[Eeglablist] ICA question

[Stephen Politzer-Ahles]

Enrico:

I don't know if it's methodologically valid to do ICA on all subjects at
once, for the reasons you pointed out, but as far as the technical side of
things is concerned, it's pretty easy to concatenate datasets using
pop_mergeset(). I suppose you would want to code the data in some way (such
as rewriting the triggers for each subject) to facilitate getting the
datasets back apart properly later on.

Best,
Steve Politzer-Ahles

On Wed, Feb 1, 2012 at 8:44 AM, Enrico Schulz <enrico.schulz at gmail.com>wrote:

> Dear EEGlab list,
>
> I have a problem with the ICA-based artefact reduction that is actually
> not just restricted to the EEGlab software.
>
> I'm struggling with a lot of high frequency- artefacts at frontal and
> inferior electrodes around the head exhibiting a much higher amplitude than
> the cortical gamma band activity I'm interested in. Although it is
> possible to remove the strongest artefacts, some muscle activity could not
> be removed in my data sets because some of the artefacts do not give rise
> to a separate component.
>
> In my naive view, in addition to the fact that there are still artefacts
> in the data set, this could lead to a bias for some subjects. In theory, if
> a strong artefact gives rise to an independent component and can, hence, be
> removed, the amount of artefacts in that data set is now lower than in a
> different data set, where that artefact is not strong enough for a distinct
> component.
>
> The problem is even more complicated if an experimental group (e.g. pain
> patients) has stronger muscle artefacts than a healthy control group.
>
> Sorry for the long introduction, but my actual question is, whether it is
> possible to concatenate all single subject files and doing the ICA for that
> big file.
> I'm aware that this approach has other disadvantages, e.g. it requires a
> similar topography for each artefact across all subjects and a fast
> machine.
>
> Any help/opinion is highly appreciated!
>
> Best regards,
> Enrico
>
>
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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