[Eeglablist] 16 Hz artifact with lower harmonics in data

Fri Apr 8 09:52:55 PDT 2022

Dear Malte,

I read this discussion with great interest. I read the blog linked by Bene.
I left a comment there but let me repeat it here with more detail.

   1. I'm convinced that the powerline for the German train system is the
   source of this artifact.
   2. But I am still curious how it can cause such a strong,
   channel-by-channel different artifact IF all the recording electrodes are
   unipolarly connected to a reference electrode AND recording equipment and
   the subject's body (animal or embryo?) is electrically connected (i.e.
   ground is shared). When you perform a salt water bucket test, do not forget
   to share a ground between the water and the EEG recorder. Actually, you
   might test what happens when ground is not shared.
   3. Your time-series data show same patterns for electrode 1&2, 3&4, 5&6,
   etc. with the same phases. Does it mean these electrode pairs were closely
   located, or their leads were paired, etc? What is your explanation for this
   pairing effect if the source of the artifact is the German powerline for
   the train system?
   4. Bene's solution reminds me of a paper for reducing TMS-induced noise
   during simultaneous TMS-EEG recordings. If you are going to follow Bene's
   solution, you might find this paper also useful. However, I still think
   that the case of TMS-EEG is very different from the case of German
   powerline for the train system on the point that the source of the artifact
   is VERY close in the former while it is very far for the latter.
   Sekiguchi H, Takeuchi S, Kadota H, Kohno Y, Nakajima Y. (2011).
   TMS-induced artifacts on EEG can be reduced by rearrangement of the
   electrode's lead wire before recording. Clin Neurophysiol. 122:984-990.
   5. Speaking of a large-amplitude environmental noise, last year I
   reported a case of nearly +60dB of line noise observed in one of my
   collaborators' lab. Although I was not there when the data were recorded, I
   can imagine the ground electrode had a problem, either not connected at all
   or hardware failure. As the Figure 2 shows, in the time domain all you can
   see is a 60 Hz sine wave with +/- 850 microV when the recovered signal
   had +/- 10 microV.
   Miyakoshi M, Schmitt LM, Erickson CA, Sweeney JA, Pedapati EV. (2021).
   Can We Push the “Quasi-Perfect Artifact Rejection” Even Closer to
   Perfection? Front Neuroinformatics. 14.
   https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.3389_fninf.2020.597079&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=-H0x6lMjc1PsxcfjKoXqDiULAp4L6M0ZepOLvBnAuP5vcOeRDpNaIU6KZ45pZa8W&s=8mbFbxvyeEuI44IUAzMAYzbA1uZBD0uWbqP02F-Mfiw&e= 
   6. When you think about the ground and reference issue, if you have not
   heard of the word 'infinity reference', I recommend you check out my Wiki
   page. When measured our EEG or whatever bioelectric potentials from our
   body using the 'infinity reference', it would be completely unusable.

   https://sccn.ucsd.edu/wiki/Makoto's_preprocessing_pipeline#Why_should_we_add_zero-filled_channel_before_average_referencing.3F_.2808.2F09.2F2020_Updated.3B_prayer_for_Nagasaki.29
   7. Read also 'Electric Field of the Brain' (Nunez and Srinivasan, 2006)
   p.42 '9. The reference Electrode'. By the way, Fig. 1-21 in p.43 is my
   favorite figure ever.

If you have follow-up info, please share it with us. I'm curious how this
issue can be solved and how the result turns out.

Makoto

On Thu, Mar 31, 2022 at 8:13 PM Malte Anders <malteanders at gmail.com> wrote:

> Hi Bene,
>
> Thank you very much!
>
> Someone already mentioned the 16 2/3 Hz thing with trains to me via private
> Email, but your blog post sheds some more light onto this. Indeed, the
> measurement is taking place in Germany, in some basement at TU Munich... I
> need to have a look at this next week.
>
> My idea is to connect an Open BCI for troubleshooting, which can be run
> from 4 x 1.5 Volt AA Batteries. In that case we would eliminate any
> external artifacts that are induced via the grounding circuit.
>
> Best wishes!
> Malte
>
> Benedikt V. Ehinger <science at benediktehinger.de> schrieb am Do., 31. März
> 2022, 21:25:
>
> > Hi!
> > We observed this with a railway line (important: in Germany) nearby:
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__benediktehinger.de_blog_science_trains-2Dand-2Deeg_&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=e6pZJC_XEDiwU7oAh8oG3hkF2MrfOHh2eni06_FGdgEvmT5Qcv5j9FM8RxQ80SdH&s=RECakigl7u0Nl4lJBABntcKX-5agXzdxePZ9ayIC_q4&e=
> . Note that 16
> > 2/3 is exactly 50Hz divided by 3. Hope that helps already :-)
> > Cheers, Bene
> >
> > Am 31.03.2022 um 12:20 schrieb Malte Anders:
> > > Dear all,
> > >
> > > We are currently trying to record EEGs on the open brain of certain
> > animals
> > > - so no "standard" human recordings. The gold electrodes are placed
> > > directly on the brain, without any conductive gel applied.
> > >
> > > We are encountering a strange ~16 Hz artifact, with harmonics around
> > ~10.x
> > > Hz and ~5.x Hz, see these images:
> > >
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_NKMcrf0&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=c88_VOjmnuVwvN-A41WN_LrcUXdxqhHwgozv6g_vBGXNTPB1AS0LrJkqDp8M8B44&s=E8I2mkOB0AmaOPUEUXwPZvKu-BkYWuzhow82gl11YCg&e=
> > >
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_Z8zkCpp&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=c88_VOjmnuVwvN-A41WN_LrcUXdxqhHwgozv6g_vBGXNTPB1AS0LrJkqDp8M8B44&s=haiZvyK3aT-jVpA4wpHVfjQQrPRs1O0cx88EnN9NitE&e=
> > >
> > > Anybody ever saw artifacts in these frequency ranges? I am trying to
> > narrow
> > > down if those artifacts stem from our recording setup itself (maybe bad
> > > impedance between the brain and the measuring electrode?), or from any
> > > other external hardware in our recording setup.
> > >
> > > Any help is much appreciated!
> > > Malte
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