strange artifact across all sites in EEG

[jdwaring]

Hello, I wondered if anyone could help me identify the source of the EEG artifact shown in the attached image . Appears across all sites and continued throughout the recording session. (64 channel system, R-hemi electrodes + EXG shown in image, but occurred on L-hemi also)
I hadn't seen it before this participant or since in subsequent data recordings.
For this person in shielded booth, lights were off, phone non-transmit, no jewelry, watch off, wasn't touching anything electrical that I could see. Offsets looked good, was wearing glasses. I haven't seen for other people in the same set-up. Ideas??? I will see if I can correct this with typical filtering, but ideally I would like to prevent recording it in the first place in future people if I can better understand where it's coming from.

Thanks!
~Jill

EEG_Noise_8.8.23.PNG (94.07 KiB) Viewed 19221 times

[Coen]

60 Hz in a shielded booth means interference by magnetic field. Bundle and twist the electrode wires to minimize enclosed loops.

Best regards, Coen (BioSemi)

[jdwaring]

Coen, Thank you for your reply.
We always bundle all the cables (A, B, + 8 EXG) and wrap the CMS-DRL lead around the bundle ~3x, and secure with a velcro strap. Can you elaborate upon your recommendation if something beyond these measures we have been implementing?

thank you,
Jill