What caused this abnormal (high frequency noise) phenomenon?
When analyzing data using EEGLab, I noticed increased amplitude and strong high frequencies in channels F3 and F4. I then checked the impedance values of channels F3 and F4, which were normal, around 25 kΩ.The reference electrode was placed on the right earlobe, and the ground electrode on the left earlobe. During preprocessing, a bandpass filter from 0.5 to 40 Hz was used, with a CZ electrode as the rereference. And I used a Cyton board and a gel EEG cap.
Comments
Hi Zenton,
I would check your environment for local EMF noise sources, that are sometimes intermittent. There are EMF meters available on Amazon and other sites, some below $50. You can also find EMF meter apps on Android and iPhone stores, if your phone has a magnetometer chip. But generally less accurate than dedicated meters.
Length and routing of your electrode leads can also have a significant impact. Are the F3 and F4 wires longer or routed differently than your other channels? Longer wires pickup more EMF. Your noise seems strongest on F3 and F4, but is also present on the other channels. Have you plotted an FFT graph? Does it show a high frequency spike? Or sub harmonics?
William
Also another obvious cause I forgot to mention, is muscle tension in the jaw, head muscles, etc. Might explain why it localized to just a few sites. When tense, these generate 'EMG' like waveforms.
https://nhimassageblog.com/2015/10/15/the-masseter/