[Eeglablist] problem getting ICA to run properly on data files

[Andreas Widmann]

Hi Emily,

> Thanks for the response!  I think we have resolved this issue (or figured out a work around, at least).  For some reason I was getting a 'boundary' code at the beginning of my imported EEG files (using the File > Import data > Using EEGLAB functions and plugins > From Brain Vis. rec .vhdr file option), with a duration of 'NaN.‘
The boundary event corresponds to the „New segment“ marker (correctly) set by default by BrainVision Recorder for the first sample of each segment (also the first one) of the recording. This event should not cause any problems for filtering. Also other recording software as e.g. Biosemi ActiView sets these markers (unfortunately the EEGLAB bdfimport plugin does not import them at all, even if the marker is not at the beginning of the file).

> This was causing errors in the filter I was using in ERPLAB related to aligning the sampling points, and this was causing ICA to not run properly.
What kind of problem causes this in the ERPLAB filter? Could you please describe what you mean by „related to aligning the sampling points“?

Thanks,
Andreas

> If I remove this code from the beginning of the data file, everything works normally again.  I'm not sure why this code was appearing (there are no event codes at that time point in the EEG data file, and we did not remove any segments in this time range offline either).  I'm also exploring other import methods, using the suggestions people have been providing in response to my other post.
> 
> Please let me know if you have any additional suggestions.
> 
> Thanks!
> -Emily
> 
> 
> On Wed, Apr 16, 2014 at 11:10 AM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
> Dear Emily,
> 
> I can think of multiple reasons, such as severe rank reduction, huge artifacts, continuous zeros, etc etc... to diagnose it I need to ask you to send me a sample data to reproduce the problem. Are you willing to do it?
> 
> Makoto
> 
> 
> 2014-04-09 16:17 GMT-07:00 Emily Kappenman <eskappenman at ucdavis.edu>:
> Hi all,
> 
> I have been using ICA for some time now to correct eye blink artifacts in EEG data files with lots of success, but I just started using a new EEG system and am running into problems getting ICA to run properly on the files.  I am encountering the following error message: error: runica(): QUITTING - weight matrix may not be invertible!
> 
> This occurs on data files from multiple subjects, of different lengths, with different sampling rates, with different reference sites (both online and offline), etc..  Sometimes ICA will run but will require multiple separate components for eye blinks (5 or 6 out of 31 components).  The number of the components in the list that relate to the eye blinks also seems to correspond to channel numbers in a systematic way (e.g., if FP2 was channel 30 in the data set, component 30 is one of the components, etc.).    
> 
> Has anyone encountered anything like this before or have any ideas what might be causing this?  Any suggestions are much appreciated!
> 
> Thanks so much!
> -Emily Kappenman
> 
> -- 
> --------------------------------------------------------------------
> Emily S. Kappenman, Ph.D.
> UC Davis Center for Mind and Brain
> 267 Cousteau Place
> Davis, CA 95618
> eskappenman at ucdavis.edu
> --------------------------------------------------------------------
> 
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> 
> -- 
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
> 
> 
> 
> -- 
> --------------------------------------------------------------------
> Emily S. Kappenman, Ph.D.
> UC Davis Center for Mind and Brain
> 267 Cousteau Place
> Davis, CA 95618
> eskappenman at ucdavis.edu
> --------------------------------------------------------------------
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