Electrical Brain Responses to an Auditory Illusion and the Impact of ...

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Jun 12, 2015 - Music Physiology and Musicians' Medicine, Hannover University of Music, Drama and Media, Hanover,. Germany ...... Epub 1963/08/01.
RESEARCH ARTICLE

Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise Christos I. Ioannou1,2, Ernesto Pereda3,4, Job P. Lindsen1, Joydeep Bhattacharya1* 1 Department of Psychology, Goldsmiths, University of London, London, United Kingdom, 2 Institute of Music Physiology and Musicians' Medicine, Hannover University of Music, Drama and Media, Hanover, Germany, 3 Electrical Engineering and Bioengineering Group, Department of Industrial Engineering, University of La Laguna, Tenerife, Spain, 4 Institute of Biomedical Technology (CIBICAN), University of La Laguna, Tenerife, Spain * [email protected]

Abstract

OPEN ACCESS Citation: Ioannou CI, Pereda E, Lindsen JP, Bhattacharya J (2015) Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise. PLoS ONE 10(6): e0129486. doi:10.1371/ journal.pone.0129486 Academic Editor: Blake Johnson, ARC Centre of Excellence in Cognition and its Disorders (CCD), AUSTRALIA Received: July 4, 2014 Accepted: May 8, 2015 Published: June 12, 2015 Copyright: © 2015 Ioannou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min) of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha) binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies.

Data Availability Statement: All data are contained within the paper. Funding: E. Pereda acknowledges the financial support of the Spanish MINECO (Ministerio de Economía y Competitividad) and MEC (Ministry of Science and Technology) under grants TEC201238453-C04-03 and PRX12/00564, respectively. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Introduction When two sinusoidal tones with a slight frequency mismatch (i.e. 200 and 210 Hz) are separately presented to each ear, the listener perceives a beating frequency equal to the frequency mismatch between the two tones (i.e. 10 Hz); this is termed binaural beating [1, 2]. The two tones combined wax and wane as the two frequencies come in and out of phase with one another, and this phase interference produces an amplitude-modulated standing wave, the

PLOS ONE | DOI:10.1371/journal.pone.0129486 June 12, 2015

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Binaural Beat and EEG

Competing Interests: The authors have declared that no competing interest exist.

binaural beat (BB). This beat is not a physical property of the presented sound but a subjectively perceived auditory illusion, which has its origin in the brainstem’s superior olivary nucleus [3, 4]. BBs are perceived for low frequency mismatch (< 100 Hz) and lower carrier frequencies (