[Eeglablist] amount of data required for an ICA decomposition of 128 channels

[Simon-Shlomo Poil]

Dear Nishant,

I would recommend you to reduce your data using PCA. It usually does
not make much sense to get 128 ICA componets. Around 15 ICA components
seems to be sufficient for artifact rejection.

Best regards,
-- 
Simon-Shlomo Poil

Neuronal Oscillations and Cognition Group (NOC)
Department of Integrative Neurophysiology (INF)
Center for Neurogenomics and Cognitive Research (CNCR)
Neuroscience Campus Amsterdam
VU University Amsterdam
De Boelelaan 1085, Room B-435
1081 HV Amsterdam, The Netherlands

E-mail: simonshlomo.poil at cncr.vu.nl
Phone: +31 20 5989408
Webpage: http://www.poil.dk/s and http://www.cncr.nl



2011/6/9 nishant seth <nishant.sth at gmail.com>:
> Hi,
> I'm running ICA on a dataset with 128 electrodes. Because I have RAM
> constraints (8GB), I wanted to know the amount of data required for a 'good'
> ICA.
> I know the questions I'm asking don't have precise answers, but a rough
> guess by anyone with some experience in EEG analysis would be better than my
> own guess.
> The wiki on 'decomposing ICA data'
> (http://sccn.ucsd.edu/wiki/Chapter_09:_Decomposing_Data_Using_ICA) has the
> following to say about this issue:
> "As a general rule, finding Nstable components (from N-channel data)
> typically requires more than kN^2 data sample points (at each channel),
> where N^2 is the number of weights in the unmixing matrix that ICA is trying
> to learn and k is a multiplier. In our experience, the value of k increases
> as the number of channels increases. In our example using 32 channels, we
> have 30800 data points, giving 30800/32^2 = 30 pts/weight points. However,
> to find 256 components, it appears that even 30 points per weight is not
> enough data."
> what would the rough value of k be for 128 channels?
> Regards,
> Nishant Seth
> - - - - - - - - - - - - - - -
> Research Associate,
> Multimedia Lab, I.I.T. Delhi
> New Delhi, India
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