[Eeglablist] Splitting EEG File in Half After Binning

[Kenneth Peter Bennett]

Hey everyone,

I am trying to compare ERPs from the 1st half to the 2nd half of my task. I have been attempting to do this after binning and artifact detection. Per a previous post from the erplab email list, I tried using the epoch subset assistant from the compute average ERPs operation. However, this requires you to specify the number of trials per bin to keep. The way my data are binned, the number of epochs per bin varies within and between subjects. I just want to simply create a separate ERP for the first half of the epochs (say, epoch 1:1296) and one for the second half of the epochs (1297:2592) - but you cannot do this using the compute average ERPs operation. So, I tried manually splitting the post-artifact detection .set file in eeglab using edit>select data>epoch range, and saving two new .set files for the 1st half and 2nd half. Then, I tried computing average ERPs for each half using erplab. However, after splitting the file the artifact detection information appears to be gone. So, I re-ran artifact detection on these separately and tried computing average ERPs again. This time, a warning occurs informing me that it cannot use the new artifact detection information because it is retaining the old information from before it was split and can only reject those trials. This is likely fine for the 1st half of the trials, but when I split the file in two, the first trial of the 2nd half changes from trial 1297 (for example) to trial 1. If it is applying artifact detection and rejection to this second half using the trial information from the original dataset, the same exact trials/epochs will be rejected for the 1st half and 2nd half, which is a problem.

Does anyone have advice on what to do? There must be a simple way to split the file in half by epochs and get new ERPs. Right? I'm trying to avoid going all the way back in the process to split the original eeg file.

Thanks,
Ken

--

Kenneth Bennett, MS
Fifth Year Clinical Graduate Student
Affective Neuroscience Laboratory
Department of Psychology
University of Wisconsin-Milwaukee
334 Garland Hall


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