[FieldTrip] phase synchronisation

[Hwee Ling Lee]

Dear all,

I'm a bit confused with the computation of phase synchronisation.

What I'm interested is to compute the phase synchronisation changes in the
second session (i.e. 1 year later) with respect to the first session. There
are 64 EEG channels in my data. I'm interested to compute the mean phase
coherence index.

>From the tutorial on 'analysis of sensor and source level connectivity, it
seems to me one has to first compute the multivariate autoregressive model,
follow by the spectral density function, follow by non-parametric
computation of the cross spectral density function and finally the
connectivity measures. However, when I tried to compute the multivariate
autoregressive model as suggested, I get an error message:

Error using chol
Matrix must be positive definite.

Error in armorf (line 40)
ap(:,:,1) = inv((chol(ap(:,:,1)/Nr*(Nl-1)))');

Error in ft_mvaranalysis (line 395)
            [ar, tmpnoisecov] = armorf(dat, numel(rpt{rlop}),
size(tmpdata.trial{1},2), cfg.order);

Can someone help me?

Thanks!

Cheers,
Hweeling
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