[Eeglablist] PSD: ICA+PCA?

[Alberto Sainz]

Hello,

I have a question regarding ICA and PCA.

Following the paper "Power Spectrum Analysis of EEG Signals for Estimating
Visual Attention" to calculate Power Spectrum by frequencies, they perform
first an ICA and then a PCA.

I understand that PCA concentrates the information in less components (in
this case in just one) so its easier to work with the data (in this case to
measure power by frequency bands). However, I think I miss something about
the ICA. My understanding is that ICA separates the signals to make them
independent. If this is the case, can anyone explain why we would perform
first an ICA and then a PCA? Which would be the sense of separating the
signals to concentrate them together again?

Also, before reading this paper, my intention was to perform an ICA,
average the power for each component in a specific frecuency band and then
average those means for the same frequency. I guess this accumulates a lot
of error, could anyone tell me if this procedure would be valid?

thanks!
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