[Eeglablist] ICA decomposition of possibly 2 different conditions....

Klados Manousos mklados at gmail.com
Tue Jan 12 14:42:17 PST 2010

Dear IIya

According to my opinion i suppose that you have to separate them because
other pools of neuron (different sources) are activated with eyes opened and
other with eyes closed...And if you see the mathematical background because
you have a two condition experiment the underlying sources will be more than
in one codition....so some sources will be merged in one component...i think
that it is not preferable...it is better to reduce "normally" your data
dimensionality by separating the recording session....and a 2 mins record is
not a short epoch for ICA...There is an heuristic rule which says that ICA
can be succesfully applied in epochs with sample points grater than
channel^2 => Sample Points>= Channels^2.

I hope to helped you...

2010/1/12 Ilya Adamchic <dr.ilya at yahoo.com>

> Dear All.
> We have an experiment set up, when a patient should sit 2 min with eyes
> closed and 2 min with eyes open and so on several times. This is a
> spontaneous recording: no actions are performed in both conditions. When we
> perform ICA decomposition, is it reasonable to leave these 2 conditions
> mixed as a continuous file and let ICA decompose the continuous file. Or we
> need to separate eyes closed from eyes open conditions and only then perform
> ICA on the short epochs, which might be to short (2 min) for the 128 channel
> decomposition.
> Thank you all for your replies in advance.
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Klados A. Manousos
 Research Assistant
Group of Applied Neurosciences
Lab of Medical Informatics, Medical School
Aristotle University of Thessaloniki
Thessaloniki, Greece
Tel: +30-2310-999332
Website: http://lomiweb.med.auth.gr/gan/mklados
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