[Eeglablist] A quick question about baseline correction after ICA

[David Groppe]

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
>>
>> _______________________________________________
>> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
>> To unsubscribe, send an empty email to
>> eeglablist-unsubscribe at sccn.ucsd.edu
>> For digest mode, send an email with the subject "set digest mime" to
>> eeglablist-request at sccn.ucsd.edu
>
>
>
> --
> 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
>
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to
> eeglablist-request at sccn.ucsd.edu
>