Dissociating harmonic and non-harmonic phase-amplitude coupling in the human brain
Janet Giehl1, Nima Noury1, Markus Siegel2
1Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; Centre for Integrative Neuroscience, University of Tübingen, Germany; MEG Center, University of Tübingen, Germany; IMPRS for Cognitive and Systems Neuroscience, University of Tübingen, Germany.
Neuroimage
|December 18, 2020
Summary
Researchers found widespread phase-amplitude coupling (PAC) in human brain activity, but it was driven by harmonic signals, not non-harmonic interactions. This study clarifies PAC measures and questions its prominent role in resting-state brain activity.
Area of Science:
- Neuroscience
- Brain Activity Analysis
- Signal Processing
Background:
- Phase-amplitude coupling (PAC) is a hypothesized mechanism for coordinating cross-frequency interactions in neuronal activity.
- The distribution and frequency involvement of PAC in the human brain remain largely uncharacterized.
- The extent to which PAC reflects artifacts or harmonic signals is unclear.
Purpose of the Study:
- To systematically characterize local PAC across the resting human brain using MEG and source-reconstruction.
- To differentiate between harmonic and non-harmonic PAC using combined cross-frequency coupling measures.
- To investigate the influence of physiological artifacts and spectral leakage on PAC.
Main Methods:
- Magnetoencephalography (MEG) combined with source-reconstruction techniques.
- Application of multiple cross-frequency coupling measures (phase-amplitude, phase-phase, amplitude-amplitude).
- Systematic characterization of local PAC in the resting human brain.
Main Results:
- All tested cross-frequency measures were sensitive to signals with higher harmonics.
- No evidence for non-harmonic local PAC was found in resting-state MEG.
- Widespread PAC, driven by harmonic signals, was observed across the cortex and spectrum.
- Physiological artifacts and spectral leakage were shown to induce spurious PAC.
Conclusions:
- Different cross-frequency interaction measures can be combined to characterize PAC.
- The study casts doubt on the presence of prominent non-harmonic PAC in human resting-state MEG.
- Observed PAC is largely attributable to harmonic signals and potential artifacts.
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