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

Sat Apr 20 08:08:27 CEST 2013

>
> Hi Jorn,
>
          Thanks for your response . It is Within subjects experiments
 design. The result remains same because the design doesn't change . They
are only  just different expression on the source statistic comparing to
sensor statistic on group level on FT tutorial.
       In my data, the cluster randomization picks something funny and
doesn't make sense while  the difference plots  is more informative and
more consistent with the topos. Technically speaking - the cluster
randomization does not test for location , but only if there is a
difference or not - thus the clusters should be interpreted with caution.
 Therefore  ,  I think about trying another statistic method as well
although  cluster randomization is wildly used within donders institute .
 Do you have any suggestion?
                                               Best,
                                               Haiteng


On 19 April 2013 11:35, <fieldtrip-request at science.ru.nl> wrote:

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> Today's Topics:
>
>    1. Re: Source statistic doesn't match grand average difference
>       at all and prior knowledge (J?rn M. Horschig)
>
>
>
----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 19 Apr 2013 11:35:44 +0200
> From: "J?rn M. Horschig" <jm.horschig at donders.ru.nl>
> To: FieldTrip discussion list <fieldtrip at science.ru.nl>
> Subject: Re: [FieldTrip] Source statistic doesn't match grand average
>         difference at all and prior knowledge
> Message-ID: <51710FF0.5040904 at donders.ru.nl>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> 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,
> J?rn
>
> 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
>
>
> --
> J?rn 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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-- 
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/
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