[FieldTrip] source statistics, group level

[jan-mathijs schoffelen]

Hi Sonja

I think you are almost there. What I am not sure about is the name of the field in the grandaverage structure which contains the concatenated individual subject data. Isn't this field called '.trial'? In that case you should specify cfg.parameter to be 'trial'. If this is not the cause of the problem, did you check the individual subject volumes? Do these contain colored data? What do you exactly mean by getting a blank mri? Does the stat.stat field contain only zeros, nans or something else?

Best,

Jan-Mathijs

On Dec 2, 2011, at 12:16 PM, Sonja Suntrup wrote:

> Dear fieldtrip users,
> I would like to do sourcestatistics on a group level with meg data. I have a
> pre and post intervention measurement for each of my 21 subjects
> (within-subjects design). After source reconstruction using an LCMV beamformer
> and volume normalization I calculated the sourcegrandaverage for the pre and
> post condition with the parameter cfg.keepindividual = 'yes'.
> However, when I use the grandaverage results in ft_sourcestatistics in the
> configuration shown below and plot the result I just get a blank anatomical
> mri. Do I have to set any additional parameters or do I make a general
> mistake? Whould you recommend to use a cluster-based permutation test
> comparable to ft_timelockstatistics and would I have to set the same
> parameters in ft_sourcestatistics then?
> 
> cfg=[];
> cfg.dim         = grandAVGsourcePre.dim;
> cfg.method      = 'montecarlo';
> cfg.statistic   = 'depsamplesT';
> cfg.parameter   = 'avg.pow';
> cfg.correctm    = 'cluster';
> cfg.numrandomization = 100;
> cfg.alpha       = 0.05;
> cfg.tail        = 0;
> 
> nsubj=length(sourcePre.trial);
> cfg.design(1,:) = [1:nsubj 1:nsubj];
> cfg.design(2,:) = [ones(1,nsubj) ones(1,nsubj)*2];
> cfg.uvar        = 1;
> cfg.ivar        = 2;
> stat = ft_sourcestatistics(cfg, grandAVGsourcePre, grandAVGsourcePost);
> 
> Your help is greatly appreciated!
> Best,
> Sonja
> 
> 
> -- 
> Dr. med. Sonja Suntrup
> Institute for Biomagnetism and Biosignalanalysis
> University of Muenster
> Malmedyweg 15
> 48149 Münster, Germany
> 
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Jan-Mathijs Schoffelen, MD PhD 

Donders Institute for Brain, Cognition and Behaviour, 
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands

Max Planck Institute for Psycholinguistics,
Nijmegen, The Netherlands

J.Schoffelen at donders.ru.nl
Telephone: +31-24-3614793

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