On cross-frequency phase-phase coupling between theta and gamma oscillations in the hippocampus
Abstract
Phase-amplitude coupling between theta and multiple gamma sub-bands is a hallmark of hippocampal activity and believed to take part in information routing. More recently, theta and gamma oscillations were also reported to exhibit phase-phase coupling, or n:m phase-locking, suggesting an important mechanism of neuronal coding that has long received theoretical support. However, by analyzing simulated and actual LFPs, here we question the existence of theta-gamma phase-phase coupling in the rat hippocampus. We show that the quasi-linear phase shifts introduced by filtering lead to spurious coupling levels in both white noise and hippocampal LFPs, which highly depend on epoch length, and that significant coupling may be falsely detected when employing improper surrogate methods. We also show that waveform asymmetry and frequency harmonics may generate artifactual n:m phase-locking. Studies investigating phase-phase coupling should rely on appropriate statistical controls and be aware of confounding factors; otherwise, they could easily fall into analysis pitfalls.
Data availability
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Multisite LFP recordings from the rat hippocampus during REM sleepAvailable at Dryad Digital Repository under a CC0 Public Domain Dedication.
Article and author information
Author details
Funding
Conselho Nacional de Desenvolvimento Científico e Tecnológico
- Robson Scheffer-Teixeira
- Adriano BL Tort
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
- Robson Scheffer-Teixeira
- Adriano BL Tort
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Frances K Skinner, University Health Network, Canada
Ethics
Animal experimentation: All procedures were approved by our local institutional ethics committee (Comissão de Ética no Uso de Animais - CEUA/UFRN, protocol number 060/2011) and were in accordance with the National Institutes of Health guidelines.
Version history
- Received: August 10, 2016
- Accepted: December 5, 2016
- Accepted Manuscript published: December 7, 2016 (version 1)
- Version of Record published: December 29, 2016 (version 2)
Copyright
© 2016, Scheffer-Teixeira & Tort
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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