I am trying to filter EEG data for time-frequency analyses, using the PSD function.
I came across this very stange looking artefacte (the wavelates).
Does anyone know what it is and how I can get rid of it ?
Thank you for your futuree answers !
I guess this is an effect of a low-pass filter at 50Hz you applied to your data.
What did you use to filter your recordings?
If you want to get rid of this: import your original recordings into Brainstorm and filter them from there. Otherwise, it wouldn't have much impact on your analysis anyway.
I used brain analyzer to interpolate one electrode, change the sampling rate from 1024 to 1000 Hz, and rearrange the markers to segmente the file for each trial.
but i didn't use other filters yet.
I am actually using the PSD function to try and detect artefacts to filter, following the instructions on the tutorial.
changing the sampling rate might have done the trick, but i only saw that on one subject
Thanks for the advice !
change the sampling rate from 1024 to 1000 Hz
This is not a good idea. When resampling recordings, always pick sampling frequencies with simple ratio. Example: 1024Hz to 512Hz (1/2), 768Hz(3/4), ...
Resampling between frequencies with non-rational factors may cause all sorts of artifacts in the signals, depending on the method used for this.
i resampled the file to 1000 Hz for technical reasons : i have to synchronize the epochs with other recordings. But I'll be careful with that.
Thanks a lot for the advice and the quick responses !