[Eeglablist] 16 Hz artifact with lower harmonics in data

Sat Apr 9 12:23:27 PDT 2022

Benedikt you are a lifesaver. Zapline plus workd for me when I enter "17
Hz" in the frequency field. It doesn't really work when I enter 16 Hz. I
think (?) this supports the hypothesis that this artifact is indeed at
16.66 Hz and may thus be coming from Deutsche Bahn. Unfortunately, zapline
does not work when I enter "16.66" in the frequency field. In any case, see
these images - those were very very bad recordings which were previously
unusable. They aren't 100% perfect now, but it's as good as it's gonna get.

Before zapline: https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_d23dP1W&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=TQ0LZx6aEl5Fe8TH8maW5njPnvkyX4dlPZzCMeWmp49Kd6BG7JFCRo3LXvMcnwB-&s=7ys4Mm6dzbNs5sPtpVa-u2VM1y2lT45mv5_1C8DqXS0&e= 
After zapline: https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_4Wz8w5s&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=TQ0LZx6aEl5Fe8TH8maW5njPnvkyX4dlPZzCMeWmp49Kd6BG7JFCRo3LXvMcnwB-&s=Fu-jSM1uR1jTJDK7dCDAa6E6jV_k_yGm9wAiHDWdMZ8&e= 
Raw EEG before/after: https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_Brm8ddt&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=TQ0LZx6aEl5Fe8TH8maW5njPnvkyX4dlPZzCMeWmp49Kd6BG7JFCRo3LXvMcnwB-&s=QXHwLs0sdx-q8Vu4zYipZrDBsdDrFFMo9Glwo4XnX_k&e= 

Thanks thanks thanks! This has helped me a lot!
Malte

Am Sa., 9. Apr. 2022 um 20:53 Uhr schrieb Benedikt V. Ehinger <
benedikt.ehinger at vis.uni-stuttgart.de>:

> Hi Malte,
>
> one more thing: zapline worked wonders for me on the 16Hz artefact,
> completly removing it - if you use matlab there is a nice toolbox
> zapline-plus that optimizes some further parameters datadriven. Of course
> reducing the artefact is the much better option, but sometimes you simply
> cant.
>
> A pitty the U-Bahn also runs with 16Hz :|
>
> Cheers, Bene
> Am 09.04.2022 um 10:10 schrieb Malte Anders:
>
> Dear Makoto, dear everybody who engaged in this,
>
> Thank you all for the time you've put into this discussion. This is highly
> appreciated.
>
> Makoto, you pointed out some things that with 20/20 hindsight I should have
> explained earlier. To shed some more light onto this, those are chicken
> embryo EEGs at different stages before hatching, like day 09 and day 18.
> Literature shows that chicken embryo develop a continous EEG somewhere
> between day 15-16 before hatching and the earliest signatures can be
> recorded somewhere around d14 (but only intermittend signal and not a
> continous eeg). They hatch at day 21. The "common" spectra of a continous
> chicken embryo EEG is not that easy to compile. What I know is that we are
> searching for delta waves mostly, and some high frequent stuff in the
> higher days (d18, d19). However, amplitudes in literature range from 50 to
> a couple of 100's microvolts, depending on the paper. A lot of the original
> research of chicken embryo eeg is from the 1960's and sometimes lacks some
> crucial information (the papers itself are good but I am sometimes missing
> stuff like the range of the Y axis in the figures...).
>
> The EEG I sent in the original post is a d11 EEG. This basically translates
> to: no brain acticity (as per existing literature) and thus, amplitudes
> should be a couple of microvolts at max. On top of that, it is NOT a
> recording from one single chicken. Those embryos are damn small and we are
> currently getting 2 electrodes placed on the head until we run out of
> space. A 16 ch chicken embryo recording would be a project for itself.
> Hence, the image I shared shows recordings from 8 different embryos, in
> pairs of 2. Electrode 1 and 2 are embryo #1, 3 and 4 embryo #2 and so on.
> Of course they don't share the same reference, and they have been recorded
> at different points in time. The only reason I visualized it like this is
> so that I can analyze the data of 8 embryos at once. This should answer
> your point number 2 and 3.
>
> Answer to 1: After a lot of more trying, I 99% agree with you.
> We tried a lot of things. First, we re-grounded the whole equipment to an
> alternative grounding post. Then, we
>
> -switched the phase (i.e., took another power outlet by using an extension
> cord. The power outlet is used for other EEG recordings in the same
> facility where the artifact is not present.
> -we added another grounding electrode to the embryo to avoid any possible
> ground loops.
> -we combined 1 and 2
>
> Right after re-grounding in the recent recordings, the artifacts where NOT
> present (or only very very slightly visible in the FFT). The abovementioned
> 3 others points did not improve the situation any further.
> However, in the raw data, there were occasional episodes (~10 seconds) with
> clearly visible 16 Hz noise. That means that the artifact is not gone once
> and for all, but I can for now just cut the parts of the data out. In a
> d19, I now see mostly delta stuff (<150 microvolts) and in a d12 embryo I
> see no activity with a random EEG around the baseline in the amplitude
> range of -10 to 10 microvolts (where it should be). For the first time I
> got an "idle EEG" for a dead-brain embyro, after 120 recordings where over
> 90% (!!!) of the recordings where contaminated with the 16 Hz artifact that
> has a higher power than our delta waves.
> Image:https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_JzXK6pG&d=DwIFaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=Zq5xPs9WDjJeoF7zJqfjYA95JujAN9tRm60Kjxz-ovscUMc9IU9ox-29kfCQ6Axo&s=k-UBc3GAcYzORyYr8P0Yiha48mJ1aB6JbEH-nevIooA&e=
>
> What has changed? Maybe, the timetable or whatever... The U-Bahn runs
> directly (!) below the basement where the recordings are carried out. On
> top of that, there is currently very heavy construction work going on.
> Other EEG machines in the building however do not pickup that artifact. I
> will have to look at further recordings and see if anything changes, for
> now, we can work the way it is. I am unsure if one of our measures
> mentioned above improved the situation.
>
> 4,5,6,7: this is very good information, I will definitely dig deeper into
> this next week. For now, we are gambling and rolling dices that more often
> than not land on the "16 Hz" side.
>
> I will keep you guys updated!
> Malte
>
>
>
> Makoto Miyakoshi via eeglablist <eeglablist at sccn.ucsd.edu> <eeglablist at sccn.ucsd.edu> schrieb am Fr.,
> 8. Apr. 2022, 19:28:
>
>
> 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> <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> <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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-- 
Mit freundlichen Grüßen,

Malte Anders