Brainwave Amplitudes as Seen During Brain Biofeedback From left to right: Delta, Theta, Alpha, SMR, low and high Beta, Busy Brain, Gamma, EMG Red bar represents highest amplitude (at 10Hz, alpha) in this second of recording
Strange to think the brain produces electricity measurable beyond the scalp. And a battery-operated device can change the course of that electricity. Or a word can.
The term for the brain’s electricity is brainwaves or oscillations. Scientists primarily use the term “oscillations”; the rest of us, “brainwaves.” As the name suggests, the brain’s electricity appears as waves, some smooth, some erratic, some big, some tiny. Brainwaves have been divided into observable patterns produced by bundles of neurons firing together, ranging from large and slow to so small they can disappear into the electrical patterns of muscle tension. Yes, muscles produce electricity, too.
Larger brainwaves reflect relaxation and sleep; the smaller ones reflect attention; then as they get smaller and smaller, they reflect alert thinking then anxiety and lastly in the most elusive of brainwaves, coherence, perhaps even consciousness. No one really knows. The brain is the final frontier, beyond Sherlock’s ken.
Delta brainwaves are the largest waves at a frequency of 0.5 to 3 Hz. Sub-delta for audiovisual entrainment (AVE) is 0.5 to 1 Hz. Delta waves appear during deep sleep, i.e., Stage 4 sleep, where researchers suggest the brain cleans house and regenerates. Delta waves produced while a person is awake are associated with daytime sleepiness and fatigue. In brain injury, they appear in damaged areas during daytime wakefulness, as if those areas are snoozing. Also, if electrical blockages interrupt the corticothalamic tract that loops between the outer and deeper areas of the brain, neurons stop producing alpha brainwaves in sync with each other and instead produce delta waves at 1 to 2 Hz, resulting in chaotic brainwave activity.
Theta brainwaves range from 3 to 7 Hz (or 5 to 8 or 4 to 8, depending on who is defining theta-wave frequency). Low theta is 3 to 5 Hz; high 6 to 7. And 7.5 to 8.5 is associated with visualization. Theta waves appear in the moments before falling asleep. It’s like being in a twilight zone. They are also associated with daydreaming or tuning out. After brain injury, if neurons produce theta, instead of alpha or beta, you feel unengaged from the world and tend to lose attention.
Alpha brainwaves are between 8 to 13 Hz (or 7.5 to 12.5 or 8-11). Low alpha is 8 to 10 (or 11). High alpha 12 (11 to 13).
Alpha waves are associated with creativity, thought, understanding, and a relaxed mind that is aware of its surroundings. High alpha is associated with the big picture when reading and with alert broad awareness at any time. Meditation enhances alpha to produce peacefulness, warmth in the hands and feet, thoughts or ideas (e.g., turning on imagination), and better immune function. People of high intelligence may have higher peak frequency, e.g., 12 Hz. Also, brain injury can markedly drop the alpha frequency, as it did with me down to 8 Hz.
Sensorimotor rhythm or SMR brainwaves at 13 to 15 Hz are generated in the sensorimotor strip that crosses the centre of the head horizontally from ear to ear between the frontal lobes and parietal lobes. They are associated with relaxed, focused attention.
Brain injury can reduce SMR and cause SMR enhancement to induce sleepiness during brain biofeedback. However, they are fundamental to restoring brain function and to being able to think calmly and reduce anxiety and impulsivity.
Beta brainwaves range from 15 to 30 Hz. Beta at 16 to 20 Hz are active when you’re awake and alert, having a stimulating conversation, debating, problem solving, deciding, or thinking. You require more beta when learning.
Beta spindles — or beta spindling — are excessive beta brainwave activity. Some have described it as cortical irritability. Imagine how you feel when irritated. That’s like your brain when producing beta spindles.
It’s unable to come out of that irritated state.
Since beta waves are about thinking and problem solving, beta spindling is that excessively. That excessiveness tips you over into worrying, obsessively revolving a thought or memory in your mind and unable to resolve it, keeping you up at night.
Where in the brain the beta spindles occur results in different effects. Research showed that those with beta spindles in the frontal lobes had higher impulsivity and hyperactivity and some degree of higher insomnia. Beta spindles at CZ, over the sensorimotor strip, are associated with sub-groups of ADD and ADHD.
Thinking is good. Excessive thinking and remembering is not. That’s the difference between beta brainwaves and beta spindles.
Another area of interesting study for beta spindles is, “A strong linkage between beta frequencies and GABA-A receptor genes has been reported, in line with the often-reported medication effects of benzodiazepines resulting in a ‘beta buzz’ (Porjesz et al., 2002).”
How does this intersect with stimulating gamma brainwaves? Is it really a beta buzz or more the “happy gamma” effect I’ve written about in my book and research into transcendental meditators and controls have found? And what effect does stimulating gamma brainwaves in the presence of beta spindles have physiologically and behaviourally? Could this lead to physical effects of a hyperstimulated brain like restless leg syndrome??
Busy brain is about 24 to 36 Hz in the beta brainwave category and associated with anxiety and what I call, “rumination on steroids.” These brainwaves are implicated in perseverating — the round and round thinking that people with brain injury get trapped in. Busy brain drives the person physiologically into worrying, indecisiveness, and perseveration. The only thing that has effectively and permanently reduced busy brain in me is inhibiting it during brain biofeedback. It’s like peeling back an onion. You inhibit the widest range first; then with each successful reduction, shrink the range. For example, you begin by reducing 21 to 35 Hz at CZ, narrowing the range down over several years to 24 to 28 Hz.
Gamma brainwaves, at about 40 Hz, are the least well known. From my own experience, they feel like the foundation on top of which all other brainwaves sit and are enhanced (see Chapter 23 and Chapter R in Concussion Is Brain Injury: Treating the Neurons and Me and the associated web pages for details).
They are the seat of feeling coherent, your brain as one harmonized unit. They open perception up so that you perceive more of the external world and can engage in it. They markedly reduce stress so that whereas before a gamma brainwave enhancement session a small problem will seem insurmountable, after enhancement the problem is suddenly solvable or at least no longer overwhelms and rockets you into an orbit of uncontrollable frustration, anger, or tears.
Some suggest gamma is associated with the conscious mind.
Glial Cells and Gamma
“Glial cells are an integral part of functional communication in the brain.” (Lee et al.)
Most of us are familiar with neurons, brain cells with long arms called “axons.” Axons carry electricity aka brainwaves along the length of the neuron to their ends. At that point, they cause the neurons to talk to each other through neurotransmitters that cross the spaces between the neurons. Glial cells are another type of cell in the brain. They include astrocytes as well as microglia, oligodendrocytes, radial glial cells, and ependymal cells. Glia mediate gamma brainwaves.
Do certain brainwaves correlate with certain neurotransmitters? That’s not known for sure. But gamma brainwaves are seen to correlate with the neurotransmitter GABA, which is also poorly understood.
Astrocytes are closely associated with synapses, the spaces through which neurotransmitters flow between neurons. They “could play a role in the modulation of neuronal GABA release.” (See Buskila et al.) Their close association with synapses also allows bidirectional interaction with neurons. Acting like a structure of two or more cells joined together, they facilitate communication to further brain regions through Ca2+ waves. Among other processes, astrocytes tightly control K+ outside the cells via a process called “K+ clearance.” The body including the brain cannot function well if there’s too much or too little K+. K+ is potassium; Ca2+ is calcium. The plus signs denote a positive charge. Current flows from positive to negative.
“activation of K+ currents has been associated with enhanced spike timing precision at gamma frequencies in both pyramidal and basket cells in the hippocampus (Penttonen et al., 1998)”
Yossi Buskila, Alba Bellot-Saez, and John W. Morley. Generating Brain Waves, the Power of Astrocytes. Front Neurosci. 2019; 13: 1125. doi: 10.3389/fnins.2019.01125
In other words, by tightly controlling K+, astrocytes influence gamma brainwave production. And they are also involved in GABA action on neurons.
Gamma and Brain Injury
Research seems to show that people with brain injury do not produce gamma under circumstances that normally would induce them. What does this mean?
“The reduction in cortical gamma oscillations was accompanied by impaired behavioral performance in the novel object recognition test, whereas other forms of memory, including working memory and fear conditioning, remained unchanged. These results support a key role for gamma oscillations in recognition memory...These data reveal an unexpected role for astrocytes as essential contributors to information processing and cognitive behavior.” (emphasis mine)
HS Lee, A Ghetti., A Pinto-Duarte, X Wang, G Dziewczapolski, F Galimi, et al. Astrocytes contribute to gamma oscillations and recognition memory. Proc. Natl. Acad. Sci. U.S.A. 111 E3343–E3352. 2014. doi: 10.1073/pnas.1410893111
This study seems to suggest that reduced gamma brainwave production underlies many cognitive issues arising from brain injury. Their method was akin to stimulating gamma brainwaves in humans who’ve experienced brain injury.
Read more plus innovative research with gamma brainwaves in my book.
EMG is muscle contraction, inhibited in the 100 to 200 Hz range, but EEG is monitored from 2 to 62 Hz. Thus, 52 to 58 Hz is chosen to reflect EMG and avoid artifact contamination by various countries’ electrical systems of 50 and 60 Hz. Muscles produce higher voltage than normal EEG. EMG is like an ocean that lifts and lowers all the brainwave boats. EEG/EMG ratios cancel out the EMG effect and show whether you’ve enhanced or inhibited the trained brainwaves. According to Dr. Lynda Thompson, “One has to be very strict about reducing muscle artifact whenever one works with EEG.”