Brainwave synchronization is the practice to entrain one's brainwaves to a desired frequency, by means of a periodic stimulus whith corresponding frequency. The stimulus can be aural as in the case of binaural beats, or visual, as with a Dreamachine.

Overview

Brainwave synchronization is a private case of functional brain connectivity concept, whereas functional connectivity is defined as the temporal correlation between spatially remote neurophysiological events, expressed as deviation from statistical independence (temporal correlation) across these events in distributed neuronal groups and areas, which produce the brainwaves (for the recent review see Fingelkurts An.A., Fingelkurts Al.A., Kähkönen S. Functional connectivity in the brain – is it an elusive concept? Neuroscience & Biobehavioral Reviews. 2005,

Binaural beats

Main article: Binaural beats

Brainwave synchronization (entrainment) may be achieved when audio signals are introduced to the brain causing a response directly related to the frequency of the signal introduced. Two tones close in frequency generate a beat frequency at the difference of the frequencies, which is generally subsonic. For example, a 500 Hz tone and 510 Hz tone will produce a subsonic 10 Hz tone, roughly in the middle of the alpha range. The resulting subsonic tone may affect the state of mind of the subject.

Brainwave frequencies

Main article: Electroencephalography

The following summary shows frequencies that might be used

• Beta: 12Hz - 38Hz. This is subcategorized into SMR, beta 1 and beta 2.
  • SMR (12Hz - 15Hz) can result in relaxed focus, improved attention.
  • Beta 1 (15Hz - 20Hz) can increase mental abilities, IQ, focus.
  • Beta 2 (20Hz - 38Hz) can result in anxiousness and hightened sense of alertness.

• Alpha: 8Hz - 12Hz. This frequency can result in a state where the brain is awake, but not processing much. Often used for meditation. Also associated with a feeling of being "in the zone" and dreaming (REM sleep) and states of creative reverie.

• Theta: 3Hz - 8Hz. Associated with the hypnogogic state right after one wakes up or begins to fall asleep (drowsiness). Can be used for self-hypnosis.
  • Theta 1 (3Hz - 5Hz) suppression can result in improved concentration and attention while reducing hyperactiveness (after the session).
  • Theta 2 (5Hz - 8Hz) can result in a very relaxed sleep. This frequency range is often related to paranormal/spiritual experience.

• Delta: 0.2 - 3Hz. This frequency range usually results in deep sleep.

Although some studies have shown that these frequencies do provide help in treating certain medical conditions, there is not a wide acceptance by the medical community to adopt the practice of brainwave synchronization for emotional/mental disorders. The fixed, constant frequency of the synchronization is less helpful than techniques such as classical neurofeedback or learning meditation, which naturally generate brain wave frequencies that differ from person to person and may vary from minute to minute.

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