[FieldTrip] strange observations using ICA
weberi at staff.uni-marburg.de
weberi at staff.uni-marburg.de
Thu Aug 9 09:26:25 CEST 2018
Dear FieldTrip community,
I have a question concerning some strange observations when using ICA.
In our lab we try to get rid of an EEG artefact induced by deep brain
stimulation.
For this purpose we compute an ICA of our EEG-channels and sort the components
relative to their similarity (quantified using mutual information)
with the raw artefact
measured directly from the stimulator. We then successively remove
the components
according to their mutual information and calculate the mean frequency
spectrum of the
back-transformed corrected data. The artefact has a very defined
frequency distribution
with peaks at multiples of 130 Hz. With our approach, we would expect
the artefactual
peaks to successively become smaller. However, this is not the case.
While the peaks
ultimately become smaller after removal of several components, the
artefactual power
even rises again after the first couple of components. How can this be
explained?
Any insights would be much appreciated,
Best regards
Immo Weber
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