Binaural-Beat Induced Theta EEG Activity and Hypnotic Susceptibility
D. Brian Brady
Northern Arizona University
Six participants varying in degree of hypnotizability (two lows, two mediums, and two highs) were exposed to three sessions of a binaural-beat sound stimulation protocol designed to enhance theta brainwave activity. The Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C) was used for pre and post-stimulus measures of hypnotic susceptibility. Time-series analysis was used to evaluate anterior theta activity in response to binaural-beat sound stimulation over baseline and stimulus sessions. A protocol designed to increase anterior theta activity resulted in a significant increase in theta measures (% activity) between pre-stimulus baseline and stimulus observations for five of six participants. Hypnotic susceptibility levels remained stable in the high-susceptible group, and increased moderately in the low and medium susceptible groups.
Differential individual response to hypnosis, has, captured the attention of hypnosis practitioners and researchers since the time of Mesmer, in the late 18th century. Despite the long recognized importance of individual variation in hypnotizability, efforts to modify or increase individual hypnotic susceptibility have proven to be problematic and controversial.
Part of the difficulty in addressing the nature of hypnotizability has been the lack of consensus regarding the basic phenomena of hypnosis. The central issue has been whether observed hypnotic responses are due to an altered stated of consciousness or merely the product of psychosocial factors.
Considering hypnosis as either an altered state or as a purely psychosocial phenomenon served to provide two opposing factions into which most theories of hypnosis could be grouped. Contemporary hypnosis researchers tend to hold less extreme positions, realizing the benefit of a perspective which is comprised of the strengths of both the special-process (i.e., altered state of consciousness) and the social-psychological theoretical domains.
Theoretical Perspectives of Hypnosis
The 1960's witnessed the advent of standardized hypnotic susceptibility measurements. Reliable standardized instruments have been developed for use with groups and individuals. Early work with the electroencephalogram (EEG) designed to identify hypnotic susceptibility also began around this time. More recent EEG / hypnosis research has focused on electrocortical correlates of both the state of, and differential individual response to, hypnosis. The concept of a reliable electrocortical correlate of hypnotic susceptibility draws attention to the recent applications of neurofeedback therapy, which has employed a number of protocols designed for individual brainwave modification. Recent advances in the application of binaural-beat technology and the associated EEG frequency following response, which can be either relaxing or stimulating, have demonstrated efficacy of brainwave modification in areas such as enriched learning, improved sleep, and relaxation (Atwater, 1997). In consideration of recent EEG / hypnosis research along with the recently demonstrated efficacy of EEG neurofeedback training research and the binaural-beat technology applications, it would seem that the lingering question of hypnotizability modification can now be addressed by utilizing brainwave modification within a systematic protocol.
As mentioned earlier, it has often been the case in the past to view the field of hypnosis as being dominated, theoretically, by two opposing camps; the special-process and the social-psychological. In general, the special-process view holds that hypnosis induces a unique state of consciousness; whereas, the social-psychological view maintains that hypnosis is not a distinct physiological state.
Popular authors of the post-Mesmeric period (i.e., mid 19th century), such as James Braid, proposed psychophysiological and sometimes neurophysiological explanations for the hypnotic phenomenon (Sabourin, 1982). In fact, Braid adopted the term "neuro-hypnology" to describe the phenomenon and is credited as the originator of the term "hypnosis" (Bates, 1994, p. 27). The work of other English physicians, such as John Elliotson and James Esdaile, on surgical anesthesia and clinical pain relief in the mid-19th century (Soskis, 1986), are indicative of the psychophysiological zeitgeist of hypnosis in that time. This physiologically-oriented perspective is reflected in Hilgard's neodissociation model (Hilgard, 1986), which suggests that hypnosis involves the activation of hierarchically arranged subsystems of cognitive control. This dissociation of consciousness is clearly manifested in the realm of hypnotically induced analgesia. Hilgard's conception of a "hidden observer" (Hilgard, 1973) as a dissociated part of consciousness, a part that is always aware of nonexperienced pain and can be communicative with the therapist, is exemplified in his description of a hypnotically analgesic individual whose hand and arm were immersed in circulating ice water as follows:
All the while that she was insisting verbally that she felt no pain in hypnotic analgesia, the dissociated part of herself was reporting through automatic writing that she felt the pain just as in the normal nonhypnotic state. (p. 398)
In Hilgard's model, the hidden observer is the communication of the above described subsystem not available to consciousness during hypnosis. It is reasonable to assume, considering hypnosis research with pain control, that such a dissociative effect of cognitive functioning (i.e., cortical inhibition) would have, as a substrate, some neuropsychophysiological correlate.
Often the social-psychological or social-learning position sees hypnotic behaviors as other complex social behaviors, the result of such factors as ability, attitude, belief, expectancy, attribution, and interpretation of the situation (Krisch & Lynn, 1995). The influence of such variables as learning history and environmental influences are described by Barber (1969). In this influential discourse, Barber presents a framework in which hypnotic responding is related to antecedent stimuli, such as expectations, motivation, definition of the situation, and the experimenter-subject relationship. Diamond (1989) proposed a variation of the social-psychological view which emphasized the cognitive functions associated with the experience of hypnosis, as described in the following:
It may be most fruitful to think of hypnotizability as a set of cognitive skills rather than a stable trait. Thus, it is conceivable that the so called "insusceptibe" or refractory S [subject] is 'simply less adept at creating, implementing, or utilizing the requisite cognitive skills in hypnotic test situations. Similarly, what makes for a highly responsive or "virtuoso" S may well be precisely the ability or skill to generate those cognitive processes within the context of a unique relationship with a hypnotist. (p. 382)
According to the social-psychological paradigm, an individual's response to hypnosis is related to a disposition toward hypnosis, expectations, and the use of more effective cognitive strategies, not because the individual possesses a certain level of hypnotic ability. An important implication of the social psychological or social-learning theory is that an individual's level of hypnotizability can be modified and thus enhanced with systematic strategies to accommodate for individual deficiencies. These two positions can no longer be perceived as a dichotomy, but more accurately as overlapping areas in a Venn diagram. It is not difficult for one to recognize the role of both individual characteristics (i.e., differential neurological activity) and contextual variables (i.e., psychosocial constructs) in measuring and determining the hypnotic response. In other words, the hypnotic response can be viewed as a product of a trance-like state of altered consciousness, which is itself moderated by psychosocial factors such as social influence, personal abilities, and possibly the effects of modification strategies. Such a perspective allows for a more complete investigation of the nature of hypnotic susceptibility by taking into account the relevant issues within each position.
Importance of Individual Differences
In the middle 1960's the focus on hypnotic research was dominated by a trait, or individual difference, approach. The use of standardized hypnotic susceptibility measurements became common. Most practitioners today tend to view hypnotic susceptibility as a relatively stable characteristic that varies across individuals. This view, and the realization of individual variability in the ability to experience hypnosis, are not new ideas, as Mesmer long ago emphasized the individual's receptivity to hypnotic process (Laurence & Perry, 1988). Braid, an English physician during the 19th century, described the remarkable differences of different individuals in the degree of susceptibility to the hypnotic experience (Waite, 1960). The importance of within-individual variability in hypnotic susceptibility is also found in Braid's comments that individuals are affected differently, and that even the same individual could react differently at different times to hypnosis (Waite, 1960). Differential responses to hypnosis were recognized by Freud in his attempts to determine which patients would be the most responsive to hypnotic training. Freud, like others at this time, was unable to identify reliable correlates of hypnotizability. Freud's frustration is reflected in his observation that "We can never tell in advance whether it VAII be possible to hypnotize a patient or not, and the only way m have of discovering is by the attempt itself' (Freud, 1966, p. 106). This view is reflected in the methodology of current standardized scales of hypnotizability which use direct measures of hypnotic responses to determine level of hypnotizability.
Differential treatment outcome, associated with individual differences in the way individuals respond to hypnosis, has been observed by practitioners for centuries. Hypnotic susceptibility may also be a relevant factor in the practice of health psychology / behavioral medicine. Bowers (1979) suggested that hypnotic ability is important in the healing or improvement of various somatic disorders. He has also provided evidence that therapeutic outcomes with psychosomatic disorders "re correlated with hypnotic susceptibility, even Men hypnotic procedures were not employed (Bowers, 1982). Significant relationships have been found between hypnotizability and the reduction of chronic pain, chronic facial pain, headaches, and skin disorders (e.g., warts, chronic urticaria, and atopic eczema) with hypnotic techniques (Brown, 1992). Support for the interaction of negative emotions and hypnotic ability as a mediator of symptoms and disease has also been provided by recent research (Wickramasekera, 1979,1994; Wickramasekera, Pope, & Kolm, 1996). A recent article by Ruzyla-Smith, Barabasz, Barabasz & Warner (1995), measuring the effects of hypnosis on the immune response, found significant increases in B-cells and helper T-cells only for the highly hypnotizable participants in the study. This report not only suggests that hypnosis can modify the activity of components of the immune system, but also highlights the importance of individual variability in response to hypnosis.
In terms of modification of hypnotizability, initial hypnotic susceptibility level may be a factor in the resulting degree of modification. In a paper discussing the issue of hypnotizability modification, Perry (1977) presented a number of studies employing a range of less susceptible individuals for modification training. Overall, the attempts to modify hypnotizability were unsuccessful in these studies. Perry suggested that successful modification tends to be more common in medium susceptible individuals. It may be that the medium susceptible individual, having already demonstrated a certain degree of hypnotic ability, possesses the underlying cognitive framework essential to the hypnotic experience. This line of reasoning could explain the differential responses of low susceptible and medium susceptible individuals to hypnotizability modification training. The high susceptible individual could also prove to be less responsive to modification strategies compared to the medium susceptible individual, as a potential exists for a ceiling effect with the high susceptible individual.
Standardized Measures of Hypnotic Susceptibility
The long observed differences in individual response to hypnosis eventually led to the development of the first viable measures of hypnotizability, the Stanford Hypnotic Susceptibility Scale, Forms A and B (SHSS:A and SHSS:B) by Weitzenhoffer and Hilgard (1959). The introduction of the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C) by Weitzenhoffer and Hilgard (1962) represented an improved version of the two earlier forms; it was comprised of a greater proportion of more difficult cognitive items. The SHSS:C is still the prevalent measure of hypnotic susceptibility in current use and is often the criterion by which other measures of hypnotizability are evaluated (Perry, Nadon, & Button, 1992). This instrument is essentially an ascending scale which begins with relatively easy hypnotic induction procedures and progressively moves to more difficult trance challenges.
A recent study by Kurtz & Strube (1996), comparing a number of hypnotic measures, described the SHSS:C as the gold standard of susceptibility tests. This study also addressed the idea of using multiple measures of hypnotic susceptibility in order to improve predictive power over using a single administered test. Kurtz & Strube (1996) concluded that the use of multiple measures of susceptibility was not warranted, and that the "rational" choice for a single measure of hypnotic susceptibility would be the SHSS:C.
Research with the EEG and Hypnotic Susceptibility
Brainwaves are the far-field electrical wave patterns set up by neurochemical activity in the living brain. The electroencephalograph (EEG) is an instrument which can measure this activity and determine its strength (higher or lower amplitude) and speed (high or low frequency). Scientists have characterized brainwaves into four broad categories: (a) beta, brainwaves above 13 cycles per second (or hertz), indicative of active consciousness; (b) alpha, a slower brainwave ranging from 8 to l2 hertz, characteristic of a relaxed conscious state of awareness; (c) theta, the next slower waves ranging from 4 to 8 hertz, often associated with dreamlike imagery and deep relaxation; (d) delta, the slowest waves from 0 to 4 hertz which can predominate during dreamless sleep.
The majority of early research with hypnosis shared a common goal: the development of a methodology to determine if, and when, an individual is hypnotized. The majority of early EEG research with hypnosis focused on the state of hypnosis, often attempting to distinguish the state of hypnosis from the state of sleep (Sabourin, 1982). Weitzenhoffer's 1953 review of studies utilizing the EEG with hypnosis concluded that hypnosis is perhaps more akin to light sleep than either deep sleep or the waking state.
A shift occurred in the late 1960's as researchers began investigating possible electrocortical correlates of hypnotic susceptibility using the EEG. The predominant focus in hypnosis research from this time forward was on individual differences rather that the hypnotic state per se. Much of the early research focused on alpha wave indices of hypnotic susceptibility. A review by Dumas (1977) found that no alpha-hypnotizability correlation existed in the general population. Additionally, a recent critical review by Perlini & Spanos (1991) offered little support for an alpha-hypnotizability relationship. Other early studies found greater resting theta wave activity with highly susceptible individuals (Galbraith, London, Leibovitz, Cooper & Hart, 1970; Tebecis, Provins, Farnbach & Pentony, 1975; Akpinar, Ulett, and ltil, 1971). Overall, the comparison of early EEG research proves difficult given the aggregate of technologies and methodologies employed over a span of time characterized by extreme variance in technological development.
Recent studies have reexamined the relationship between EEG measures and hypnotic susceptibility based on rigorous subject screening and control, along with enhanced recording and analytic techniques. Sabourin, Cutcomb, Crawford, and Pribram (1990) found highly hypnotizable subjects to generate substantially more mean theta power than did low hypnotizable subjects in frontal, central, and occipital derivations during resting nonhypnotic baseline, with largest differences observed in the frontal (F3, F4) locations. According to a review by Crawford and Gruzeiler (1992), theta activity, which is strongly and positively related to hypnotic susceptibility, is the most consistent EEG correlate of hypnotic susceptibility. The results of a recent study by Graffin, Ray & Lundy (1995) indicate that highly hypnotizable subjects demonstrate significantly more theta activity in frontal (F3, F4) and temporal (T3, T4) areas in comparison to low hypnotizable subjects at baseline measures. The studies by Sabourin et al. (1990) and Graffin et al. (1995) are alike in that each employed fast Fourier transformation (FFT) and power spectral analysis of monopolar EEG derivations, which allows for the examination of activity within each component frequency of each EEG epoch.
The position which is most supported in the contemporary literature is a consistent pattern of EEG activity which can differentiate individuals according to standardized hypnotic susceptibility scores. It is suggested that high-susceptible individuals produce more anterior theta activity as compared to low-susceptible individuals. This baseline individual difference is an important neuropsychophysiological indicator of hypnotizability and could prove to be a more stable individual difference measure than standard psychometric measures (Graffin et al., 1995).
Theta Waves and Perceptual Variations
The relationship between theta activity and selective attentional processes lends further support to a coexistent relationship with hypnotizability. The concepts of Class I and Class 11 inhibition have been presented by Vogel, Broverman, & Klaiber (1968). Class I inhibition is described as being correlated with a general inactivity or drowsiness, whereas Class 11 inhibition is related to more efficient and selective attentional processes. The Class 11 concept of slow wave activity is described by Vogel et al. (1968) as "a selective inactivation of particular responses so that a continuing excitatory state becomes directed or patterned (p. 172)". Sabourin et al. (1990) suggested that the theta activity observed in highly hypnotizable subjects reflects involvement in greater absorptive attentional skills. As in the Sabourin et al. (1990) study, Graffin et al. (1995) provide suggestions regarding the selective attentional component of theta: " high hypnotiizables either possess, or can manifest, a heightened state of attentional readiness and concentration of attention" (p. 128). The relationship between greater attentional readiness and frontal theta has also been suggested in psychophysiological studies (Bruneau et al., 1993; Ishihara & Yoshii, 1972; Mizuki et al., 1980). Another possible supportive line of research involves the examination of psychological absorption and hypnotizability relationships. Studies have found absorption to be consistently correlated with hypnotizability (Glisky, Tataryn, Tobias, Kihlstrom, & McConkey, 1991; Nadon, Hoyt, Register, & Kihlstrom, 1991; Tellegen & Atkinson, 1974). In a review of psychological correlates of theta, Schacter (1977) described the relationship between the hypnagogic state and the presence of low voltage theta activity. Green & Green (1977) described the theta state as that of reverie and hypnogogic imagery. They employed theta neurofeedback training to induce quietness of body, emotions, and mind, and to build a bridge between the conscious and unconscious. In describing theta EEG brainwave biofeedback, the Life Sciences Institute of Mind-Body Health (1995) associated increased theta activity with "states of reverie that have been known to creative people of all time" (p. 4).
Considering these findings related to theta activity, a relationship between individual levels of hypnotizability, selective inhibition, hypnogogic reverie, and theta activity is more easily understood. Relatively high theta activity may be indicative of a characteristic brainwave pattern which reflects an underlying cognitive mechanism that relates to a type of selective inhibition and hypnogogic imagery.
Research with Neurofeedback Training
Neurofeedback training works on the brain's ability to produce certain brainwaves the way exercise works to strengthen muscles. EEG biofeedback instruments show the kinds of brainwaves an individual is producing, making it possible for that individual to learn to manipulate the observed brainwaves.
Demonstrated individual success acquiring the ability to self-regulate characteristic brainwave patterns is evident in the neurofeedback literature. Various protocols have been employed by many practitioners to enhance both relaxation (an increase in production of slow waves, such as theta, and a decreased production of fast beta waves) and mental activity (a decrease production of excessive slow wave, such as delta and lower frequency theta; with an increase in the production of 'fast" beta waves). An impressive number of recent studies have demonstrated the efficacy of brainwave neurofeedback training. The work by Peniston and others with individuals with alcohol abuse issues (Peniston & Kulkosky, 1989, 1990, 1991; Saxby and Peniston, 1995) has provided remarkable results. Peniston has shown 13 month follow-up relapse rates of 20% (compared to 80% using conventional medical training), significant reductions in Beck Depression Inventory scores, and decreased levels of beta-endorphin in subjects treated with Alpha-Theta brainwave training. The area of attention deficit hyperactivity disorder (ADHD) has received strong attention from neurofeedback researchers (Barabasz & Barabasz, 1995; Lubar, 1991; Rossiter & Vaque, 1995). Lubar's work has provided strong support for the effectiveness of a protocol designed for Beta-training (16-20 Hz) and Theta inhibition (4-8Hz ), with 80% of 250 treated children showing grade point average improvements of 1.5 levels (range 0-3.5) (Lubar, 1991). Objective assessments of the efficacy of neurofeedback training for ADHD have shown significant improvements on the Test of Variables of Attention (T.O.V.A.) scales and Wechsler Intelligence Scale for Children-Revised (WISC-R) IQ scores with subjects who demonstrated significant decreases in theta activity across sessions (Lubar, Swaamod, Swartwood, & O'Donnell, 1995). Additional studies with post-traumatic stress disorder (PTSD) with Vietnam veterans (Peniston, 1990; Peniston & Kulkosky, 1991; Peniston, Marrinan & Deming, 1993) have provided unprecedented results with a condition often very resistant to training with other interventions.
The work by Ochs (1994) with the use of light and sound feedback of EEG frequencies, EEG disentrainment feedback (EDF), is also promising in terms of modification of EEG patterns. However, unlike traditional EEG biofeedback, with Dr. Ochs' device there is no need for the individual to be consciously involved in the process. The visual and auditory stimuli respond to and match the individual's brainwaves and these stimuli are in turn generated by the overall frequency of the individual's brainwaves. The aptitude of this system is the capacity for the clinician to alter the feedback frequencies upward or downward, in effect, providing flexibility into a "set" or "characteristic" brainwave pattern.
The flexibility of individual neurofeedback training is evident in the various approaches designed to intensify certain types of EEG activity either by itself, or to intensify certain types of EEG activity and decrease other types of EEG activity occurring at the same time. Overall, the relatively high number of recent neurofeedback training studies with consistent positive results strongly demonstrate the changes in cognitive and behavioral variables resulting from the alteration of individual brainwave patterns.
Research with Binaural-Beat Sound Stimulation
Binaural-beat stimulation is an important element of a patented auditory guidance system developed by Robert A. Monroe. In fact, Robert Monroe has been granted several patents for applications of psychophysical entrainment via sound patterns in (Atwater, 1997). In the patented process referred to as Hemi-SyncŪ, individuals are exposed to factors including breathing exercises, guided relaxation, visualizations, and binaural beats. Extensive research within the Monroe Institute of Applied Sciences, which has documented physiological changes associated with Hemi-Sync use, along with consistent reports of thousands of Hemi-Sync users, appears to support the theory that the Hemi-Sync process encourages directed neuropsychophysiological variations (Atwater, 1997).
The underlying premise of the Hemi-Sync process is not unlike that adopted by many EEG neurofeedback therapists, that an individuals' predominant state of consciousness can be reflected as a homeostatic pattern of brain activity (i.e., an individual differential bandwidth activity within the EEG spectrum) and can often be resistant to variation. Atwater (1997) reported that practitioners of the Hemi-Sync process have observed a state of hypnagogia or experiences of a kind of mind-awake/body asleep state associated with entrainment of the brain to lower frequencies (delta and theta) and with slightly higher-frequency entrainment associated with hyper suggestive states of consciousness (high theta and low alpha). In line with current EEG research relating to ADHD (see Lubar,1991), Hemi-Sync researchers have noted deep relaxation with entrainment of the brain to lower frequencies and increased mental activity and alertness with higher frequency entrainment. The Monroe Institute has been refining binaural-beat technology for over thirty years and has developed a variety of applications including enriched learning, improved sleep, relaxation, wellness, and expanded mind-consciousness states (Atwater, 1997).
Binaural beat stimulation can be further understood by considering how we detect sound sources in daily life. Incoming frequencies or sounds can be detected by each ear as the wave curves around the skull by detraction. The brain perceives this differential input as being "out of phase", and this waveform phase difference allows for accurate location of sounds. Stated simply, less noise is heard by one ear, and more by the other. The capacity of the brain to detect a waveform phase difference also enables it to perceive binaural beats (Atwater, 1997). The presentation of waveform phase differences (different frequencies), which normally is associated with directional information, can produce a different phenomenon when heard with stereo headphones or speakers. The result of presenting phase differences in this manner is a perceptual integration of the signals; the sensation of a third "beat" frequency (Atwater, 1997). This perception of the binaural-beat is at a frequency that is the difference between the two auditory inputs.
Binaural beats can easily be heard at the low frequencies (<30 Hz) that are characteristic of the EEG spectrum (Austere, 1973). This perception of the binaural-beat is associated with an EEG frequency following response (FFR). This phenomenon is described by Atwater (1997) as EEG activity which corresponds to the fundamental frequency of the stimulus, such as binaural-beat stimulation.
The sensation of auditory binaural beating occurs when two coherent sounds of nearly similar frequencies are presented one to each ear with stereo headphones or speakers. Originating in the brainstem's superior olivary nucleus, the site of contralateral integration of auditory input (Oster, 1973), the audio sensation of binaural beating is neurologically conveyed to the reticular formation (Swann, Bosanko, Cohen, Midgley & Seed, 1982) and the cortex where it can be observed as a frequency-following response with EEG equipment. The word reticular means 'net-like' and the neural reticular formation itself is a large, net-like diffuse area of the brainstem (Anch, et al. 1988). The RAS regulates cortical EEG (Swann et al. 1988) and controls arousal, attention, and awareness - the elements of consciousness itself (Tice & Steinberg, 1989; Empson, 1986). How we interpret, respond, and react to information (internal stimuli, feelings, attitudes, and beliefs as well as external sensory stimuli) is managed by the brain's reticular formation stimulating the thalamus and cortex, and controlling attentiveness and level of arousal (Empson, 1986). Binaural beats can influence ongoing brainwave states by providing information to the brain's reticular activating system (RAS). If internal stimuli, feelings, attitudes, beliefs, and external sensory stimuli are not in conflict with this information, the RAS will alter brainwave states to match the binaural-beat provocation.
A recent study by Foster (1991) was conducted in an effort to determine the effects of alpha-frequency binaural-beat stimulation combined with alpha neurofeedback on alpha-frequency brainwave production. Foster found that the combination of binaural-beat stimulation and alpha neurofeedback produced significantly higher alpha production than that of neurofeedback alone, but that the group which received only binaural-beat stimulation, produced significantly higher alpha production than either group. In a review of three studies directed towards the effects of Hemi-Sync tapes on electrocortical activity, Sadigh (1994) reported increased brainwave activity in the desired direction after virtually minutes of exposure to the Hemi-Sync signals.
Research to date, therefore, has suggested that the use of the binaural-beat sound applications can contribute to the establishment of prescribed variation in individual psychophysiological homeostatic patterns (brainwave patterns), which can precipitate alterations in cognitive processes. The relationship between individual patterns of cognitive variables and characteristic brainwave patterns affords not only a methodology for change, but also an objective unit for measure of change.
Purpose of the Present Study
The present study was an effort to develop, and to test the efficacy of, techniques designed to increase anterior theta activity and susceptibility to hypnosis as measured by currently employed standardized instruments. Contemporary hypnosis / EEG research studies have found individual electrocortical differences (anterior theta activity) to be reliable predictors of hypnotic susceptibility. Clinicians and researchers within the field of neurofeedback training have also demonstrated the efficacy of prescribed changes in individual EEG patterns and behavioral variables, with a number of medical and psychological disorders. Practitioners and researchers utilizing the binaural-beat technology developed by the Monroe Institute have produced impressive changes in individual EEG patterns. Given the strong support of brainwave modification, and the efficacy of the binaural-beat sound patterns to modify brainwave patterns, it is logical and advantageous to make use of a binaural-beat sound based protocol. Since theta activity is positively related to individual level of hypnotic susceptibility, it follows that the employment of a protocol designed to increase frontal theta activity could also mediate an increase in hypnotic susceptibility. It was proposed that a binaural beat protocol designed to increase anterior theta activity will result in a significant increase in theta measure (% activity), and a related increase in hypnotic susceptibility, as measured by standardized instruments. In consideration of the previous association between hypnotic susceptibility and anterior theta activity, the potential exists for differential increases in theta activity relative to hypnotizability group. The examination of potential differential changes in theta activity relative to initial level of hypnotizability could provide further data supporting the association of theta activity and hypnotic susceptibility.
Hypothesis l. Increases in hypnotic susceptibility, after exposure to binaural-beat sound stimulation protocol, will be observed for all participants from pre to post-measures. The Significant Change Index (SCI) was used to evaluate change between pre and post SHSS:C scores. Graphing was used to provide visual interpretation of individual level of hypnotizability.
Hypothesis 2. Theta activity will increase in all individuals as a result of the binaural beat sound stimulation protocol. The C Statistic was performed on the time series of theta measures across baseline and stimulus sessions for each individual.
Hypothesis 3. Increases in theta activity after exposure to binaural-beat sound stimulation protocol YAII be of greatest significance in individuals in the medium-hypnotizable group. The C Statistic was performed on the time series of theta measures across baseline and stimulus sessions for each individual.
Hypothesis 4. Increases in theta activity after exposure to binaural-beat sound stimulation protocol will be of least significance in individuals in the low hypnotizable groups. The C Statistic was performed on the time series of theta measures across baseline and stimulus sessions for each individual.
Six participants were selected from a pool of Northern Arizona University (NAU) undergraduates who were administered the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C, Weitzenhoffer & Hilgard, 1962). The six participants were grouped according to varying degrees of hypnotizability (two lows, two mediums, and two highs) for participation in the stimulus sessions. The variations in hypnotic susceptibility within each group were minimal, assuring the participants were relatively homogeneous in terms of initial hypnotic susceptibility measures. To reduce the risk of attrition during this study, participants were paid $40.00 each for participation in the study.
Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C). Each participant's score on the SHSS:C served as a baseline measure of hypnotic susceptibility. Also, after completion of the three stimulus sessions, raw scores were obtained on the SHSS:C for each participant a second time. The raw scores obtained in this post4reatment evaluation provided an index of each participants' hypnotic susceptibility level after exposure to the binaural-beat stimulus protocol. The following general hypnotizability level designation and raw-score ranges are used with the SHSS:C: (a) low hypnotizable (0-4), (b) medium hypnotizable (5-7), (c) high hypnotizable (8-10), and (d) very-high hypnotizable (1 1-12).
The Kuder-Richardson total scale reliability index, which provides a measure of the degree of consistency of participants' responses, was reported by E. R. Hilgard (1965) as .85, with retest reliability coefficients ranging from .60 to .77 over the range of twelve items on the SHSS: C.
EEG-Recording. The NRS-2D (Lexicor Medical Technology, Inc.) is a miniaturized two channel Electroencephalograph (EEG) system. The device is approximately one inch tall, three inches wide, and six inches long and is connected directly to a 486 computer via the parallel port. It has a built in impedance meter and operates with both BIOLEX (BLX) neurotherapy software and NeuroLex (NLX) EEG acquisition software. The BLX and NLX systems comprise an array of tools including an audio/visual display system, graphing and reporting features, fast Fourier transformation and spectral analysis of complex wave forms, as well as conventional EEG recordings. An artifact inhibit feature stops all recording v,/hen the artifact (e.g., eye movement or other muscle signals) exceeds the selected artifact inhibit amplitude threshold. The computerized system was used to measure participants' theta activity for each 2-second epoch. In the EEG data analysis, fast Fourier transformation was performed, and a power spectrum calculated, for each epoch.
Binaural-Beat Sound Tapes. The audio cassette tapes used in this study were produced by the Monroe Institute specifically for this study. Both a control tape and experimental tape were used in this study. The binaural beats provided in the experimental tape are unique in that they were designed to be complex brain-wave-like patterns rather than simple sine waves. The right-left differences in stereo audio signals on these tapes were assembled in a sequence to produce a dynamic wave pattern (brain-wave-like) as compared to a static, uniform sine wave pattern. Specifically, the experimental tape used in this experiment was produced with a binaural-beat pattern that represents a theta brainwave pattern of high hypnotic susceptibility. The Monroe Institute provided objective data verifying the binaural-beat components imbedded in the experimental tape, both in wave form and frequency spectra formats.
The experimental tape was produced with pink sound and theta binaural beats imbedded in carrier tones. The control tape was produced with pink sound and tones without binaural beats.
Increases in hypnotic susceptibility, after exposure to binaural-beat sound stimulation protocol, will be observed for all participants from pre to postmeasures. As mentioned earlier, the participants who demonstrated a significant increase in hypnotic susceptibility were Participants LOW1, LOW2, MEDI, and MED2. The participants in the high-hypnotizable group did not change in the measure of hypnotic susceptibility. Graphical analysis allowed for a simplified examination of the changes in hypnotizability levels from the pre to post binaural-beat stimulation administrations.
In relation to the effects of binaural-beat sound stimulation on hypnotic susceptibility, these data reveal mixed conclusions. An interesting point is that Participant MED1 demonstrated the largest increase in hypnotic susceptibility and also a significant decrease in theta activity in response to the binaural-beat sound stimulation. In contrast, Participant MED2 demonstrated the most significant increase in theta activity in response to the binaural-beat sound stimulation. Therefore, these data indicate that theta activity is not the only contributing factor in hypnotic susceptibility, suggest that modification of hypnotizability with medium susceptible individuals using binaural-beat stimulation can be effective, and highlight the importance of individual variation. These data can provide a meaningful direction for researchers and practitioners of hypnosis interested in increasing hypnotic susceptibility. High-Hypnotizable Group. The two participants in the high-hypnotizable group demonstrated no change in SHSS:C raw-score values. The possibility exists for a ceiling-effect with individuals scoring at the upper end of the SHSS:C scale. Both participants HIGH1 and HIGH2 had the same pre and post raw-scores, 9 and 10, respectively. The items or skills an individual must demonstrate to increase in raw score above 9 are cognitive items of greater difficulty including, negative and positive hallucination tasks. This potential ceiling-effect is also evident in Hilgard's (1965) report on relative item difficulty within the SHSS:C, in which only nine percent of participants in the normative base passed the positive and negative hallucination tasks. These data suggest that those who are high in hypnotizability, in terms of the SHSS:C, may be less responsive to binaural-beat stimulation relative to individuals who demonstrate less hypnotic ability. Perhaps there is a ceiling effect on an individual's ability to produce theta as well.
Theta activity will increase in all individuals as a result of the binaural-beat sound protocol This hypothesis was supported in data from five of six participants, each showing an upward intersession trend in theta activity across stimulus periods. The subject in the medium hypnotizable group with the 5-minute baseline (MED1) demonstrated a downward intersession trend in theta activity across stimulus periods. The theta activity of Participant MED1 changed significantly in session-3. No significant change or trend in theta activity was observed for this participant prior to session-3. These data indicate that some confounding factor(s) may have been in effect during the session-3 stimulation/recording period of participant MED1.
Factors of primary interest in relation to theta activity are internal feelings, attitudes, beliefs, and overall mood-state. As theta is related to an overall relaxed state, any negative affect related to these factors could adversely affect theta production.
These data highlight the power of individual differences in relation to theta brainwave activity. The observation that the initial recording of stimulus data seemed predictive of a differential theta activity response over time may be particularly important is this analysis. It may be that the significance of an initial theta activity response to binaural-beat sound stimulation is positively related to the significance of the theta activity response over time.
The data in this study relative to hypnotizability suggest support for the stability of hypnotic susceptibility over time and suggest support for previous data showing differential response to modification of hypnotizability relative to initial susceptibility level. This support is evident in the fact that no participant decreased in hypnotic susceptibility over time and in the differential participant responses across general hypnotic susceptibility levels. Surprisingly, the most significant increase in hypnotic susceptibility was observed in the participant with the most significant decrease in theta activity in response to the binaural-beat sound stimulation. Even though the significance of the decrease in theta activity for this participant was explained entirely by third session recordings, it is difficult to draw conclusions regarding the relationship of theta activity to hypnotic susceptibility when reviewing the findings of this study. Overall, this study indicates that theta activity is related to, but cannot uniquely explain, the variation in hypnotic susceptibility.