Order in preprocessing and different filters before and after ICA

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  • MNE version: 1.7.0
  • operating system: Windows 11

Hello, I wanted to ask in this post about the relationship abouth highpass filters and ICA(fit and apply).

I know that ICA should be applied on 1 hz (or higher) high pass filtered data, as recomendded in MNE tutorials, and other papers. My question is basically**, can you fit ICA on 1 hz highpass filtered epochs** , and then apply it to raw (no filter at all, no epochs) and then highpass filter again (this time at 0.1hz or other values).

I have seen some posts about it like Filter low-pass and high-pass for EOG artifac correction with ICA but I don´t get a clear picture

Basically my pipeline is:

  • highpass/lowpass filtering (1-40) hz
  • epoching of 2 seconds
  • removal of artifacts with autoreject (of 2 second epochs)
  • ICA fit on epochs [without epoch removed by autoreject] (
  • ICA apply on RAW signal
  • 2Âş - highpass/lowpass filtering (0.5-40) hz
  • re-epoching (38 seconds now, i work with very long epochs)
  • autoreject on 38 s epochs

Thanks in advance! Please let me know if you want the code I used or any other information

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Hello, yes, this seems reasonable to me!

Best wishes,
Richard

1 Like
3

Okey thanks so much Richard!

I would like to ask, why filtering AFTER applying ICA, rather than BEFORE applying it , i don´t really understand the reasons behind that decision (although people always do it after filtering), shouldn´t it be the same?

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Hello, I’m sorry, I actually mis-read parts of your suggested proposal above (I responded on my phone while changing trains … maybe not the best strategy!)

May I ask why you want to apply ICA on your continuous data before filtering, if you want to later epoch your data anyway? Why not filter the raw data, epoch it (to receive “dirty” epochs), apply ICA & auto reject (to receive “clean” epochs)?

Best wishes,
Richard