[FieldTrip] computing threshold for PLV

[Sheraz Khan]

Most of the previois discussion targeted toward event related plv for
continous data may be look at Hipp 2012 Nature Neuroscience orthogonal
correlation paper
On May 18, 2013 3:42 PM, "Subramaniam Iyer" <eeguser at hotmail.com> wrote:

>  Dear FT Experts
>
> Thank you for your inputs. I should add here that I have continuous EEG
> data (so effectively single trial). The way I am computing PLV is by
> dividing my data into windows of 2 seconds each and computing PLV for each
> window and then I finally average the PLV values of all the windows.
>
> So when we talk of shuffling trials, in my case should i consider each of
> 2 second window as a trial ? Sorry if this sounds stupid as I am new to
> this kind of analysis.
>
> ------------------------------
> From: smoratti at psi.ucm.es
> Date: Sat, 18 May 2013 20:11:11 +0200
> To: fieldtrip at science.ru.nl
> Subject: Re: [FieldTrip] computing threshold for PLV
>
> Dear Sheraz,
>
> You might consult the following article: Lachaux, J. P. et al. 1999.
> Measuring Phase Synchrony in Brain Signal. Human Brain Mapping 8: 194-208.
> In principle you have to create surrogate data that represent the null
> hypothesis that there is no phase locking between your electrodes, sources,
> etc. Then you create hundreds or thousands of surrogate data sets and
> calculate each time you PLV. That way you create a distribution of your PLV
> values under the Null hypothesis. Then you check in what percentile your
> observed PLV lies (e. g. if its beyond the 95% percentile you would reject
> the Null hypothesis).
>
> Hope that helps,
>
> Stephan
>
>
>
> ________________________________________________________
> Stephan Moratti, PhD
>
> see also: http://web.me.com/smoratti/
>
> Universidad Complutense de Madrid
> Facultad de Psicología
> Departamento de Psicología Básica I
> Campus de Somosaguas
> 28223 Pozuelo de Alarcón (Madrid)
> Spain
>
> and
>
> Center for Biomedical Technology
> Laboratory for Cognitive and Computational Neuroscience
> Parque Científico y Tecnológico de la Universidad Politecnica de Madrid
> Campus Montegancedo
> 28223 Pozuelo de Alarcón (Madrid)
> Spain
>
>
> email: smoratti at psi.ucm.es
> Tel.:    +34 679219982
>
> El 18/05/2013, a las 18:21, Subramaniam Iyer escribió:
>
> Dear FT Experts,
>
> I have calculated PLV for a set of EEG data from 5 different patients. Now
> I want to convert the PLV matrix of each patient into a binary matrix. For
> this I need a threshold PLV value below which I can assume the phase
> locking is zero.
> My question is, how do I compute this threshold. I know hard thresholding
> is one option ( for ex setting 0.1 or 0.2 as threshold), but I guess it is
> not a very good option.
>
> Can somebody suggest a better and robust (statistical) way of determining
> the threshold ?
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