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Abstract
Some deficiencies in attention are associated with anomalous slow-wave
activity in the brainwave frequency spectrum. A common feature of many
treatment protocols is the suppression of EEG activity in the 4-8Hz
frequency band. An auditory subliminal treatment has been developed which
appears to s uppress Theta activity. This treatment is self- administered in
situ without interfering with ongoing activities. Several preliminary cases
are discussed in the context of patient self-administered treatment
adjunctive to more established protocols. The use of auditory subliminal
stimulation to reduce autonomic arousal with patients with stress
exacerbated attention deficits is also discussed.
Broadly speaking, there appear to be three approaches to the modification of
the brainwave spectrum. The first is EEG biofeedback in which specific
frequencies or frequency bands are displayed which patients are instructed
to enhance or inhibit. For conditions characterized by cortical underarousal,
patients are trained to enhance faster frequencies and/or inhibit low
frequency activity. For conditions of hyperarousal or insufficient low
frequency amplitudes patients are taught to enhance low frequency
amplitudes. What is striking about EEG biofeedback is the generality of the
technique and the range of disorders effectively treated. In the treatment
of attention deficits, hyperactivity, anxiety, pain, learning disabilities,
epilepsy, sequela of closed head injury, sleep disorders, and asthma, the
unifying factor underlying the conditions appears to be some abnormal EEG
pattern. Treatment protocols reported as effective for these disorders vary
considerably with regard to electrode location, size, type, and electrode
montage.
Feedback frequencies likewise differ
considerably with some clinicians favouring single frequencies while others
favour feedback frequency bands. Further, the frequency bands used in
training differ among various clinical settings, with apparently equivalent
results. This suggests that the different protocols may train the same
mechanism but perhaps through different processes. If the anomalous EEG
activity is excessive low frequency activity then training to inhibit 4-8
Hz, or to enhance 12-15 Hz, 16- 20 Hz, or 14 Hz, activity may all be
effective. The fact that the effects of training can be accomplished with
different electrode placements suggest that change is being effected
subcortically.
The second approach involves administering auditory, visual or
microelectrical stimulation that entrains brainwaves. The rationale for
these procedures is that if psychophysiological states are associated with
identifiable brainwave densities, then these states can be enhanced by
entraining the appropriate EEG frequency with auditory, visual or
somatosensory stimulation. Research has indicated that alpha brainwave
activity is associated with subjective euphoria (Lucas, 1991), relaxation
(Benson, 1983), increased creativity (Hardt & Gale, 1993), decreased pain (Melzack
& Perry, 1975), decreased anxiety and increased hypnotic susceptibility (Delmonte,
1984). Depression, on the other hand, has been found to be related to
reduced Beta and enhanced Theta in the frontal cortex (John et al., 1989;
Schatzberg et al., 1986).
Auditory and visual stimulation of set brainwave frequencies have been found
to enhance the amplitude of brainwaves at the same frequency (Barlow et al.,
1960; Ohatrian et al., 1960). The rationale for the light and sound machines
which present visual and auditory rhythmic stimulation in the range of about
4 to 30 Hz, is that enhancement of the amplitude of particular frequencies
will be accompanied by subjective psychophysiological changes associated
with the increases in brainwave densities. Thus, stimulation in the Alpha
range should have a calming and relaxing effect. Theta stimulation might
enhance susceptibility to suggestions while stimulation in the Beta ranges
might have a stimulating influence.
Cranial Electrical Stimulation (CES) refers to the transcranial application
of electricity in the microamperage range. Devices approved by the United
States Food and Drug Administration usually deliver less than 1.0 mA at a
pulsating frequency of 100 Hz. As with EEG biofeedback, CES treatment also
appears robust to variations in electrode type and placement. Although the
stimulation frequency is well beyond those frequencies commonly associated
with EEG treatment, research has indicated that CES treatment increases the
amplitude of the slow EEG frequencies in the frontotemporal (Jarzembski,
1985) and in the occipital cortex (Cox & Heath, 1975).
The third general approach is that of teaching the patient self-regulatory
behaviours that have an effect on the brainwave spectrum. Hypnotic states,
for example, are associated with increases in central Theta and decreases in
Alpha in posterior regions (Schwartz et al., 1993). Breath control and PCO2
feedback normalizes the EEG of seizure sufferers by attenuating Theta and
increasing Alpha (Fried, 1993). And, of course, meditation has long been
recognized as a method for decreasing cortical arousal as reflected in
increases in Alpha and Theta (Delmonte, 1984; Hardt, 1993). Experienced
meditators exhibit these increases even when not meditating and very
advanced meditators (no thought) appear to inhibit the electrocortical
activity of both hemispheres (Meissner & Pirot, 1983). Further, many
relaxation protocols are associated with increased Alpha with attendant
reductions in stress and anxiety (Benson, 1983).
As the above brief review indicates, the curious aspect of the burgeoning
field of neuronal regulation is that so many apparently different treatment
protocols appear effective for a rather wide range of disorders. The
unifying concept for many of these treatment protocols is that
irregularities in the EEG spectrum are rendered more normalized as a result
of treatment. The concept of neuronal regulation as a treatment modality is
based on the premise that anomalies in the brainwave spectrum are associated
with specific disorders, and that these anomalies can be normalized with
attendant reduction in the associated symptomatology. The great variation in
treatment protocols that appear effective for normalizing the EEG and/or
reducing symptomalogy is indicative that a more fundamental neurological
change is taking place than surface EEG recordings reveal.
The notion that a fundamental abnormality is being redressed by the various
treatment protocols is also related to findings that EEG abnormalities often
vary with regard to location. In substance abusers for example, EEG
anomalies are sometimes observed in the frontal, temporal, parietal, and
occipital lobes (Braverman et al., 1990). Further, the fact that
anticonvulsant medication has been found useful for many different
psychiatric disorders (Post et al., 1989) also suggests some fundamental
underlying neurological abnormality. The fact that many of these disorders
respond to treatments that vary in terms of site of intervention and
training frequency suggests that the various treatments have the effect of
regularizing the central nervous system. This regularization presumably can
occur as a result of protocols that inhibit or potentiate brainwave
frequencies that are anomalous. Hence, elevated Theta during cognitive tasks
such as reading or arithematic indicates deficient attention and can be
remediated with interventions that inhibit excessive Theta activity.
In clinical practice, one encounters many manifestations of attention
deficiency. Some patients cannot concentrate because they are too anxious
whereas others complain of inability to concentrate based on depressed
emotional states. Many patients in treatment for psychological distress also
complain of physiological conditions that interfere with attentional focus.
These complaints vary. Some maintain that their vision becomes "foggy" or
"blurred" which accompanies a feeling of mental "fuzziness". Others do not
report physiological sensations but rather state that they often forget what
they are doing or find that they are very easily distracted. Still others
report simply that they learn very slowly and easily forget what they have
been taught.
Attention deficiencies that are related to physiological underarousal or
overarousal have been effectively treated with relaxation protocols, EMG
biofeedback (Carter & Russell, 1985; Potashkin & Beckles, 1990) and sensory
stimulation (Mangina & Beuzeron-Mangina, 1992). The latter procedure is
particularly interesting. It involves the presentation of tones to the right
and/or left ear whenever the electrodermal activity (EDA) level falls below
6.5lmhos on either hand. Tone presentation is contralateral to the EDA
measurement. When the EDA of either hand exceeds 8.5 lmhos, various
relaxation techniques are used to reduce the EDA level. When the bilateral
EDA is within the 6.5 to 8.5 lmhos window, visual or auditory learning tasks
of increasing complexity are presented.
This procedure has been found to be a very effective treatment for "learning
disabled" students. Improvements in school grades are marked and are
sustained at two-year post- treatment follow-up. However, like brainwave
treatment, many sessions are required. Although improvements are observed
after 30 sessions, marked change is apparent after 60 sessions. It is also
interesting to note that the learning disabled subjects were selected on the
basis of poor school grades. About one-third of the subject population
satisfied the DSM-III-R criteria for Attention Deficit Disorder with
Hyperactivity.
The research cited above on EEG and other physiological activity has been
done with supraliminal sounds. The work of Zenhausern and his associates
(1973, 1974) and work I have done indicates that effects on the EEG and
performance can also occur with subliminal auditory stimuli. Subliminal
auditory messages have been shown to affect mood, memory, motor performance,
physiological state, problem-solving, and aesthetic judgement (Swingle,
1992). However, of particular relevance to the treatment of attention
deficiencies are reports that nonverbal auditory subliminal stimulation can
affect performance (Zenhausern et al., 1973; Zenhausern & Hansen, 1974),
autonomic arousal (Swingle, August 1992) and brainwave activity (Swingle,
March 1993).
One day, several years ago, I was in my laboratory trying to perfect a slow
wave modulating supraliminal tone to be used in a recording to guide
patients in a paced breathing relaxation exercise. One of my graduate
students emerged from his office, which was about 20 feet away, complaining
that he had suddenly become quite fatigued and simply could not concentrate.
While pondering the cause of his dilemma, it occurred to us that the sound I
was working on, although clearly audible to me, might have been subliminal
in his office and responsible for his fatigue. We checked this out and
indeed the sound could not be heard in the student's office. Extrapolation
of the drop in sound pressure over distance from the sound measured at the
source indicated that the sound would have been in the effective subliminal
range (Swingle, 1992) of approximately - 18 dB(C). We prepared an audio tape
of this modulating tone embedded 18 dB(C) below masking white noise, so that
the tone would be subliminal, and found the tape clinically useful for many
patients with sleep disturbance. The sound was a single sinusoidal tone that
modulated between 285 Hz and 315 Hz at about 7 cycles per minute.
This serendipitous episode motivated an investigation of the effects of
subliminal presentation of compound sinusoids of the type used in light and
sound relaxation devices. The decision to test sounds in the conventional
EEG spectrum and to use compound sinusoids was guided by published research,
reviewed previously, indicating that such sounds will entrain brainwave
activity.
To present stimuli at frequencies within the audible range, two sinusoidal
tones, close in frequency, were simultaneously presented at equal
amplitudes. When two sinusoids are presented which differ in frequency,
beats will be heard. This phenomenon is apparent up to frequency differences
of about 60 Hz after which the partials of the compound sound will be heard
(Plomp, 1976). The rate of the beating is equal to the difference in
frequency of the two sinusoids and the loudness of the beats is maximum when
the amplitude of the two sinusoids is equal (Green, 1976).
One might expect the effects of subliminal presentation of the beat
frequencies to parallel supraliminal presentation. There is, however,
considerable evidence indicating independent processing of supraliminal and
subliminal stimuli (Swingle, 1992). Further, the evidence also indicates
that subliminal stimuli, the content of which is unavailable to recipients'
selective attention, give rise to qualitatively different responses as
compared with supraliminal presentation (Swingle, 1992).
The stimulus tapes used in the following laboratory studies and clinical
trials were all prepared as described in detail in Swingle (1992). Briefly,
two equal amplitude sinusoidal tones, one at 300 Hz and the second up to 25
Hz higher in frequency, are embedded in filtered white noise. The subliminal
sounds are presented at a maximum Sound Pressure Level (SPL) of -17 dB(C)
relative to the white noise embedding medium. Tapes prepared for clinical
use usually have two different embedding SPL sound tracks, one on each side
of the tape. On one side, the embedding is at -17 dB(C), whereas the flip
side of the tape is embedded at -25 dB(C). The two different SPL tracks
coincide with different effective ranges for males and females, and
facilitate patient participation in the determination of an effective
treatment sound
level (Swingle, 1992).
Several studies with college student volunteers indicate a reliable decrease
in heart rate and ratings of subjective arousal with brief presentations of
beta frequency subliminal sounds. Presentations of frequencies of 10 Hz and
below, on the other hand, give rise to increased heart rate and higher
ratings of subjective arousal (Swingle, August 1992).
The heart rate changes associated with the subliminal presentations range
from -3.5% to +4.0% over baseline measurements. The average heart rate
change associated with tones in the beta range of 15 Hz and 25 Hz were
between -1.2% and -3.5%. Heart rate changes for subliminal tones in the
slower frequencies of 2 Hz, 5 Hz, 8 Hz, and 10 Hz were between +2.2% and
+4.0%.
The beta range tapes have been used clinically with patients who complain of
anxiety or stress exacerbated conditions. The effect of the subliminal on
the patients' heart rate is determined during standard psychophysiological
assessment procedures. Patients who demonstrate heart rate reductions
associated with a one-minute presentation of the subliminal are given a
treatment cassette for home use. The average heart rate change observed
during the one-minute presentation is about a 3% reduction.
A treatment choice protocol (Swingle, 1992) in which patients are required
to select the active subliminal from a control sound track, white noise
without embedded subliminal tones, revealed that of 7 patients with diverse
complaints, all selected the active subliminal as most beneficial.
As Benson (1983) has stated, relaxation is associated with decreased heart
rate and increases in cortical Alpha. The 25 Hz subliminal (SUB/B) and the
10 Hz subliminal (SUB/A) tones were presented alternately, every 5 minutes,
during 35-minute Alpha brainwave biofeedback sessions for two patients. The
mean time over threshold (10 lv) for the 7.5 Hz- 13 Hz Alpha range was 32.2%
higher and 51.8% higher when SUB/B was presented as compared to when SUB/A
was presented (difference in time over threshold between SUB/A and SUB/B
presentations divided by time during SUB/A presentation). The above two
averages were for an alcoholic and a manic depressive patient, respectively.
Since subliminal tones can affect arousal and the brainwave spectrum it
seemed plausible that a self-administered treatment could be developed for
some people with attention deficits. It also seemed quite plausible that the
treatment could be administered in-situ with headphones and a portable
cassette player. Further, if presented at a low volume, treatment could be
self-administered as needed without interference with ongoing activities. In
short, patients could self-administer the treatment at work or school and
still read, listen to lectures, carry on conversations, and the like.
The most critical feature of the treatment, however, is that the patients
must be able to recognize when they are experiencing attention problems. In
practice, I have found that many patients are quite capable of making this
judgement. As discussed above, some patients report mental "fuzziness" or
visual blurring, whereas others simply feel (or are told) that they are not
adequately attending to task.
A unifying factor in all of the brainwave treatment protocols for attention
deficit is the inhibition of amplitude in the 4-8 Hz band. Hence, the
inhibitory effects of the subliminal 10 Hz tone (SUB/A) on 4-8 Hz brainwave
frequency band was determined for 11 patients as part of the
psychophysiological assessment completed on intake. The testing procedure
involved presenting SUB/A or a contrast condition alternately every 2
minutes. The various electrode placements used (all references and ground
placements on earlobes) included unipolar Cz; midway between Fz - Cz and Cz
- Pz, bipolar; bipolar F3 and F4; and unipolar Fz. Contrast conditions
included no sound, white noise only (i.e., no subliminal), a subliminal 25
Hz tone (SUB/B), and a subliminal 300 Hz tone also embedded in white noise.
With each patient, SUB/A was presented, alternately with a contrast
condition, for a minimum of six 2-minute presentations. The first effect
observable in every case was that white noise, with or without an embedded
subliminal signal, reduced Theta. This would appear to be consistent with
the treatment procedure developed by Mangina and Beuzeron-Mangina (1992), in
which tones were used to enhance arousal during cognitive training. Also in
every case, however, SUB/A reduced 4-8 Hz amplitude more than any other
condition. The range of Theta amplitude reductions with SUB/A as compared
with other noise contrast conditions was from 3.9% to 37.2% In every case,
the Theta amplitude reduction was statistically significant. The Theta
amplitude reduction during SUB/A presentation relative to no sound contrast
conditions ranged from 10.9% to 37.5%
At the time of this writing, 22 patients referred with the diagnosis of
Attention Deficit Disorder (ADD), are being treated with SUB/A. The ages of
the patients range from 6 to 50. In each case, SUB/A was found to suppress
Theta amplitude relative to a no-sound contrast by at least 20%. Patients
were instructed to wear headsets with a portable cassette player and listen
to the tape as needed. If involved in a task such as school work or other
work related activity, the patients were instructed to listen to the sound
until they felt that they could continue the activity with adequate
attentional focus. They were instructed to keep the volume low enough to be
able to converse with others if necessary. They were also told to vary the
volume until they found the most effective range. In most cases, the patient
could readily determine when attention deficits or feelings of cognitive
fuzziness were being experienced. Younger patients were often told by
parents or teachers that they were being inattentive or disruptive and
instructed to self-administer SUB/A. A note from the therapist explaining
the treatment procedure was provided for teachers or employers.
It is important to note that most of the patients were involved in some
other treatment in addition to the self-administration of SUB/A. These other
treatments included various biofeedback modalities including EEG, EEG
disentrainment, psychotherapy and hypnosis. Further these other treatments
were, in some cases, administered by therapists other than the present
author. Patients for whom SUB/A was prescribed were those found to show
Theta inhibition with SUB/A testing during intake. The results reported on
the effects of as needed application of SUB/A are based on the reports from
patients, teachers and parents.
Unsolicited school progress reports of children using SUB/A indicate
increased attentional focus in a variety of areas including reading,
listening, independent study, science, interdisciplinary studies,
social-emotional development and sports.
Initial concern that children may become dependent on SUB/A, much like
dependence on stimulants such as Ritalin, arouse from teachers' statements
such as "...needs (SUB/A) to stay focused.", "...good work if using
(SUB/A).", "...interacts well (with other children) when using (SUB/A).",
"...remarkable improvement (in sport activity) with (SUB/A)."
However decreased use of SUB/A has been reported by patients as they
progress in other neuronal regulation treatments.
Two patients requested SUB/A treatment alone, although they had been
referred for EEG training. Both of these patients, high school students,
reported improved attention and reduced time required to complete homework.
Neither has requested further treatment and both have discontinued use of
SUB/A in school but both continue to use SUB/A, at times, while doing
homework.
Every patient has noted improvement in attentional focus and each reported
that attentional deficiency improved immediately upon self-administration of
SUB/A. One patient had lost several jobs and she was, at the time of
referral, at risk of losing her present job. Her employer reported marked
improvement as does the patient. Parental report of one of the patients
indicates reduced self-stimulating behavior and improved "attitude" toward
school work. Finally, a patient who experienced visual blurring and
"spaciness" reported that the tape markedly improves her condition to the
point where she can engage in activities previously precluded by her
symptoms.
A major feature of SUB/A is that it provides immediate benefit resulting
from EEG Theta suppression without any observed negative side effects. SUB/A
is also very inexpensive, particularly relative to CNS stimulants such as
Ritalin, and appears to facilitate neurofeedback treatment for ADD. Further,
since patients experience immediate relief with the use of SUB/A,
neurofeedback sessions can be less frequent and therefore affordable to more
families.
Given the in-situ self-administered protocol of SUB/A treatment, it may well
be found to potentiate EEG biofeedback training for the remediation of
ADD/ADHD. Ideally, for that group of clients who can discriminate states of
adequate attention from states of inadequate attention, the self-application
of SUB/A may facilitate learned control of Theta inhibition in a manner
similar to that accomplished with EEG Theta inhibition training. Such
learning does appear to occur with some clients exposed to EEG biofeedback
training for ADD. Steve Stockdale (personal communication) described cases
in which after biofeedback training, children learn to switch on adequate
focus. In one case that he described, the child would say to himself "get
BIG", an acronym for Brain-in-Gear to help access focused attention.
The effects of SUB/A and SUB/B on autonomic arousal and the EEG spectrum
appear robust but are nonetheless counterintuitive. Supraliminal tones, and
flashing lights, in the Alpha and Beta ranges have been found to produce
autonomic and EEG changes opposite to those found with subliminal auditory
presentations. If the compound sinusoids of SUB/A (i.e., blended 300Hz and
310Hz tones) are presented above auditory threshold one hears the 10Hz beat
frequency. However, the blended sinusoids have other acoustic properties
that are not readily available to phenomenal representation. Even at a
supraliminal level, there are harmonics of the blended sinusoids that may be
subliminal. When the carrier and the beat frequencies are subliminal there
are presumably many other acoustic properties of the sounds that are also
subliminal. Hence, it is possible that the properties of the subliminal
signal that are influencing the autonomic and central nervous systems are
those other than the fundamental beat frequencies.
The clinical application of SUB/A is data driven in the sense that EEG Theta
suppression was observed. Fundamental work on the effects of manipulating
the many acoustic properties of subliminal signals will facilitate an
understanding of the apparent clinical effects of subliminal auditory
stimulation. Finally given that SUB/A suppresses EEG Theta, it is possible
that SUB/A presentations during neurofeedback may facilitate treatment
efficacy. This possibility is presently being investigated.
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