[Eeglablist] Correcting skin potential artifact for ERP studies

[周云晖]

Hello Volodymyr,


Do you mean re-reference to average reference? I have already done it. The artifact is caused by changing skin potential (such as sweating), and it is not uniform across scalp electrodes.


I am also checking the book by Steven J. Luck (2014), but up to now I can't find a good way to correct these artifacts.



Best,


Zhou



-----Original Messages-----
From:"Vladimir Bogdanov" <vlabogd at yahoo.com>
Sent Time:2019-12-04 18:45:06 (Wednesday)
To: "周云晖" <yhzhou17 at fudan.edu.cn>
Cc:
Subject: Re: [Eeglablist] Correcting skin potential artifact for ERP studies


Dear Zou,


Did you mean-reference?


This must remove most of the drift, since it might be pretty uniform across scalp electrodes.


if the drift is just in few electrodes, I would exclude them.


Sincerely yours,
Volodymyr


On Wednesday, December 4, 2019, 09:00:59 AM GMT+1, 周云晖 <yhzhou17 at fudan.edu.cn> wrote:




Dear colleagues,



I am trying to analyze visual event related potentials (ERP) from some EEG data, but a few subjects showed quite long period of skin potential artifacts throughout the experiment. We previously removed

most of these artifacts by high-pass filtering at 1 Hz, but now for ERP analysis I set the cut-off frequency at 0.1 Hz. After epoching (900 ms long) I see lots of epochs with baseline drift.



I found that many epochs with such drift can be corrected by linear detrending, and some may need further correction by parabolic detrending, but I am not sure how this will affect the ERP shape. Or

I can reject all the epochs with such drift, but that means significant data loss for these subjects.



The data was recorded by actiCHAMP (Brain Products) with 64 active electrodes, and we lowered the impedance of all electrodes to below 10 kOhm. The experiment was performed recently in winter and the room

was cool and dry. I hope some experts in ERP can give me some suggestions on dealing with skin potentials.



Thanks,



Zhou











_______________________________________________

Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html

To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.ucsd.edu

For digest mode, send an email with the subject "set digest mime" to eeglablist-request at sccn.ucsd.edu