Hello, I am new to EEG and cannot for the life of me figure out what is causing this noise. Could someone help me out with ideas of what these artifacts are? Thank you in advance.
What equipment are you using? Usually people starting out with EEG, are working with many fewer channels than the 19 or so you show here. This looks like a clinical EEG system.
The upward drift is not good, and is usually removed by proper DSP digital signal processing filtering. For example a bandpass filter from say .5 Hz to 45 Hz. The middle section of channels show a huge amount of high frequency noise. Could be power line mains noise. Or could be the subject muscle tension out of control on those channels. Normally for EEG you want to be as calm and relaxed as possible.
What is the trace on the bottom of the screen? It does not seem affected by the drift.
William
Hi William,
Thank you for your response! I am using a brain vision actiCHamp, with 32 channels. The trace on the bottom of the screen is our HEO’s and VEO’s (the noisy one being the HEO, the flat one VEO). I have had issues getting them to work properly and am waiting on a replacement.
This does look like powerline mains noise however I’ve been collecting data in the same room this whole time and only recently am having issues–but it’s possible something in the environment changed. Do you think the upward drift could be caused by a loose reference electrode, or sweating in that area? This participant appeared calm and very still, though you never know .
Zack
Yes, could be an issue with your reference, since all channels except the bottom ones, are affected. Very likely a reference issue. Maybe try another location or electrode for the reference. If you are using gel with this cap, that is more conductive than sweat. But maybe you have some conductive bridges going on?
What is the electrode material? If silver chloride, it’s possible there may be excessive wear on some electrodes, exposing the silver layer below. Do you do impedance tests on your channels? Check what is going on in those middle channels.
