[Eeglablist] acceptable electrode impedance

[Ivan Gligorijevic]

Hi Jinwon,

Of course - what I will say is my opinion (EEG hardware/software producer)
- so you can take it with a grain of salt.

The 10kohm (or 20kohm) mark was a heuristic measure tied to some older EEG
devices - where basically people "looked" at the signals and backtraced
what the impedance was. But, essentially, how good the signals are is
determined by the input impedance of the amplifier - or - in cases of
active or dry (active) electrodes - the pre-amps on the electrodes
themselves. That left some of the very good recordings in the very high
impedance ranges if you know what I mean. So, to conclude, in my opinion it
is completely acceptable to have higher impedance if your signals are
looking good.

I don't know what electrodes are using, but if its passive wet (I doubt
they are based on description but still) - you can always check/cite the
Ferree/Tucker paper (https://urldefense.com/v3/__https://pubmed.ncbi.nlm.nih.gov/11222977/__;!!Mih3wA!Hg1g56hFgViZPRgXjU4YX1cHz4W9HP3-KBCYra99Rbn1gIQeSr6VCuZkw0ppZWuRH2eUKiESgQQLtvkYKDiY$ ) for up to
40kohm.

There is also the question of common-mode rejection - a separate but also
connected issue - and, if the amplifier has a very good CMMR then your
signals will be and look better. For this you can also check the Luck paper
(https://urldefense.com/v3/__https://pmc.ncbi.nlm.nih.gov/articles/PMC2902592/?utm_source=chatgpt.com__;!!Mih3wA!Hg1g56hFgViZPRgXjU4YX1cHz4W9HP3-KBCYra99Rbn1gIQeSr6VCuZkw0ppZWuRH2eUKiESgQQLtu5e4fKF$ ).

If you are using some of the dry systems - you can reach out to the
manufacturer company - I am sure they have references why this is
acceptable - because they would be in trouble if they didn't :)

Hope this helps!

All the best,
Ivan



On Sun, Nov 23, 2025 at 11:42 PM 장진원 via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Dear all,
>
> The guideline usually recommends to use <10k ohm for electrodes in eeg
> study. As far as I know, this is important to preclude artifacts and
> noise. But there are many published studies with >50k ohm.
>
> Is it acceptable to use high-impedace electrodes if all signals look good
> by an eye? Maybe these "good" signals might not mean real good
> representations of cortical sources.
>
> Best,
> Jinwon
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