[Eeglablist] ICA and signal phase content

[Makoto Miyakoshi]

Dear Georges,

If you remove IC and reconstruct channel EEG by backprojecting the
remaining ICs, of course it changes channel EEG phase!

Here is our EEGLAB workshop 2013 materials. You can find several
powerpoint/pdf files that explains how ICA works on data cleaning.
http://sccn.ucsd.edu/wiki/EEGLAB_2013_UCSD

Makoto

On Sat, Sep 13, 2014 at 7:50 AM, otte georges <georges.otte at pandora.be>
wrote:

> Dear ICA experts
>
>
>
> There is some discussion going on about the evidence that reconstructing
> an multichannel EEG after ICA decomposition and removing one or two
> artefact components could result in  scrambling the phase content (and
> coherence) of the reconstructed signals. Fi starting from a 19 ch EEG,
> removing two components with fi electrode pops and sweat artefacts ,
> reconstructing the 19 ch EEG from 17 components (taking out the artefact
> containing ones)  without those artefacts.
>
>
>
> Others say that this is not the case and that ICA respects the phase.
> However many authors (Zeman, Thatcher..) have published very convincing
> data to the contrary.
>
>
>
> Any suggestions how to evaluate this ? Is it known from the algorithm what
> the reconstruction  will do to the phase content (imaginary part of the
> signal) ?
>
>
>
> All help is very welcome
>
>
>
> Sincerely
>
>
>
> Georges
>
>
>
>
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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