We are livingin busy pace of modern life, which causes stress and anxiety. Stress andanxiety in turn leads many problems such as memory loss and inability toconcentrate in human brains, depression, irritability, sleep disorders andother problems. Some researchers havealso assessed that pressure will destroy the body’s hormones, brainneurotransmitters, immune function and metabolism(1). Moreover, anxiety and stress are among the mostunpleasant experiences in patients undergoing all scans and operationsbecause of being in an unfamiliar environment, drug used and their effects,expectation of good test results, separation fromfamily and other possible complications. All above mentioned are factors thatcan lead patients to be anxious in the waiting room before imaging andoperations, resulting in bad diagnosis and treatment.
Although stimulantmedications are commonly prescribed to treat the symptoms of anxiety and stress,many people are interested in using another method such as musical interventionto decrease drug’s side effects. Binaural auditory beat stimulation as a musicalintervention or relaxation drug can reduce symptoms such as anxiety and stressin people felt anxious. Binauralbeats are auditory waves occurring when applying head phones, right and leftears are separately exposed to two tones with a little different frequency that the superior olivarynucleus in the brainstem interprets the phase difference between the two tones,hence the binaural beat (2). For instance, if a clear tone of 400 Hz is presented to theleft ear and a tone of 410 Hz is presented to the right ear this produces aperceived frequency of 405 Hz which modulates in amplitude with a frequency of10 Hz. This modulated signal is often referred to as a beat and can be producedwhen the difference in frequency between the two carrier tones ranges frombetween 2 and 30 Hz (3). It should be noted thatfrequency range of binaural beats are in the alpha, beta, and theta/delta EEG frequencybands, precisely like frequency range of the brain, so this is the reason why many studies have linked binaural beats to some formof physiological and psychological effects Such auditory stimulation or binaural beats hasbeen reported to affect behaviour and cognition via the process of corticalentrainment because they may entrainelectrocortical activity and enhance cognition functions such as attention andmemory(4). Also, some studies have reported that binaural beats can modify physiologicaland cognitive processes through synchronization of the brain hemispheres, whichcan in turn cause reducing anxiety, increasing pain threshold, improved vigilance andmemory, increased levels of hypnotic susceptibility, severity ratings oftinnitus and self-reportedpsychologic measures (5-10). According to the assumption that the human brain canmodify its dominant MEG frequency towards the frequency of the externalstimulus, so we can evaluate the effects of binaural beats on the brainwave.
Over the past few years, the use of thesebeats as a therapeutic tool has gained interest among neurophysiologists andclinicians (11), so it is so curial to complete their theoretical aspects and practicalimplications. However, the perceptual strength of a binaural beat signalstill remains unanswered and as well as there is alack of research regarding the possible effects of listening to binaural beatsand why and how they can influence on brainwaves. Garcia?Argibay et al. Have demonstrated that the presentation of binauralauditory beats can affect long-term memory both positively and negatively,depending on the frequency used, but the exact frequencies are not clear yet(4).
Karnio et al. have shownthat theta (6.6 Hz) binaural beats can elicit changes when measured using avery short exposure window of 1000 ms (12), but Goodin et al. andWahbeh et al. could not find any evidence of cortical entrainment when theta (7Hz) binaural beats were constantly presented for 2 min, or for periods of up to30 min(10, 13). The reason can be thatcontinuous and prolonged exposure to a binaural beat results in the brain tohabituate to the signal. Since withthe nature and frequency of the carrier tones used to present the binauralbeats and the duration of exposure, binaural beats can have different effectson the brainwaves, so understanding about those parameters can mainly help usdesign and refine future entrainment protocols. During the project, we will address followingquestions: 1.
The evaluation of the effect of binaural beats on thedifferent band frequencies in resting state by Magentoencephalography (MEG) 2. Understandingabout whether the binaural beats can influence on the right and left hemisphereof the brain uniformly or not.3. What are the effects of binaural beats onbrain connectivity and what is the mechanism of binaural beats in the brain. 4.
Investigation of autonomic nervoussystem alteration in correlation with MEG recordings during exposure tobinaural beats to better understand how and to what extent these special tonescan affect anxiety state.