Statistical testing of coherence differences

Eric Maris maris at NICI.RU.NL
Thu Aug 16 10:44:20 CEST 2007

Dear Fieldtrip Discussion List Readers,

I have received several emails froms FT-users who want to statistically test
coherence differences in single subjects. This methodology was described in
a recent paper in the Journal of Neuroscience Methods (Maris, Schoffelen,
and Fries, 2007). To perform the same analysis on your own data using FT,
you should take the following into account:

1. You must use the FT-function clusterrandanalysis. This is the oldest
statistics function in FT, and was written for the most part by Eric Maris.
Robert Oostenveld has recently set up a completely new statistics framework.
However, this framework does not yet contain functionality to do statistical
testing of coherence differences. This is in the pipeline, but at this
moment you still have to use the old clusterrandanalysis.

2. You can test coherence differences for (1) all channel pairs or (2) for
all channel pairs that have a common reference channel. Only the latter
analysis was described in JNM paper and is also the one that was most
extensively tested. I strongly advice you to stick to the reference channel
analysis. Most likely, you will get memory problem with the other option.
>>From now on, I assume that you will be doing a reference channel analysis.

3. The input data for clusterrandanalysis is the output of two freqanalysis
runs, one every experimental condition.

4. cfg.statistic must be 'indepsamplesZcoh'.

5. cfg.channelcmb must contain a Mx2 cell array of pairs of channel labels
that all contain the reference channel.

6. cfg.chancmbgeom must be 'refchan'.

Good luck,

Eric Maris

dr. Eric Maris

NICI/Biological Psychology and

F.C. Donders Center for Cognitive NeuroImaging

University of Nijmegen

P.O. Box 9104

6500 HE Nijmegen

The Netherlands

T:+31 24 3612651 (NICI)

T:+31 24 3610754 (FCDC)

F:+31 24 3616066 (NICI)

E: maris at

MSc Cognitive Neuroscience : <>

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