Physiology and Clinical Applications of Audio-Visual Entrainment Technology

by Siegfried Othmer | May 5th, 2004

Part 1 of 3. See bottom for PDF version.

Articles on:
Physiology and Clinical
Audio-Visual Entrainment
by Dave Siever C.E.T.
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Audio-Visual Entrainment: I. History and Physiological Mechanisms
David Siever¹, Edmonton, Alberta, Canada
Abstract: Since the discovery of photic driving by Adrian and Matthews in 1934, much has been
discovered about the benefits of brain-wave entrainment (BWE) or audio-visual entrainment
(AVE) as it is commonly known today. Studies are now available on the effectiveness of AVE in
promoting relaxation, hypnotic induction and restoring somatic homeostasis, plus improving
cognition, and for treating ADD, PMS, SAD, migraine headache, chronic pain, anxiety,
depression and hypertension.
Clinical reports of flicker stimulation appear as far back as the dawn of modern medicine. It was
at the turn of the 20th century when Pierre Janet, at the Salpêtrière Hospital in France, reported
that when he had his patients gaze into the flickering light produced from a spinning spoked
wheel in front of a kerosene lantern, it lowered their depression, tension and hysteria (Pieron,
1982). Then, in 1934, Adrian and Matthews published their results showing that the alpha
rhythm could be “driven” above and below the natural frequency with photic stimulation (Adrian
& Matthews, 1934).
This discovery further propagated a host of small physiological outcome studies on the “flicker
following response” by many well respected researchers (Bartley, 1934, 1937; Durup & Fessard,
1935; Jasper, 1936; Goldman, Segal, & Segalis, 1938; Jung, 1939; Toman, 1941). Finally in
1956, W. Gray Walter published the results on thousands of test subjects comparing flicker
stimulation with the subjective emotional feelings it produced (Walter, 1956).
Meanwhile, William Kroger accomplished other important developments in photic stimulation.
Kroger was a physician investigating why radar operators were going into trances in front of
their radar sets and of course, leaving the ship or plane at great risk to the enemy. He concluded
that the rhythmic “blip” of the radar was “pulling” the radar operators into a trance state. These
findings compelled Kroger to team up with Sydney Schneider of the Schneider Instrument
Company of Ohio to construct and market the first electronic clinical photic stimulator, called
the “Brainwave Synchronizer.” It comprised an intense xenon strobe light complete with a
rotating dial that could be set to the frequencies of the standard four brain wave rhythms. They
found the Brainwave Synchronizer had powerful hypnotic qualities and soon published a study
on hypnotic induction (Kroger & Schneider, 1959). They also prompted other studies involving
hypnotic induction in surgery and dentistry, and studies of general interest to the hypnosis
profession (Sadove, 1963; Margolis, 1966; Lewerenz, 1963).
n 1981, Comptronic Devices Limited was incorporated, with a focus on designing TENS units
and EMG feedback devices for dental (TMJ) applications. In 1984, I designed the “Digital
Audio-Visual Integration Device” (DAVID1), used for hypnotic induction and to calm anxiety in
performing arts students at the University of Alberta. The “light and sound” (L&S) market at this
time was in its infancy and resided primarily within the new age sector. There was little “known” Page 3
research to support L&S technology, and professionals by and large showed disinterest in L&S
technology. Due in part to poor quality L&S products and a lack of research, about 40 L&S
companies have come and gone, most of them during the 1980s and 1990s. However, since the
time of Adrian and Matthews, a considerable number of studies have verified photic and auditory
“driving” of the EEG. I have since re-named this phenomenon as “audio -visual entrainment” or
AVE, as any given frequency of stimulation that is reflected in brain wave activity and
observable on an EEG or QEEG can be entrained. Many more studies on photic or combined
audio/photic stimulation exist than pure audio stimulation studies, however audio-only
stimulation studies have confirmed audio entrainment (Chatrian, Petersen, & Lazarte, 1959) and
its effect on calming masseter muscle tension (Manns, Miralles, & Adrian, 1981).
Physiology of Audio-Visual Entrainment
n order for entrainment to occur, a constant, repetitive stimuli of sufficient strength to “excite”
the thalamus must be present. 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 cortexes.
Figure 1 shows the visual pathway with the retina of both eyes becoming excited and sending
pulses down the optic nerve, through the optic chiasm, and into the lateral geniculate of both
thalami. From here, the visual signals are passed onto the visual and cerebral cortexes for further
processing. Notice that there is very little delay from the onset of the flash to the response in the
optic nerve, but a delay of approximately 100 msec occurs by the time the visual evoked
potential (VEP) is elicited in the visual cortex. This delay may be why entrainment occurs best at
the natural alpha frequency — as 100 msec equates to 10 Hz.
Figure 1. The EEG Photic Stimulation Path
Photic entrainment begins its process as a series of overlapping evoked potentials (Kinney,
McKay, Mensche, & Luria, 1973). Kinney broke down a simple VEP into its various
components (Figure 2) representing the passage of time for 4, 8, 12 and 20 Hz. As can be seen,
much of the VEP occurs within 250 msec, correlating to four Hz. The various overlapping parts Page 4
were then vector summed into the mathematical VEP and compared with the actual VEPs
observed by EEG at the higher, entrained frequencies, shown in Figure 2.
Figure 2. EEG Wavelet
When this mathematical model was compared with the actual observed EEG of the entrained
stimuli (Figure 3), a high degree of predictability was observed, demonstrating that photic
entrainment is indeed a vector summation of VEPs and not a novel neuronal process.
Figure 3. EEG VEPs – Vector Addition (theoretical) Model vs Observed EEG
By definition, entrainment occurs when an EEG reflects the brain wave frequency duplicating
that of the stimuli, be it audio, visual or tactile (Siever, 2002). Entrainment occurs best near one’s
own natural alpha frequency (Toman, 1941; Kinney et al., 1973). LEDs and xenon strobe lights
contain much harmonic content due to the “squareness” or rapid turn-on and turn-off transitions
of the stimuli and these harmonics are reflected within the EEG. Figure 4 shows a strong and
pure entrainment at 12 Hz. The harmonics (small wavelets) seen in the EEG are a reflection of
the actual harmonics contained within the stimulus. Square wave stimulation is associated with
an increased risk of seizure (Joyce & Siever, 2000; Ruuskanen-Uoti, 1994). The only way to
produce entrainment without harmonics is via sine wave stimulation in which the stimuli turn on
and turn off in slow, gentle transitions and do not contain harmonics. (Van der Tweel, 1965;
Townsend, 1973; Regan, 1966; Siever, 2002). Page 5
Figure 4. EEG Showing Photic Entrainment
AVE at 18.5 Hz has also been shown to produce dramatic increases in EEG amplitude at the
vertex (Frederick, Lubar, Rasey, Brim, & Blackburn, 1999), where it was found that:
a) eyes-closed 18.5 Hz. photic entrainment increased 18.5 Hz EEG activity by 49%.
b) eyes-open auditory entrainment produced increased 18.5 Hz. EEG activity by 27%.
c) eyes-closed auditory entrainment produced increased 18.5 Hz EEG activity by 21%.
d) eyes-closed AVE produced increased 18.5 Hz. EEG activity by 38.3%.
Entrainment primarily shows itself frontally and near the vertex (Siever, 2002). Figure 5 is a
QEEG, or “brainmap” from the SKIL (Sterman-Kaiser Imaging Labs) database, in 1Hz bins
showing the frequency distribution of AVE at 7.8 Hz. The area within the circle at 8Hz shows
maximal effects of AVE in central, frontal and parietal regions (at 10uv in this case) as
referenced with the oval area on the legend. It is through these effects that AVE has proven
effective in treating depression, anxiety and attentional disorders. A harmonic is also present at
16 Hz. (the circled image), which is typical of semi-sine wave (part sine/part square wave)
Figure 5. Brain Map in 1Hz Bins — During 7.8 Hz AVE (SKIL-Eyes Closed)
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Body/Mind Effects of Audio-Visual Entrainment
We conceptualize AVE as achieving its effects through several mechanisms at once (Siever,
2000). These include:
1) dissociation / hypnotic induction,
2) increased neurotransmitters,
3) possible increased dendritic growth,
4) altered cerebral blood flow, and
5) normalized EEG activity.
Dissociation is described as a process in which feelings, memories and physical sensations are
kept apart from other information with which they would normally be logically associated. In
pathological terms, dissociation is a maladaptive disruption in integrated functioning typically
associated with depersonalization, stress, identity, amnesia and depersonalization disorders
(Brownbeck & Mason, 1999).
On the other hand, dissociation occurs when we meditate, exercise, read a good book, take in a
movie or enjoy a sporting event, because we get drawn into the present moment and dissociate
from all of our daily hassles, worries, anxieties and the resulting unhealthy mental chatter.
Several techniques such as dot staring and stimulus depression have been shown to induce
dissociation (Leonard, Telch, & Harrington, 1999). Audio dissociation analgesia using white
noise and/or has been shown to effectively increase pain threshold and pain tolerance during a
dental procedure (Morosko & Simmons, 1966).
Regardless of the activity, this type of dissociation reduces our weekly stress load, whether we
are aware of it or not. In essence, when we focus on something, we dissociate from other things.
The saying, “ a change is as good as a rest,” has much more truth to it than initially meets the eye
(Siever, 2000).
The first study on dissociation induced via entrainment involved hypnotic induction, and found
that photic stimulation at alpha frequencies could easily put subjects into hypnotic trances
(Kroger & Schneider, 1959; Lewerenz, 1963). Figure 6 shows the results of Kroger and
Schneider’s study in which nearly 80% of the participants in the study were in a hypnotic trance
within six minutes of photic entrainment.
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Figure 6. Photic Stimulation Induction of Hypnotic Trance (Kroger & Schneider, 1959)
Psychologists have been looking for ways to dissociate their clients as a part of fear and phobia
treatment. Inducing dissociation using AVE delivered by the DAVID1 was found to be more
effective than dot staring or stimulus deprivation (Leonard, Telch, & Harrington, 1999) as shown
in Figure 7.
Figure 7. AVE Induced Dissociation (Leonard, et al., 1999)
Furthermore, Leonard completed a second study with people who experience dissociative
anxiety (Leonard, Telch & Harrington, 2000). People with dissociative anxiety feel a need to
have a sense of control in their lives and become anxious or panicky when they dissociate, be it
driving home, at the office, or in a clinical setting. The Acute Dissociation Inventory (ADI) is a
35-item self-report scale (Leonard,, 1999). It assesses dissociative sensations (ADI-Dissoc)
and subjective anxiety, or dissociative anxiety in response to dissociative provocation (ADIAnx).
Leonard and her colleagues clinically dissociated people who become anxious when
dissociating, by using a DAVID Paradise HemistepTM alpha session. As expected, the
participants’ anxiety (ADI-Anx) had almost doubled by the end of the AVE session. The
surprise, however, was that their heart rate actually decreased, contrary to normal anxiety
reactions (Figure 8). With the ability to clinically dissociate these people, yet simultaneously
calm them down somatically, AVE can be used as a desensitization tool for reducing dissociative
anxiety. Page 8
Figure 8. Dissociative Anxiety and Somatic Arousal (Leonard, et al., 2000)
A dissociative mindstate or hypnotic trance may be described in terms of an altered state of
consciousness (ASC) in which the subject (or an independent observer of the subject) observes a
qualitative shift in the normal pattern of mental functioning (Glicksohn, 1986-87). ASCs
produced via overstimulation also occur when a person is bombarded with higher than normal
levels of sensory input, usually in more than one sensory modality (Hear, 1971, Lipowsky, 1975,
Goldberger, 1982). Glicksohn studied photic entrainment and the ASCs produced. He monitored
the EEGs of subjects during photic entrainment. They all described a wide variety of reactions to
the stimulation with some reporting incredible imagery consisting of items they had seen before
in their lives, intertwined with geometrical patterns while others reported no visual changes at
all. At the end of the study, Glicksohn concluded that:
1) It is the increase in alpha activity created by photic driving, and not the natural
alpha activity itself, that is conducive to an ASC.
2) The appearance of visual imagery is neither necessary nor all that is involved to
indicate the experience of an ASC.
3) If a photic driving response is not elicited, the subject will not experience an ASC.
Glicksohn’s observations support the concept that in order for AVE to occur, the stimulating
frequency must have a direct impact on brain wave frequency and be observable on an EEG.
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Dissociation and Restabilization
Dissociating clients with trauma histories, during the course of treatment is important. The state
of mind that a person has at any given moment is made up of the brainwave activity associated
with apprehension, anxiety, physical tension (proprioceptive/afferent associations), destructive
thoughts, and conditioned responses relating to the colors, smells, sounds, etc. Once the mind is
clear, all of these tensions, conditioned responses (bracing habits), fearful thoughts and the
effects of afferance (sensory information) subside, allowing the mind and brain to relax, become
more malleable and open to new healthy thoughts, post-hypnotic suggestions, brainwave activity
and so on. During AVE, the EMG and electro-dermal responses fall, finger temperature increases
and breathing becomes smooth and diaphragmatic. These changes reflect a return to homeostasis
or restabilization, hence the term dissociation and restabilization (DAR) (Siever, 2000).
Figure 9 shows a typical reduction in forearm EMG and Figure 10 shows a typical increase in
finger temperature. Notice that restabilization begins after about six minutes of AVE, when the
user begins dissociating. Figure 11 shows normalization of breathing and heart rate variability
following exposure to AVE at 7.8 Hz.
Figure 9. Forearm EMG Levels During AVE (Hawes, 2000)
Figure 10. Peripheral Temperature Levels During AVE (Hawes, 2000)
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Dendritic Growth
There is evidence that blood serum levels of serotonin, endorphine, and melatonin rise
considerably following 10 Hz., white-light AVE (Shealy, 1989). Increases in endorphines reflect
increased relaxation while increased norepinephrine along with a reduction in daytime levels of
melatonin, indicate increased alertness (Figure 11).
Figure 11. Neurotransmitter Levels Following AVE (Shealy, 1989)
There is evidence that stimulating neurons with mild electrical stimulation promotes growth of
dendrites and dendritic shaft synapses in the cells being stimulated (Beardsley, 1999; Lee,
Schottler, Oliver, & Lynch, 1980). However, studies do not yet exist on the influence of AVE on
dendritic growth, although it is suspected because many people with autism, palsy, stroke and
aneurysm (Russell, 1996) have gained significant motor and cognitive function following a
treatment program of AVE.
Cerebral Blood Flow
Cerebral blood flow (CBF) is essential for good mental health and function. SPECT and FMRI
imaging of CBF show that hypoperfusion of CBF is associated with many forms of mental
disorders. CBF increases dramatically during AVE (Fox & Raichle, 1985; Sappy-Marinier et al.,
1992). Figure 18 shows an increase of 28% in cerebral blood flow within the striate cortex, a
primary visual processing area within the occiput. As an interesting note, maximal CBF occurs at
7.8 Hz, the Schumann Resonance of the earth. Page 11
Figure 12. Cerebral Blood Flow at Various AVE Repetition Rates (Fox & Raichle, 1985)
Following Fox & Raichle’s study came a whole head PET analysis of visual entrainment at 0, 1,
2, 4, 7, &14 Hz (Mentis, et. al., 1997). This study on 19 healthy, elderly (mean age=64 years)
found that regional cerebral blood flow (rCBF) was activated differentially with the:
1) left anterior cingulate showing maximal increases in rCBF at 4 Hz.
2) right anterior cingulate showing decreases in rCBF with frequency.
3) left middle temporal gyrus showing increases in rCFB at 1 Hz.
4) striate cortex showing maximal rCBF at 7 Hz.
5) lateral and inferior visual association areas showing increases in rCBF with frequency.
While there may be benefits to increasing occipital CBF, there is even greater concern regarding
conditions involving hypoperfuson of CBF in frontal regions. Frontal disorders include: anxiety,
depression, attentional and behavior disorders, and impaired cognitive function (Amen, 1998).
Figure 13 shows an increase in frontal CBF recorded on Hershel Toomin’s “Thinking Cap” (or
“Hemoencephalogram”) using infra -red light to measure perfusion of CBF. Notice that CBF at
FPZ increases by 15% in 10 minutes (Toomin, personal communication).
Figure 13 Hemoencephalographic Measure of Cerebral Blood Flow During 10 Hz AVE
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Normalized EEG activity
Figure 14 shows a fairly typical brain map in 1 Hz bins of a person with mild depression and
anxiety as shown on the Skil database. Notice that alpha is slowed and approaching +2SD from
the norm and that some beta frequencies (16-18 Hz) are high (>1SD) in central frontal areas.
Figure 14. Brain Map in 1 Hz Bins of Individual with Depression and Anxiety (SKIL-Eyes
Following an AVE session of 7.8 Hz., both alpha and beta activity are normalized as shown
below in Figure 15.
Figure 15. Brain Map Following 7.8 Hz AVE (SKIL-EO)
n closing, AVE has the ability to quickly and effectively relax people out of high sympathetic
activation and traumatic states of mind, bringing about a return to homeostasis. AVE may be Page 13
used alongside hypnotic suggestions on tape/CD or live via a microphone. At the same time
however, AVE exerts a powerful influence on brain/mind stabilization and normalization. At the
end of an AVE session, the user may realize that he/she has never felt so relaxed for years —
perhaps not since childhood.
Parts II of this article series will address several studies where AVE was the clinical intervention.
Part III will address the application of AVE in treating attention deficit and cognitive disorders.
1. For more information, address all correspondence to:
David Siever, Mind Alive / Comptronic, 9008-51 Avenue, Edmonton, Alberta, Canada T6E
5X4. Toll Free: 800-661-6463, Phone: 780-461-9551, Web:, Email:
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