[Eeglablist] ICA question

[Enrico Schulz]

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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