[Eeglablist] 16 Hz artifact with lower harmonics in data

[Malte Anders]

Dear all,

We are currently trying to record EEGs on the open brain of certain animals
- so no "standard" human recordings. The gold electrodes are placed
directly on the brain, without any conductive gel applied.

We are encountering a strange ~16 Hz artifact, with harmonics around ~10.x
Hz and ~5.x Hz, see these images:
https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_NKMcrf0&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=c88_VOjmnuVwvN-A41WN_LrcUXdxqhHwgozv6g_vBGXNTPB1AS0LrJkqDp8M8B44&s=E8I2mkOB0AmaOPUEUXwPZvKu-BkYWuzhow82gl11YCg&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__ibb.co_Z8zkCpp&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=c88_VOjmnuVwvN-A41WN_LrcUXdxqhHwgozv6g_vBGXNTPB1AS0LrJkqDp8M8B44&s=haiZvyK3aT-jVpA4wpHVfjQQrPRs1O0cx88EnN9NitE&e= 

Anybody ever saw artifacts in these frequency ranges? I am trying to narrow
down if those artifacts stem from our recording setup itself (maybe bad
impedance between the brain and the measuring electrode?), or from any
other external hardware in our recording setup.

Any help is much appreciated!
Malte