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On the binaural brain entrainment indicating lower heart rate variability
Abstract
Products based on binaural beat technology are popular as these claim to relax the user by altering (i.e. entraining) the brain’s neuronal rhythm and a Google search will result in more than a million hits [1]. Whilst this is possible in certain approaches, for example in photic frequency following effects such as in brain-computer interfaces [2]; binaural brain entrainments uses two beats (usually sinusoidal tones) that are different in frequency by a small amount that generates a third pseudo-rhythm at the difference of the two frequencies [3]. Furthermore, binaural brain entrainment is also claimed to allow altered states of consciousness and hemispheric synchronisation [4]. However, the effects of this entrainment on the cardiac rhythm appear to be understudied, though equally important as the effects on the brain. Hence, the investigation here is set out with this aim.
... Beyond EEG entrainment and cognitive enhancement, binaural-beat stimulation has also been related with other clinically relevant dimensions, such as parasympathetic activation and self-reported relaxation (McConnell et al., 2014), heart rate variability (Palaniappan et al., 2015) and acute pre-operative anxiety (Padmanabhan et al., 2005), for theta-, alpha-and delta-beat stimulation, respectively. On the other hand, a recent comprehensive review concludes a diminishing impact of binaural-beat stimulation on anxiety levels . ...
... In contrast, there was a decrease in skin conductance along the block with theta-beat stimulation, suggesting a relaxation effect with beats in this range, independently of the type of beat (see Figure 8B). Such trends along the session occur only with the two slowest beat frequencies studied here, theta and alpha, the typical beat frequencies reported in previous studies as related to clinically relevant psychophysiological dimensions (Padmanabhan et al., 2005;McConnell et al., 2014;Palaniappan et al., 2015). ...
... Our results on heart rate and skin conductance do no support the proposal suggesting an effect of binaural beats on measures related with emotional arousal. In contrast with previous findings on heart rate variability (Palaniappan et al., 2015), parasympathetic activation (McConnell et al., 2014) or anxiety (Padmanabhan et al., 2005), we did not find a specific effect of binaural beat on heart rate and skin conductance for any of the beat frequencies tested here. On the other hand, our results go in accordance with the findings of Chaieb et al. (2015) regarding diminishing effects of binaural-beat stimulation on anxiety levels. ...
When two pure tones of slightly different frequencies are delivered simultaneously to the two ears, is generated a beat whose frequency corresponds to the frequency difference between them. That beat is known as acoustic beat. If these two tones are presented one to each ear, they still produce the sensation of the same beat, although no physical combination of the tones occurs outside the auditory system. This phenomenon is called binaural beat. In the present study, we explored the potential contribution of binaural beats to the enhancement of specific electroencephalographic (EEG) bands, as previous studies suggest the potential usefulness of binaural beats as a brainwave entrainment tool. Additionally, we analyzed the effects of binaural-beat stimulation on two psychophysiological measures related to emotional arousal: heart rate and skin conductance. Beats of five different frequencies (4.53 Hz -theta-, 8.97 Hz -alpha-, 17.93 Hz -beta-, 34.49 Hz -gamma- or 57.3 Hz -upper-gamma) were presented binaurally and acoustically for epochs of 3 min (Beat epochs), preceded and followed by pink noise epochs of 90 s (Baseline and Post epochs, respectively). In each of these epochs, we analyzed the EEG spectral power, as well as calculated the heart rate and skin conductance response (SCR). For all the beat frequencies used for stimulation, no significant changes between Baseline and Beat epochs were observed within the corresponding EEG bands, neither with binaural or with acoustic beats. Additional analysis of spectral EEG topographies yielded negative results for the effect of binaural beats in the scalp distribution of EEG spectral power. In the psychophysiological measures, no changes in heart rate and skin conductance were observed for any of the beat frequencies presented. Our results do not support binaural-beat stimulation as a potential tool for the enhancement of EEG oscillatory activity, nor to induce changes in emotional arousal.
... Комплекс немедикаментозных мероприятий включает физиотерапию, лечебную физкультуру, бальнеотерапию, массаж, лечебное и профилактическое питание, мануальную терапию, рефлексотерапию, а также психотерапию. Ряд авторов в качестве одного из перспективных направлений совершенствования системы лечебно-реабилитационных мероприятий рассматривают применение метода бинауральных ритмов [4,5]. Бинауральные ритмы воспринимаются слухом как биения на частоте, равной разности частот, слышимых левым и правым ухом. ...
... По одной из гипотез эффективность метода ББ обусловлена способностью подпороговых звуковых стимулов синхронизировать кортикальную активность больших нейронных популяций. Представляется, что весьма перспективным может быть применение метода в области коррекции психосоматических расстройств, в первую очередь -тревожно-депрессивных [4,5]. Очевидно, что преимуществами использования ББ являются неинвазивность и простота данного подхода, а к недостаткам можно отнести длительность проведения процедуры. ...
Objective. To increase the efficiency of the complex of therapeutic and rehabilitation measures in preparation for hip joint endoprosthetics. Materials and methods. 66 patients in whom it was planned to perform hip joint endoprosthetics took part in the research. They were divided into two groups. The main group (n = 32) included patients who underwent 5 binaural beats as a relaxation program. In the comparison group (n = 34) the patients received a standard set of measures to prepare for this operation. All patients were screened for depression and anxiety using the standardized hospital scale for anxiety and depression (HADS) before the study. We also recorded the initial levels of reactive and personality anxiety using the Spielberger Hanin test. We repeated the test in both groups after 7 days to evaluate the dynamics of the test. Results. The conducted research showed that in the main group on the background of binaural beating procedures, reactive (from 57.2 3.8 to 42.4 5.2 points, p = 0.014) and personal anxiety (from 58.9 4.1 to 44.7 3.8 points, p = 0.003) were significantly reduced. In addition, the application of binaural beats method resulted in a significant decrease of HADS alarm subscale indexes (p 0.001) in patients of the base group from 12.8 2.8 to 8.5 0.7 points. While patients in the comparison group had significantly less expressed decrease of this parameter from 11.7 3.1 to 10.9 1.6 points (p 0.01). On the HADS depression subscale there was also a marked decrease in the main group to 7.1 0.8 points, this value was statistically significantly lower (p = 0.011) than in the comparison group 10.2 1.2 points. Conclusion. The conducted research has shown that the use of the binaural beats method in the complex of measures to prepare patients for hip joint endoprosthetics helps to improve their psycho-emotional status. This is manifested by a decrease in personal and reactive anxiety in the Spielberger Hanin test, as well as the severity of depression and anxiety on the HADS scale. The advantages of the method are non-invasive and easy to use, and the disadvantages include the duration of the procedure and poorly studied mechanism of action.
... A number of applied studies demonstrate the positive impact of listening to BBs on behavior and cognitive processes [5,6], but there is also evidence to the contrary [7,8]. Most authors believe that the observed therapeutic effects are associated with the relaxing effect of BBs. ...
... (Fig. 1a). This combination of carrier frequencies and beats was chosen because it is close to the one implemented in audio recordings of the company's Monroe Products, which certain authors [5,8] use in their studies as a means of improving sleep and cognitive functions. ...
Beats are the physical phenomenon appearing when two oscillation processes of close frequencies are superimposed. In acoustics, there is also the concept of binaural beats, a subjective feeling of the listener when acoustic tones of slightly different frequencies are applied separately to each ear. Commercial products based on the effect of binaural beats enjoy steady popularity in the market of the modern technological tools for psycho- and physiotherapy. In particular, they are applied to improve sleep. But it is the objective evaluation of the physiologic effect of binaural beats on the sleep onset process that has very little evidence for support. This paper provides comparative analysis of the time to fall asleep determined by the onset of the second daytime sleep stage (sleep spindle appearance). The subjects listened to a monotonous sound of three similar kinds: a combination of binaural beats with pink noise, a similar sound with a combination of monaural beats, and a similar sound without any beat. Stimulation by the combination of binaural beats is shown to produce the least sleep onset time as compared to the similar sound containing monaural beats and to the similar sound without beats. Further investigation is required to obtain results that are more consistent.
... This was mainly due to a series of studies in the 2000's that investigated ASSRs using EEG and MEG, which provided first reliable neuroscientific evidence for specific responses in human brain activity after binaural beat stimulation [4,13,24]. The newly available empirical data on electrocortical responses to binaural beats led to a growing interest in the neuro-physiological correlates [27][28][29]. ...
Binaural beats are an auditory phenomenon that occurs when two tones of different frequencies, which are presented separately to each ear, elicit the sensation of a third tone oscillating at the difference frequency of the two tones. Binaural beats can be perceived in the frequency range of about 1–30 Hz, a range that coincides with the main human EEG frequency bands. The brainwave entrainment hypothesis, which assumes that external stimulation at a certain frequency leads to the brain’s electrocortical activity oscillating at the same frequency, provides the basis for research on the effects of binaural beat stimulation on cognitive and affective states. Studies, particularly in more applied fields, usually refer to neuroscientific research demonstrating that binaural beats elicit systematic changes in EEG parameters. At first glance, however, the available literature on brainwave entrainment effects due to binaural beat stimulation appears to be inconclusive at best. The aim of the present systematic review is, thus, to synthesize existing empirical research. A sample of fourteen published studies met our criteria for inclusion. The results corroborate the impression of an overall inconsistency of empirical outcomes, with five studies reporting results in line with the brainwave entrainment hypothesis, eight studies reporting contradictory, and one mixed results. What is to be noticed is that the fourteen studies included in this review were very heterogeneous regarding the implementation of the binaural beats, the experimental designs, and the EEG parameters and analyses. The methodological heterogeneity in this field of study ultimately limits the comparability of research outcomes. The results of the present systematic review emphasize the need for standardization in study approaches so as to allow for reliable insight into brainwave entrainment effects in the future.
... A study with tinnitus patients proved subjectively the effectiveness of BRB and TRT with a decrease in the degree of tinnitus disturbance pre-treatment and post-treatment (David et al., 2010). In this sense, BRB may be used as a tool beyond entraining brain rhythms by focusing on inducing parasympathetic activity (Palaniappan et al., 2015) in tinnitus sufferers that could decrease anxiety (McConnell et al., 2014) and sleep disorders (Chaieb et al., 2015). The increased latency in the ERP components of tinnitus patients to the TBB may be a product of central processes that begin at the brainstem level and adaptive processes that occur upstream cortically, and may represent an enhanced perception to the TBB sound as a learning mechanism that may initially suppress the tinnitus perception (Kaltenbach, 2011). ...
Introduction
So far, Auditory Event-Related Potential (AERP) features have been used to characterize neural activity of patients with tinnitus. However, these EEG patterns could be used to evaluate tinnitus evolution as well. The aim of the present study is to propose a methodology based on AERPs to evaluate the effectiveness of four acoustic therapies for tinnitus treatment.
Methods
The acoustic therapies were: (1) Tinnitus Retraining Therapy (TRT), (2) Auditory Discrimination Therapy (ADT), (3) Therapy for Enriched Acoustic Environment (TEAE), and (4) Binaural Beats Therapy (BBT). In addition, relaxing music was included as a placebo for both: tinnitus sufferers and healthy individuals. To meet this aim, 103 participants were recruited, 53% were females and 47% were males. All the participants were treated for 8 weeks with one of these five sounds, which were moreover tuned in accordance with the acoustic features of their tinnitus (if applied) and hearing loss. They were electroencephalographically monitored before and after their acoustic therapy, and wherefrom AERPs were estimated. The sound effect of acoustic therapies was evaluated by examining the area under the curve of those AERPs. Two parameters were obtained: (1) amplitude and (2) topographical distribution.
Results
The findings of the investigation showed that after an 8-week treatment, TRT and ADT, respectively achieved significant neurophysiological changes over somatosensory and occipital regions. On one hand, TRT increased the tinnitus perception. On the other hand, ADT redirected the tinnitus attention, what in turn diminished the tinnitus perception. Tinnitus handicapped inventory outcomes verified these neurophysiological findings, revealing that 31% of patients in each group reported that TRT increased tinnitus perception, but ADT diminished it.
Discussion
Tinnitus has been identified as a multifactorial condition highly associated with hearing loss, age, sex, marital status, education, and even, employment. However, no conclusive evidence has been found yet. In this study, a significant (but low) correlation was found between tinnitus intensity and right ear hearing loss, left ear hearing loss, heart rate, area under the curve of AERPs, and acoustic therapy. This study raises the possibility to assign acoustic therapies by neurophysiological response of patient.
... et al. 2017;Goodin et al. 2012). Clinical symptoms targeted with different BB protocols include depression, memory, parasympathetic activation, and self-reported relaxation (McConnell et al. 2014), heart rate variability (Palaniappan et al. 2015), anxiety (Chaieb et al. 2015;Padmanabhan et al. 2005), hypertension, sleep, pain, schizophrenia, Alzheimer's disease, and mental states (Garcia-Argibay et al. 2019;Gkolias et al. 2020;McDermott et al. 2018;Wahbeh et al. 2007). Studies also reported improvement of vigilance (Lane et al. 1998), increase in hypnotic susceptibility (Brady and Stevens 2000), or increase in some forms of creativity (Reedijk et al. 2013). ...
Binaural beat (BB) is a promising technique for memory improvement in elderly or people with neurological conditions. However, the related modulation of cortical networks followed by behavioral changes has not been investigated. The objective of this study is to establish a relationship between BB oscillatory brain activity evoked by stimulation and a behavioral response in a short term memory task. Three Groups A, B, and C of 20 participants each received alpha (10 Hz), beta (14 Hz), and gamma (30 Hz) BB, respectively, for 15 min. Their EEG was recorded in pre, during, and post BB states. Participants performed a digit span test before and after a BB session. A significant increase in the cognitive score was found only for Group A while a significant decrease in reaction time was noted for Groups A and C. Group A had a significant decrease of theta and increase of alpha power, and a significant increase of theta and decrease of gamma imaginary coherence (ICH) post BB. Group C had a significant increase in theta and gamma power accompanied by the increase of theta and gamma ICH post BB. The effectiveness of BB depends on the frequency of stimulation. A putative neural mechanism involves an increase in theta ICH in parieto-frontal and interhemispheric frontal networks.
... Heart rate variability (HRV), an indicator of the functioning of the autonomic nervous system (ANS), has been used as a psychophysiological index of mental stress, 12 and studies have begun to explore the physiological effects of BBs on stress using HRV. [13][14][15] The current pilot study explored the buffering effects of theta BB technology (TBB) on the physiological markers of stress and perceived psychological stress after a stressinduction procedure. ...
Context:
Distress has deleterious effects on health. While complementary and alternative medicine (CAM) is a growing system of practices in the treatment of health and mental-health conditions, many individuals have limited access to mind-body interventions. Creating accessible stress-inoculation strategies may augment traditional mental-health interventions and services.
Objective:
This pilot study intended to assess the effectiveness of a theta binaural beat (TBB) auditory stimulus on heart rate and self-reported stress, which was experimentally induced by the Trier Social Stress Test (TSST).
Design:
The repeated measures study compared the stress levels after a stimulus and stressor for two groups, within an experimentally induced psychological stress paradigm, the Trier Social Stress Test (TSST).
Setting:
The study occurred at a private Midwestern university.
Participants:
Participants were 64 US adults recruited from undergraduate classes at the university, with a mean age of 19 years and a range from 18 to 30.
Intervention:
Participants were randomly assigned to the intervention or the control group. The intervention group listened to pink sound, carrier tones, and embedded TBB, while the control group listened to pink sound and carrier tones without embedded TBB.
Outcome measures:
Participants completed self-report assessments about the auditory stimulus, perceived stress, and mindfulness and then engaged in the Trier Social Stress Test (TSST). Subsequently, they completed measures on perceived stress using a visual analogue scale (VAS), and heart rate variability (HRV) was recorded throughout the study.
Results:
With respect to the evaluation of subjective stress using the VAS, psychological stress increased significantly between the exposure to the stimuli and the TSST-F(1.28, 53) = 42.76, P = .01, partial η2 = 0.44. The change in stress levels for the intervention group, however, was not significantly different from that of the control group at any time point F(1.28, 53) = 1.03, P = .33, partial η2 = 0.02. With respect to the evaluation of physiological response to stress using the HRV, the changes in HF HRV between the 4, five-minute segments during stimulus exposure were not significantly different between the groups F(3, 55) = 0.90, P = .44, partial η2 = 0.02. A significantly greater change-F(1, 55) = 4.84, P = .03 partial η2 = 0.08-in the HF HRV occurred over the TSST period for the intervention group compared to the control group suggesting that on average across the TSST stress tasks, those in the intervention group demonstrated higher HF signals.
Conclusions:
The current study found that the intervention group, who listened to TBBs, had greater parasympathetic dominance during TSST than the control group. This suggests that TBB exposure may dampen subsequent stress responses to an acute, psychological stressor. This finding, however, should be interpreted with caution, because further research and independent replication are warranted.
It is well known that the decrease of the Heart Rate Variability (HRV) is related to a number of important pathologies involving cardiovascular system as well as psychological and psychiatric disorders. In such case a prompt recover of HRV and, in particular, of parasympathetic modulation is required in the ANS (Autonomic Nervous System). In order to pursue this objective in the present paper. The physical technique of the brain entrainment has been used. We have recorded R-R time intervals estimated from the QRS complex in the ECG. One time the R-R signal has been recorded during rest condition of the subject and the second time during alpha brain stimulation. The following step has been to analyze the data performing the Fast Fourier Analysis that is able to quantify the ANS activity of modulation on heart rhythm. We have found that, respect to the rest case, alpha brain stimulation induces a constant improvement in the total power spectral density (and thus induces an increase in total heart rhythm variability) and in particular in the parasympathetic (HF) band spectrum. The result is of interest for further consideration by clinicians and researchers of brainwave entrainment (BWE) as basic therapeutic tool in a so serious field of neurology and related pathologies.
The steady state visual evoked protocol has recently become a popular paradigm in brain-computer interface (BCI) applications. Typically (regardless of function) these applications offer the user a binary selection of targets that perform correspondingly discrete actions. Such discrete control systems are appropriate for applications that are inherently isolated in nature, such as selecting numbers from a keypad to be dialled or letters from an alphabet to be spelled. However motivation exists for users to employ proportional control methods in intrinsically analogue tasks such as the movement of a mouse pointer. This paper introduces an online BCI in which control of a mouse pointer is directly proportional to a user's intent. Performance is measured over a series of pointer movement tasks and compared to the traditional discrete output approach. Analogue control allowed subjects to move the pointer faster to the cued target location compared to discrete output but suffers more undesired movements overall. Best performance is achieved when combining the threshold to movement of traditional discrete techniques with the range of movement offered by proportional control.
A number of benefits from meditation have been claimed by those who practice various traditions, but few have been well tested in scientifically controlled studies. Among these claims are improved performance and decreased sleep need. Therefore, in these studies we assess whether meditation leads to an immediate performance improvement on a well validated psychomotor vigilance task (PVT), and second, whether longer bouts of meditation may alter sleep need.
The primary study assessed PVT reaction times before and after 40 minute periods of mediation, nap, or a control activity using a within subject cross-over design. This study utilized novice meditators who were current university students (n = 10). Novice meditators completed 40 minutes of meditation, nap, or control activities on six different days (two separate days for each condition), plus one night of total sleep deprivation on a different night, followed by 40 minutes of meditation.A second study examined sleep times in long term experienced meditators (n = 7) vs. non-meditators (n = 23). Experienced meditators and controls were age and sex matched and living in the Delhi region of India at the time of the study. Both groups continued their normal activities while monitoring their sleep and meditation times.
Novice meditators were tested on the PVT before each activity, 10 minutes after each activity and one hour later. All ten novice meditators improved their PVT reaction times immediately following periods of meditation, and all but one got worse immediately following naps. Sleep deprivation produced a slower baseline reaction time (RT) on the PVT that still improved significantly following a period of meditation. In experiments with long-term experienced meditators, sleep duration was measured using both sleep journals and actigraphy. Sleep duration in these subjects was lower than control non-meditators and general population norms, with no apparent decrements in PVT scores.
These results suggest that meditation provides at least a short-term performance improvement even in novice meditators. In long term meditators, multiple hours spent in meditation are associated with a significant decrease in total sleep time when compared with age and sex matched controls who did not meditate. Whether meditation can actually replace a portion of sleep or pay-off sleep debt is under further investigation.
Stress and anxiety are risk factors for cardiovascular (CV) disease. Worry might be a mediator of their risks by prolonging their cognitive representation and concomitant CV activity. We hypothesized that daily stressors and worry, and trait anxiety and trait worry would be associated with high heart rate (HR) and low heart rate variability (HRV) during waking and the subsequent nocturnal sleep period, and that worry would mediate the effects of daily stressors. Low HRV and high HR are physiological risk factors for CV disease. Using an hourly diary, stressors, worry frequency and duration, and biobehavioral variables were measured during one day in 52 healthy subjects. During this time and the subsequent nocturnal sleep period, ambulatory ECG was measured. Stressors, worry and traits were related to higher HR and lower HRV during waking, and the effects of stressors and worry were extended into the sleeping period. Worry duration mediated the effects of stressors. The results were largely independent of biobehavioral variables including sleep quality. The results support the notion that worry, by prolonging CV activity, is a mediator of the CV risks of stress. They also imply a role for unconscious cognitive representation of stress.
In this paper, we: propose a technique to identify individuals using features extracted from QRS segment of electrocardiogram (ECG) signals. A total of 2000 samples from 10 subjects from the Arrhythmia Laboratory at Boston's Beth Israel Hospital (now the Beth Israel Deaconess Medical Center) database were used. These data are available as MIT-BH Normal Sinus Rhythm database and consist of 18 hour long-term recordings with 2 ECG signals. The commonly used features like R-R interval, R amplitude, QRS interval, QR amplitude and RS amplitude were used. In addition to these features, we propose the use of form factor of the QRS segment. Form factor has been used previously in electroencephalogram analysis and it is a measure of the complexity of the signal. These six features were then used by two neural network classifiers: Multilayer Perceptron - Backpropagation (MLP-BP) and Simplified Fuzzy ARTMAP (SFA). The data were split equally for MLP-BIP and SFA training and testing. The results gave classification performance tip to 97.6%. This indicates that ECG has the potential to be used as a biometric tool.
Exposure to binaural beats in an environment of restricted stim- ulation coupled with a guidance process can safely provide access to and ex- periences in many propitious states of consciousness. This method requires a unique combination of well-understood psycho-physiological inductive techniques with the addition of a refined binaural-beat technology. Binaural beats provide potential consciousness-altering information to the brain's reticular activating system. The reticular activating system in turn interprets and reacts to this information by stimulating the thalamus and cortex - thereby altering arousal states, attentional focus, and the level of awareness, i.e., the elements of consciousness itself. This effective binaural-beat process offers a wide variety of beneficial applications and vehicle for the ex- ploration of expanded states of consciousness.
A high degree of heart rate (HR) variability is found in compensated hearts with good function, whereas HR variability can be decreased with severe coronary artery disease, congestive heart failure, aging and diabetic neuropathy. To test the hypothesis that HR variability is a predictor of long-term survival after acute myocardial infarction (AMI), the Holter tapes of 808 patients who survived AMI were analyzed. Heart rate variability was defined as the standard deviation of all normal RR intervals in a 24-hour continuous electrocardiogram recording made 11 +/- 3 days after AMI. In all patients demographic, clinical and laboratory variables were measured at baseline. Mean follow-up time was 31 months. Of all Holter variables measured, HR variability had the strongest univariate correlation with mortality. The relative risk of mortality was 5.3 times higher in the group with HR variability of less than 50 ms than the group with HR variability of more than 100 ms. HR variability remained a significant predictor of mortality after adjusting for clinical, demographic, other Holter features and ejection fraction. A hypothesis to explain this finding is that decreased HR variability correlates with increased sympathetic or decreased vagal tone, which may predispose to ventricular fibrillation.
Binaural beat sensations depend upon a central combination of two different temporally encoded tones, separately presented to the two ears. We tested the feasibility to record an auditory steady state evoked response (ASSR) at the binaural beat frequency in order to find a measure for temporal coding of sound in the human EEG.
We stimulated each ear with a distinct tone, both differing in frequency by 40Hz, to record a binaural beat ASSR. As control, we evoked a beat ASSR in response to both tones in the same ear. We band-pass filtered the EEG at 40Hz, averaged with respect to stimulus onset and compared ASSR amplitudes and phases, extracted from a sinusoidal non-linear regression fit to a 40Hz period average.
A 40Hz binaural beat ASSR was evoked at a low mean stimulus frequency (400Hz) but became undetectable beyond 3kHz. Its amplitude was smaller than that of the acoustic beat ASSR, which was evoked at low and high frequencies. Both ASSR types had maxima at fronto-central leads and displayed a fronto-occipital phase delay of several ms.
The dependence of the 40Hz binaural beat ASSR on stimuli at low, temporally coded tone frequencies suggests that it may objectively assess temporal sound coding ability. The phase shift across the electrode array is evidence for more than one origin of the 40Hz oscillations.
The binaural beat ASSR is an evoked response, with novel diagnostic potential, to a signal that is not present in the stimulus, but generated within the brain.