[Eeglablist] Eye Movement Artifacts and Filtering

Mon Mar 24 19:21:12 PDT 2008

i would start by looking over some of the relevant papers, available at the
eeglab website, makeig's homepage and jung's homepage

eg,

http://www.sccn.ucsd.edu/~jung/pdf/PSY00.pdf
fig2a/b {19 eeg, 1 ear and 2 eog channels before/after ica-filtering w ICs}

On Mon, Mar 24, 2008 at 7:58 AM, Edward Justin Modestino, M.Phil. <
modestino at ccs.fau.edu> wrote:

> 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
>
> ---------------------------------------------------
> 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
> ---------------------------------------------------
>
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-- 
Alexander J. Shackman
Laboratory for Affective Neuroscience
Waisman Laboratory for Brain Imaging & Behavior
University of Wisconsin-Madison
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