[Eeglablist] [EXTERNAL] 16 Hz artifact with lower harmonics in data

[Malte Anders]

Hi Brian, thanks for answering.

Yes, I agree that the fft looks unusable. This is due to the fact that the
EEG I've sent is an "EEG" of a not fully developed embryo where we would
normally expect a flat line, except maybe some movement artifacts. In other
words, this is just some electrodes in living tissue where the brain will
be later on. That tissue should not produce 16 Hz amplitudes of 900
microvolts.

The eeg is recorded with a hardware bandpass between 0.1 - 100 Hz and
refiltered in EEGLAB between 1-40 Hz. No further processing. Setting the
hardware filter to 1 - 100 Hz with 50 Hz notch produces the same artifact
on the online recording screen, so the raw data should be imported
correctly.

Thanks,
Malte


Brian Harvey <brian.harvey at biogen.com> schrieb am Do., 31. März 2022, 17:33:

> The FFT has an unusual 1/f characteristic. Question(s)
>
>
>
>    1. Awake or anesthetized (if so what anesthesia)
>    2. Did you perform any filtering, referencing, or resampling?
>    3. Have you looked at the raw data, plot the raw traces outside of
>    EEGlab
>
>
>
> Brian
>
>
>
> *From:* eeglablist <eeglablist-bounces at sccn.ucsd.edu> * On Behalf Of *Malte
> Anders
> *Sent:* Thursday, March 31, 2022 6:21 AM
> *To:* EEGLAB List <eeglablist at sccn.ucsd.edu>
> *Subject:* [EXTERNAL] [Eeglablist] 16 Hz artifact with lower harmonics in
> data
>
>
>
> 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 ZjQcmQRYFpfptBannerStart
>
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> 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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