[Eeglablist] Help with Channel locations and ICA for 32-channel BrainVision data?

[Natalie Prowse]

Hi,


We're trying to process 32-channel Brain Vision files in EEGLab, but are running into an issue in ICA where the component headmaps all look the same, so I'm not sure if it's an issue with the ICA or with the electrode channel file we are using.

Here is an example ICA plot and the electrode .ced file.

https://dl.dropboxusercontent.com/u/47453764/ICA-HEADMAPS-32CH.png?

https://dl.dropboxusercontent.com/u/47453764/32ch_BrainVision.ced


 I'm open to any suggestions as to what to do.   We DON'T have Brain Vision Analyzer - everything was recorded with Pycorder and exported as .vhdr, .vmrk and .eeg files.


We are using EEGLAB 13_1_1b


Because the events were unfortunately coded with characters and numbers (e.g. "S  8", "S  7" ), I had to read all the data in via small program that calls via pop_loadbv() and then strips the string portion of the event, and merges using pop_mergeset  to produce a single merged .set file.  I cannot seem to get the events to be properly recognized if I use pop_biosig to read the files.


I read in another post that said you don't need a channel location file if you are bringing data in from BrainVision Analyzer, but we don't have the Analyzer software - we only use pycorder.  To get the .CED file I loaded a text .elp with just the channel numbers and names, used the "Look up locs" button in EEGLAB and applied the "Use BESA file for 4-shell dipfit spherical model". I am REALLY new to this so I'm not sure that this was the right thing to do at all.  Can someone please help out with either recommendations on how to get the correct locations for BV data that DOESN'T come from the Analyzer software?


Many thanks,

-Natalie
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