[Eeglablist] ICA for eye movement rejection

[Budd, Mary-Jane]

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