[FieldTrip] Source statistic doesn't match grand average difference at all and prior knowledge

["Jörn M. Horschig"]

Dear Haiteng,

I think in the example the design matrix is wrongly computed. If you 
compare the single and the group-level example, it is described exactly 
the same, which does not make much sense. Afaik it should be this 
instead (analogue to freq statisics on group level):

/subj = numel(sourceA.trial);
design = zeros(2,2*subj);
for i = 1:subj
   design(1,i) = i;
end
for i = 1:subj
   design(1,subj+i) = i;
end
design(2,1:subj)        = 1;
design(2,subj+1:2*subj) = 2;
/
Let me know if this makes things better (not in today, working from 
home, so better reply to this lis).

Best,
Jörn

On 4/19/2013 10:25 AM, Haiteng Jiang wrote:
> Hi FTer,
>    I am  doing Cluster-based permutation statistic  after 
> beamforming on two condition over subjects following the tutorial 
> http://fieldtrip.fcdonders.nl/example/source_statistics, but I get 
> something funny.
>  In my case , I would expect decreased activity in  the visual and 
> posterior area.  The effect is quite strong, which  is showed in the 
> grand average  difference (log ratio to reduce inter subject 
> variability).  However ,  from the statistic ,  the identified areas 
> go to  the temporal area , which doesn't make sense at all .   Please 
> see the below and attached  pictures.    I understand cluster-based 
> permutation  test doesn't necessary pick the peak difference, but  in 
> general it should find main different area.  Any comment would be 
> greatly appreciated.
>
> Average:
>
> Inline images 2
>
>
>
> Statistic:
> Inline images 1
>                Best,
>                Haiteng
>
> -- 
> Haiteng Jiang
> PhD candidate
> Neuronal Oscillations Group
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognitive Neuroimaging
> Radboud University Nijmegen
>
> Visiting address
> Room 2.32
> Donders Centre for Cognitive Neuroimaging
> Kapittelweg 29
> 6525 EN  Nijmegen
> the Netherlands
>
>  Tel.: +31 (0)243668291
>  Web: https://sites.google.com/site/haitengjiang/
>
>
> _______________________________________________
> fieldtrip mailing list
> 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:
E-Mail: jm.horschig at donders.ru.nl
Tel:    +31-(0)24-36-68493
Web: http://www.ru.nl/donders

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands

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