[FieldTrip] connectivity analysis with rereferenced EEG data

[Victoria Schröder]

Thank you very much Jörn!

Have a nice day
Best
Victoria

2014-01-06 09:21 skrev Jörn M. Horschig:
> Hi Victoria,
>
> exactly, since the rank of your matrix is reduced, you need to remove
> one channel from your data before computing the connectivity. I am 
> not
> sure whether it is best to compute EEG-connectivity with
> average-referenced data or with a single channel reference. In case 
> of
> a single-channel reference, you can of course remove the reference
> channel, so that'd be the easiest in that sense. Maybe check
> http://www.ncbi.nlm.nih.gov/pubmed/10619414 and related papers and
> decide for yourself how to reference ;)
>
> Best,
> Jörn
>
>
> On 1/3/2014 4:38 PM, Victoria Schröder wrote:
>> Hello
>>
>> I am trying to do a connectivity analysis with Fieldtrip. I recorded 
>> the EEG data with a BioSemi system without choosing a reference 
>> channel.
>> Thus i need to select a reference in Fieldtrip. I did that during 
>> ft_preprocessing(cfg) by using the following code:
>> cfg.reref='yes';
>> cfg.refchannel='all';
>> Data=ft_preprocessing(cfg);
>>
>> however when i later want to do the ft_mvaranalysis(cfg, Data) i get 
>> the following error:
>> Matrix must be positive definite
>>
>> I read that this error probably occurs because the cfg.reref 
>> procedure changes the ranks of the data matrix.However, i need to 
>> rereference my data.
>>
>> Do somebody know a solution?
>>
>> All the best and thank you in advance
>> Victoria
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>> fieldtrip at donders.ru.nl
>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
> --
> Jörn M. Horschig
> PhD Student
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognitive Neuroimaging
> Radboud University Nijmegen
> Neuronal Oscillations Group
> FieldTrip Development Team
>
> P.O. Box 9101
> NL-6500 HB Nijmegen
> The Netherlands
>
> Contact:
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