# [Eeglablist] Hilbert

Sazonov, A.V. A.Sazonov at tue.nl
Tue Nov 1 23:36:20 PST 2005

```Dear Peter,

There are plenty or articles about phase locking. You could look it up in:

Tass, P., Rozenblum, M. G., Weule, J., Kurths, J., Pikovsky, A., Volkmann, J., Schnitzler, A., and Freund, H.-J., "Detection of n:m phase locking from noisy data: application to magnetoencephalography," Phys.Rev.Lett., vol. 81, no. 15, pp. 3291-3294, Oct.1998.

and in several other articles from Pikovsky and Rosenblum. There is also a book chapter from them about this matter (unfortunately I forgot the title, but you can search for it using the names).

Technically, you can transform data by using standard hilbert() function in Matlab. The output is the analytical signal which is complex-valued and has some special properties. The instantaneous phase of a complex-valued signal can be computed by angle() or imag(log()). Then you may want to quantify the phase difference by using the phase locking index gamma:

gamma = abs(mean(exp(i*PhaseDiff)));

However, there are other indices for that as well. It is advised to narrow band filter data, and to take care of boundary effects when you cut it into epochs . All this things are described in literature.

The best way to use this method is when you are interested in phase relationships rather than in amplidutes. It can be usefull when you study (chaotic) oscillatory systems.

Regards,

Andrei

-----Oorspronkelijk bericht-----
Van: eeglablist-bounces at sccn.ucsd.edu namens Lin, Peter (NIH/NINDS) [F]
Verzonden: di 1-11-2005 20:18
Aan: eeglablist at sccn.ucsd.edu
CC:
Onderwerp: [Eeglablist] Hilbert

Hi I am working with movement data (finger abduction and sequence) with EEG and studying phase lag and coherence.  Is there any way to use EEGlab to Hilbert transform the data?  What is the best way to study phase locking using this technique?  Any help would be appreciated…

Thanks

peter

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