[Mne_analysis] 50Hz artefact for time frequency analysis

[Elisabeth Fonteneau]

Dear MNE users,

I have some data in which we did have some problem during the acquisition of
MEG/EEG combined.

Indeed some EEG electrodes picked up the frequency oscillation of the HPI
coils. It should not be a problem as the coils frequency is above 300 HZ.
However I just noticed  in my data that some EEG electrodes (4 out of 70 in
average) have an harmonic around 50HZ.

If I'm doing ERF/ERPs, my data will be filtering this artefact, but
unfortunately I want to do time-frequency analysis on sensors & source
level.

On unfiltered data (1-100Hz) , those EEG electrodes are picked as artefact
and rejected (amplitude of oscillation ~ 300-400uV). To pass the data I
needed to mark those electrodes as bad in MNE.

 

Now I thought about different solution to remove this and would like to have
your advice on which one to do, or maybe you will have a better suggestion..

a)      Use a notch filter, but then what about the gamma band? Will I still
be able to analyse it or not?

b)      Interpolate those specific electrodes, there are maximum 4 out of 70

c)       As power computation is baseline corrected it should not be a
problem; the oscillations are also in the baseline and then will be
automatically removed (same for PLV?)

 

Thanks for your help

Elisabeth

 

 

 

__________________________________________________________

 

Dr Elisabeth Fonteneau

Neurolex Group

Department of Psychology

University of Cambridge

Downing Street, Cambridge CB2 3EB, UK

Phone: +44 1223 333 548

Email:  <mailto:ef309 at cam.ac.uk> ef309 at cam.ac.uk

Web:  <http://www.neurolex.psychol.cam.ac.uk/directory/ef309@cam.ac.uk>
www.neurolex.psychol.cam.ac.uk/directory/ef309 at cam.ac.uk

 

 

 

 

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