Brainwave synchronization

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

Overview
Brainwave synchronization, also called brainwave entrainment, 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, 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."

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, 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" (i.e. the 500 Hz in the example above), is also said by some to affect the quality of the transformative experience. Holosync's brainwave entrainment program emphasizes the progressive lowering of the carrier frequencies, for instance.

Although some studies have reported 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.

Overview
Brainwave synchronization, also called brainwave entrainment, 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, 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."

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, 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" (i.e. the 500 Hz in the example above), is also said by some to affect the quality of the transformative experience. Holosync's brainwave entrainment program emphasizes the progressive lowering of the carrier frequencies, for instance.

Although some studies have reported 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.