Our brain is made up of nerve cells called neurons. Neurons communicate with each other through electrical and chemical signals. Brain waves are rhythmic and repetitive patterns that occur with electrical activities in the brain. Brain functions such as planning thoughts, emotions and behaviors are realized by electrical activities in the brain. The pattern of brain waves changes according to a person’s state of consciousness and cognitive processes. For example, when we feel tired and sleepy, slower brain waves become dominant.

Brain activity often involves a combination of various wave types. Depending on the situation, a certain type of wave may dominate the others. If the balance between brain waves is disturbed, psychiatric or neurological diseases may occur.

Brain waves were first discovered by German neurologist Hans Berger in the 1920s.

Brain waves are recorded with a technique called electroencephalogram (EEG), which receives signals with electrodes placed on the scalp. EEG is most affected by the activity of pyramidal neurons in the cerebral cortex. Because these neurons are arranged in an orderly manner and they produce signals together. The signals from the deeper cells weaken until they reach the electrodes on the scalp. EEG records the synchronized activities of groups of neurons, not individual neurons. Since its discovery, the EEG has been a useful tool for assessing mental state and function. EEG is used to diagnose problems such as epilepsy, sleep disorders and Alzheimer’s disease .


Five types of brain waves have been identified, classified according to their frequency.

  • Delta waves (1-4 Hz) are the slowest brain waves. It occurs in deep meditation and dreamless sleep. It can be a sign of healing and renewal.
  • Theta waves (4-8 Hz) occur during sleep and rest. It is associated with introspection, dreams, and vivid daydreaming.
  • Alpha waves (8-12 Hz) occur during quiet, thoughtful times. It may indicate that the brain is in a resting state. It is the first type discovered.
  • Beta waves (12-25 Hz) are the most common pattern during normal wakefulness. Beta waves predominate when the person is awake and focused on solving a problem.
  • Gamma waves (25-70 Hz) are the fastest type and are associated with higher level mental processes.
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Brain Waves During Sleep

The brain is highly active during sleep, and different stages of sleep are associated with different types of brain waves.

Stage 1: In this stage, theta waves take the place of alpha waves as the person falls asleep from the resting state. Sleep is light and easily disrupted.

Stage 2: Brain waves slow down, alpha waves disappear completely, and thetas become dominant.

Stages 3 and 4: Deep sleep stages. Brain activity slows down and delta waves form. Sleepwalking and nightmares occur during these stages.

Stage 5 (REM): In the REM stage, the muscles are temporarily paralyzed, rapid eye movements are observed. Dreams can also occur at this stage. Brain wave patterns are similar to those in stages 1 and 2, but sleep is deeper.

Relationship with Diseases

There is a close relationship between brain waves and mental health. For example, if certain areas of the brain are overstimulated, a person may develop problems such as anxiety, sleep problems, impulsivity or aggression. Decreased activity can lead to problems such as depression, chronic pain, and insomnia. Instability in brain rhythms may be associated with obsession, panic attacks and epilepsy. In epileptic seizures, neurons become hypersynchronous, almost causing an electrical storm. An excess of gamma waves may occur with problems such as schizophrenia, hallucinations, and delusions.

Neurofeedback is a treatment technique that aims to improve mental health by monitoring and regulating brain wave patterns. The predominant abnormal activity in the EEG is evaluated and the formation of the desired type of waves is rewarded. For example, in someone with depression, visual and auditory stimuli are used to create beta waves to reduce complaints. Brain waves are also used to create a brain-computer interface.

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