Non parametric test on coherence

Wed Apr 28 23:50:29 CEST 2010

Hi Matteo,

There is an old thread on the FT discussion list about the details of
coherence testing using indepsamplesZcoh combined with clustering. You can
find it via the FT homepage.

Best,

Eric

dr. Eric Maris
Donders Institute for Brain, Cognition and Behavior

Center for Cognition and F.C. Donders Center for Cognitive Neuroimaging

Radboud University
P.O. Box 9104
6500 HE Nijmegen
The Netherlands
T:+31 24 3612651
Mobile: 06 39584581

F:+31 24 3616066
E: e. <mailto:e.maris at donders.ru.nl> maris at donders.ru.nl

From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of jan-mathijs schoffelen
Sent: woensdag 28 april 2010 14:05
To: FIELDTRIP at NIC.SURFNET.NL
Subject: Re: [FIELDTRIP] Non parametric test on coherence

Hi Matteo,

As far as I know, the indepsamplesZcoh only works properly if you compute
your TFR using ft_freqanalysis with cfg.output = 'fourier'.

Note that the output of the statistics-function probably gives differential
coherence spectra between all pairs of channels. The clustering will in this
case not work, because the spatial channel neighbourhood structure supported
to my knowledge only works with univariate test-statistics. This means that
you shouldn't specify cfg.correctm = 'cluster'.

Cheers,

Jan-Mathijs

On Apr 28, 2010, at 1:57 PM, Matteo Demuru wrote:

Dear Eric,

I have tried the between-trials experiment too, but the two problems still
remain (the statfun_indepsamplesZcoh looks for label field. Furtheremore if
I add it the reshape function crashes). Any other suggestions?

I have also another question relative to your reply: the baseline and
activation trials were already divided in the within-trials experiment, the
only difference with the between-trials experiment are relative to the
configuration parameters (i.e.  in between-trials only cfg.ivar is set while
in within-trials cfg.ivar and cfg.uvar are set) am I wrong?

Regarding the 'label field' problem, it seems a required field for the
configuration struct because it is used in statfun_indepsamplesZcoh to
calculate the channel combinations for the coherence.

Thanks a lot

Matteo

On Wed, Apr 28, 2010 at 9:17 AM, Eric Maris <e.maris at donders.ru.nl> wrote:

Dear Matteo,

The statfun indepsamplesZcoh can only be used in a between-trials
experiment. You could cut out your baseline and activation segments
separately and then compare them in a non-paired fashion.

Best,

Eric

From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Matteo Demuru
Sent: dinsdag 27 april 2010 16:21
To: FIELDTRIP at NIC.SURFNET.NL
Subject: [FIELDTRIP] Non parametric test on coherence

Dear all,

I have a problem using freqstatistics to calculate significance for
coherence.

Specifically I have a subject and I am performing a within-trials experiment
using 'indepsamplesZcoh' as statistic.

I calculate the TFR of my data with the cfg.output='powandcsd' and
cfg.keeptrials='yes' parameters. Then I call freqstatistics to compare my
different experimental conditions (baseline vs activation).

The function crashes with this output:

??? Reference to non-existent field 'label'.

Error in ==> statfun_indepsamplesZcoh at 76

  nchan = length(cfg.label);

I have tried to add this field to the cfg struct assigning the cell that
contains the interested channels. However this time I have another error:

??? Error using ==> reshape

To RESHAPE the number of elements must not change.

Error in ==> clusterstat at 178

      posclusobs = findcluster(reshape(postailobs,
[cfg.dim,1]),channeighbstructmat,cfg.minnbchan);

Any suggestions?

Thanks in advance

Matteo Demuru

----------------------------------

The aim of this list is to facilitate the discussion between users of the
FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
EEG analysis.

http://listserv.surfnet.nl/archives/fieldtrip.html

http://www.ru.nl/fcdonders/fieldtrip/

----------------------------------

The aim of this list is to facilitate the discussion between users of the
FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
EEG analysis.

http://listserv.surfnet.nl/archives/fieldtrip.html

http://www.ru.nl/fcdonders/fieldtrip/

----------------------------------

The aim of this list is to facilitate the discussion between users of the
FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
EEG analysis.

http://listserv.surfnet.nl/archives/fieldtrip.html

http://www.ru.nl/fcdonders/fieldtrip/

Dr. J.M. (Jan-Mathijs) Schoffelen

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

J.Schoffelen at donders.ru.nl

Telephone: 0031-24-3668063

----------------------------------

The aim of this list is to facilitate the discussion between users of the
FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
EEG analysis.

http://listserv.surfnet.nl/archives/fieldtrip.html

http://www.ru.nl/fcdonders/fieldtrip/

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.
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