[Eeglablist] ICA and phase

[otte georges]

Dear all

 

If we reject some artefacts in eeg recordings by zeroing their components
and then reconstruct the "original" EEG by multiplying the rest of the
components matrix with the inverted unmixing matrix, the time points of the
"reconstructed" eeg are a weighted linear interpolation and hence there will
be changes in phase angle between channels.

 

This is a topic that is rarely mentioned in ICA literature although some
simulation studies have been done (Montefusco at al)
http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=6696198 showing
that the phase distortion is largest at the origin of the artefact (due to
weighting coefficients) and within its frequency range , yet the effect is
not stationary.

 

Is there a way, a strategy, a method , when using ICA for rejecting EEG
artefacts , to avoid this phase distortion problem ?

 

Sincerely

 

Georges

 

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