[Eeglablist] Eye Movement Artifacts and Filtering

[Edward Justin Modestino, M.Phil.]

O.K., I guess it was too ignorant of a question and that is why nobody
answered me.  I will assume that if ICA truly does remove the component
associated with the eye movements, that the EOG channels will be
relatively flat.  Of course, I can confirm this by doing so.

Furthermore, I have not looked into the exact filtering options in EEGLAB
in detail.  I guess I can always try to find the mathematics behind an
acausal FIR filter if this does not already exist in EEGLAB and just
create it and filter it on my own.

Thanks!
---------------------------- Original Message ----------------------------
Subject: [Eeglablist] [Fwd:  Eye Movement Artifacts and Filtering]
From:    "Edward Justin Modestino, M.Phil." <modestino at ccs.fau.edu>
Date:    Fri, March 14, 2008 1:18 pm
To:      eeglablist at sccn.ucsd.edu
--------------------------------------------------------------------------

Can someone please respond to my queries below, someone who knows perhaps
from the EEGLAB creators, about EOG channels in EEGLAB, using ICA to
remove eye artifacts, etc.  I need to know if I should format my data to
include the EOG channels or not, this has put me on hold. Also, I need to
know that ICA will not see the EOG channels as EEG channels.  If I truly
remove the eye movement artifacts using ICA, the EOG channel averages
should be relatively flat or reasonably free of eye movements.  My advisor
will want me to include them to be able to show the EOG channel averages
are clean.  But, if this will not work, I am unsure what to do.

Thanks!

---------------------------- Original Message ----------------------------
Subject: [Eeglablist] Eye Movement Artifacts and Filtering
From:    "Edward Justin Modestino, M.Phil." <modestino at ccs.fau.edu>
Date:    Mon, March 10, 2008 10:41 am
To:      eeglablist at sccn.ucsd.edu
--------------------------------------------------------------------------

Hello,
I am planning to use ICA in EEGLAB to remove eye movement artifacts.  I
know that ICA does not use EOG channels locate the component associated
with eye movements.  However, my advisor will want me to show ERP averages
of the EOG channels as evidence that the eye movements have been removed
using ICA.  So, I will be including the EOG channels (bipolar, but
represented as individual difference waves as one channel, for HEO and
VEO).

So, first I need to make sure that there is a way to use the EOG channels
with appropriate locations in the location file.  Second, I need to show
via averages of the eye movement channels that eye movements have been
removed by ICA.  If I have the EOG channels in the array of EEG channels,
will EEGLAB running ICA see these as EEG channels or EOG channels?  Or
does this matter? My fear is that EEGLAB using ICA may see the EOG
channels as EEG channels and thus not see all the eye movement artifact
contributions as truly that, but perhaps part of an EEG ERP components,
and thus leave them in!

Finally, I need to run an acausal FIR high pass filter at 1 Hz. [which
will not change the temporal components of the EEG] on the data before
running ICA, as there is an extreme trend in the data that made automated
and even manual eye movement removal inadequate using the raw data outside
of EEGLAB. Also, the trend needs to be removed anyway.  However, removing
the linear trend will not adequately alter the tend in the continuous data
as the FIR filter will.  So, I wish to use such a filter. [I may remove
the linear trend once the data is epoched per condition, but not on the
continuous data.] What sort of filters does EEGLAB have built in? Is this
filter already available?

Thanks,
Ed

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Edward Justin Modestino, M.Phil.
Ph.D. Candidate in Complex Systems and Brain Sciences
Cognitive Neurodynamics Laboratory
Center for Complex Systems and Brain Sciences
Florida Atlantic University
(561) 297-2238
Fax: (561) 297-3634
modestino at ccs.fau.edu
http://www.ccs.fau.edu/~modestino/
Lab: http://www.ccs.fau.edu/~bressler/CNL_CCSBS/CNL_CCSBS_FAU.html
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---------------------------------------------------
Edward Justin Modestino, M.Phil.
Ph.D. Candidate in Complex Systems and Brain Sciences
Cognitive Neurodynamics Laboratory
Center for Complex Systems and Brain Sciences
Florida Atlantic University
(561) 297-2238
Fax: (561) 297-3634
modestino at ccs.fau.edu
http://www.ccs.fau.edu/~modestino/
Lab: http://www.ccs.fau.edu/~bressler/CNL_CCSBS/CNL_CCSBS_FAU.html
---------------------------------------------------