Does offline lowpass filtering impact the following time frequency analysis

Hi, Mike,
Suppose EEG was recorded at a sampling of 512 Hz and then was applied with a lowpass of, say, 35 Hz during the EEG preprocessing. Can I extract frequency band not beyond 35 Hz (e.g., 1-35 Hz) safely during the following time frequency analysis? This question seems a bit stupid, but I want to ask for your confirmation :slightly_smiling_face:.
Best,
Ya

Hey Ya. Not a stupid question :wink:

Yes, you can extract frequencies up to 35 Hz. But keep in mind that filters have transition zones where the energy is dampened. You can examine the frequency response of the low-pass filter to see what that looks like, but I guess that frequencies down to ~32ish Hz are probably not very reliable.

Mike, it is very helpful for me. Thanks for your quick reply.