[Eeglablist] Persistent 20 Hz Harmonic Line Noise in EEG Data

[Maeghal Jain]

Dear EEGLAB List,

I am currently dealing with persistent line-noise contamination in my EEG
recordings, specifically strong peaks around 20 Hz and its harmonics (40
Hz, 60 Hz, etc.). The contamination remains substantial even after multiple
preprocessing attempts.

Raw Data PSD for reference: https://urldefense.com/v3/__https://ibb.co/5WbNqYCW__;!!Mih3wA!EfdhaFV_tpprT4Wc8_HcfK7KDVTXA0O0NPLW3Ws732nxP-TmPxHUXI_qXevcPIO8hfndJk8euI6BWbB1_dCuBxHG_A$ 

I have already tried:

   -

   Average re-referencing before notch filtering
   -

   Average re-referencing after notch filtering
   -

   Multiple full-rank average reference implementations, including:
   -

      Makoto’s fullRankAveRef()
      -

      Manual full-rank average reference using (nchan + 1) denominator

Despite this, a large amount of the harmonic noise is still present in the
spectra.

For reference, the issue looks somewhat similar to this discussion:
https://urldefense.com/v3/__https://mne.discourse.group/t/line-noise-eeg/11817__;!!Mih3wA!EfdhaFV_tpprT4Wc8_HcfK7KDVTXA0O0NPLW3Ws732nxP-TmPxHUXI_qXevcPIO8hfndJk8euI6BWbB1_dB2ZPVDPg$ 

I would greatly appreciate advice on how people in the EEGLAB community
typically handle this kind of persistent harmonic contamination.

Would you recommend CleanLine, Zapline-plus, spectrum interpolation, ASR,
ICA-based approaches, or something else?

Thank you very much for your help.

Best regards,
Maeghal Jain
BISE Lab