Phase synchronization between alpha and beta oscillations in the human electroencephalogram

doi:10.1016/j.neuroscience.2005.10.031

Neuroscience

Volume 137, Issue 2, 2006, Pages 647-657

https://doi.org/10.1016/j.neuroscience.2005.10.031 Get rights and content

Abstract

Coordination of neuronal oscillations generated at different frequencies has been hypothesized to be an important feature of integrative brain functions. The present study aimed at the evaluation of the cross-frequency phase synchronization between electroencephalographic alpha and beta oscillations. The amplitude and phase information were extracted from electroencephalograms recorded in 176 healthy human subjects using an analytic signal approach based on the Hilbert transform. The results reliably demonstrated the presence of phase synchronization between alpha and beta oscillations, with a maximum in the occipito-parietal areas. The phase difference between alpha and beta oscillations showed characteristic peaks at about 2 and −1 radians, which were common for many subjects and electrodes. A specific phase difference might reflect similarity in the organization and interconnections of the networks generating alpha and beta oscillations across the entire cortex. Beta oscillations, which are phase-locked to alpha oscillations—alpha-synchronous beta oscillations—were largest in the occipito-parietal area with a second smaller maximum in the frontal area, thus demonstrating a topography, which was different from the conventional alpha and beta oscillations. The strength of the alpha-synchronous beta oscillations was not exclusively defined by the amplitude of the alpha rhythm indicating that they represent a distinct feature of the spontaneous electroencephalogram, which allows for a refined discrimination of the dynamics of beta oscillations.

Section snippets

Subjects

Healthy subjects (n=176, mean age 36.9 years, range 14.3–65.5 years; 95 males and 81 females) without history of neurological or psychiatric disorders were recruited randomly by the aid of the Swedish population register. During the experiment the subjects were in a semi-supine position and were instructed to relax and keep their eyes closed. Every 60 s the technician asked the subjects to open their eyes for 5 s and then to close their eyes again, but apart from this instruction the subjects

1:2 Phase synchronization

The mean peak frequencies of the alpha and beta oscillations, averaged across all subjects and electrodes, were 9.6±0.02 and 19.1±0.05Hz (mean±standard error of mean), respectively. The mean beta/alpha frequency ratio was 2.0±0.01 when calculated separately for each subject and electrode.

In 98% of all data sets (19 electrodes×176 subjects) the distribution of the cyclic relative phase was significantly different (P<0.05) from the uniform distribution (Kolmogorov-Smirnov test), thus

Factors contributing to phase synchronization between alpha and beta oscillations

Data obtained from a large number of normal subjects reliably showed the presence and topographic specificity of phase synchronization between alpha and beta oscillations. As previously described (Carlqvist et al 2005, Palva et al 2005) alpha–beta synchronization was strongest in the posterior areas, and in addition it showed slight inter-hemispheric differences, which might be specific to the resting condition with closed-eyes. Since the amplitude and phase, extracted with the analytic signal

Acknowledgments

This project was supported by grants from Karolinska Institutet and the Montel Williams MS Foundation. Mrs. Ann-Marie Åberg is gratefully acknowledged for her skillful performance of the EEG recordings. We thank Dr. Guido Nolte for useful discussions.

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Research paperSystems neurosciencePhase synchronization between alpha and beta oscillations in the human electroencephalogram

Abstract

Section snippets

Subjects

1:2 Phase synchronization

Factors contributing to phase synchronization between alpha and beta oscillations

Acknowledgments

Int J Psychophysiol

Neuroscience

Neuroimage

Neurobiol Aging

Brain Cogn

Brain Res

Trends Neurosci

Neuroimage

Int J Psychophysiol

J Neurosci Methods

J Physiol Paris

Neurophysiol Clin

Electroencephalogr Clin Neurophysiol

Int J Psychophysiol

Int J Psychophysiol

Neuron

J Neurosci Methods

Neuroscience

Random data-analysis and measurement procedure

Amplitude and phase relationship between alpha and beta oscillations in the human EEG

Med Biol Eng Comput

Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. I. Alpha and beta event-related desynchronization

Brain

Research paper
Systems neuroscience
Phase synchronization between alpha and beta oscillations in the human electroencephalogram