[Eeglablist] Channel interpolation before ICA vs. channel interpolation following ICA

Daniel Roberts drobertc at gmu.edu
Mon Jul 24 07:55:17 PDT 2017

A question that has frequently come up on this list is whether to perform
bad channel interpolation before or after ICA. Of course if you interpolate
prior to ICA it is necessary to indicate the reduced rank of the data to
the ICA algorithm. In various threads it is recommended to interpolate
before ICA, or alternatively, interpolate after ICA. I’m curious if anyone
is aware of any empirical data on which method is preferable, or the
potential detriments of one method or the other.

I noticed that EEGLAB generates a warning / error when interpolating then
average referencing following ICA: ““Error: some channels not used for ICA
decomposition are used for rereferencing the ICA decomposition has been
removed” which would seem to suggest interpolating prior to ICA if an
average reference is required. However, this warning seems to only remove
ICA decomposition but maintains the channel space data. So perhaps it is
not an issue if ICA was used only for artifact removal and the rest of the
analysis will be in channel space.

Thanks for any thoughts on the issue,

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