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

Daniel Hähnke daniel.haehnke at lrz.tu-muenchen.de
Tue Sep 15 12:10:30 CEST 2015

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 Hähnke
PhD student

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

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

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