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Brainwave synchronization or "brainwave entrainment," is any practice that aims to cause brainwave frequency to fall into step with a periodic stimulus having a frequency corresponding to the intended brain-state (for example, to induce sleep). It depends upon a "frequency following" response, a naturally occurring phenomenon where the human brain has a tendency to change its dominant EEG frequency towards the frequency of a dominant external stimulus. Such a stimulus may be aural, as in the case of binaural beats, monaural beats, and isochronic tones, or else visual, as with a dreamachine, a combination of the two with a mind machine, or even electromagnetic radiation.
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Overview
Brainwave synchronization with binaural beats is said to help 'synchronize the two hemispheres of the brain', hence the Hemi-Sync (by Monroe Institute) example product. There is dispute over the efficacy of the practice.citation needed
It is also 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.1
Binaural beats
Binaural beats deserve special mention because of the intriguing manner in which the desired frequencies are obtained. 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, called binaural beats. 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. The "carrier frequency" (e.g., the 500 Hz in the example above), is also said by some to affect the quality of the transformative experience.citation needed Note that this effect is achieved without either ear hearing the pulse when headphones are used. Instead, the brain produces the pulse by combining the two tones. Each ear hears only a steady tone. Although some have claimed that these frequencies do provide help in treating certain medical conditions,2 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, also which naturally generate brain wave frequencies that differ from person to person and may vary from minute to minute.citation needed
See also
Notes
- ^ 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, 28(8):827-836). As the authors have stated, "the functional brain connectivity has become one of the most influential concepts in modern cognitive neuroscience, especially given the current shift in emphasis from studies of functional segregation to studies of functional integration."
- ^ The Clinical Guide to Light and Sound, Thomas Budzynski, Ph.D.
External links
- Brainwave Entrainment to External Rhythmic Stimuli - Interdisciplinary research and clinical perspectives symposium (Stanford University)
- Auditory Driving - Overview of sonic entrainment methods
- Virtual Light & Sound Machine Psychologist's unique program simulates non-binaural brainwave entrainment using flashes on computer monitor (Freeware).
Wikipedia content modification information:
- This page was last modified on 22 December 2008, at 19:09.
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