It was observed that clicks produced as powerful an effect in the auditory region as light flashes do at the same frequency in the visual cortex. Research has shown that “clicks” produce powerful AE (Chatrian, Petersen & Lazarte, 1959). The three auditory sounds often used for entrainment are clicks, isochronic tones and binaural beats. Personal acceptance is an important factor when choosing the “right” kind of tone When using tones for the purpose of entrainment, the result needs to meet both physiological (the actual evoked response) and psychological (a person’s emotional acceptance of the tones) criteria to be effective. By definition, entrainment occurs when the brain wave frequency duplicates that of the stimuli, whether audio, visual or tactile (Siever, 2003) as can be seen on an EEG. “Cleanliness” of sound is an all-important, yet often overlooked aspect of AE. This also means that while listening to entraining media clicks, pops, scratches and other interfering sounds will produce their own evoked potentials within the brain and temporarily impede the entrainment process. Entrainment only occurs from the thalamic relay point and not through the olivary bodies where binaural beats are heard. Another point is the medial geniculate (a relay point) from where auditory information is then transmitted into the thalamus on its way to the main cortex and the auditory cortex simultaneously. In the superior olive, the minute differences in the timing and loudness of the sound in each ear are compared, and from this you can determine the direction the sound came from. The signals from these nerves are carried down to several locations. Sounds pass through the ear into the cochlea where the auditory nerves are located. Neural Pathways of the Auditory Systemįigure 1 shows the neural pathway of hearing. The thalamus then passes the stimuli onto the sensory-motor strip, the cortex in general and associated processing areas such as the visual and auditory cortices in the temporal lobesįigure 1. ![]() Physiology of Auditory Entrainment: In order for entrainment to occur, a constant, repetitive stimulus of sufficient strength to "excite" the thalamus must be present. ![]() While audio stimulation methods would likely have a dissociative aspect to them, do they produce entrainment? Auditory entrainment is exempt from US-FDA, Health Canada and European Community Regulations as a medical device in its pure form unless medical claims are being made. There are presently upwards of 100 producers of “entraining” audio for relaxation, cognition, sleep, performance, etc. However, if a person has a fear of birds (ornithophobia), then chirping birds might be quite distressing.Īuditory Entrainment CDs and audio downloads for the purposes of auditory entrainment (AE) have become very popular. ![]() The sound of chirping birds in a forest produces even harmonics and will be more relaxing than the sounds from a factory (odd harmonics), not just because of the associations people make with sounds of nature versus factories, but also because of the harmonic content. Spooky sounds can make people feel anxious and scared, whereas up-tempo sounds can make people feel energetic and lively. Although sounds appear to be a personal experience, humans around the world are hard-wired to have similar experiences to certain sounds. ![]() Sound can have profound effects on people.
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