R&D VisionQuest “One of the most striking facts about our ears is that we have two of them— and yet we hear one acoustic world; only one voice per speaker” ###### History Two individuals played a significant role in initiating research on binaural beats. They were :- Heinrich Wilhelm Dove and Gerald Oster. Dove initiated this research in the 19th century under a journal (Repertorium der Physik) It was given less attention until the 20th century when Oster published the article of "Auditory beats in the brain”, which polished Oster’s article and added fresh research into it. The history of binaural beats goes back to the 19th century, when the German scientist Heinrich Wilhelm Dove discovered a phenomenon that would later become known as binaural beats. Dove noticed that the brain produces a third tone when it hears two different tones with a small difference in frequency.  [[Auditory Illusion∞]](https://goodvibesofficial.com/blog/history-of-binaural-beats/) This third tone was later called binaural beat. In the 1930s and 1940s, scientists such as Gerald Oster and Robert Monroe began exploring the potential of binaural beats. Oster published an article in 1973 in which he showed that binaural beats can help improve mental performance, such as concentration and creativity. Robert Monroe, founder of the Monroe Institute, pioneered research into binaural beats. He experimented with binaural beats and developed his own method of producing and applying them.  [[Brainwave Synchronization∞]](https://goodvibesofficial.com/blog/history-of-binaural-beats/) He discovered that binaural beats could help achieve a state of deep relaxation and induce out-of-body experiences. In the 1990s and 2000s, binaural beats became more popular and accessible thanks to the rise of digital technology and the internet. Since then, countless apps, websites, and sound files have become available that allow people to listen to and apply binaural beats for various purposes, such as relaxation, meditation, and sleep. Today, binaural beats are still widely used and researched by scientists and therapists. While there is still controversy about the effectiveness and safety of binaural beats, many people swear by its positive effects on their mental and physical well-being. [[Cognitive enhancement∞]](https://goodvibesofficial.com/blog/history-of-binaural-beats/) ###### Binaural Beats, What are they? A Binaural Beat is when two tones of slightly differing frequencies are played (in separate ears simultaneously, mostly via headphones), our brain perceives the creation of another wave, a ‘third wave’. This acoustic illusory is a binaural beat [[Sleep Cycle Reduction∞]]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10198548/So if Clarke hears a tone of 215 Hz in one ear and a tone of 225 Hz in the other, he would be listening to a binaural beat with a 10 Hertz frequency (i.e: the difference between the two frequencies he is already hearing).  ###### The Cocktail Party Effect When we are in a crowded area, we have the ability to focus our ears on the sources of our choice. We have the ability to divert the attention of our ears to the desired source (for example we can focus it to hear a person in a noisy room, with a lot of background noise) This can be experienced from the following video:-: (https://www.youtube.com/watch?v=8EPLG0ihdcs) You will hear what you want to hear. If you think about brainstorm you will hear brainstorm, if you think about green needle, you will hear green needle. Although this effect has been researched for more than half a century, but only the previous decade gave detail to the research. [[Hemispheric Coordination∞]]https://www.audiology.org/scientists-discover-that-your-ears-speak-to-your-eyes-and-vice-versa/#:~:text=In%202018%2C%20Gruters%20and%20colleagues,Lovich%20et%20al%2C%202023). Research indicates that the brain networks that coordinate attentional control to auditory sources largely overlap with those for vision.[[Heinrich Wilhel Dove, 19 century∞]]https://www.audiology.org/the-cocktail-party-effect/ https://www.audiology.org/scientists-discover-that-your-ears-speak-to-your-eyes-and-vice-versa/#:~:text=In%202018%2C%20Gruters%20and%20colleagues,Lovich%20et%20al%2C%202023). “You can actually estimate the movement of the eyes, the position of the target that the eyes are going to look at, just from recordings made with a microphone in the ear canal,” - Jennifer Groh, Ph.D. In 2018, it was discovered by Jennifer Groh that the ears make a gradual and slow noise whenever the eyes move! [[Superior Olivary Complex∞]]https://www.audiology.org/scientists-discover-that-your-ears-speak-to-your-eyes-and-vice-versa/#:~:text=In%202018%2C%20Gruters%20and%20colleagues,Lovich%20et%20al%2C%202023). As per a report, in the journal of the proceedings of the national Academy of Sciences, It suggests that this subtle noise can actually determine where the eyes are looking at! This works vice versa too, just by obtaining the eye movement of a subject the team was able to predict the waveform of the subtle noise produced by the ears. Groh links the production of these sounds with the stimulation caused by the eye movements to the brain for the contraction of ear cells or the middle ear muscles. “We think this is part of a system for allowing the brain to match up where sights and sounds are located, even though our eyes can move when our head and ears do not,”-Groh.[[Neural Entrainment∞]]https://www.audiology.org/scientists-discover-that-your-ears-speak-to-your-eyes-and-vice-versa/#:~:text=In%202018%2C%20Gruters%20and%20colleagues,Lovich%20et%20al%2C%202023). ###### AUDITORY SPATIAL ATTENTION Auditory Spatial Attention may be confused with the cocktail party effect as both focus around auditory perception but they are different[[Delta Waves∞]]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920769/ The ability of our mind to determine the location in space (where the sound is coming from)  is the basic phenomenon of Auditory spatial attention.. So it is the ability (can be practiced) to determine the location from where the sound is originating from, whereas the cocktail party effect is our ability to divert our attention to the sound we want to hear ( provided there are background noises, etc) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920769/ Even with closed eyes we can determine the direction of sound. Modern Neuroimaging tools such as functional magnetic resonance imaging (fMRI) and event-related potential (ERP)  have played a significant role to gather fresh insight beyond just the behavioral into the realms of Functional Form of Auditory Spatial Attention. The research related to auditory attention is little as compared to the ones done already on visual attention.[[Auditory Spatial Attention∞]]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920769/ ###### Examples The CockTail Party Effect Let us suppose Zaid is with some friends, in a crowded place such as a food street(a lot of background noise) When talking to a friend even in a crowded place, Zaid’s ears when talking to his friend will give maximum attention and will focus on the speaker’s voice, This ability of hearing and giving attention to the sound of his friend out of all the sounds that are originating in time is known as The cocktail Party effect. Auditory Spatial Attention Now let us suppose that Zaid entered a dark room that he is not aware of. For the sake of this example, let's assume that zaid has no equipment that can help him leave this dark room other than a guiding voice of a friend who is outside the place.  When Zaid shouts out for help to escape the dark place, his friend will respond with a loud voice, affirming help. To escape the place Zaid has to follow his friend’s voice to escape the dark room. Zaid will rely on his ears to successfully manage to obtain the objective of escaping that room, which would be done by zaid following the sound of his friend.  #### The superior olivary complex and binaural beats The superior olivary complex is the first part of our brain that processes the sound input from both the ears. Being Located in the brain stem, the superior olivary complex synchronizes Various activities of the many neurons present in the brain. This complex responds when it hears two slightly different frequencies and creates a binaural beat, which changes the brain waves. The synchronization of the neural activities across the brain is called as entrainment.  Research Shows that Entrainment is not just related to binaural beats but is a common part of brain function. Studies show that specific binaural beats cause an increment in the strength of certain brain waves/ This can either increase or decrease different brain functions that control thinking and feeling. ## TYPES OF BRAIN WAVES Thoughts, emotions and behaviors are created by the electrical signals used by Neurons. When the Neurons are synchronized they create Brain waves. Electroencephalography (EEG) is a technique by which brain waves can be measured, this involves electrodes to be placed on the scalp to record the electric signals. Brain Waves ranges from high frequency to low amplitude and low frequency and high amplitude. The brainwaves create binaural beats, leading to different mental state which can affect the brain in different ways. ###### Delta Brain waves ( 0.5 - 4 hz ) Delta is the lowest frequency range and it can be linked to : 1) Deep Sleep (Think more clearly, learn new information more effectively, improve memory) 2) Meditation (Improve attention span and reaction time) 3) Healing and pain relief 4) Potential control over the unconscious mind 5) Anti-Aging: Cortisol reduction/DHEA increase Delta waves are the slowest recorded brain waves, which are found mostly in infants and newborns. These waves are associated with deepest levels of relaxation and healing sleep.[[Theta waves∞]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmDelta is prominently seen in learning problems, severe ADHD and Brain injuries. Now we shall dissect the relation between deep sleep and delta brain waves.[[Alpha Waves∞]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htm Initially it was understood that there were only two stages of sleep based on the respective eye movements: non-rapid and rapid eye movement, or NREM and REM Sleep.[[Beta Waves∞]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmNow we have learned more about the NREM stage which is now further subdivided into 4 stages, named NREM stages 1,2,3 and 4. Stage 1: This is the initial and lightest stage of sleep where brain waves are just initiating to settle down the alpha waves. This stage only lasts for a few minutes and is easy to be woken from. [[Gamma Waves]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmStage 2:  this stage continues the brain’s descent towards theta activity, and is usually around 20-25 minutes. Our brain also produces “Sleep spindles” (i.e: short bursts of activity in the range of 12-14 Hz that are often linked with improving memory and learning)[[Mental Performance]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmSlow-wave Sleep (SWS) or Stages 3 & 4: These stages are the deep stages of sleep and are difficult to wake from them. They might even be referred to as “slow-wave sleep” because of the slow delta brain wave activity that occurs.[[Therapeutic Uses]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmREM : During this stage the brain becomes more active and our eyes will twitch. During the REM stage most dreams occur.[[Meditation∞]] ]https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htmSo, these stage of sleep are characterized by a progression from lighter to deeper sleep and again. Cycling through all these stages may take between 80-100 minutes. On average there are usually 4 to 6 full cycles each night. LINK BETWEEN DELTA WAVES AND DEEP SLEEP:- Delta waves occur during Stage 3 and Stage 4, which are deep sleep stages. Delta waves are the slowest which the brain produces (0.5-4Hz). As mentioned in Stage 2 description above, that there are sleep spindles in stage 2, along sleep spindles our brain also creates the ‘K-COMPLEX’ which may be similar to sleep spindles but are different..[[Cocktail Party Effect∞]] ]https://dictionary.apa.org/k-complexK-complexes are impulsive, sharp waves and can be named as one of the largest events that we can locate in the brain. They are said to help us maintain our sleep by suppressing outside stimuli, but they also seem to precede delta waves.[[Frequency Following Response]] ]https://dictionary.apa.org/k-complexWith the help of k-complexes we can successfully transition from stage 2 to deep sleep stages. When we fall asleep, we initially spend more time in the deep sleep (somewhere between 45-90 minutes) in the first cycle, but this time decreases with the coming cycles. Overall 13-24 % of our night sleep is under deep sleep. .[[Groh's Research, linking auditory and visual attention∞]] ]https://dictionary.apa.org/k-complexDelta waves have said to be associated with the release of Growth Hormone, which is significant for physical growth and repair. So Delta waves can help with, 1) Deep sleep (Delta waves are instrumental in inducing deep sleep) 2) Physical Restoration (Delta waves have also been linked to tissue repair and muscle growth) 3)  Hormonal Regulation (delta waves are linked with hormones that regulate metabolism) 4) Learning and Creativity (Research indicates that deep sleep with delta wave activity enhances memory) ###### Theta Brain Waves ( 4 - 8 hz ) Theta brain waves occur when we are sleeping, but not in the deep phases (i.e: SWS STAGE as discussed above) They can also occur when that feeling of fading away to sleep occurs or the the phase just before we wake up. Theta Brain waves can occur also when we are awake, provided we are in a very deeply relaxed state of mind, which some may refer to as ‘autopilot’. However, excess of theta brain waves while awake can induce feelings of “being sluggish or scattered”. [[Functional Magnetic Resonance Imaging(fMRI)∞]] ]https://www.healthline.com/health/theta-waves#theta-waves-vs-other-wavesExperts link theta waves crucial for processing information and making memories, learning more about theta waves the researchers link them to different types of Learning. With limited research, there is little information about theta waves. Let us study a 2017 Brain Wave study. The researchers analyzed the results of wireless implants that recorded brain wave activity in four volunteers. Research shows, that there was an increment in the oscillations of theta waves when the volunteers were trying to move around in an “Unfamiliar environment” Additionally, it was also discovered that the theta wave activity increased when the volunteers moved faster! Another 2017 study links theta wave activity with a specific type of learning, “Implicit learning” Implicit learning is the process of learning or acquiring knowledge or a type of skill without conscious awareness of learning that knowledge or the skill itself. Examples of Implicit learning can be Language acquisition, Emotional responses etc[[Electroencephalography (EEG)]] ]https://www.healthline.com/health/theta-waves#theta-waves-vs-other-wavesResearch also suggests that they have the potential to use the evidence of theta wave activity to detect disorders like Alheimer’s disease. Additionally, earlier research suggests that discovering ways to increment certain theta wave activity could also help people reduce anxiety in people suffering from Generalized Anxiety Disorder (GAD) https://www.healthline.com/health/theta-waves#theta-waves-vs-other-waves ###### Alpha Waves (7-12 Hz):- Alpha waves are located at the center of our brain wave spectrum. When operating at the alpha frequency our brain can absorb new information with a significant increment in creativity. Due to the 86 billion nerve cells present in our brain, there is always some type of electrical activity present in the brain - the types at which the brain operates varies with time. Just after waking up, our brain passes from Slow delta waves to the low frequency Theta waves that act as a ‘portal’ between the dreams and the waking worlds. Then comes the beta waves, when we are engaged in problem solving or decision making, then even the faster gamma waves, when we are full of energy and adrenaline. https://www.betterhelp.com/advice/general/what-are-alpha-brain-waves/ The Gold standard for focus are the alpha waves. This is when we are fully engaged with the subject of matter, yet completely relaxed. Alpha waves oscillate between the theta and beta waves. To activate these we need to slow things down, deepen our breaths, lower our heart rate, and calm the electrical activity in our mind. A 2015 study found evidence that meditation and mindfulness could help unlock this ‘alpha’ state of mind. Benefits of alpha brain waves include improved memory, increased intelligence, increased alertness and increased creativity. Alpha waves may be produced by listening to binaural beats, utilizing neurofeedback and meditating. Alpha waves can be found in the posterior regions of the head on either side, with higher amplitudes on the dominant sides. https://www.betterhelp.com/advice/general/what-are-alpha-brain-waves/ Physiologically, alpha waves are salient during relaxed wakefulness (resting visual cortex) Alpha waves have been linked with emotional regulation meaning that they can reduce stress and anxiety levels, enhancing cognitive performance and an increased ability to focus. https://www.betterhelp.com/advice/general/what-are-alpha-brain-waves/ ###### Beta Waves (12-40Hz): The Beta waves are involved in conscious thought and logical thinking, having high-frequency with a low-amplitude. Tending to have a stimulating effect, just the right amount of beta waves can help us to focus. Excess of Beta waves can cause High Arousal, Anxiety, stress and an inability to stress. However, Repression of beta waves can affect ADHD,  DEPRESSION, POOR COGNITION AND DAYDREAMING. https://neurosciencenews.com/cognitive-control-beta-waves-25970/Just the right amount of Beta waves can help with memory, problem solving and even conscious focus. Beta waves are further divided : - Low beta waves(12-15 Hz) or ’beta-one’ associated with focused and introverted concentration - Mid-range Beta waves (15-20Hz) or ‘beta-two associated with increased energy and anxiety - High Beta Waves(18-40Hz) or ‘beta-three’ associated with significant stress, paranoia, high energy, high arousal and anxiety Beta waves may be observed bifrontally and attenuate with eye opening, alerting, or movement. BETA ACTIVITY IS COMMONLY INCREASED BY BENZODIAZEPINES, BARBITURATES AND CHLORAL HYDRATE. https://neurosciencenews.com/cognitive-control-beta-waves-25970/Beta activity as per a 2016 research, is present in the background of most subjects. If completely missing it may showcase an abnormality depending on other features of the EEG. Maximal beta amplitude is mostly in the frontocentral regions, but it can be widespread. Beta waves reflect desynchronised active brain tissue, and it is usually seen on both sides in symmetrical distribution and is most evident frontally, being mostly absent or reduced in areas of cortical damage. Beta waves are regarded as normal rhythm and is the dominant rhythm in those who are alert or anxious or who have their eyes open, It is the state that most of our brain is listening and thinking during analytical problem solving, judgment, decision making and processing information. Bursts of beta activity are associated with a strengthening of sensory feedback in static motor control and reduced when there is movement change. Beta activity is increased when movement has to be resisted or suppressed. https://neurosciencenews.com/cognitive-control-beta-waves-25970/ ###### Gamma Brain Waves (30-44Hz): Gamma brain waves have the highest frequency among all the brain waves, being associated to high levels of thought and focus. The effect of gamma brain waves may vary on their levels in our brain. https://www.healthline.com/health/gamma-brain-wavesIf our brain produces low levels of gamma waves, we may develop learning and memory problems. As a result, we may experience lower concentration, attention span and mental ability. Lower levels of gamma waves can also lead to learning disabilities and mental disorders. If our brain produces higher levels of gamma waves, we tend to be more receptive and happier, also increasing our IQ with a better concentration. https://www.healthline.com/health/gamma-brain-waves Studies have suggested that an increment in gamma brain wave activity can promote higher states of awareness and an increased brain function during meditation. Researchers indicate that gamma brain waves may be used to treat the following https://news.mit.edu/2024/evidence-gamma-rhythm-stimulation-can-treat-neurological-disorders-emerging-0118#:~:text=Researchers%20are%20finding%20that%20stimulating,disorders%20such%20as%20Alzheimer's%20disease. - Alzheimer’s disease  - Schizophrenia - Mild traumatic brain injury  - Stroke  - ADHD  - Depression  - Epilepsy     ## Frequency Following Response (FFR) Frequency following response or the envelope following response is a neurological phenomenon that occurs as a reaction to auditory stimuli, specifically when the brain synchronizes its neural activity to match the frequency of an auditory input. This means that our brain has the potential to synchronize with rhythmic audio https://www.nature.com/articles/s41467-019-13003-w It is also showcased that the temporal pattern of phase-locked brainstem neural activity that is generating the FFR may contain information with relevance to the binaural processes underlying spatial release from masking (SRM) in challenging listening environments[https://www.nature.com/articles/s41467-019-13003-w ## Hemispheric synchronization We have two ears, why don’t we hear everything twice? “While this helps us to determine which direction sounds are coming from, it also means that our brain has to combine the information from both ears. Otherwise, we would hear an echo.” -Basil Presig of the department of Psychology at the University of Zurich. Research Indicates that input from the right ear arrives at the left brain hemisphere first, while input from the left ear arrives at the right brain hemisphere first. These two hemispheres play different roles during Speech Processing. The left side is responsible for distinguishing phonemes and syllables, whereas the right side recognizes the speech rhythm and prosody. https://www.cia.gov/readingroom/docs/CIA-RDP96-00788R001200060018-5.pdfAlthough both the hemispheres receive input at a different time and process different features of speech, the brain integrates what it hears into a unified speech sound. This mechanism has been linked with Gamma waves by Basil Presig, claiming that the process of integrating what we hear is directly linked to synchronization by Gamma waves. https://www.cia.gov/readingroom/docs/CIA-RDP96-00788R001200060018-5.pdf Signals act together to create a resonance that is reflected in unique brain wave forms characteristic of specific states of consciousness. The result is a focused, whole-brain state known as hemispheric synchronization, where the left and right hemispheres are working together in a state of coherence. https://hemi-sync.com/learn/how-hemi-sync-works/  ## BrainWave Entrainment Brainwave entrainment, also called neural entrainment or brainwave synchronization, refers to the observation that, provided a rhythm of periodic external stimuli, such as flickering lights, speech, music or tactile stimuli will make the brain waves synchronize with them. https://hapbee.com/blogs/hapbee/everything-you-need-to-know-about-brainwave-entrainmentNeural oscillations can be defined as rhythmic or repetitive electrochemical activity in the central nervous system and the brain itself. These oscillations can be characterized by their frequency, phase and amplitude. Neural Tissue, the main component of the neural system, has the ability to generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. So, this means they may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli. https://hapbee.com/blogs/hapbee/everything-you-need-to-know-about-brainwave-entrainment The Functional role of neural oscillations is not fully understood;  however there has been evidence that NEURAL OSCILLATIONS CORRELATE WITH EMOTIONAL RESPONSES, MOTOR CONTROL, AND A NUMBER OF COGNITIVE FUNCTIONS INCLUDING INFORMATION TRANSFER, PERCEPTION, AND MEMORY. https://hapbee.com/blogs/hapbee/everything-you-need-to-know-about-brainwave-entrainment The theta activity are linked to memory functioning and coupling between theta and gamma activity is considered to be vital for memory functions https://bigthink.com/neuropsych/entrainment-perceptual-learning/#:~:text=For%20example%2C%20recent%20research%20shows,%2C%20or%20cycles%20per%20second). ##### FLICKERING LIGHTS AND ALPHA WAVES Researchers have linked ongoing alpha amplitudes and perception. Studies indicate that an occipital alpha amplitude declines after stimulation, which was later shown to reflect event-related desynchronization of the ongoing alpha rhythm. Experimental data largely reveal this state to represent an electrophysiological correlate of activation. ## ALPHA-THETA TRAINING Alpha Theta neurofeedback training guides the brain through gentle oscillations between alpha and theta dominant states.  The idea is that memories are accessed during theta dominance that can then be safely processed during alpha modulation. https://neurofeedback.io/how-does-it-work/alpha-theta This practice is usually done in a quiet room. The idea is that memories are accessed during theta dominance that can then be safely processed during alpha modulation. When the slower theta is dominant, the brain is typically closer to sleep and our cortical activity is relatively lower. Whereas, alpha is a state of disconnected relaxation which represents the core organizational frequency of our cortex. https://neurofeedback.io/how-does-it-work/alpha-theta A session is usually thirty minutes, with the feedback being auditory as two differing yet relating soundscapes ( waves vs waterfall) smoothly transition, signaling to the brain which state is prevalent (alpha or theta) https://neurofeedback.io/how-does-it-work/alpha-theta  ## SIDE EFFECTS Researchers at the Centre for Cognitive Neuroscience have put forward several hypotheses. One suggests that binaural beats somehow interfere with brain waves and lower their frequency so that brain activity is mismatched with the task at hand https://www.news-medical.net/news/20230713/Binaural-beats-can-worsen-cognitive-performance-study-finds.aspx The second hypothesis refers to the fact that most of our daily cognitive tasks are highly variable and, therefore, it is not advisable to modulate only one frequency when performing them. Binaural beats thus may temporarily block brainwave frequencies specific to performing a particular part of the task. An article with the results of this project has just been published in the journal Scientific Reports, one of the Nature Portfolio journals. https://www.news-medical.net/news/20230713/Binaural-beats-can-worsen-cognitive-performance-study-finds.aspx ###### REFERENCES  [1]  [Binaural beats to entrain the brain? A systematic review of the effects of binaural beat stimulation on brain oscillatory activity, and the implications for psychological research and intervention - PMC ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10198548/) [2] [The Cocktail Party Effect - American Academy of Audiology ](https://www.audiology.org/the-cocktail-party-effect/) [3][Scientists Discover That Your Ears Speak to Your Eyes and Vice Versa - American Academy of Audiology](https://www.audiology.org/scientists-discover-that-your-ears-speak-to-your-eyes-and-vice-versa/#:~:text=In%202018%2C%20Gruters%20and%20colleagues,Lovich%20et%20al%2C%202023).) [4] [Auditory Spatial Attention Representations in the Human Cerebral Cortex - PMC](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920769/) [5] [Beta Rhythms May Be Master Regulators of Cognitive Control - Neuroscience News](https://neurosciencenews.com/cognitive-control-beta-waves-25970/) [6] [Gamma Brain Waves: Uses, Purpose, Benefits, Function, More](https://www.healthline.com/health/gamma-brain-waves) [7] [Evolving perspectives on the sources of the frequency-following response | Nature Communications](https://www.nature.com/articles/s41467-019-13003-w) [8] [CIA](https://www.cia.gov/readingroom/docs/CIA-RDP96-00788R001200060018-5.pdf) [9] [How Hemi-Sync Works – HemiSync](https://hemi-sync.com/learn/how-hemi-sync-works/) [10] [What Are Delta Waves? | BetterSleep](https://www.bettersleep.com/blog/what-are-delta-waves/) [11] [Stages of Sleep: REM Sleep, Deep Sleep, and Circadian Rhythm](https://www.helpguide.org/harvard/biology-of-sleep-circadian-rhythms-sleep-stages.htm) [12] [K complex](https://dictionary.apa.org/k-complex) [13] [Theta Brain Waves: Frequency, Sleep, Binaural Beats, and More](https://www.healthline.com/health/theta-waves#theta-waves-vs-other-waves) [14] [What Are Alpha Brain Waves? | BetterHelp](https://www.betterhelp.com/advice/general/what-are-alpha-brain-waves/) [15 ][Evidence that gamma rhythm stimulation can treat neurological disorders is emerging | MIT News](https://news.mit.edu/2024/evidence-gamma-rhythm-stimulation-can-treat-neurological-disorders-emerging-0118#:~:text=Researchers%20are%20finding%20that%20stimulating,disorders%20such%20as%20Alzheimer's%20disease.) [16][https://hapbee.com/blogs/hapbee/everything-you-need-to-know-about-brainwave-entrainment](https://hapbee.com/blogs/hapbee/everything-you-need-to-know-about-brainwave-entrainment) [17][Entrainment: How synching lights with brainwaves can speed up learning](https://bigthink.com/neuropsych/entrainment-perceptual-learning/#:~:text=For%20example%2C%20recent%20research%20shows,%2C%20or%20cycles%20per%20second).) [18] [History Of Binaural Beats | And Its Evolution - Good Vibes: Transform Your Well-being](https://goodvibesofficial.com/blog/history-of-binaural-beats/) [19] [Alpha Theta Neurofeedback Training](https://neurofeedback.io/how-does-it-work/alpha-theta) [20][https://www.news-medical.net/news/20230713/Binaural-beats-can-worsen-cognitive-performance-study-finds.aspx](https://www.news-medical.net/news/20230713/Binaural-beats-can-worsen-cognitive-performance-study-finds.aspx) ### Additional Research  [Binaural Beats: Up-to-date evidence.](https://examine.com/other/binauralbeats/#examine-database) [A Meditation Gamechanger: Binaural Beats + An Experiment - Intuitive and Spiritual](https://www.intuitiveandspiritual.com/2017/01/a-meditation-gamechanger-binaural-beats-an-experiment/) [[Anxiety and depression treatment.∞]] [[Athletic performance enhancement.∞]] [[Audio-visual entrainment devices.∞]]     3.5