[Eeglablist] A quick question about baseline correction after ICA

[zhu zhu]

Dear Scott and David,

Thank you so much!

Best regards,
Zude

2010/1/5 David Groppe <dgroppe at cogsci.ucsd.edu>

> Hi Zhu,
>   The results Scott mentions are in the following paper:
> Groppe, D.M., Makeig, S., &  Kutas, M. (2009) Identifying reliable
> independent components via split-half comparisons. NeuroImage, 45
> pp.1199-1211.
> http://www.cogsci.ucsd.edu/~dgroppe/PUBLICATIONS/Groppe2009.pdf
>
> cheers,
>  -David
>
>
> On Wed, Dec 23, 2009 at 10:02 AM, Scott Makeig <smakeig at gmail.com> wrote:
> > Zhu -
> >
> > David Groppe pointed out that running ICA after baseline-correcting
> > individual data epochs essentially adds a new (baseline mean) map to each
> > trial, one that depends on the length of the epoch as well as on the
> > underlying data sources. He found that he got better ICA decompositions
> when
> > he (1) applied high-pass filtering (as however appropriate) to the
> > continuous data, (2) extracted event-related epochs of interest, (3)
> > performed ICA decomposition on the concatenated epochs, and then (4)
> applied
> > baseline correction to the epochs. This seems theoretically sound -- I
> > suggest trying this approach.
> >
> > Scott Makeig
> >
> > ps. Below you don't say exactly what you mean by A and B ...
> >
> >
> > On Tue, Dec 22, 2009 at 1:59 AM, zhu zhu <zhuzude at gmail.com> wrote:
> >>
> >> Dear All,
> >> I have a puzzle when extract epochs from ICA-back projected data. Let'
> >> say, I selected one component after ICA, when I extract epochs for a
> >> specified marker (condition), should I use baseline correction (default
> =
> >> -200 0)? The reason I ask this question is that I the data was baseline
> >> corrected before ICA, and sometimes the baseline correction during
> >> extracting epochs will change the relative amplidute( i.e. A > B without
> >> baseline correction, but A < B after using baseline correction). Any
> comment
> >> is highly appreciated!
> >> Thank you!
> >> Best regards,
> >> Zude
> >>
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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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