[FieldTrip] Calculation of significant spike-LFP phase-locking (pairwise phase-consistency) from a surrogate distribution

[Daniel Hähnke]

Dear Fieldtrip community,

I would like to calculate significant spike-LFP phase-locking against a randomly shuffled surrogate null distribution, to find significantly locked electrode pairs. As a measure for phase-locking I use the pairwise phase-consistency (PPC0).

However, I am not quite clear as to what I should be shuffling to get the surrogate distribution. The input to ft_spiketriggeredspectrum_stat is the spike-triggered spectrum from ft_spiketriggeredspectrum (let’s say this structure is named STS).
Nothing changes in the PPC values if I shuffle the sequence of STS.time or STS.trial. This is a bit odd, as I am not computing PPC for the entire trial, and changing the spike timing should at least have some impact.

So now all I can think of is either shuffling the imaginary part of STS.fourierspctrm to generate random phases OR shuffling the trial sequence of spikes or LFPs prior to computing the spike-triggered spectrum. The latter of course will be very computationally demanding.

Any ideas?

Best wishes,

Daniel
--
Daniel Hähnke
PhD student

Technische Universität München
Institute of Neuroscience
Translational NeuroCognition Laboratory
Biedersteiner Straße 29, Bau 601
80802 Munich
Germany

Email: daniel.haehnke at lrz.tum.de
Phone: +49 89 4140 3356

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