[Eeglablist] facial EMG

[Stephanie Chen]

Hi everyone,

I've been trying to learn how to use eeglab for facial EMG work alone (no
scalp recordings) and I've hit a few spots where I can't seem to find any
answers. Please reply if you can help with any of the items below (or if
you have any training resources that you can pass along)

1) When importing data, to choose a reference, another user on the list
suggested just choosing a scalp electrode like Cz. However, I didn't record
from the scalp (we use BioSemi equipment and Actiview for recording. It
keeps 32 scalp channels even though nothing is recorded). Should I just
enter a blank reference anyway? For example, choosing Cz even though
nothing was recorded there? This doesn't make sense to me but I just need
to clarify.
2) I record from two flat electrodes at each site for biploar recording. I
need to take the difference in their waveforms, but can't find how to do
this in eeglab (for example, create a "new" channel by subtracting channel
34 from channel 33)
3) How to rectify data? I found this suggestion: EEG.data = abs(EEG.data)
but if anyone can confirm that this works let me know.

Thank you very much!!
Stephanie
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