skin potential?

[vrenicarol]

Hello,

we are currently facing a problem I did not find in the forum yet - that`s why I created a new topic.

We are running a BioSemi Active-Two system since last October and everything went quite well so far. But now we face the problem that if the temperature outside is quite high (around 30° Celsius) we face severe artefacts in our EEG recording. Did anybody face similar problems so far? And what can we do to minimize the problem?

I first thought that the temperature in the laboratory itself might be the problem, but cooling down the room actually does not help so far.
Therefore, my actual suggestion is that it occurs if subjects enter the laboratory with a sweaty head and you then put electrodes on top.

To give you an idea of how the arfefact looks like, I have attached two snapshots from one recording session. To me it looks like a skin potential, but in such a massive way which I do not know from our previous EEG system.

Any suggestions from your side are welcome!

Many thanks in advance

[tombullock]

Hello,

We're having a similar issue with our EEG acquisition (also using a Biosemi Active Two with 32 channel recording). Huge low frequency deflections, particularly in the frontal channels, pretty much exactly like what is shown in your screenshots. Did you ever get any feedback on this issue, and were you able to resolve it?

Our recording takes place in an air conditioned electrically shielded chamber, and subjects are not sweating excessively before we start recording (at least, not as far as I can tell)!

Any advice on how to deal with this would be much appreciated.

Thanks!

Tom

[ygao1]

Hi all,

We have been having a similar problem as well. We're using a 128 cap. In about 1/10 of subjects, we would see a lot of drift in all the electrodes, especially the frontal ones. Whenever subjects beginning responding to button presses, the drifts will begin. This drift is not seen during resting or passive observation of stimuli. I've attached an example. I could also send a segment of the bdf files if anyone is interested.

Any assistance would be greatly appreciated!

Feifei

[Jai Prakash]

Hi,
we are also facing the same problem. But this is happening only in the rest condition EEG not in the during the task condition. out of 12 subject 2 subject rest state EEG we got like this. if any one has solution or suggestions please share it.



Thnx