[Eeglablist] Order of Channel Removal+Interpolation and ICA (removing noisy components)

[Naviya Lall]

Hello all,

My name is Naviya and I work with EEG data in a lab in Delhi, India. I have
a question about EEG data channel interpolation and its order in
preprocessing pipelines.

   - We record data with high density EEG (128 channels).
   - I tried to perform ICA without removing any channels and it was giving
   me noise heavy components (I use ICA to remove noisy components of eye,
   heart, muscle etc.)
   - I just want to remove 2-4 channels in some participants or certain
   sessions.
   - The GUI has very easy direct interpolation
   steps- Tools>Interpolate>select from data channels which skips the
   "Removal" step altogether.
   - In code I feel that it would be easier to "remove" the noisy
   channel(s) and use this -  original_chanlocs = EEG.chanlocs; (to save
   original locations) and then  EEG = pop_interp(EEG, original_chanlocs,
   'spherical');
   to interpolate the removed data- *Is that right?*
   - My main question is if I should perform interpolation before ICA or
   after ICA?
   - I read through some older exchanges on EEGLABLIST Archive from 2015,
   2017, 2023 and 2025 however I am still unsure of the ideal order of
   performing interpolation.
   - My logical thought is to remove + interpolate before running ICA so
   that the rank and number of components generated is not affected but most
   people advise to remove channel, then ICA and then interpolate.
   - Please advise on the method of channel removal+interpolation and the
   order of channel interpolation and ICA?


Thank you so much.


Best regards,
Naviya

--
Naviya Lall
Junior Research Fellow
Cognitive Science Lab
IIIT Delhi
naviyalalluni.wixsite.com <https://urldefense.com/v3/__https://naviyalalluni.wixsite.com/naviyalall__;!!Mih3wA!AK4IIr3bl7l5vstVMLfS9SvOU__IwE4KJfUqRptsvdt6mN4V6stqKqyZVfvP6h_-ebr4vwz6RSNGbePI1sed-hDQ$ >