gmail.com>写道：

> Hello Mary-Jane,
>
> My understanding of this (and what I have been doing for my own datasets)
> was that the effectiveness of the ICA can be improved by first removing
> epochs or artifacts that are unrelated to the artifact you're trying to
> clean up with ICA--for example, when I run ICA to clean up ocular
> artifacts, I first go through the data and reject epochs with a lot of
> muscle artifacts or electrode drifts (I guess a similar thing could be
> accomplished using high- and low-pass filters rather than manual artifact
> rejection). Then I run the ICA, hopefully get a slightly better
> decomposition, and proceed to remove the eye-related components and go back
> through the data to reject any epochs that might have eye movement
> artifacts remaining after the ICA. But I would also love to hear some more
> experienced users' take on this issue.
>
> Best,
> Steve Politzer-Ahles
> Department of Linguistics
> University of Kansas
>
>
> On Thu, Mar 15, 2012 at 11:30 AM, Budd, Mary-Jane <mbudd at essex.ac.uk>wrote:
>
>> Dear All,
>> I know that this has been a much discussed topic but I am rather confused
>> by
>> some of the responses. I am looking at children's datasets that include
>> many
>> eye movements (both blinks and  horizontal movements). I have run ICA and
>> identified eye blinks and distinct muscle artifacts. If I remove these
>> components and then run an automatic rejection procedure (+-75microvolts
>> on
>> all electrodes) over half the epochs are rejected due to there still being
>> eye movements on the eye and frontal electrode channels. I have read that
>> I
>> should not remove the components but instead scan the components and
>> remove
>> 'noisy' epochs (I assume this means removing epochs where eye blinks are
>> present). RE-running the ICA will then result in 'cleaner' components
>> which
>> hopefully will remove the eye movements from my data. I have a couple of
>> questions regarding this:
>> 1. It would be good to avoid removing epochs as the children blink a  lot
>> and so I am likely to lose much data.
>> 2. I thought this was the benefit of using ICA for artifact removal as the
>> components are removed form the data leaving you with all (or as many as
>> possible) epochs to analyse.
>> 3. What if after the second ICA I am still left with eye movements i.e.
>> can't clearly identify which component is responsible for the eye
>> movements?
>>
>> Have I misunderstood something here? Please help,
>> Mary-Jane
>>
>> Dr Mary-Jane Budd
>> Senior Research Officer
>> Department of Psychology
>> University of Essex
>> Wivenhoe Park
>> Colchester CO4 3SQ
>> UK
>>
>> Room 4.726
>>
>>
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>
>
>
> --
> Stephen Politzer-Ahles
> University of Kansas
> Linguistics Department
> http://www.linguistics.ku.edu/
>
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-- 
Yuan-Fang Chao
School of Psychology
SouthWest University
Beibei,Chongqing,China
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