Artifacts in PSD

Dear MNE community,

I’m working with a recorded EEG dataset that is relatively noisy. When inspecting the power spectral density of the raw data, I noticed that a subset of electrodes shows a pronounced, rhythmic-looking pattern in the spectrum (see attached figure). Interestingly, this pattern also seems to extend to a number of other channels.

Has anyone encountered similar patterns before or have any ideas about what might be causing them?

Many thanks in advance for any thoughts or suggestions!

These bumps are probably caused by one (or more) large artifacts somewhere in the data. I would mark all extremely large artifacts with annotations starting with “bad” and then recompute the PSD (which will exclude all artifact segments).