[Eeglablist] search for spike

[S.Andrews]

Dear all,
Is there any remedy for the inverted curves produced by ICA when we plot P3
signals?
S.Andrews
----- Original Message -----
From: "Scott Makeig" <smakeig at ucsd.edu>
To: "Camilo José Borrego Abello" <cjborrego at yahoo.es>
Cc: <Eeglablist at sccn.ucsd.edu>
Sent: Wednesday, March 10, 2004 8:16 AM
Subject: Re: [Eeglablist] search for spike


> What is your experience in working with ICA components that explain
> spikes? In this case, you would not need to choose a portion of the
> spike to fit - that is, ICA would suggest a solution to this problem.
>
> Scott Makeig
>
>
> Camilo José Borrego Abello wrote:
> > Hi Arno and Jeff:
> >
> > Thanks for your mail.You are quite right. The best is
> > to use menu Plot>component ERP>with scalp component
> > maps. The first component in the top line of the
> > window was found around the same location for the 3
> > epoch lenght used by dipfit.
> >
> >  The current opinion ( Scherg, Ebersole group´s,
> > Lantz-see J. Clin. Neurophysiol. 20(5):311-319,2003)
> > is to work with the rise part of the spike. Certainly
> > Gotman group´S is not very clear at this matter. They
> > use segments lenght of 320 ms and 640 ms (see
> > Kobayashi et al, Clin. Neurophysiol. 112(2001):
> > 405-413 page 407),or increasing the number of spikes,
> > the "density", minimizing the background of EEG
> > without success. In the last case they said that it
> > was because of the kurtosis is affected, as spikes
> > became small and not peaky, but this may not be true
> > because the kurtosis is in reality not affected, it is
> > just a scale adjustement in the printed drawing.
> >
> > That was the reason behind our question of the ideal
> > lenght for a good ICA decomposition in
> > epilepsy.Increasing the number of channels perhaps is
> > not the complete solution.
> >
> > This is a warning for people who work on this area
> > with DIPFIT as it is possible to miss the right
> > location, until a reasonable length is found. The
> > ideal epoch length remain to be determined.
> >
> > Best regards,
> >
> > Camilo Borrego
> > Universidad de Antioquia
> > Medellin, Colombia
> >
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