Introduction to Beta Waves
Beta waves (12-30 Hz) are low amplitude, fast brain waves that are linked to the conscious mind. Beta waves are the baseline frequency in our hyperproductive society. They are produced when we are actively engaged in mental and physical activities such as thinking, focusing, talking, sensing, and moving. Too much Beta can cause anxiety, stress, overarousal, and an inability to relax. Too little Beta can result in ADHD, depression, and poor cognition.
Like the other frequency bands, Beta can be broken down into several sub-bands, including Beta 1 (12-15 Hz), Beta 2 (15-18 Hz), and Beta 3 (18-30 Hz). Beta 1 and Beta 2 are associated with active states (thinking, planning, calculating, focusing), while Beta 3 is associated with hyperactivity, such as anxiety, stress, tension, and overarousal.
Beta waves are most evident frontally. They are produced by deep layers of the prefrontal cortex. Evidence exists that Beta is produced in subcortical regions, notably the basal ganglia, and then propagated to the cortex via the thalamus. Although an array of non-motor functions are associated with the basal ganglia, this group of subcortical structures are primarily responsible for motor control. Two side-by-side thalami are present, one in each cerebral hemisphere above the brainstem. They can be thought of as relay stations, given that much information proceeding to the cerebral cortex is first brought to the thalami before being sent off to its cortical destination.
Beta Functions
Beta is crucially involved in top-down controlled processing. One of the dominant frameworks in current neuroscience is called the “Predictive Coding” framework. The Predictive Coding framework sees the brain as a dynamic predictor of our environment based on our past experiences. In this framework, higher brain regions carry feedback predictions about the incoming input from lower regions, and mismatches between the predicted and actual input are represented as prediction errors, which are propagated in a feedforward manner to update the predictions. As a top-down process, Beta carries feedback information about the predictions, while Gamma carries bottom-up, feedforward information about the prediction errors (Betti et al. 2021).
Beta: A Frequency of Many Hats
Beta has been linked to a plethora of motor and cognitive operations, including movement, visual perception, reward processing, working memory, decision-making, and language processing (Spitzer & Haegens 2017). Recent studies have sought to unify its functional role across these domains.
Researchers initially thought Beta was the idling rhythm of the motor system because Beta increases during periods of non-movement and consistent, steady movement. It decreases when movement stops or starts. Accumulating evidence suggests that Beta may be an active process that maintains the current motor activity while preventing neural processing of new movements.
This “continuation-of-the-status-quo” function of Beta extends beyond the sensorimotor system into the cognitive domain as well. Beta decreases in cognitive tasks such as sensory perception that require little top-down control*. Beta increases In cognitive tasks like focused attention that require strong top-down control. Beta band activity is especially prominent when a current cognitive task must be maintained and no change is expected. For example, Beta increases during the delay period in working memory tasks when the stimulus must be maintained to detect a matching stimulus.
In memory functions, Beta acts as a control signal that gates access to working memory. Increases in prefrontal Beta clear out working memory and can act as a switch from one thought to another. Similar to Beta’s role in the motor system where it supports the stopping of action, Beta (in the right frontal region) functions to prevent long-term memory retrieval (Schmidt et al. 2019).
*Top-down signals originate from higher cognitive areas such as the prefrontal cortex (PFC) and are associated with modulating functions such as selective attention. Weak top-down tasks are largely stimulus driven.
Beta and Meditation
Beta’s Role in Beginning Meditators
Since Beta is associated with active mental states such as thinking, it may seem logical that we would want to broadly decrease Beta during meditation to settle the thinking mind. This is true for beginners who are focusing on relaxing and quieting the mind. For instance, the relaxation response protocol for beginners rewards diminished high beta (for relaxation) and diminished low beta (for thinking).
However, once beginners transition to Focused Awareness meditations, these meditations are no longer calming, as the brain is working hard to maintain a focus on the object of attention. Because Beta is a top-down control frequency, beginning Focused Awareness meditators will require more Beta to keep the mind on a single track of focus. Ample amounts of Beta are needed to sustain cognitively-demanding tasks, such as giving a job to the monkey mind.
Beta and Focused Awareness Meditations
Focused Awareness (FA) meditations in general are characterized by increases in high-frequency Beta waves (Travis and Shear 2010). Beta waves in the prefrontal cortex increase when we are engaged and noticing the salient features of our object of attention. Both novice and advanced FA meditators need Beta to maintain fine-tuned internal concentration. Novices need much more Beta than advanced practitioners, however, because at advanced levels focusing efforts are sustained by more effortless, well-ingrained, bottom-up habits.
Beta and Open Monitoring Meditations
Open Monitoring (OM) meditators (such as in Vipassana, Mindfulness, and Zen traditions) are not trying to keep their mind on track with a single point of focus, as they have an open awareness of whatever contents of consciousness arise. Thus, OM meditators do not require the top-down control afforded by Beta. This is especially true for advanced OM meditators who have developed well-trained bottom-up brain processes for keeping their thoughts from straying without the need for top-down Beta control.
Several OM meditations are associated with less posterior beta, a finding that has been interpreted differently for different meditation styles. Mindfulness meditators showed reduced midline and right posterior Beta during their practice, which correlated with a reduced sense of self. Given that midline Beta is involved with processing bodily sensations, it makes sense that one’s sense of self is reduced in tandem with reductions in Beta (Dor-Ziderman et al. 2013).
Zen Shikantaza meditators produce fewer Beta waves in posterior brain regions while maintaining open and detached awareness. Since these regions are involved in visual processing, reduced activity in these areas is associated with reduced visual imagery, especially visual processing involved in moving (Faber et al. 2015).
Beta Reductions in Quiet Mind/TM Meditations
Quiet Mind/TM (Transcendental Meditation) meditators see a decrease in Beta in the front and back of the brain, as they are trying to surrender attention rather than focus it (Travis et al. 2010). TM meditators show less internal dialog and enhanced present moment awareness during the practice, which is in part reflected in reduced Beta in right posterior regions, namely the right temporal regions (Travis & Parim 2017). The right temporal region is responsible for memory and motor aspects of speech production, so beta reductions here reflect a decrease in internal mental dialog.
Note: Quiet Mind/TM is neither FA nor OM.
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