[Eeglablist] ICA vs. regression-based artifact correction effects on sensor level phase

Tue Feb 21 10:22:05 PST 2012

Dear Baris,

In the study I had visually inspected the artifactual ICs, but in the plug
in i provide two ways for the identification of the artifactual ICs. First
Fractal Dimension [1] and second the correlation with the EOG signals.
Regarding the EOGs, they are bipolar which is mentioned inside the
manuscript. I report how they were extracted...Honestly I am not sure if it
is correct to take monopolar EOGs. In this study I haven't included the EOG
in the ICA, but in another study [2] I have compared the performance of
artifact rejection when the signals are included during the ICA
decomposition and when they are not...

Regarding you initial question, in my master thesis (which is in Greek) I
have used PLV (phase locking value) in order to see the phase distortion
intoduced by several regression-based, ICA-based and REGICA based artifact
rejection techniques, but the results was the absolute zero, for all the
techniques...You can check it by your self employing an estimator about the
introduced error by the artifact rejection techniques you want to compare...

Regarding the connectivity... Althought now functional connectivity is one
of my primary fields of interest I haven't tried to assess the performance
of different artifact rejection techniques in cerebral networks...May be
I'll do it in the future...

If you need anything else don't hesitate to contact with me :)
Manousos Klados

[1] http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4052205
[2] http://www.sciencedirect.com/science/article/pii/S0304394011008421

2012/2/21 Baris Demiral <demiral.007 at googlemail.com>

> Hi Manousos,
>
> Thank you for pointing out the link, I am actually aware of your
> paper, and I think it is a good alternative to just taking out the
> artifactual ICs by visual inspection.
> I have some questions though:
>
> a) As I understand, you apply regression based correction on the
> artifactual ICs by using EOG channels. How do you decide which ICs are
> artifactual at the first place?
>
> b) Are the EOGs recorded as monopolar or bipolor? I assume they are
> monopolar. Does it matter?
>
> c) Do you include EOGs in the ICA?
>
> Overall, my question initially was theoretical, to asses how much
> impact such corrections have on phase information and connectivity.
>
> Thanks,
> Baris
>
>
> On Sat, Feb 18, 2012 at 2:21 PM, Manousos Klados <mklados at med.auth.gr>
> wrote:
> > Dear Baris,
> >
> > Check this out-->
> > http://www.sciencedirect.com/science/article/pii/S1746809411000061
>  Manousos,
>
>
> >
> > REGICA is a hybrid method combining the ICA with the regression-based
> > techniques, dealing with the known problems of both methodologies...
> >
> > If you search the EEGLAB site you can find the REGICA plugin...
> >
> > Best Regards
> >
> > Manousos Klados
> >
> > 2012/2/16 Baris Demiral <demiral.007 at googlemail.com>
> >>
> >> Hi,
> >>
> >> Here are the questions:
> >>
> >> a) If we take out artifactual ICs (say, eye blinks), do the final
> >> sensor data loose their crucial phase information?
> >> b) If we apply linear regression based algorithms to exclude
> >> artifacts, will this influence the sensor level phase information?
> >> c) How do these two methods influence sensor based connectivity
> analysis?
> >> d) Which sensor-based connectivity measures are robust against volume
> >> conduction?
> >>
> >> I favor source- and ICA-based multivariate connectivity analyses where
> >> you really do not need to take out ICs, but work on the components of
> >> interest.
> >> But, there are plenty of papers out there reporting only pairwise
> >> sensor connectivity while ignoring the effects of volume conduction
> >> and artifact correction.
> >>
> >> Thanks,
> >> Baris
> >> --
> >> Ş. Barış Demiral, PhD.
> >> Department of Psychiatry
> >> Washington University
> >> School of Medicine
> >> 660 S. Euclid Avenue
> >> Box 8134
> >> Saint Louis, MO 63110
> >> Phone: +1 (314) 747 1603
> >>
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> >
> >
> >
> >
> > --
> > Manousos A. Klados
> > ________________________________________________
> > B.Sc Mathematics
> > M.Sc Medical Informatics
> > ________________________________________________
> > PhD Candidate -- Research Assistant
> > Group of Applied Neurosciences
> > Lab of Medical Informatics
> > School of Medicine
> > Aristotle University of Thessaloniki
> > P.O. Box 323 54124 Thessaloniki Greece
> > _________________________________________________
> > Tel: +30-2310-999332
> > Fax:+30-2310-999263
> > Website: http://lomiweb.med.auth.gr/gan/mklados
> >
> > ________________________________________________________________
> > Δρώ γιατί Αντιδρώ: Δεν τυπώνω αυτό το mail γιατί προστατεύω το
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> > ________________________________________________________________
> >
>
>
>
> --
> Ş. Barış Demiral, PhD.
> Department of Psychiatry
> Washington University
> School of Medicine
> 660 S. Euclid Avenue
> Box 8134
> Saint Louis, MO 63110
> Phone: +1 (314) 7477 1603
>

-- 
Manousos A. Klados
________________________________________________
B.Sc Mathematics
M.Sc Medical Informatics
________________________________________________
PhD Candidate -- Research Assistant
Group of Applied Neurosciences
Lab of Medical Informatics
School of Medicine
Aristotle University of Thessaloniki
P.O. Box 323 54124 Thessaloniki Greece
_________________________________________________
Tel: +30-2310-999332
Fax:+30-2310-999263
Website: http://lomiweb.med.auth.gr/gan/mklados

________________________________________________________________
Δρώ γιατί Αντιδρώ: Δεν τυπώνω αυτό το mail γιατί προστατεύω το περιβάλλον.
Acting by Reacting: By not printing this e-mail I help protect the
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