[FieldTrip] Negative values with debiased weighted phase lag index

Shephard, Elizabeth elizabeth.1.shephard at kcl.ac.uk
Fri Feb 17 12:05:54 CET 2017

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 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

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