[Eeglablist] Problem processing EEG signals
tiago.lopes56 at yahoo.com
Fri Mar 3 04:30:43 PST 2017
Dears EEGLAB list,Hope you all are doing well.I am having a problem processing EEG signals of individuals with chronic pain. That's why I would like to know if you ever had a similar issue at your laboratory.
I first run a script to: establish the sampling rate (600 Hz), filter the data (.5 - 40 Hz) and re-ref them to the mean of all 30 electrodes we used, define channel locations, divide files in epochs (1280 ms), run ICA, and remove components 1 and 2.
When I run a second script to remove epochs by amplitude (+/- 750 microV), I have the problem of rejecting different number of epochs for some files when compared to my colleague analyzing the same data.
My colleague (Researcher A) and I are using the same version of Matlab (2014a) and EEGlab (13.6.5b). We are also using the same scripts. Note that when I say the same script, it really is the SAME in EVERYTHING. We checked line by line and confirmed that the commands written in one script is written exactly in the same way on the other. The only difference is the path to open the files (same files, of course).
However, when we reject epochs, there are differences in some of the files. For instance, for one file, while the Researcher A gets 1 epoch rejected, I get 5 epochs rejected. What would be the explanation for this?
We thought it was an error in data manipulation. Then we run the script in DEBUG mode to find possible differences in the variables generated by the scripts. We did that simultaneously and did not find any differences among our variables.
Then I ran that same file on the third computer with MATLAB 2015 and it rejected a different number of epochs than we had rejected (for that file that she rejected 1 and I rejected 5, third computer rejected 6).Other examples of inconsistency for the number of epochs rejected:A) Researcher A rejects 27 epochs, I reject 26 epochs, third COMPUTER rejects 27 epochs.B) Researcher A rejects 4 epochs, I reject 5 , third COMPUTER rejects 6.B) Researcher A rejects 40 epochs, I reject 45, third COMPUTER rejects 45.D)Researcher A rejects 60 epochs, I reject 60, third COMPUTER 60 epochs. (for several files we all reject the same number of epochs) Have you ever had this problem at your lab?If yes, how did you solve it? If not, would you have any insights about what could be happening? What would be your advice about this problem? Tiago Lopes, MSHealth Sciencies Institute - Federal University of Bahia Att. Tiago Lopes
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