[Eeglablist] BrainVision files

[Gregor Volberg]

Dear Lars,

I cannot answer your second question, but I had similar problems with reading 
large files (~ 2.5 GB, 5000Hz sampling rate) from combined EEG/fMRI 
recordings. You might  get it working with the following tricks:

(1) I moved from a 32-bit windows to 64-bit Linux and added RAM (8 GB; 16 GB 
would be ideal but the mainboards of our standard Dell computers do not 
support this). I also tried out the performance on the same hardware with a 
dual boot (Windows/Linux) setup and found that the Linux system produced 
generally less out-of-memory errors. 

(2) Even with the 8GB RAM/64bit Linux I could not read in the whole 2.5 GB 
*eeg file. I used the pop_loadbv function to read in slices of of data 
(corresponding to our experimental blocks), performed the gradient artifact 
correction, and then downsampled and re-merged the slices. If the are 
reasonable cut-points in your data, e. g. pauses between blocks, you might 
use a similar strategy. Cut-points might be identified by reading in only the 
header file, without data, and then look for an adequate sample point range. 

info = read_event('eh_w_22_l.vmrk') % reads in an event structure
% then identify reasonable sample 

EEG = pop_loadbv(path, file, [start1 stop1]); %read in slice
EEG = pop_fmrib_fastr(EEG,0,4,21,'R128',1,0,0,0,0,0.0125,[],'auto');
EEG = pop_resample(EEG, 500);
[EEG ALLEEG] = pop_saveset(EEG, 'filename', 'slice1.set', 'filepath', 
filepath);

Finally, merge the slices with pop_mergeset (or via the eeglab GUI).

Hope that helps,
Gregor


Am Mittwoch, 28. Oktober 2009 16:34 schrieb Michels Lars:
> Dear EEGlab members,
>
>
>
> I am currently performing a MR gradient correction for simultaneously
> recorded EEG-fMRI data in EEGlab.
>
>
>
> In principle it works, however, it works only for files with a sampling
> rate well below 5000 Hz. Otherwise I get an error message: Out of memory. I
> thought the correction will work best for files with the (original)
> sampling rate of 5000 Hz. Is there any way to import the large raw file to
> EEGlab (file size is about 600 MB)?
>
>
>
> Second question: There is an option to export the file to BrainVision in
> EEGlab. Does anybody now whether the (exported) file can be read/imported
> in BrainAnalyzer?
>
>
>
> Best
>
> Lars
>
>
>
> Dr. phil. Lars Michels
> Postdoctoral Fellow
> Universitäts-Kinderspital
> Steinwiesstrasse 75
> 8032 Zürich
> Tel.  0041 44 266 78 28
> Fax  0041 44 266 71 53
> http://www.kispi.uzh.ch/af/ForschungLehre/zentrum_de.html

-- 
Dr. rer. nat. Gregor Volberg <gregor.volberg at psychologie.uni-regensburg.de>
Institute for Experimental Psychology
University of Regensburg
Universitätsstraße 31
D-93053 Regensburg
Germany
Tel: +49 941 943 3862 
Fax: +49 941 943 3233
http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html
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