<p>Every electronic device generates internal noise (e.g., <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664708/" rel="nofollow noreferrer">Stronks <em>et al</em>., 2019</a>), including EEG machines. Further, environmental factors, most notably electrical devices and circuitry, may also impose noise on the EEG signal, think clinical equipment in hospitals, mobile phones <em>etc</em>. So even 'flat EEG's', <em>i.e.</em>, isoelectric EEGs obtained in 'brain dead' organisms, aren't perfectly flat. Such EEGs are devoid of physiological (cortical) electrical activity, yet environmental and internal electronic noise still show up in the EEG recording.</p>
<p><sub><strong>Reference</strong><br />
<strong>-</strong> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664708/" rel="nofollow noreferrer">Stronks <em>et al</em>., <em>Ear Hear</em> (2019); <strong>40</strong>(6): 1457–66</a></sub></p>

CC BY-SA 4.0
2021-08-11T15:28:09.167Z
You wouldn't even need a brain dead organism or even a brain: just put your electrodes in some conductive agar, saline solution, whatever: you'll never get a flat record for all the reasons pointed out here.
Bryan Krause
CC BY-SA 4.0
2022-05-16T00:49:37.187Z
So the conclusion is everything regardless whether it is living or not always have electrical activities.
SnoopyKid
CC BY-SA 4.0
2022-05-16T00:51:06.013Z
Even with no interferences from internal noises or external factors, I don't think brain waves can ever be totally flat and zero.
SnoopyKid
CC BY-SA 4.0
2021-08-11T15:25:33.717Z
2021-08-12T14:02:55.273Z
2021-08-12T14:02:55.273Z
AliceD
<p>I just look at several flat line EEG brain waves and all of them are not exactly at zero microvolt, in the sense there seems to be always a small signal or irregularities to be seen, as well as baseline offsets. Is it possible for flat line EEG brain wave to be 100% zero microvolt?</p>
<p>These are some examples to be found of non-flat EEGs in the literature, e.g., <a href="https://www.researchgate.net/figure/Isoelectric-EEG-pattern-recorded-at-the-time-when-brainstem-reflexes-were-absent_fig1_281427802" rel="nofollow noreferrer">here</a> and <a href="https://www.researchgate.net/figure/Sample-isoelectric-EEG-Simultaneous-Sedline-EEG-top-and-10-lead-EEG-bottom-recording_fig1_334395823" rel="nofollow noreferrer">here</a> and <a href="https://www.researchgate.net/figure/Isoelectric-recording-2A-This-EEG-is-isoelectric-in-horse-10-before-the-end-of-the_fig5_273835899" rel="nofollow noreferrer">here</a>.</p>

<measurement><eeg><electrophysiology>
Why are flat line EEG recordings not perfectly zero microvolt?
SnoopyKid
# Why are flat line EEG recordings not perfectly zero microvolt?

(Asked by: username_0 on 2021-08-11)

I just look at several flat line EEG brain waves and all of them are not exactly at zero microvolt, in the sense there seems to be always a small signal or irregularities to be seen, as well as baseline offsets. Is it possible for flat line EEG brain wave to be 100% zero microvolt?

These are some examples to be found of non-flat EEGs in the literature, e.g., [here](https://www.researchgate.net/figure/Isoelectric-EEG-pattern-recorded-at-the-time-when-brainstem-reflexes-were-absent_fig1_281427802) and [here](https://www.researchgate.net/figure/Sample-isoelectric-EEG-Simultaneous-Sedline-EEG-top-and-10-lead-EEG-bottom-recording_fig1_334395823) and [here](https://www.researchgate.net/figure/Isoelectric-recording-2A-This-EEG-is-isoelectric-in-horse-10-before-the-end-of-the_fig5_273835899).

**Tags:** measurement, eeg, electrophysiology


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## 1 answers

### Answer by username_1 on 2021-08-11. Score: 2

Every electronic device generates internal noise (e.g., [Stronks *et al*., 2019](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664708/)), including EEG machines. Further, environmental factors, most notably electrical devices and circuitry, may also impose noise on the EEG signal, think clinical equipment in hospitals, mobile phones *etc*. So even 'flat EEG's', *i.e.*, isoelectric EEGs obtained in 'brain dead' organisms, aren't perfectly flat. Such EEGs are devoid of physiological (cortical) electrical activity, yet environmental and internal electronic noise still show up in the EEG recording.

**Reference**  
**-** [Stronks *et al*., *Ear Hear* (2019); **40**(6): 1457–66](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664708/)

> **Comments:**
> **username_2**: You wouldn't even need a brain dead organism or even a brain: just put your electrodes in some conductive agar, saline solution, whatever: you'll never get a flat record for all the reasons pointed out here.  
> **username_0**: So the conclusion is everything regardless whether it is living or not always have electrical activities.  
> **username_0**: Even with no interferences from internal noises or external factors, I don't think brain waves can ever be totally flat and zero.  

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