The Binaural Beat Percept
Binaural beats are like optical illusions for the ears. When two different pure tones are presented simultaneously to each ear of a listener, the listener hears the illusion of a third tone. For example, if you play a 350 Hertz (Hz) tone in the left ear and a 360 Hz tone in the right, it yields a beat with a frequency of 10 Hz. This third beat is the binaural beat. The brain then uses a process known as ‘frequency following response’ to follow along at the new frequency (10 Hz) producing corresponding brainwaves that can affect behavior and memory encoding.
Today, binaural beats are being explored as a ‘digital drug,’ with claimed effects ranging from pain relief to memory enhancement.
Science is only just beginning to unravel this mysterious phenomenon, or identify which brain regions are involved in generating the binaural beat percept.
These auditory illusions were first described in 1839 by Prussian physicist, Heinrich Wilhelm Dove. His unusual experiment, involving tuning forks, was later replicated by Gerald Oster, who envisioned binaural beats as a tool in research and medicine. Oster published his findings in Scientific American in 1973 with the suggestion that they be used to investigate the neuronal basis of hearing.
How Binaural Beats effect Memory
The precise effects of beats remain to be fully established, however a new wave of research is beginning to reveal their potential in memory and cognition.
One study examined the effects of binaural beats on working memory, which is the ultra-short term form of memory that enables you to navigate a task in real time. Working memory has been described as the “sketchpad of consciousness.” When you clear working memory out, the information is forgotten. If you hold that information in mind, by thinking about it, you allow it to traverse to the next stages of memory processing (that occur largely during sleep).
They found that listening to binaural beats not only increased memory but also modified cortical network activity in a way that was characteristic of high information transfer.
Following a similar line of enquiry, researchers at Mahidol University found that listening to 40 Hz binaural beats for 20 min enhances working memory function. They also observed that this intervention induced specific oscillations, termed gamma and beta, in regions of the brain associated with learning.
However, not all beats are created equal. A paper published in Psychological Research stated that the presentation of binaural auditory beats can affect long-term memory both positively and negatively, depending on the frequency used. This is likely a result of the fact that brain waves – which are defined by the frequencies they oscillate at – are each associated with different tasks or mental states.
How exogenous Brain Waves effect the brain
Neurons, or brain cells, get excited, light up, and fire continuously in response to information or internal dialogue. Even distant neurons are able to talk to each other by sending information through their complicated network. As groups of neurons fire, they produce brain waves that oscillate at particular frequencies. This constant hum of activity plays a critical role in communication between different parts of the brain. Transmission between brain cells and structures happens in the form of electrical impulses. Accumulated together, these impulses create rhythmic oscillations, or brain waves, that can be measured using an electroencephalogram (EEG). In short, this technique records the activity of many neurons using electrodes placed on the scalp.
Neuroscientists housed at MIT found that two brain regions that are key to learning — the hippocampus and the prefrontal cortex — use different brain-wave frequencies to communicate during a learning activity. Furthermore, these oscillations can reinforce correct information while repressing errors, helping the brain learn new information.
The researchers are now investigating whether they can speed up learning by delivering noninvasive electrical stimulation that oscillates at particular frequencies. This form of low voltage electrical stimulation, like binaural beats, represents a method of brain wave manipulation.
Dempsey and Morison were the first to suggest that individuals could intentionally change their brain wave patterns through exposure to different elements, like light and sound. More recently, Journal of Neuroscience published a paper investigating the effect of binaural beats on EEG rhythms. In this study, 10 epilepsy patients were implanted with intracranial electrodes, and the researchers recorded their EEG response to both monaural and binaural beats to see how the beats influence brain waves.
They found that when the patients listened to 10 Hz and 40 Hz binaural beats EEG power increased, meaning there were stronger brain waves at these frequencies. This entrainment had previously been described for 40 Hz binaural beats, which are termed “gamma” frequency waves.
How Gamma & Beta Waves effect Memory
Gamma waves are a pattern of neural oscillation (typically 40 Hz) associated with memory and attention. Gamma oscillation plays a role in sensory integration, a process by which several brain areas are activated for perception of a stimulus. Cortical activity and perception are not driven by the external stimulus alone. Sensory information has to be integrated with various other internal constraints such as expectations, recent memories, planned actions as well as motor execution. In this way, the brain waves provide channels of communication between many groups of neurons needed to compute a task.
Beta oscillation (with a frequency range of between 12.5 and 30 Hz) is also involved in interpreting a received stimulus and occurs following gamma oscillation. This process is known as gamma-to-beta transition, which helps to filter out errors or unnecessary information from a context. This is essential to the action of learning and memory, awarding us the ability to receive information from our environment, rapidly filter through it to focus on the important features and begin the process of long-term memory consolidation.
While gamma activity acts as the conductor of information processing, beta is acting like a signal that gates access to working memory. It clears out working memory, and can act as a switch from one thought or item to another.
Our memories are blinking in and out of existence; each time a memory blinks on, it is riding on top of a wave of activity in the brain.
The first recorded gamma waves were from monkeys, but scientists quickly found that measuring an individual’s brain gamma waves could provide information about the person’s cognitive state and abilities. In fact, individuals whose brains produce more gamma waves may experience higher levels of cognition and creativity. Therefore, gamma waves might also be a key to improving mood and sparking creativity in individuals.
How Gamma Waves Affect Memory & Attention
Nobel prize winning scientist, Sir Francis Crick believes that the 40Hz frequency may be the key to human consciousness. By studying one aspect of consciousness, visual awareness, Crick and his colleague, Christof Koch, concluded that memory and attention rely upon the brain’s ability to generate semi-synchronous oscillations in the 40-70 Hz range.
In a 2011 study, researchers measured EEG activity through a range of emotional stages. Researchers found that induced gamma activity distinguished different mechanisms of attention regulation when the brain was trying to determine the emotional valence (negative or positive) of a stimulus. This ability to categorize information into emotion catalogues is a key feature of human cognition, a skill we rely upon to navigate daily life. These researchers suggested that induced gamma activity may be a useful tool to uncover the mechanism of cognitive control of emotion.
This ability to regulate emotions is certainly an indicator of individuals who are well adapted to thrive in society. But gamma waves are more than just a helpful method of detection. The value of gamma wave activity may be highlighted by considering what happens in the brain without them.
Gamma wave “deficiency” is a hallmark of patients with degenerative brain diseases, like Alzheimer’s, and many other cognitive problems like sleep dysfunction, an inability to practice meditation, or a lack of self-awareness. In fact, as the amount of gamma waves decrease, an individual is increasingly prone to depression, stress, impulse or lack of focus.
Gamma waves are even being used in medical science as a biomarker for schizophrenia. The 40 Hz auditory steady-state response (ASSR) involves playing a 40 Hz tone and measuring brain wave entrainment using an EEG. While neurotypical patients respond to this tone by generating gamma waves in the cortex, patients with schizophrenia demonstrate no entrainment response.
In recent years, it has been shown that binaural beats have an impact on cognitive ability, attentional focusing, information processing, and creativity, which are all characteristic of gamma oscillation.
Though direct causal links between neural activity and binaural beats are yet to be demonstrated, it’s clear that brain wave activity and behavior can be influenced with this mysterious tool. The basic assumption is that listening to binaural beats in a specific frequency band will entrain the same frequency in the brain, as seen in the ASSR. This means that the activity of the brain will match to a certain frequency set by an external stimulus, creating optimal conditions for a chosen task, like learning.
This process of entrainment is termed neural synchronization. This means that binaural beats represent a neural entrainment technique where the brain “takes over” or synchronizes its activity based on external acoustic stimulation.
Be sure to choose your beats wisely
Binaural beats are not restricted to gamma frequency synchronization, however. Alpha wave activity (8-12 Hz), for example, is associated with idle or restful mental states.
Though there are no known side effects, it’s wise to choose your beats according to the precise effects you’re hoping to yield. Slipping into a restful mindset when you’re preparing for exam may not be the best strategy. But by subjecting the brain to gamma waves it is possible to promote cortical stimulation and synchronization, thus improving cognitive processes.
Listening to binaural beats while learning is one way to boost memory, but beats can also be used to enhance sleep, during which memories are consolidated from short- to long-term. Studies have shown that beats are particularly effective at increasing the time and quality of particular stages of sleep
The balance between two types of electrical activity in the sleeping brain can influence whether we remember or forget tasks that were learned the previous day. Animal studies have shown that the same neurons involved in forming the initial memory of a new task or experience are reactivated during sleep to consolidate these memory traces in the brain.
This is represented by slow oscillations and delta waves (both 1-4 Hz), which are hallmarks of so-called non-REM (NREM) sleep. Memory consolidation happens during this time as various structures in the brain, including the hippocampus, communicate through rhythmic oscillations to replay information from the previous day.
By exposing the brain to beats that create low-frequency tones in the brain, these sound waves generate slower frequency brainwaves that promote deeper states of sleep and more efficient memory integration.
Though neuroscientists are still hard at work decoding the mystery of binaural beats and their impact on the brain, they offer up a promising and low risk intervention to improve memory. As we learn more about the rhythms of the brain, the mechanisms of binaural beats may become clearer. Until then, try it at home!