[FieldTrip] Negative values with debiased weighted phase lag index

Julian Keil julian.keil at gmail.com
Fri Feb 17 12:10:17 CET 2017

Dear Lizzie,

this comes up from time to time on the Mailinglist.
Check for example this response by Martin Vinck:

Quote: The debiased WPLI estimator gets negative however as a consequence of the debiasing method - different issue.



Am 17.02.2017 um 12:05 schrieb Shephard, Elizabeth:

> Dear all
> I am using FieldTrip to explore connectivity in resting-state EEG data and aimed to use the debiased weighted phase lag index (dwPLI) to index this. However, I am finding a lot of negative values in my connectivity matrices when I compute the dwPLI, and I am unsure why this might be - has anyone found this previously, or have an idea of why this might be happening? I do not get this if I compute other connectivity measures (e.g. coherence) and I have a decent amount of clean trials (around 80 per subject) on which to run the connectivity. I am computing the dwPLI from fourier coefficients exported from a straightforward FFT.
> Many thanks in advance for any advice
> Best wishes
> Lizzie
> ---------------------------------------------------------------------------
> Lizzie Shephard, PhD
> Postdoctoral researcher
> 2.21 MRC SGDP Centre
> Institute of Psychiatry, Psychology, & Neuroscience
> King’s College London
> De Crespigny Park
> London, SE5 8AF
> 0207 848 5272
> elizabeth.1.shephard at kcl.ac.uk
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> https://mailman.science.ru.nl/mailman/listinfo/fieldtrip

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