[Eeglablist] How to extract EMG onset time

[Ranjan Debnath]

Dear EEG Experts
I was reading old EEGLab archive and found a post related to my problem. (http://sccn.ucsd.edu/pipermail/eeglablist/2008/002456.html). I want to make event marker or trigger out of EMG onset time. I want to plot my data EMG lock. I was visually adding event marker in EEGLab. However, I have read some articles, which reported creating event marker out of EMG onset by algorithm. In reply of the above mentioned post, Brad Voytek also suggested using an algorithmic method for extracting EMG onsets, "as it's much faster, and less likely to be biased." Is there any specific program, software or Plugin for extracting EMG onset time?

I have some questions about EMG data processing:

I have collected EMG data simultaneously with EEG data. While I visually mark the EMG onset, I process them with rest of 32 channels. For example, I change the sampling rate, highpass filter and then scroll the data in eegplot() to mark EMG onset. Then I subtract the two EMG channels to further process rest of the channels. Is this appropriate procedure?? Or alternatively,

Do I need to subtract two EMG channels first and then process them separately to find EMG onset time? Then I import the EMG onset file as event marker or trigger in EEGLab GUI.

Which of the above process should I follow?? Or should I discard both of them?

I highly appreciate your suggestions.

Thanking You

With Regards

Ranjan Debnath
Action, Brain and Cognition Lab
Department of Psychology
University of Otago
Dunedin, New Zealand
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