[Eeglablist] [Fwd: Eye Movement Artifacts and Filtering]
Viviane Monteiro Braconi
viviane at sarah.br
Fri Jun 27 10:39:35 PDT 2008
Hi
I want write to Matlab script to call the eeg functions.....I don't want to use the EEGLAB menu. But the first command that I need is >>eeglab....and the menun is open.....I would like that the menu is not open......Do you know if it is possible?
Example:
>> eeglab
>>eeg = pop_loadset()
>> and so on
And......I don't want to open a eeglab menu. I would like to make everything using script...
Thanks
Viviane
> ----------
> From: eeglablist-bounces at sccn.ucsd.edu[SMTP:eeglablist-bounces at sccn.ucsd.edu] on behalf of Timothy O'Keefe [BROWN][SMTP:timothy_okeefe at brown.edu]
> Sent: quinta-feira, 15 de maio de 2008 09:56
> To: eeglablist at sccn.ucsd.edu
> Subject: Re: [Eeglablist] [Fwd: Eye Movement Artifacts and Filtering]
>
> EEGLAB Users,
>
> I might try to "inject" my opinion here, for whatever it's worth.
>
> Among other endeavors involving ICA, I've had significant dealings with
> ocular artifact "correction" using EEGLAB/ICA. Now, while I'm not an
> "expert" by any means, I would like to provide some food for thought.
> What it will feed has yet to be determined :)
>
> So far as introducing bipolar electrodes - or anything for that matter -
> into the input matrix, I was always under the assumption that it should
> not matter as ICA should not determine any relationships which include
> these nonsense(?) data.
>
> As for "cleaning" EEG data. This is one problem that I've found
> particularly frustrating. My inner demon has me questioning *exactly*
> which components EOG - or the influences of EOG - manifest?
> How does one test this with a measurable degree of certainty? Better
> yet, how does one test this without making assumptions? How good of an
> indicator of "cleanliness" is a "flat" EOG ERP anyways? Pretty good?
> Good enough? Is it enough to bet your life on (where some of us might
> be!!)?
>
> Best,
> Tim
>
> Scott Makeig wrote:
> > ICA can decompose common reference and bipolar channel pairs
> > simultaneously, since the sources sum linearly at all these channels
> > proportional to the difference in source projection strengths to the
> > 'active' and 'reference' channels. However, plotting the scalp maps of
> > ICA components including both types of channels is not apt to be wholly
> > accurate, since the baselines for the two channel types are
> > different.However, iIt should be possible to reconstruct the full
> > component scalp maps (at least for 'dipolar' components) using a forward
> > (BEM) head model... In the absence of such a procedure, one can always
> > remove the bipolar channels *after* running ICA decomposition, using the
> > EEGLAB 'remove channels' function. This will allow plotting the
> > component maps based on the (common reference) montage.
> >
> > Scott Makeig
> >
> > On Sun, Apr 20, 2008 at 3:45 PM, Nicolas Robitaille
> > <nicolas.robitaille at umontreal.ca
> > <mailto:nicolas.robitaille at umontreal.ca>> wrote:
> >
> > Dear Arno,
> >
> > Just a related idea:
> >
> > Would it be a better practice to simply include the EOG channels as
> > if they were just others EEG electrodes (if they were all recorded
> > with say a left-earlobe reference, as the others EEG channels, or
> > reference-free using a Biosemi system) instead of bipolar channels,
> > when possible? In my mind, this would help ICA to isolate these
> > signals (which is not always trivial for horizontal eye movements,
> > which are smaller and can be less frequent than eye blinks),
> > according that at least some channels would have clear eye-related
> > signals. This would also avoid the difference in referencing methods
> > across channels you mentionned.
> >
> > Nicolas
> >
> > > Date: Sun, 20 Apr 2008 23:13:52 +0200
> > > From: arno at ucsd.edu <mailto:arno at ucsd.edu>
> > > To: modestino at ccs.fau.edu <mailto:modestino at ccs.fau.edu> >
> > > CC: eeglablist at sccn.ucsd.edu <mailto:eeglablist at sccn.ucsd.edu>
> > > Subject: Re: [Eeglablist] [Fwd: Eye Movement Artifacts and Filtering]
> >
> > >
> > > Dear Justin,
> > >
> > > > 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).
> > > >
> > >
> > > It is OK to include bipolar channels for that purpose. ICA should be
> > > able to detect the difference in reference (although you might
> > have to
> > > search for the component that accounts for that). Then you may
> > compute
> > > ERP for your EOG channels. A better idea though would be to do
> > that for
> > > frontal channels such as FPz.
> > >
> > > > 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?
> > > >
> > >
> > > Yes, there are 2 types of filters available in EEGLAB by default. I
> > > would advise to use the non-linear IIR filter which has better
> > design
> > > than the linear FIR filter (and does not introduce phase distortion
> > > because it is applied in both directions). There is also an
> > additional
> > > plugin that allows more advanced filtering.
> > >
> > >
> > http://www.uni-leipzig.de/~biocog/content/widmann/eeglab-plugins/#firfilt
> > <http://www.uni-leipzig.de/%7Ebiocog/content/widmann/eeglab-plugins/#firfilt>
> > >
> > > Sorry for the late answer. Answer do come in time if you are patient.
> > >
> > > Best regards,
> > >
> > > Arno
> > >
> > > _______________________________________________
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> >
> > ------------------------------------------------------------------------
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> >
> >
> >
> > --
> > Scott Makeig, Research Scientist and Director, Swartz Center for
> > Computational Neuroscience, Institute for Neural Computation, University
> > of California San Diego, La Jolla CA 92093-0961,
> > http://sccn.ucsd.edu/~scott
> >
> >
> > ------------------------------------------------------------------------
> >
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> --
> --------------------------
> Timothy M. O'Keefe
> Brown University
> Department of Neuroscience
> 185 Meeting Street
> Providence, RI 02912
>
> Voice: +1.401.863.1258
> --------------------------
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