Drop at 50 Hz with raw.plot_psd() function

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  • MNE version: e.g. 0.24.0
  • operating system: Windows 10

Hello everyone,
I noticed a weird drop at 50 Hz with the raw.plot_psd() function. Does someone know what it means?

This is my code:

dat = mat73.loadmat(file)

# create info 
n_channels = 29
sfreq = 250  # in Hertz
ch_names = ['time','event','bad1','Fp1','Fp2','F3','Fz','F4','T7','C3','Cz','C4','T8','P3','Pz','P4','O1','O2','Oz','bad2','bad3','bad4','bad5','bad6','bad7','bad8','bad9','bad10','bad11']

info = mne.create_info(ch_names=ch_names, sfreq=sfreq ,ch_types='eeg')

# create raw
raw = mne.io.RawArray(file,info) 

# drop channels 
raw.drop_channels(['time','event','bad1','bad2','bad3','bad4','bad5','bad6','bad7','bad8','bad9','bad10','bad11'])

montage =  mne.channels.make_standard_montage('biosemi16')
raw.set_montage(montage, match_case=False)

# extract channels 
picks = mne.pick_types(raw.info, eeg=True,include=['Fp1','Fp2','F3','Fz','F4','T7','C3','Cz','C4','T8','P3','Pz','P4','O1','O2','Oz'],exclude='bads')

# filter between 1. and 60. Hz 
filt_raw = raw.copy().filter(l_freq=1., h_freq=60,picks=picks)

filt_raw.plot_psd()
raw.plot_psd()

image

2

your data has been corrected with a notch filter for the land line noise

Alex