The fluctuation in frequency equals the difference in the two pure tones that are presented. The superior olivary complex is believed to be the first nucleus that receives auditory information from both sides of the ears, and binaurally activated phase-sensitive neurons are also found in the inferior colliculus ( Kuwada et al., 1979 McAlpine et al., 1996, 1998 Spitzer and Semple, 1998 Schwarz and Taylor, 2005 Karino et al., 2006). The beat in this phenomenon is generated within the brain and is referred to as a binaural beat. The dichotic presentation of two almost equivalent pure tones but with slightly different frequencies leads to perceive fluctuations sounds which occurs as amplitude modulation generated by the two pure tones, or so-called beat, in the brain. Thus, a 6-Hz binaural beat on a 250 Hz carrier tone was suggested as a stimulus for inducing a meditative state. Moreover, tension factor of BRUMS was decreased in experimental group compared to control group which resembled the meditation effect. The pattern recorded for 10 min of exposure appeared to be brain functions of a meditative state. Compared to the control group, theta activity was also induced at the frontal and parietal-central regions, which included the Fz position, and left hemisphere dominance was presented for other exposure durations. The results showed that theta activity was induced in the entire cortex within 10 min of exposure to the stimulus in the experimental group. Emotional states were evaluated by Brunel Mood Scale (BRMUS) before and after exposing to the stimulus. Twenty-eight participants were divided into experimental and control groups. Quantitative electroencephalography (QEEG) was utilized as the recording modality.
Exposure to a 6-Hz binaural beat on a 250 Hz carrier tone for 30 min was utilized in this study. The brain responses to binaural beats remain controversial therefore, the aim of this study was to investigate theta activity responses to a binaural beat by controlling factors affecting localization, including beat frequency, carrier tone frequency, exposure duration, and recording procedure. Brain-Computer Interface Laboratory, Department of Biomedical Engineering, Faculty of Engineering, Mahidol University, Nakhorn Pathom, ThailandĪ binaural beat is a beat phenomenon that is generated by the dichotic presentation of two almost equivalent pure tones but with slightly different frequencies.Nantawachara Jirakittayakorn * and Yodchanan Wongsawat *
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