Notch filter on .edf EEG file

Discussions
1

Hi Brainstorm,

I’m a little confused about how to apply a notch filter on EEG data. I am currently trying to do pre-processing on raw EEG data in .edf file format.

There seem to be two options: the filter tab on the right side of the brainstorm window, and via the Process 1 tab at the bottom. What is the difference between the two? I dont get errors when i used the simple options on the right hand side but I also dont see any changes in the time series montage. When I try to use the Process 1 tab “run” option I get an error saying that brainstorm can only do pre-processing on .ctf files (which is consistent with what the tutorials say). Is there a way to get pre-processing to work on .edf files? should I convert to .ctf?

Also what is the difference between importing EEG data via right click subject> “Review Raw file” and right click subject > import MEG/EEG? when I import as “review raw file” i get the pre-processing error, but when i import as MEG/EEG i dont get the error (but again montage seems unchanged).

Thanks,
Julie

2

Hi Julie,

The Filter tab sets filters for visualization only (click on the HELP button for help).
The proper way to filter a file is with the Process1 tab. As you said, the .edf format is not yet implemented for the frequency filters and the sinusoid removal.
The EEG/Epilepsy tutorial illustrates how to get around this limitation:
http://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy

The menu “Review raw file” links the original file to the database, everything you run on this file read directly the original file.
The menu “Import MEG/EEG” extracts segments of the original files and saves hard copies of them in the database, in .mat format.
If you are not comfortable with this difference, please follow again carefully all the 12+3 introduction tutorials.

Cheers,
Francois