[Mne_analysis] Noise > 50 Hz in IC's, despite filtering

Eric Larson larson.eric.d at gmail.com
Tue May 21 12:43:20 EDT 2019
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You should try changing the `h_trans_bandwidth` to be narrower, by default
it will use 0.25 times the `h_freq` so in this case 12.5 Hz, which means
that 60 Hz is in the transition band rather than the stop-band. See (though
there is a bug in the table; the values under `h_trans_bandwidth` for 45
and 48 Hz should be 11.25 and 12, respectively):


You could also use fir_window='blackman', which will give you a longer
filter but also better stop-band attenuation. In 0.18 doing
`mne.filter.create_filter(..., verbose=True)` will give you useful
information about the filter you are using.


On Tue, May 21, 2019 at 12:33 PM Dillan Cellier <cellierdillan at gmail.com>

>         External Email - Use Caution
> Hello MNE community,
> I have a question related to the screenshot below. In my preprocessing
> script I've gone through the following steps:
> -Import raw data with *raw=mne.io.read_raw_egi(raw_file, montage=mne.channels.read_montage(kind='GSN-HydroCel-129'),preload=True,
> verbose=True)*
> -filter data with *raw.filter(1,50)*
> -interpolating bad electrodes: *raw.interpolate_bads()*
> -rereferencing with a global avg with *mne.set_eeg_reference(raw,
> ref_channels=scalp_electrodes+ext_electrodes) *
> -then, *ica = ICA(n_components=90,random_state=25)*
> I've also tried running it with *method=infomax*, but the problem still
> persists of high-frequency noise in several IC's in every subject. This is
> despite the high and low pass filtering mentioned above.
> Any thoughts as to why I might still be seeing this would be greatly
> appreciated.
> Thank you!
> Best wishes,
> Dillan Cellier
> [image: Screen Shot 2019-05-20 at 12.00.07 PM.png]
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