[Mne_analysis] notch filter for removing power chord signal

Denis-Alexander Engemann d.engemann at fz-juelich.de
Thu Sep 13 08:38:31 EDT 2012
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Dear Sheraz and Hari  -- thanks for the good pointers!

(I hope you did not receive this already, my mail application was
going wild this morning...)

2012/9/13 Hari Bharadwaj <hari at nmr.mgh.harvard.edu>:
> Hi Denis,
>    The multitaper based rmlinesc() routine in Chronux to remove line noise
> works well:
> http://www.chronux.org/downloads/chronux/chronux/documentation/chronux_2_00/spectral_analysis/continuous/rmlinesc.html
>
> The following is a reference that describes the technique:
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1300074/
>
> Also, most of the time I don't remove it so when I do time-frequency
> decompositions I know that I have the scales correctly done when I see the
> line components at the correct frequency..
>

Actually very neat. I haven't thought of that..

> Regards,
> Hari
>
>
>
> On Wed, September 12, 2012 10:27 pm, sheraz at nmr.mgh.harvard.edu wrote:
>> Hi Denis,
>>
>> As Alex said SSP cant be used to remove line frequency, as its comes from
>> electronics.
>>
>> If you go mne-Matlab way, you can use eegfilt to have notch filter or try
>> harmonics filter which works better for line frequency. For reading and
>> writing raw fif file look at mne_ex_read_write_raw.m.
>>
>> sheraz
>>
>>
>>
>>> 2012/9/12 Alexandre Gramfort <gramfort at nmr.mgh.harvard.edu>:
>>>> hi Denis,
>>>>
>>>>> I wonder whether there is a MNE-way of removing power-chor artifacts
>>>>> from wide-band MEG data (1-200 Hz).
>>>>
>>>> you mean the AC current and the harmonics of 50 or 60Hz?
>>>
>>> yes.
>>>
>>>>
>>>>> As there does not seem to be a notch filter available, empty room SSPs
>>>>> might be the way to do it.
>>>>
>>>> yes don't use SSP for this.
>>>>
>>>
>>> ok, thanks though
>>>
>>>> You need a notch like filter but I am not aware of any with mne or
>>>> mne-python.
>>>>
>>>> Alex
>>>>
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>
>
> --
> Hari Bharadwaj
> PhD Candidate, Biomedical Engineering,
> Boston University
> 677 Beacon St.,
> Boston, MA 02215
>
> Martinos Center for Biomedical Imaging,
> Massachusetts General Hospital
> 149 Thirteenth Street,
> Charlestown, MA 02129
>
> hari at nmr.mgh.harvard.edu
> Ph: 734-883-5954
>
>



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