[Eeglablist] Problem processing ​EEG signals

tiago lopes tiago.lopes56 at yahoo.com
Mon Feb 27 09:17:16 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 script​s​. Note that when I say the same script, it really is the SAME in EVERYTHING. We check​ed​ line by line and confirm​ed​ 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​. W​hat ​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 difference​s​ in the variables generated by the scripts. W​e did that simultaneously and ​did not find any differences among our variables. Then I ran th​at 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
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