[FieldTrip] source statistics, group level

[Sonja Suntrup]

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