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

[Makoto Miyakoshi]

Hi Naviya,

   - My main question is if I should perform interpolation before ICA
or after ICA?

Do it BEFORE ICA.
If you perform channel interpolation after ICA, your EEG.icasphere does not
have columns for the added channel.

Makoto

On Tue, May 26, 2026 at 2:19 PM Naviya Lall via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> 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$
> >
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