Brainwave entrainment was first identified in 1934, although its effects had been noted as early as Ptolemy.
Not long after the discovery of the Alpha brainwave by Hans Berger in 1929, researchers found that the strength of the wave could be "driven" beyond its natural frequency using flickering lights. This is called "Photic Driving", which is another word for brainwave entrainment using photic (light) stimulation. In 1942 Dempsey and Morison discovered that repetitive tactile stimulation could also produce entrainment and in 1959, Dr. Chatrian observed auditory entrainment in response to clicks at a frequency of 15 per second.
By the 1960s entrainment started to become a tool rather than a phenomenon of the brain. Anesthesiologist M.S. Sadove, MD, used photic stimulation to reduce the amount of anesthesia needed for surgery. Bernard Margolis published an article on brainwave entrainment used during dental procedures, noting less anesthesia required, less gagging, less bleeding and a general reduction in anxiety.
In a 1973 issue of Scientific American, Dr. Gerald Oster examined how combining 2 pure tones resulted in a rhythmic beat which he called Binaural and Monaural Beats. In comparing Binaural beats against Monaural beats, Oster noted that Monaural beats were shown to elicit extremely strong cortical responses, which is the electrical activity responsible for entrainment. Oster concluded that while Binaural Beats produced very little neural response (because the depth of a Binaural Beat is only 3db or 1/10 the volume of a whisper), they could be useful in diagnosing certain neurological disorders.
In the 1980's studies continued with Dr. Glen Solomon and others researching entrainment for headache relief as well as general relaxation. In 1981, Arturo Manns published a study showing the effectiveness of Isochronic Tones as a means of audio-based brainwave entrainment. This was later confirmed by others such as David Siever. Michael Hutchison also wrote his landmark book MegaBrain in 1981, outlining the many possible uses of entrainment from meditation to enhancing creativity. In 1980, Tsuyoshi Inouye and associates at the Department of Neuropsychiatry at Osaka University Medical School in Japan found that photic stimulation produced "cerebral synchronization". The effect was confirmed in 1984 when Dr. Brockopp analyzed audio-visual brain stimulation and hemispheric synchronization during EEG monitoring.
Studies continued into the 90's with researchers such as Dr. Russell and Dr. Carter who explored the potential of using entrainment with ADD and learning disorders. Research has also been conducted into Chronic Fatigue, Chronic Pain, Seasonal Affective Disorder, Hypertension and a number of other disorders.
Brainwave entrainment research continues today with the work of Dr. Thomas Budzynski, David Siever, psychologist Michael Joyce, Dr. Tina Huang and many others.
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