[Eeglablist] ICA analysis and Interpolation

[Andrea Helo]

Dear all,

I have an issue regarding ICA for artifact correction that I really would
appreciate some help with. I would also  appreciate if someone could
approve or suggest any modifications in my pre-processing order.

Here is some background information:
I have recorded children data (24-month-olds) with EGI, 128 channels.
The experiment contains 144 trials (72 per condition) where a picture is
presented during 500 ms  followed by a word (700 ms) then there is an
intertrial of 2500 ms (I trigger the trials manually when the child is
looking at the screen).
I exported the data, and I am currently starting to pre-process the data
using EGGLab.
I have created epochs of 3500 ms in order to run ICA to detect eye-movement
artifacts (I have chosen 3500ms because I would like to keep as much data
as possible for ICA. I would like to compare ERP in shorter epochs of 1000
ms later).

My pre-processing order is the following:

Filtering (1HZ-30Hz),
Reducing number of channels to 64 and then removing bad channels
Re-referencing to average
Epoching (3500ms),
Removing baseline,
Removing bad epochs
Running ICA to detect artifacts

*One thing I am not sure about is whether I am re-referencing- at the right
point.*

Another issue is interpolation. I have read that it is not recomended
interpolate before running ICA . So I am removing bad channels before
running ICA but as a consequence I am having different amount of channels
per subject. I have also read that it is possible interpolate after running
ICA but I am not sure how to do it and I have two doubts related to that:

1- *Is it possible interpolate channel in epoched data or is it  better to
always interpolate in continuous data?* I have run ICA in epoched data
first and after that I will have to interpolate in the epoched data.
2- I have removed bad channels to run ICA, so those channels are not in the
list of channels to be interpolated anymore after ICA.


*So, is there a way to interpolate after removing channels?*Thanks in
advance for your help,

--
Andrea
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