How do i create a common channel file?

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11

Hi Josh,

Looking at the subjects you sent me, I would do the following:

  1. Update Brainstorm: I just posted a few more modifications that will help you understand what is happening
  2. Delete all the files in (Global common files) and (Inter-subject) because what is in there is all messed up, the files where not standardized correctly before averaging.
  3. Fix the sampling rate:
    3.1) Chose only one sampling rate for all the subjects because you’re not going to be able to average files with different sampling rates.
    3.2) Delete all the subjects for which the sampling rate is different.
    3.3) Resample all your files at the same sampling rate (eg. 1000Hz). You need to resample the continuous files, resampling the short epochs would lead to inaccurate results. You can do this either with your acquisition software or with Brainstorm, following the guidelines in the “EEG & epilepsy” tutorial (import full file, process, epoch): http://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy
    3.4) Re-import the correctly sampled files
  4. Delete the folders containing the “Link to raw file”, because they cannot be fixed with the process “Standardize > Uniform list of channels”
  5. Make a copy of your database, just in case something bad happens
  6. Drag all the files from all the subjects to the Process1 tab, and run “Standardize > Uniform list of channels”, and select the option “keep only the common files” (see the two attached screen captures)

A few additional recommendations (that require you start everything over):

  1. I would recommend you band-pass filter the entire continuous file BEFORE you epoch and import it. Filtering small epochs leads to important edge effects, those filters perform much better on long time signals. You can do this either with your acquisition software or with Brainstorm.
  2. When running this band-pass filter, you can add a high-pass filter at 0.5Hz, to get rid of the slow fluctuations in the recordings. This way you also don’t have to select the option “Remove DC offset”
  3. I noticed most of your files contain strong power line contamination. You should run the sinusoid removal process to get rid of the 50Hz contamination before you apply any other filter, as illustrated in the introduction tutorials: http://neuroimage.usc.edu/brainstorm/Tutorials/TutRawSsp

Cheers,
Francois