Binaural beat induced Theta EEG activity and hypnotic susceptibility: Contradictory results and technical considerations

Stevens, Larry

The present study offered a constructive replication of an earlier study which demonstrated significant increases in theta EEG activity following theta binaural beat (TBB) entrainment training and significant increases in hypnotic susceptibility. This study improved upon the earlier small-sample, multiple-baseline investigation by employing a larger sample, by utilizing a double-blind, repeated-measures group experimental design, by investigating only low and moderate susceptible participants, and by providing 4 hours of binaural beat training. With these design improvements, results were not supportive of the specific efficacy of the theta binaural beat training employed in this study in either increasing frontal theta EEG activity or in increasing hypnotic susceptibility. Statistical power analyses indicated the theta binaural beat training to be a very low power phenomenon on theta EEG activity. Furthermore, we found no significant relationship between frontal theta power and hypnotizability, although the more hypnotizable participants showed significantly greater increases in hypnotizability than the less hypnotizables. Results are discussed within the context of participant selection and classification factors, technical considerations in the presentation of TBB training, and theta blocking.

Key Words: Activity, binaural beat, brainwave, EEG, hypnosis, hypnotic susceptibility, hypnotizability, theta

In the July 2000 volume of this journal, Brady and Stevens (2000) reported the results of a study designed to test the efficacy of a unique approach to increasing hypnotic susceptibility by driving the brain into states of consciousness reportedly associated with increased susceptibility (Crawford, 1990; Crawford & Gruzelier, 1992). This new technology, called Binuaral Beat Brainwave Entrainment, presented two slightly different waveforms to each ear via stereophonic headphones, with the generation of a third "beat" frequency occurring as the difference between the frequency of the two auditory inputs (Atwater, 1995; Oster, 1973). In this study, this third beat was designed to fall within the theta EEG frequency range (4.0-8.0 Hz), and frontal EEG's recorded during binaural beat exposure revealed significantly increased EEG frequencies within the theta range. Additionally, differences between pre- and post-training Stanford Hypnotic Susceptibility Scale: Form C (SHSS:C; Weitzenhoffer & Hilgard, 1962) scores were statistically significant and only so for low and moderate susceptible individuals (Brady & Stevens, 2000).

Theta EEG brainwave frequencies were selected for change in this original study because of an established relationship between theta (4-8 Hz) wavebands and both hypnotizability and hypnotic trance states (Akpinar, Ulett, & Itil, 1971; Galbraith, London, Leibovitz, Cooper, & Hart, 1970; Tebecis, Provins, Farnbach, & Pentony, 1975). More recently, in technologically more sophisticated and better controlled studies, this theta hypnotizability EEG frequency has been identified as more specific to frontal (DePascalis & Ray, 1998; DePascalis, Ray, Tranquillo, & Amico, 1998; Sabourin, Cutcomb, Crawford & Pribram, 1990) and to frontotemporal (Graffin, Ray & Lundy, 1995) brain regions. In fact, Crawford and Gruzelier (1992) report frontal theta, and perhaps more specifically frontal high theta (5.5-7.5 Hz), EEG frequencies as the most consistent EEG correlate of hypnotic susceptibility. This well-established relationship notwithstanding, no study prior to our earlier investigation had endeavored to directly change frontal theta and to observe a subsequent change in hypnotic susceptibility.

The results of the Brady and Stevens (2000) study were also clinically important for a number of reasons. First, hypnotic susceptibility has been shown to play an important role in the maintenance of health and in the prevention and treatment of disease. For example, significant relationships have been reported in the research literature between hypnotizability and the reduction of chronic pain, headaches, skin disorders, and asthma symptoms (Bowers, 1979, 1982; Brown, 1992) and increased immunocompetence (Ruzyla-Smith, Barabasz, Barabasz, & Warner, 1995). And a recent meta-analysis of psychological treatments employed in research studies to influence immunocompetence revealed hypnotic suggestions to be one of the most consistently effective treatments compared with stress management, relaxation, disclosure, and conditioning interventions, and this effect was most robust for highly hypnotizable participants (Miller & Cohen, 2001). The ability to easily and effortlessly increase hypnotic responsiveness, even modestly, could have a profound impact on a patient's response to therapeutic suggestions and could increase the clinical efficacy of hypnosis with a broader range of patients.

Secondly, increasing hypnotic susceptibility has been a problematic and controversial enterprise for decades, with many practitioners and researchers accepting individual hypnotic responsiveness as a relatively stable, immutable characteristic (Perry, 1977). Nonetheless, a number of experiences have been shown to increase hypnotic susceptibility, including sensory deprivation, biofeedback, psychotomimetic drugs, hypnotic training, personal growth, and natural developmental changes (Bowers, 1976). And some of these changes in hypnotizability have been rather dramatic. For example, Barabasz (1982) was able to demonstrate a 147% increase in susceptibility following 6 hours of sensory restriction, and Gorassini and Spanos (1986) produced not only a 129% increase in objective hypnotizability but similar increases in the subjective components of hypnotic experience following 1 hour of coaching, practice, and modeling of cognitive strategies mediating responsiveness to suggestions, interpretational sets, and attitudes toward hypnosis.1

A difficulty with existing susceptibility change procedures is that either the technology required (e.g., sensory deprivation and biofeedback) or the time and response cost (e.g., hypnotic training, psychotomimetic drugs, personal growth, and developmental changes) often prohibit their use by the clinician. If an easily administered and low response-cost procedure could be shown to statistically and clinically increase hypnotic susceptibility, then hypnosis practitioners could simply prescribe such conditioning interventions, ideally as homework, prior to formal inductions to increase the range of applicability and power of their interventions. Binuaral Beat Brainwave Entrainment holds promise as just such an intervention, one which is also quite affordable and available to the general public through compact disks and tapes. Additionally, a number of other studies have rather reliably demonstrated a frequency-following response to auditory binaural beat stimulation similar to those reported in our earlier study (Atwater, 1996; Lane, Kasian, Owens, & Marsch, 1998; Sadigh & Kozicky, 1994), so this technology appears to merit further investigation in order to validate and to extend its clinical possibilities.

The purpose of this study was to replicate our earlier study demonstrating statistically significant, but marginally clinically significant, increases in hypnotic susceptibility with binaural beat training. We hoped to increase the potential clinical impact of this training program by extending the duration of training from 1 hour to 4 hours and to better test effectiveness through a double-blind, repeated-measures group design utilizing a larger number of low and moderate susceptible participants. Only low and moderate susceptible participants were used in this study because of our prior findings of an enhancement effect only in this group and because of theoretical bases for expecting susceptibility enhancement primarily in medium and low participants (Perry, 1977; Brady & Stevens, 2000).

Method

Participants

Over 100 undergraduate college students at Northern Arizona University were pre-screened as a part of another study of hypnotic susceptibility measures with Tellegen and Atkinson's (1974) Psychological Absorption Scale, Wilson and Barber's (1978) Creative Imagination Scale, and Weitzenhoffer and Hilgard's (1962) Stanford Hypnotic Susceptibility Scale: Form C (SHSS:C). Respondents scoring low (0-4) and moderate (57) on the SHSS:C were invited to participate on a first-signup basis in the present study. Twenty-seven participants, 13 lows and 14 moderates, agreed to complete the 2 weeks of intensive binaural beat training and received $50.00 each for their participation at the end of the study2.

Participants ranged in age from 18-31 years with a mean age of 21.35 years; 21 were females and 6 were males. Only 5 had experienced hypnosis before; 10 had experienced some form of meditation practice in the past; 4 had participated in directed relaxation training in the past; only 2 had had an EEG prior to the study; 3 had sustained a mild head injury without neurological sequellae in the past; 6 reported a brief period of unconsciousness in the distant past; and all but one were right handed. The mean score for the lows on the SHSS:C was 2.46 and for the moderates was 6.50.

Instrument

The Stanford Hypnotic Susceptibility Scale: Form C (SHSS:C) was employed as the measure of hypnotic susceptibility in this study (Weitzenhoffer & Hilgard, 1962). The SHSS:C has been recognized as "the gold standard" of hypnotic susceptibility testing (Kurtz & Strube, 1996) against which all other measures are compared. The SHSS:C has a very satisfactory Kuder-Richardson total scale reliability of .85, with validity correlations of .72 with the SHSS:A and .68, .60, and .57 with the HGSHS:A (Kurtz & Strube, 1996; Perry, Nadon, & Button, 1992).

Apparatus

EEG Recording

The NRS-2D (Lexicor Medical Technology, Inc., Boulder, Colorado) Electroencephalograph (EEG) was used to measure participants' 4.0-8.0 Hz theta activity during training. The NRS-2D records EEG data from 2 channels at a sampling rate of 128 Hz across 2-second epochs at a frequency resolution of 0.5 Hz. Low pass and high pass filters are set at 32 Hz and 0.5 Hz respectively, with notch filtering factory definable at 60 Hz. A built-in impedance meter allows convenient measurement of electrode impedances, with valid results obtained for impedances as high as 20K ohms; for the present study, electrode impedances were held at lOK ohms or less. An artifact inhibit feature stops all recording when the artifact (e.g., eye movement or other muscle signals) exceeds the selected artifact inhibit amplitude threshold. The NRS-2D was supported by a 486DX2 PC operating with BIOLEX (BLX) neurotherapy EEG acquisition software, comprising an array of tools including an audiovisual display system, graphing and reporting features, Fast Fourier Transformation, and spectral analysis of complex wave forms, as well as conventional EEG recordings. For the EEG data analysis, Fast Fourier Transformation (FFT) was performed and a power spectrum was calculated for each 2second epoch and integrated across baseline and treatment components.

Auditory Binaural Beat Stimulation

Since the aim of this study was to increase the duration of the binaural beat exposure provided in the previous study, the original 20-minute tapes utilized in the Brady and Stevens (2000) study were sequentially duplicated in order to produce a 40-- minute experimental and control tape and compact disk. The original binaural beat tapes were produced for our research purposes by the Monroe Institute (Atwater, 1996). Both a control tape/CD and an experimental tape/CD were used. The experimental tape/ CD was produced with a complex theta brainwave binaural beat pattern imbedded in carrier tones and pink sound. In order to encourage listener vigilance, carrier tones were changed periodically according to the following sequence: 0-3 minutes, C-Major-7th (292 Hz, 330 Hz, 392 Hz, 466 Hz); 3-6 minutes, C-Major (292 Hz, 330 Hz, 392 Hz, 523 Hz); 6-10 minutes, G-Major (196 Hz, 247 Hz, 294 Hz, 392 Hz); 10-15 minutes, D-Minor (294 Hz, 349 Hz, 440 Hz); 15-20 minutes, C-Major (292 Hz, 330 Hz, 392 Hz, 523 Hz). The theta effect for the experimental tape was generated by continuously varying a 7 Hz left-right frequency difference by plus or minus 1.5 Hz over a period of 4 seconds; the theta stimulus thus cycled from 5.5 Hz to 8.5 Hz and back to 5.5 Hz over a period of 4 seconds. The control tape/CD was produced with pink sound and the same tones as the experimental tape/CD but without binaural beats, so that the control and experimental tapes/CD's were perceptually indistinguishable. An auditory spectrum analysis of the waveforms on the duplicated tapes and CD's conducted after the study was completed revealed a binaural beat effect on the theta training media within the theta range. Both participants and experimenters were blind as to presentation of control or experimental media. During all sessions, participants wore stereophonic headphones providing either the control or the experimental recording. Signal volume was adjusted by each participant to a comfortable sound level and maintained at that level throughout stimulus presentation.

Procedures

EEG Configuration

During all training sessions, earlobe and forehead electrode sites were prepped with Ten-20 Abrasive EEG Prep Gel to decrease skin resistance. Ten-20 EEG conductive paste was used as a conduction medium to fill silver-chloride electrode cups. One monopolar EEG derivation was used, located according to the International 10-20 system (Jasper, 1958) at FZ3, 30% of the nasion-inion distance along the longitudinal midline; the reference for this study was the left ear, with forehead (Fp) common/ground.

Double-Blind, Repeated Measures Design

Participants were identified as either Low Hypnotizable (LH) or Moderate Hypnotizable (MH) on the basis of SHSS:C scores and were scheduled individually for three training sessions over each of two consecutive weeks, for a total of six training sessions for each participant. In a repeated-measures design, each participant received 10 minutes of pre-training baseline EEG recording, followed by 40 minutes of stimulus training, followed by 10 minutes of post-training baseline in each of the training sessions. Baseline periods consisted of sitting quietly with eyes closed with no auditory stimulation. Of the original 27 participants recruited for the study, 5 (3 LH, 2 MH) were randomly selected to receive the control, pink noise only training4; the remaining 22 (10 LH, 12 MH) participants were assigned to receive Theta Binaural Beat (TBB) stimulation training. Participants and all experimenters involved in the training program and posttraining SHSS:C testing were blind as to participant hypnotizability and training status.

For each training session, the participant was seated comfortably in a recliner with back upright but slightly reclined and with feet and legs resting on the foot rest. Each electrode site was prepped, electrodes were attached, impedances were checked and held below lOK ohms, EEG recording equipment was activated and a clear EEG trace was established, participants were advised about noise artifact and requested to remain as still as possible, and headphones were secured in place. Participants were asked to remain awake, with eyes closed, and passively attentive as the 10-minute pretraining baseline phase was initiated, followed by 40 minutes of auditory stimulation training, followed by the 10-minute post-training baseline, with frontal EEG's recorded throughout. At the conclusion of each training session, electrodes were detached and cleaned, and participants were asked about their experiences during the session. Immediately (within 2 hours) following the final training session, each participant was administered the SHSS:C again.

Data Analysis

Since the primary hypothesis of this study was that 4 hours of TBB training with low and moderate hypnotizable individuals would significantly increase hypnotizability, pre- and post-training hypnotizability scores for each group were analyzed by a simple between-groups, repeated-measures 3 (LH vs MH vs Controls) x 2 (Pre-training vs Post-training) ANOVA. As a measure of the efficacy of TBB training in enhancing frontal theta, frontal EEG's within the theta frequency band were averaged across the 10-minute pre-training and post-training baselines and each 10-minute quarter of the training session for each participant. Averages were computed for LH, MH, and Control participants separately and were examined for significant changes by a 3 (groups) x 5 (training phases) between-groups, repeated-measures ANOVA. To control for baseline differences among subjects, dependent variables in EEG analyses were the differences between the respective EEG training and initial baseline measures.

An additional prediction of this study was that there would be a significant positive relationship between frontal theta power and hypnotizability, such that those participants who produced higher frontal theta power were expected to be higher in hypnotizability at baseline. This relationship was tested by separate one-way ANOVA's. As this was an investigational study, alpha levels for statistical significance were set at .10 in all analyses.

Results

Analysis of Theta Changes

Analysis of frontal theta EEG's indicated a within-subjects main effect for changes in theta power across training (F(4, 21) = 9.285, p

Author Note

This study was conducted as part of a National Science Foundation Research Experience for Undergraduates conducted by Zach Haga and Brandy Queen under the direction of Larry Stevens. Parts of this study were presented by Zach Haga as a part of a symposium on The Neurological Bases of Hypnosis at the 43rd Annual Scientific Meeting and Workshops on Clinical Hypnosis of the American Society of Clinical Hypnosis held in Reno, Nevada, March 23-27, 2001.

The authors would like to express their appreciation to the Scientific Editor and to two anonymous reviewers for their very helpful suggestions on an earlier version of this manuscript.

1Gorassini, Sowerby, Creighton, and Fry (1991) have condensed this 1-hour cognitive skills training program into a 10-minute educational manipulation and have shown significant increases in susceptibility in one study using this brief intervention. However, this 10-minute training program has not been supported on replication (Milling, Kirsch, & Burgess, 1999).

2Two participants scoring 8 on the SHSS:C were included in the data analysis because of moderate scores on both the Psychological Absorption Scale and the Creative Imagination Scale, as well as an empirical justification for including such scorers in a "high medium" category (Perry, Nadon, & Button, 1992).

3A single monopolar site was used in this study because of data recording limitations of the NRS-2D Biolex software. Although the NRS-2D records and reports EEG data averages across a session for two channels, epoch-by-epoch data are only available for analysis on one channel. As F3 and F4 sites have been reported in research to be sensitive to theta frequency changes, a single site between F3 and F4, FZ, was identified for the present study.

4As we anticipated a rather dramatic effect of the TBB training on frontal theta EEG production and a stable non-effect of the control condition, a small control group not receiving theta training was run as a normative base for comparison of EEG change

References

Akpinar, S., Ulett, G.A., & Itil, T.M. (1971). Hypnotizability predicted by computer analyzed EEG pattern. Biological Psychiatry, 3, 387-392.

Andersen, P. & Andersen, S.A. (1968). Physiological basis of the alpha rhythm. New York: Appleton-Century-Crofts.

Atwater, F.H. (1995). The Monroe Institute's Hemi-Sync Process [On-Line serial]. Available at: http://www.monroeinstitute.org/research/hemi-sync-atwater.html. Atwater, F.H. (1996). Binaural beats and the frequency-following response: A pilot study. Unpublished manuscript.

Barabasz, A.F. (1982). Restricted environmental stimulation and the enhancement of hypnotizability: Pain, EEG alpha, skin conductance and temperature responses. The International Journal of Clinical and Experimental Hypnosis, 30(2), 147-166.

Bem, D.J. (1993). The ganzfeld experiment. Journal of Parapsychology, 57, 101-110. Bowers, K.S. (1976). Hypnosis for the seriously curious. Belmont, CA: Wadsworth Publishing Company.

Bowers, K.S. (1979). Hypnosis and healing. Australian Journal of Clinical and Experimental Hypnosis, 7(3), 261-277.

Bowers, K.S. (1982). The relevance of hypnosis for cognitive-behavioral therapy. Clinical Psychology Review, 2(1), 67-78.

Brady, B., & Stevens, L. (July 2000). Binaural beat induced theta EEG activity and hypnotic susceptibility. American Journal of Clinical Hypnosis, 43(1), 53-69. Brown, D.P. (1992). Clinical hypnosis research since 1986. In E. Fromm & M. Nash

(Eds.), Contemporary hypnosis research (pp. 427-486). New York: Guilford Press.

Crawford, H.J. (1990). Cognitive and psychophysiological correlates of hypnotic responsiveness and hypnosis. In M. L. Fass & D. P. Brown (Eds.), Creative mastery in hypnosis and hypnoanalysis: A festschrift for Erika Fromm (pp. 47-54). New York: Plenum Press.

Crawford, H., & Gruzelier, J. (1992). A midstream view of the neuro-psychophysiology of hypnosis: Recent research and future directions. In E. Fromm & M. Nash (Eds.), Contemporary hypnosis research (pp. 227-266). New York: Guilford Press.

DePascalis, V. & Ray, W.J. (1998). Effects of memory load on event-related patterns of 40-Hz EEG during cognitive and motor tasks. International Journal of Psychophysiology, 28, 301-315.

DePascalis, V., Ray, W.J., Tranquillo, I., & Amico, D. D. (1998). EEG activity and heart rate during recall of emotional events in hypnosis: Relationships with

hypnotizability and suggestibility. International Journal of Psychophysiology, 29, 255-275.

Empson, J.A.C. (1986). Human brainwaves: The psychological significance of the electroencephalogram. New York: Stockton Press.

Fisch, B.J. (1999). Fisch and Spehlmann's EEG primer: Basic principles of digital and analog EEG. Amsterdam: Elsevier Science BV.

Galbraith, G.C., London, P., Leibovitz, M.P., Cooper, L.M., & Hart, IT. (1970). EEG and hypnotic susceptibility. Journal of Comparative and Physiological Psychology, 72, 125-131.

Gorassini, D. R. & Spanos, N. P. (1986). A social-cognitive skills approach to the successful modification of hypnotic susceptibility. Journal of Personality and Social Psychology, 50(5), 1004-1012.

Gorassini, D., Sowerby, D., Creighton, A., & Fry, G. (1991). Hypnotic suggestibility enhancement through brief cognitive skill training. Journal of Personality and Social Psychology, 61, 289-297.

Graffin, N.F., Ray, W.J., & Lundy, R. (1995). EEG concomitants of hypnosis and hypnotic susceptibility. Journal of Abnormal Psychology, 104(1), 123-131.

Jasper, H.H. (1958). Report of the committee on methods of clinical examination in electroencephalography. Electroencephalography and Clinical Neurophysiology, 10, 370-375.

Kurtz, R.M. & Strube, MT (1996). Multiple susceptibility testing: Is it helpful? American Journal of Clinical Hypnosis, 38(3), 172-184.

Lane, J.D., Kasian, S.J., Owens, J.E., & Marsh, G.R. (1998). Binaural auditory beats affect vigilance performance and mood. Physiology and Behavior, 63(2), 249252.

Miller, G.E. & Cohen, S. (2001). Psychological interventions and the immune system: A meta-analytic review and critique. Health Psychology, 20(1), 47-63.

Milling, L.S., Kirsch, I., & Burgess, C.A. (1999). Brief modification of suggestibility and hypnotic analgesia: Too good to be true? The International Journal of Clinical and Experimental Hypnosis, 47(2), 91-103.

Oster, G. (1973). Auditory beats in the brain. Scientific American, 229, 94-102.

Pekala, R.J. & Kumar, V.K. (2000). Operationalizing "Trance" I: Rationale and research using a psychophenomenological approach. American Journal of Clinical Hypnosis, 43(2), 107-135.

Perry, C. (1977). Is hypnotizability modifiable? The International Journal of Clinical and Experimental Hypnosis, 25(3), 125-146.

Perry, C., Nadon, R., & Button, J. (1992). The measurement of hypnotic ability. In E. Fromm & M. Nash (Eds.), Contemporary hypnosis research (pp. 459-490). New York: The Guilford Press.

Ruzyla-Smith, P., Barabasz, A., Barabasz, M., & Warner, D. (1995). Effects of hypnosis on the immune response: B-cells, T-cells, helper and suppressor cells. American Journal of Clinical Hypnosis, 38(2), 71-79.

Sabourin, M.E., Cutcomb, S.D., Crawford, H.J., & Pribram, K. (1990). EEG correlates of hypnotic susceptibility and hypnotic trance: Spectral analysis and coherence. International Journal of Psychophysiology, 10, 125-142.

Sadigh, M. R. & Kozicky, P. W. (1994). The effects of Hemi-Sync on electrocortical activity: A review of three empirical studies [On-line]. Available at: http://

www.monroeinstitute.org/research/effects-of-hemi-sync-on-electrocortical-- activity.html.

Shellenberger, R. & Green, J. A. (1986). From the ghost in the box to successful biofeedback training. Greeley, CO: Health Psychology Publications. Tebecis, A. K., Provins, K. A., Farnbach, R. W., & Pentony, P. (1975). Hypnosis and the

EEG: A quantitative investigation. Journal of Nervous and Mental Disease, 161, 147.

Tellegen, A. & Atkinson, G. (1974). Openness to absorbing and self-altering experiences ("absorption"), a trait related to hypnotic susceptibility. Journal of Abnormal Psychology, 83, 268-277.

Weitzenhoffer, A.M. & Hilgard, E. R. (1962). Stanford Hypnotic Susceptibility Scale, Form C. Palo Alto, CA: Consulting Psychologists Press.

Wickramasekera, I. (1999). How does biofeedback reduce clinical symptoms and do memories and beliefs have biological consequences? Toward a model of mindbody healing. Applied Psychophysiology and Biofeedback, 24(2), 91-105.

Wilson, S. & Barber, T. (1978). The Creative Imagination Scale as a measure of hypnotic responsiveness: Applications to experimental and clinical hypnosis. American Journal of Clinical Hypnosis, 20, 235-249.

Larry Stevens

Zach Haga

Brandy Queen

Brian Brady

Deanna Adams

Jaime Gilbert

Emily Vaughan

Cathy Leach

Paul Nockels

Patrick McManus

Northern Arizona University

Address correspondence to and request reprints from:

Larry C. Stevens

Department of Psychology

NAU Box 15106

Northern Arizona University

Flagstaff, AZ 86011

E-mail: Larry.Stevens@nau.edu

Copyright American Society of Clinical Hypnosis Apr 2003
Provided by ProQuest Information and Learning Company. All rights Reserved