Coherence differences and factorial designs

[Eric Maris]

Dear Suresh,



>     In a fixed effects context I have been obtaining coherence
> estimates. I have been reading Maris et al 2007 and the theory there
> describes how to test between two different conditions
> I would like to extend the theory in that paper (2.7.1) to k sample
> (one factor eg 1 x 3 ANOVA) and two-way (e.,g. 2 x 2 designs). I was
> wondering if anyone had attempted such a thing if it can be done, and
> in particular how one might go about constructing an apprppriate test
> statistic and surrogate distribution? Prior implementation in fieldtrip
> isnt needed its more the theory behind it I am asking about

Statistical comparison of coherence estimates in k samples is discussed by
Amjad et al (2007) in J. Neurosc. Methods.

In the permutation framework there is no analogue of the factorial ANOVA
(involving both main and interaction effects) for the simple reason that the
interaction null hypothesis cannot be tested in the permutation framework.
There is at least one thread in the Fieldtrip Discussion list that deals
with this issue. However, it is possible to test multiple conditional null
hypotheses (main effect of one factor separately for each of the levels of
another factor) and this comes close to an interaction effect test.


Good luck,

Eric Maris






> Thanks for your help,
> Dr Suresh Muthukumaraswamy
>
> Suresh Muthukumaraswamy, PhD
> CUBRIC
> Cardiff University
> Park Place
> Cardiff, CF10 3AT
> United Kingdom
> email: sdmuthu at cardiff.ac.uk
> Phone: +44 (0)29 2087 0354
> http://www.cf.ac.uk/psych/contactsandpeople/researchstaff/muthukumarasw
> amy-suresh-dr-overview_new.html
>
> ----------------------------------
> 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.

----------------------------------
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.