[Mne_analysis] 50Hz artefact for time frequency analysis

[Virginie van Wassenhove]

I'd preserve the alpha peak response (~10Hz) providing it is present (and
to the same extent) in the non-cHPI part of your dataset. /V

On Wed, Oct 8, 2014 at 1:30 PM, Elisabeth Fonteneau <ef309 at cam.ac.uk> wrote:

> Hi all,
>
> Thanks for your reply,
>
> Indeed the artefacts are coming from the cHPI (I did not say that it is
> not picking up the electrical mainline)
>
> But here is a snapshot (see files in the link below) of one
> participant/part with the artefact
>
> You have view of few electrodes and this is raw data
>
> The green line correspond to the start of the cHPI
>
> You could see that before some electrodes were bad and remain unchanged
>
> However some EEG were good before and with cHPI they have picked up some
> high frequency
>
> Also In general you could see that all EEG picked up some level of
> artefacts
>
> I gave you also a plot for this subject/part of frequency decomposition
>
> The EEG have 50z, 150z & around 330Hz
>
> See files in art2/art4
>
> https://www.dropbox.com/sh/hm7pdbhoc98yxf2/AABlCIdmLs4sWHw3W0sHesYGa?dl=0
>
>
>
> Elekta is aware about this problem as it was recurrent in our recent
> recordings and they are investigating
>
>
>
> For the analysis,
>
> I started to use a notch filter and it seems that it is removing the
> artefacts as I would like (filtering the 3 sensors together)
>
> However by comparing the unfilter vs notch filter data
>
> I noticed that the filter data have another low frequency component added
> (around 10Z) , effect present in the Mag
>
> See figure art5 in the same dropbox..
>
>
>
> I am using MNE_python for this notch filter with the command
>
> raw.notch_filter(np.arange(50, 251, 50), method='fft', n_jobs=4)
>
>
>
> any tips for this low frequency band addition?
>
>
>
>
>
>
>
> Thanks for your answers
>
> Elisabeth
>
>
>
>
>
>
>
> __________________________________________________________
>
>
>
> Dr Elisabeth Fonteneau
>
> Neurolex Group
>
> Department of Psychology
>
> University of Cambridge
>
> Downing Street, Cambridge CB2 3EB, UK
>
> Phone: +44 1223 333 548
>
> Email: ef309 at cam.ac.uk
>
> Web: www.neurolex.psychol.cam.ac.uk/directory/ef309 at cam.ac.uk
>
>
>
>
>
>
>
>
>
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-- 
Virginie van Wassenhove
+33(0)1.69.08.1667
Virginie.van.Wassenhove at gmail.com
https://sites.google.com/site/virginievanwassenhove/
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