Notes on Brainwaves

Posted: 2024-08-26
Tags: Brain

Brainwaves (rhythmic activation of many neurons) are associated with many activities.

• Brainwave Types
• Brainwaves in the Brain
• Cognitive Correlations
  • Delta Waves
  • Alpha Waves
  • Beta Waves
  • Gamma Waves
• Brainwaves During Sleep
  • Delta Waves
  • Theta Waves
  • Alpha Waves
• Misc.

Brainwave Types¹

There is not a good concensus on these ranges. Sources all have slightly different frequency ranges.

Note: An entirely different scheme is repeated elsewhere on Wikipedia⁵⁸: Delta wave (0.1-3 Hz), Theta wave (4-7 Hz), Alpha wave (7-12 Hz), Beta wave (12-30 Hz), Gamma wave (30-100 Hz).

Brainwaves in the Brain⁹

“The cortex is organized anatomically into six layers, no matter whether you look at mice or humans or any mammalian species, and this pattern is present in all cortical areas within each species.”

“[E]ach layer has its own distinctive combination of cell types and connections with other brain areas.”

“[I]n the topmost layers, neuron activity is dominated by rapid oscillations known as gamma waves. In the deeper layers, slower oscillations called alpha and beta waves predominate.”

Miller’s lab at MIT has a theory that “the brain’s spatial organization helps it to incorporate new information, which carried by high-frequency oscillations, into existing memories and brain processes, which are maintained by low-frequency oscillations.”

“Under this theory, imbalances between high- and low-frequency oscillations can lead to either attention deficits such as ADHD, when the higher frequencies dominate and too much sensory information gets in, or delusional disorders such as schizophrenia, when the low frequency oscillations are too strong and not enough sensory information gets in.”

Cognitive Correlations

Delta Waves

Delta wave activity (during sleep) has also been purported to aid in declarative and explicit memory formation².

Alpha Waves

Researchers “measured increases of up to 25% in alpha brain wave activity before mistakes occurred”⁴. Using the logic: “alpha waves indicate idleness, and mistakes are often made when a person is doing something automatically, or ‘on auto-pilot’, and not paying attention to the task they are performing. After the mistake was noticed by the subject, there was a decrease in alpha waves as the subject began paying more attention”⁴.

Researchers found “entrainment substantially accelerated learning in a discrimination task to detect targets embedded in background clutter or to identify radial vs. concentric Glass patterns embedded in noise compared to entrainment that does not match an individual’s alpha frequency”⁴.

Beta Waves

Beta states are the states associated with normal waking consciousness⁵.

There are three sub-types of beta waves:

• Low Beta Waves (12.5–16 Hz, “Beta 1”) —
• Beta Waves (16.5–20 Hz, “Beta 2”) —
• High Beta Waves (20.5–28 Hz, “Beta 3”) —

Gamma Waves

“Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer’s disease, epilepsy, and schizophrenia”⁸.

Gamma stimulation may have therapeutic potential for Alzheimer’s disease and other neurodegenerative diseases⁸.

“Entrainment or synchronization of hippocampal gamma oscillations and spiking to 40 Hz via non-invasive stimuli in the gamma-frequency band, such as flashing lights or pulses of sound, reduces amyloid beta load and activates microglia in the well-established 5XFAD mouse model of AD. Subsequent human clinical trials of gamma band stimulation have shown mild cognitive improvements in AD patients who have been exposed to light, sound, or tactile stimuli in the 40 Hz range.”⁸

“Hypersensitivity and memory deficits due to Fragile X syndrome may be linked to gamma rhythm abnormalities in the sensory cortex and hippocampus”{^9].

Brainwaves During Sleep

Delta Waves

Associated with deep (aka “slow wave”) sleep².

Reduced delta waves during deep sleep are associated with Parkinson’s disease (which is further associated with dementia), schizophrenia, diabetes, and other disorders.

Alcohol disrupts delta wave sleep and GABA precursors improve it².

Theta Waves

Associated with transition states between sleep and awareness³.

Alpha Waves

Alpha waves occur during REM sleep.

During studies “subjects report non-refreshing sleep and have EEG records reporting high levels of alpha intrusion into sleep”⁴.

Chronic fatigue patients exhibit “alpha wave intrusion” (alpha instead of delta waves in non-REM sleep)⁴. It appears amplify symptoms of the disorder.

Misc.

“Diets very low in carbohydrates, such as a ketogenic diet, have been shown to increase the amount of delta activity and slow wave sleep in healthy individuals”².

Older source, does not include gamma waves.