[Eeglablist] facial EMG

[Makoto Miyakoshi]

Dear Stephanie,

>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.

Probably you don't need to enter anything there. Just import the data and
run average reference (which subtracts the mean of your two channels from
each channel's data).

>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)

Try this: suppose you have channel 1 and channel 2 and perform ch1-ch2 and
store the result to ch1,

EEG.data(1,:) = EEG.data(1,:)-EEG.data(2,:);
Just in case, save the dataset immediately after this process and load the
data for further analysis.

>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.

Yes it should work. Type 'help abs' and you'll find more explanation.

Makoto

2013/3/8 Stephanie Chen <sdeochen at umich.edu>

> 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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-- 
Makoto Miyakoshi
JSPS Postdoctral Fellow for Research Abroad
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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