The pairwise phase consistency: A bias-free measure of rhythmic neuronal synchronization
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1
University of Amsterdam, Netherlands
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2
University of Western Ontario, Canada
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3
Ernst Strungmann Institute, Germany
Oscillatory activity is a widespread phenomenon in nervous systems and has been implicated in numerous functions. Signals that are generated by two separate neuronal sources often demonstrate a consistent phase-relationship in a particular frequency-band, i.e. they demonstrate rhythmic neuronal synchronization. This consistency is conventionally measured by the PLV (Phase-Locking Value) or the spectral coherence measure. Both statistical measures suffer from significant bias, in that their sample estimates overestimate the population statistics for finite sample sizes. This is a significant problem in the neurosciences where statistical comparisons are often made between conditions with a different number of trials, or between neurons with a different number of spikes. We introduce a new circular statistic, the PPC (pairwise phase consistency). We demonstrate that the sample estimate of the PPC is a bias-free and consistent estimator of its corresponding population parameter. Our numerical simulations show that the population PPC is linearly related to the population PLV for a large range of PLVs. The variance and mean squared error of the PPC and PLV are compared. A procedure is proposed to weigh phases by the signals’ amplitudes to obtain a more robust measure of phase consistency, while avoiding the influence of amplitude co-variations, which is a known problem for the coherence measure. Finally, we demonstrate the practical relevance of the method in actual neuronal data recorded from the orbitofrontal cortex of rats that engage in a 2-odour discrimination task. We find a strong increase in rhythmic synchronization of spikes relative to the Local Field Potential (as measured by the PPC) for a wide range of low frequencies (including the theta-band) during the anticipation of sucrose delivery in comparison to the anticipation of quinine delivery.
Conference:
Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010.
Presentation Type:
Poster Presentation
Topic:
Poster session I
Citation:
Vinck
M,
Van Wingerden
M,
Womelsdorf
T,
Fries
P and
Pennartz
C
(2010). The pairwise phase consistency: A bias-free measure of rhythmic neuronal synchronization.
Front. Neurosci.
Conference Abstract:
Computational and Systems Neuroscience 2010.
doi: 10.3389/conf.fnins.2010.03.00070
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Received:
19 Feb 2010;
Published Online:
19 Feb 2010.
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Correspondence:
Martin Vinck, University of Amsterdam, Amsterdam, Netherlands, martinvinck@gmail.com