Audio-Visual Brainwave Entrainment (AVBE) · Philips Restricted TN-2009/00642 Section 1 Introduction This report gives an overview of the eld of audio-visual brainwave entrainment

Technical note TN-2009/00642

Issued: 2/2010

Audio-Visual Brainwave Entrainment(AVBE)

Ronald M. Aarts

Nicolle H. van Schijndel

Pedro Fonseca

Philips Research Eindhoven

Philips Restricted

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TN-2009/00642 Philips Restricted

Concerns: End Report

Period ofWork:

2009

Notebooks: None

Authors’ address R. M. Aarts [email protected]

N. H. van Schijndel [email protected]

P. Fonseca [email protected]

c© KONINKLIJKE PHILIPS ELECTRONICS N.V. 2010All rights reserved. Reproduction or dissemination in whole or in part isprohibited without the prior written consent of the copyright holder.

ii c© Koninklijke Philips Electronics N.V. 2010

Philips Restricted TN-2009/00642

Title: Audio-Visual Brainwave Entrainment (AVBE)

Author(s): Ronald M. Aarts ; Nicolle H. van Schijndel ; Pedro Fonseca

Reviewer(s): A. Kohlrausch, S.C. Pauws

TechnicalNote:

TN-2009/00642

AdditionalNumbers:

Subcategory:

Project: Emotions 2009 (2008-404)

Customer: Philips Research

Keywords: brainwave entrainment (BWE), audio-visual entrainment, brain en-trainment, audio-visual stimulation, auditory entrainment, binauralbeats, and photic stimulation

Abstract: This report gives an overview of the field of audio-visual brainwaveentrainment (AVBE), focusing on scientific literature that investigatesthe effect on health and wellbeing. The term ‘brainwave entrainment’refers to the use of periodic sensory stimuli to stimulate targeted fre-quencies in the brain. Such sensory stimuli can be auditory, visual or acombination of the two. First auditory entrainment will be discussed,with special attention for a specific form of auditory entrainment stim-uli: binaural beats. This chapter is followed by a chapter on visualentrainment, and a chapter that compares the two types of entrain-ment. Subsequently, the effect of entrainment on performance is dis-cussed. The following chapters are about the lasting (positive) effectsof entrainment and potential negative effects. Finally, some tentativeconclusions are formulated.

Conclusions: Rhythmic sensory (auditory or visual) stimuli can have a profound ef-fect on the brain. Consequences of entrainment for human behaviorand underlying neurological mechanisms for that are less established.Preliminary evidence suggests positive effects on aspects like short-term stress relief, pain, and cognitive abilities (attention, memory), butthis is not yet without controversy. Comparing auditory with visualentrainment, auditory entrainment is favored, because visual entrain-ment has a (small) risk of evoking (epileptic) seizures. In conclusion,preliminary findings are promising, but further research is required.

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iv c© Koninklijke Philips Electronics N.V. 2010


Contents

1 Introduction 1

2 Auditory entrainment 32.1 Binaural beats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Visual entrainment 5

4 Auditory versus visual entrainment 7

5 Enhancing performance 85.1 Auditory entrainment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.2 Visual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95.3 Combined audio-visual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6 Lasting effects of entrainment 12

7 Negative effects 13

8 Summary 14

9 Conclusions 15

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Section 1

Introduction

This report gives an overview of the field of audio-visual brainwave entrainment (AVBE).An early publication on this sensory stimulation method is [1] and a large stream of pub-lications have followed since. The present report does not give an exhaustive literaturereview on general brainwave entrainment, but its scope is mainly limited to literatureinvestigating the effect on health and wellbeing, for example by alleviating stress. Themain purpose of the report is to bring non experts to a certain level of understandingabout brainwave entrainment, without going too much in depth. Other forms of audio-visual stimulation like music-assisted relaxation [2] will not be discussed. The text isheavily based on the chapter ”Audio-visual entrainment” in David Vernon’s book [3]about techniques to enhance human performance and Huang’s comprehensive reviewpaper on the psychological effects of brainwave entrainment [4].

The term ‘entrainment’ is used for the effect that two oscillating systems interactingwith each other tend to approach each other in terms of frequency. A simple exampleof this is the self-synchronizing clocks at the wall an effect which was noticed by theDutch mathematician and physicist Christiaan Huygens (see e.g. Wikipedia’s entries‘Entrainment’ and ‘Odd sympathy’). The term ‘brainwave entrainment’ (also called‘audio-visual entrainment’ (AVE), ‘brain entrainment,’ ‘audio-visual stimulation’, ‘audi-tory entrainment’ and ‘photic stimulation’) refers to the use of rhythmic sensory stimulito stimulate targeted frequencies in the brain. Such sensory stimuli can be auditory,visual or a combination of the two. Research has repeatedly confirmed that stimuli withfrequencies between about 8 and 12 Hz, which corresponds with the alpha range of theelectroencephalogram (EEG), induce a frequency-following response in the brain as visi-ble in EEG recordings ([5, 6, 7, 8, 9, 10, 11]). There is also entrainment possible beyondthis frequency range, but for wellbeing applications the range is usually restricted to theEEG-alpha range.

As stated earlier, we limited the scope of this report. As a consequence we will notdiscuss some related topics like the artist Brion Gysin (see http://en.wikipedia.org/wiki/Brion_Gysin) who created the Dream Machine (light bulb, turn table, rotatingcylinder with cut outs) who thought he would change the world by photic stimulationin the sixties (see http://en.wikipedia.org/wiki/Dreamachine).

The remainder of this report is organized as follows. First auditory entrainment willbe discussed, with special attention for a specific form of auditory entrainment stimuli:binaural beats. This chapter is followed by a chapter on visual entrainment, and achapter that compares the two types of entrainment. Then, Chapter 5 will go into the

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http://en.wikipedia.org/wiki/Brion_Gysin

http://en.wikipedia.org/wiki/Brion_Gysin

http://en.wikipedia.org/wiki/Dreamachine


effect of entrainment on performance. The subsequent chapters are about the lasting(positive) effects of entrainment and potential negative effects. The report ends with asummary and conclusions.

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Section 2

Auditory entrainment

For auditory entrainment, rhythmic (repetitive) sounds are used to promote rhythmicbrain activity of a particular frequency. The most commonly used methods for genera-tion of such stimuli are 1) isochronic beats: single tone that periodically increases anddecreases in amplitude, or, in the extreme case, turns on and off. 2) monaural beats: twotones presented to the same ear, close in frequency, which are perceived as one beatingtone with the beat frequency equal to the frequency difference between the two tones, 3)binaural beats: two tones, one presented to the right ear, the other one to the left ear,which are also perceived as a beating tone similar as in method 2. Since the auditorysystem has very low sensitivity for tones below 20 Hz (an important frequency range forentrainment), simple generation of a sinusoid with such a low frequency can not be usedfor auditory entrainment. Instead one could generate a pulse train with the inter-pulseinterval corresponding to the entrainment frequency.

Since almost all research investigating the effect of auditory entrainment on healthand wellbeing used binaural beats, these stimuli are discussed below in more detail.

2.1 Binaural beats

“In 1839 the German experimenter H. W. Dove found that when he presented a par-ticipant with two separate frequencies composed of different wavelengths, one to eachear, this produced the sensation of a third phantom frequency called a binaural beatin addition to the two carrier frequencies [12]. The difference between the two carriersignals waxes and wanes as the two distinct frequencies mesh in and out of phase withone another. These differences produce an amplitude modulated standing wave, thebinaural beat, which can be perceived. In this sense, the binaural beat is a fluctuatingrhythm perceived as the frequency of the difference between the two auditory carriersignals. For example, if a 100-Hz tone is presented to the left ear and a 110-Hz toneis simultaneously presented to the right ear, one perceives the frequency difference asa distinct frequency component of 10 Hz. However, this binaural beat of 10 Hz is not’heard’ in the literal sense of the word, but rather the brain encodes it as an auditorybeat, and as such it can be used to entrain the neural activity of the brain via thefrequency following response.”[3]

“Clear evidence that a binaural beat can entrain the electrocortical activity of thebrain comes from researchers who have found that binaural beats produce an auditoryevoked response as measured with an electroencephalograph [13, 14, 15]).”[3]. Recently



Pratt et al. [16] found that neural activity with slightly different volley frequencies fromleft and right ear converges and interacts in the central auditory brainstem pathways togenerate beats of neural activity to modulate activities in the left temporal lobe. Cor-tical potentials recorded to binaural beats are distinct from onset responses. The brainactivity corresponding to the auditory illusion of low frequency beats can be recordedfrom the scalp. See [17] for a more elaborated literature review on binaural beats. See5.1 for information about the behavioral and cognitive effects of listening to binauralbeats.



Section 3

Visual entrainment

For visual entrainment, visual (photic) stimulation can be achieved by flashing lights intothe eyes of the individual using any source of flickering light with a fixed wavelength. Itis typically implemented with general purpose LEDs which can be mounted on a supportat a short distance to the eyes of the subject, either on the center or on the peripheryof his field of vision (see Figure 3.1). “The LEDs then flash out a pre-set frequencypattern entraining the brain via the optic nerve, where it has been shown to inducethe EEG of the brain to match the frequency of the flickering lights. This is based onearly research showing that rhythmic electrical potential changes can be recorded fromthe occipital region of the scalp when an individual is required to look at a flickeringlight field and that the elicited waves are of the same order of magnitude and rhythm asthe flickering field [19]. Over time this finding stimulated researchers to examine whathappens to the electrocortical activity of the brain when an individual is exposed toflickering lights (see e.g. [20, 21, 6]). For instance, when [6] recorded the EEG of peopleexposed to a flickering light he found they exhibited flicker-following potentials in boththe occipital and central regions of the scalp. These potentials represent a frequencyfollowing response to visual stimuli.”[3]. Because EEG recordings of the occipital cortexhave a good signal to noise ratio, especially when compared with recordings of otherareas of the cortex, this effect, called steady-state visually evoked potential (SSVEP forshort) has received significant attention since very early (see [22] for a review of earlywork and [23] for a recent review on this area). Since then a number of researchers haveconfirmed this effect [24, 25, 11]. Because SSVEPs are so easily visible in the EEG itled researchers to implement brain-computer interfaces (BCI) based on this principle.This has been done for decades with quite some success for disabled subjects (see [26]

Figure 3.1: LED boxes with diffusion panel used for SSVEP BCI [18].



for a comprehensive review) and, more recently, for healthy subjects [27], [28]. Therehas been relevant recent work done in this area in Philips Research [18, 29].

Intermezzo about the alpha range of the EEG In the previous text the alpharange of the EEG was mentioned and specified to be between 8 and 12 Hz. Let ushave a closer look at this. This intermezzo is also applicable to auditory and combinedaudio-visual entrainment. “Although the EEG has traditionally been divided into anumber of components with generally agreed upon frequency ranges, there is increasingevidence that the frequency range of a specific component can vary between individuals(e.g., [30]). [30] has suggested that instead of using a generic frequency range for every-one, each person’s EEG should be identified individually using the peak of their EEGactivity as an anchor point. In this way, rather than alpha simply representing a fixedfrequency range of 8 – 12 Hz it would represent a 2-Hz window either side of an individ-ual’s peak frequency. This has been referred to as the individual alpha frequency (IAF)range.”[3]. This idea that EEG frequency ranges can vary between individuals has ledsome to suggest that the audio-visual entrainment mechanisms might differ from subjectto subject. It might be that when the stimulus frequency matches the individual’s peakalpha frequency as opposed to using the midpoint of a traditional bandwidth [31], theentrainment effect is stronger.

Apart from personal differences in EEG frequency ranges, it is now clear that sev-eral cognitive factors such as attention [32] significantly alter the entrainment and thecorresponding SSVEP. “Although visual entrainment engages predominantly with theprimary visual cortex, research has shown that it is capable of eliciting changes in cor-tical activity that are widely distributed across the cortex [33].”[3]. The effects of suchentrainment may thus spread beyond the localized regions of the visual cortex, althoughits effectiveness at entraining a particular frequency component of the EEG may dependon the individual’s resting baseline activity, mental state and current cognitive activity.To further confirm this point, pioneering work by Silberstein [34] has shown that cogni-tive processes have an important effect on the amplitude of SSVEPs recorded on differentlocations of the cortex, even outside the occipital region. Further work has confirmedthat mental and emotional states have an impact on SSVEPs ([35, 36, 37]), giving birthto a technique called steady-state visual evoked potential topography, which is used e.g.to assess which cortical areas are active following determined cognitive processes.



Section 4

Auditory versus visualentrainment

After discussing entrainment with auditory or visual stimuli, the issue remains whichstimulus type is most effective and whether it is beneficial to combine the two sensorymodalities. The study of [24] addresses this, comparing the effectiveness of auditorystimulation, visual stimulation and combined audio-visual stimulation. The study didnot include any condition where the subjects had their eyes open when focusing on thelight source and therefore the effects of visual entrainment are expectedly lower. “The en-trainment procedure involved a single seven minute period during which the participantwas stimulated at a frequency of 18.5 Hz. Post training examination of the EEG revealeda significant increase in the amplitude of each person’s EEG at 18.5 Hz for all types ofstimulation. This is consistent with previous research and confirms that audio and/orvisual entrainment can produce a frequency following effect in the brain. Importantly,additional analysis comparing the different modalities of entrainment showed that theauditory eyes-closed condition produced the most effective change in EEG.”[3]. “It mayseem counter-intuitive that the combined audio-visual entrainment did not produce moreof an effect on the EEG than either audio or visual conditions alone. However, Fredericket al. [24] account for this by suggesting that simultaneous stimulation in both the au-ditory and visual domains interferes with, rather than reinforces, the entrainment effect.Overall, data resulting from a direct comparison of the effectiveness of audio to visualentrainment is limited and as such any conclusions reached at this stage are necessarilytentative.”[3]. While the results of this study suggest higher effectiveness when usingaudio, the study design did not include any condition where the subjects had to look andkeep visual attention on the flickering light. Extensive work on SSVEP-based BCI hasshown that visual entrainment is extremely strong and predictable as well as being veryeasily measured with EEG. Furthermore, the relative size of the occipital cortex makesthis modality particularly attractive for entrainment purposes since it comprises a largernumber of neural assemblies that synchronously fire when a particular stimulus is given.It is very difficult to conclude that one modality is more effective than the other. Theytarget different processes and therefore different cortical areas. Furthermore, the reasonwhy there is entrainment in the first place is not yet understood and any conclusions,even when based on these kinds of studies, will inevitably suffer from under-completionand will not be exhaustive in nature.



Section 5

Enhancing performance

From the previous chapter it can be concluded that audio-visual entrainment causes afrequency-following brain response, but the question still remains what this means forhuman wellbeing and health, as manifesting itself in cognition, mood, stress, and pain.Although research agrees that in general emotional and cognitive changes are reflected inchanges in the EEG, the amount of research addressing the psychological and cognitiveeffects of brainwave entrainment is limited. Below a summary is given.

5.1 Auditory entrainment

With respect to cognitive skills, more specifically attention, a study by Lane et al. [38]found a significant positive effect of binaural beats testing 29 healthy adults. “They useda three-stage procedure which involved participants initially completing a range of ques-tionnaires, with included measuring mood, followed by a task measuring attention andthen a second set of questionnaires which again measured mood. The participants com-pleted this procedure three times, listening to different audiotapes during performance ofthe attention task each time. During the first session they listened to a tape containingonly pink noise. This was used to obtain baseline levels of mood and cognition. Duringthe second session they were presented with an audiotape containing binaural beats of1.5 Hz and 4 Hz, aimed at entraining delta and low theta activity. In the third sessionthe audiotape contained binaural beats of 16 and 24 Hz and was aimed at entraining betaactivity. The presentation order of the tapes was counterbalanced across the group andinterestingly the participants didn’t know that they were listening to auditory binauralbeats, they were simply told that the tones presented through their headphones were toblock out any external sounds. [38] found that the participants detected more targetsduring the attention task when they were simultaneously listening to a tape containingbinaural beats entraining beta and produced more false alarms when they were listeningto a tape entraining delta and theta.”[3]. In addition, Joyce et al. [39] found a positiveeffect on attention within a group of 34 students diagnosed with ADHD. A study ofWahbeh et al. [40] however did not find an effect on attention, which may be due to thesmall number of subjects (4 healthy subjects) and the low binaural beat frequency of 7Hz (theta stimulation).

On mood, the study of Lane et al. [38] also found a significant positive effect (lessnegative mood in the case of beta-frequencies). An uncontrolled pilot study (8 subjects)of Wahbeh et al. [41] suggests the same. However, the later randomized double-blind



crossover study with 4 subjects of Wahbeh et al. [40] did not show an effect on moodusing theta stimulation.

With respect to short-term stress relief, Le Scouarnec et al. [42] found a significantreduction in anxiety using binaural beats within a group of 14 adults seeking help formild anxiety problems (pre-post design). Moreover, Padmanabhan et al. [43] showedthat pre-operative anxiety significantly reduced for a group of 36 adults listening tobinaural beats embedded in a music track as compared to a control group of 36 listeningto the same music track but without the beats and a control group of 36 without acousticstimuli. Differences in this randomized double-blind study were substantial with mean[95% confidence intervals] decreases in anxiety scores of 26.3% [19 – 33%] in the binauralgroup (p = 0.001 vs. music group, p < 0.0001 vs. control group), 11.1% [6 – 16%] in themusic group (p = 0.15 vs. control group) and 3.8% [0 – 7%] in the control group. Thesmall study with theta stimulation of Wahbeh et al. [40] again did not find any effectson short-term stress.

The studies of Le Scouarnec and Wahbeh [42, 41] also looked into more long-termstress and burnout. [42] did not find a significant effect; the small uncontrolled pilotstudy of [41] (8 healthy subjects) found a significant positive effect on trait anxiety,quality of life and insulin-like growth factor-1 and dopamine.

Pain was significantly reduced in a study by Manns et al. [44]. They applied acombination of electromyographic biofeedback and auditory entrainment within a groupof 33 adults with a pain dysfunction syndrome in a pre-post study design. This time nobinaural beats are used, but isochronic tones of constant frequency and duration thatwere adjusted and selected by the patient.

5.2 Visual

“The use of visual stimulation to entrain the EEG has been shown to impact on thepsychological status of a person and affect imagery ability as well as arousal levels[45, 46, 47]. For instance, [45] proposed that visual entrainment may be one of theeasiest methods to bring about a hypnagogic state and facilitate the emergence intoconscious awareness of visual imagination images. A hypnagogic state refers to thedreamlike experience that often represents the state between being fully awake andfalling asleep which may be accompanied by physical immobility and lucid visual andauditory hallucinations. To test this idea they examined the visual entrainment effectof three different frequencies (6 Hz, 10 Hz and 18 Hz) on the imagery ability of a groupof female students. They found that entrainment of the lower frequency ranges of 6and 10 Hz led participants to produce more complex images compared to when a higherfrequency of 18 Hz was used. [46] attempted to extend these results by examiningthe effects of visual entrainment on imagery across five different frequencies (5, 10, 15,20 and 25 Hz). They found that such visual stimulation induced a range of compleximagery phenomena similar to the images perceived during sleep onset and dreaming.The work of [45] is encouraging, although more needs to be done to explore possibledifferential effects resulting from entrainment of a 6 Hz frequency compared to one of10 Hz. Unfortunately, the work of von Gizycki and colleagues is less robust and assuch its results are more ambiguous. For instance, their procedure involves the visualentrainment of five distinct frequencies. Yet it remains unclear what the rationale was forusing such a wide range of frequencies and in addition to this they fail to identify which



of the five frequencies, or combination, was responsible for eliciting the effect on imagery.They also failed to include any controls and as such it is difficult to attribute the allegedeffects on enhanced imagery to visual entrainment. An alternative approach adoptedby [10] involves the use of a flicker training paradigm to induce visual entrainment andinfluence cognition. Rather than repeatedly flash a light into the eyes of a participantshe is presented with a flickering stimulus on a computer screen, such as a rectangle thatchanges color from gray to white, which is set to change color, or flicker, at a specificfrequency. Williams (2001) used this paradigm to induce a visual entrainment effectusing a flickering stimulus at one of three distinct frequencies (8.7 Hz, 10 Hz and 11.7Hz). Each time the flickering stimulus was shown it was immediately followed by thebrief presentation of a three letter trigram forming either a nonsense word (e.g., TEF)or a real word (e.g. BID) and participants were asked to classify the trigram as eithernonsense or real as quickly as they could. The fact that a target immediately followeda flickering stimulus may make this paradigm more sensitive to the subtle changes incortical activity brought about by visual entrainment, particularly if they fade overtime. The different frequencies of the flickering stimulus were found to have no effecton the speed of participant’s responses with regard to whether a trigram was classifiedas nonsense or real. However, in a follow up memory task participants were requiredto recognize which were the ’old’ trigrams they had seen during the classification taskwhen presented with a randomly mixed group of old and new trigrams. Williams (2001)found that participants recognized significantly more of the trigrams that followed the10-Hz flicker compared to those that followed either the 8.7 Hz or the 11.7 Hz flicker. Inaddition Williams (2001) was also able to show that the flickering stimulus was capable ofentraining EEG activity, with each of the entrainment frequencies showing an increase inamplitude following presentation of the flickering stimulus. These findings suggest that a10-Hz flicker is sufficient to elicit changes in cortical activity1 and that such changes arecapable of improving recognition memory. This is consistent with research showing thatbetter memory performance is associated with greater amplitude in the alpha (8 – 12 Hz)frequency range of the EEG [48].”[3]. Although this is suggestive of a confirmation of theresults of the study, it should be taken with care since the relation between alpha andcognitive performance is not fully understood. “More recently [49] used a similar visualflicker entrainment paradigm to show that frequencies close to 10 Hz can improve therecognition of elderly participants aged between 67 – 92 years. This led them to proposethat visual entrainment can selectively facilitate the neural mechanisms of the brain, asevidenced by changes in EEG, and that such changes in cortical activity can directlyinfluence psychological states. Overall, use of the flicker paradigm provides compellingevidence that visual stimulation at 10 Hz can produce clear changes in the EEG and leadto enhanced memory performance. Furthermore, the fact that such a finding has beenshown to be stable across different age groups suggests that it may produce a generaleffect on cognition.”[3].

5.3 Combined audio-visual

A few studies [50, 51, 52] used combined audio-visual stimulation in their entrainmentprocedure.

With respect to cognitive skills, the study of Olmstead [50] found that AVE improved

1Not only a rate of 10 Hz, but a wide range of stimulation frequencies change cortical activity.



arithmetic skills of children with learning difficulties in a pre-post study design. Acombination of flickering lights and binaural beats was used with a frequency changingbetween 14 Hz and 40 Hz. This study did not look into the effects of the differentstimulation modalities (light vs. sound) separately.

With respect to anxiety, the patients in the study of Morse and Chow [51] experiencedsignificantly less fear during a dental procedure in case the routine method of calmingwords of the dentist was combined with AVE (10 Hz) compared to only the routinemethod. In addition to this control group (10 persons) and the AVE group (10 persons),there was a group of 10 persons that only had visual entrainment of 10 Hz (in addition tothe calming words). This group also experienced significantly less anxiety as comparedto the control group. Compared with the AVE group, no significant differences wereobserved. Morse and Chow report that an advantage of adding the auditory stimuli isthat these mask disturbing sounds from dental procedures such as drilling.

With respect to stress and burnout, Ossebaard [52] found small (significant) effectson short-term stress, but no long-term effects. This study used combined audio-visualstimulation of the alpha range with frequencies of 10 Hz and stimulation of the betarange with frequencies of 30, 25 and 16 Hz.

On the beneficial effects of AVE, these studies provide some limited preliminaryevidence. Even less is known, unfortunately, about whether visual stimulation is moreeffective than auditory stimulation or vice versa, or about whether there is an advantageof combining the two.



Section 6

Lasting effects of entrainment

“Given that AVE can affect the amplitude and/or frequency of the electrocortical activityof the brain, which in turn may enhance an individual’s ability to perform certain tasks,an important point to consider is the duration of such effects. Are such changes enduringor does such training elicit only short-term benefits? [25] examined what effect an eightminute period of visual entrainment within both the alpha (10 Hz) and beta frequency(22 Hz) ranges would have on participants EEG. They found that stimulation withinthe alpha frequency produced only a transient enhancement and was moderated byindividual’s baseline activity. However, entrainment of the beta frequency componentproduced more prolonged changes in the EEG that were maintained for up to 24 minutes.Thus, a single session of entrainment can generate changes in the EEG that can lastbeyond the end of the stimulation period itself, albeit for a limited amount of time. Thiswould suggest that the entrainment of a specific frequency component may affect thebrain’s natural ability to produce that frequency and in so doing, facilitate its productionbeyond that of the entrainment period. Moreover, [25] points out that more robustentrainment effects may be elicited if individual differences in baseline EEG activity aretaken into account. Nevertheless, [31] found that changes in electrocortical activity as aresult of entrainment failed to last for very long. They examined the effects of AVE onthe human EEG and found that a single twenty minute session, where those taking partwere either stimulated at their dominant alpha frequency or at twice their dominantalpha frequency, exhibited a significant change in their EEG in the desired direction.However, EEG recordings taken 30 minutes after the entrainment ended showed littleevidence of these effects persisting. Taken together these results would suggest that asingle period of entrainment is capable of producing changes in the EEG in the desiredfrequency range, but that such changes may last for up to 24 minutes, but not beyond.Such results, while limited, are encouraging. If a single entrainment session is capable ofproducing changes in the EEG that last beyond the stimulation itself, it seems probablethat a more persistent effect may be obtained with a greater number of sessions. Moreresearch is needed which not only takes into account individual differences in baselineEEG activity but also compares the effectiveness of the various entrainment methods toascertain which is the most effective at producing long-term effects and why.”[3].



Section 7

Negative effects

One should be cautious with audio-visual entrainment, in particular with visual en-trainment. Repetitive visual stimulation, e.g. of flashing lights or visual patterns, mayprovoke photic- or pattern-induced seizures. Especially people with a (family) history ofseizures or epilepsy have to be cautious; for extreme cases, even an electric toothbrushcan induce seizures [53]. However, also people without such history may suffer fromseizures after repetitive visual stimulation as was seen in the Pokemon cartoon incidentin Japan [54, 55]. Fisher et al. write: “Photosensitivity, an abnormal EEG response tolight or pattern stimulation, occurs in approximately 0.3 – 3% of the population. Theestimated prevalence of seizures from light stimuli is approximately 1 per 10,000, or 1 per4,000 individuals 5 – 24 years old. People with epilepsy have a 2 – 14% chance of havingseizures precipitated by light or pattern. In the Pokemon cartoon incident in Japan,685 children visited a hospital in reaction to red-blue flashes on broadcast television.Only 24% who had a seizure during the cartoon had previously experienced a seizure.Photic or pattern stimulation can provoke seizures in predisposed individuals, but suchstimulation is not known to increase the chance of subsequent epilepsy. Intensities of0.2 – 1.5 million candlepower are in range to trigger seizures. Frequencies of 15 – 25Hz are most provocative, but the range is 1 – 65 Hz. Light-dark borders can inducepattern-sensitive seizures, and red color also is a factor. Seizures can be provoked bycertain TV shows, movie screen images, videogames, natural stimuli (e.g, sun on water),public displays, and many other sources.” [54].



Section 8

Summary

This report gives an overview of the field of audio-visual brainwave entrainment (AVBE),focusing on scientific literature that investigates its effect on health and wellbeing. Theterm ‘brainwave entrainment’ refers to the use of rhythmic sensory stimuli to stimulatetargeted frequencies in the brain. Such sensory stimuli can be auditory, visual or acombination of the two. First auditory entrainment will be discussed, with specialattention for a specific form of auditory entrainment stimuli: binaural beats. Thischapter is followed by a chapter on visual entrainment, and a chapter that comparesthe two types of entrainment. Subsequently, the effect of entrainment on performance isdiscussed. The following chapters are about the lasting (positive) effects of entrainmentand potential negative effects. Finally, some tentative conclusions are formulated.



Section 9

Conclusions

Rhythmic sensory (auditory or visual) stimuli have a profound effect on the brain. Firstscientific evidence of this entrainment effect has already been reported as early as 1934[19]. Since then, many papers have been published, mostly in less known journals. Thisyear, however, proof appeared in the high-impact journal Clinical Neurophysiology [16].

Consequences of entrainment for human behavior and underlying neurological mech-anisms for that are less established. Preliminary evidence suggests positive effects onaspects like short-term stress relief, pain, and cognitive abilities (attention, memory),but this is not yet without controversy.

Comparing auditory with visual entrainment it is still unclear which sensory type ismore effective. Synergy in combining the two has not been reported so far. Since visualentrainment has a (small) risk of evoking (epileptic) seizures, auditory entrainment isfavored. In addition, auditory stimulation better fits eyes-closed situations such as duringrelaxation.

In summary, preliminary findings are promising, but further research is required.



Bibliography

[1] V.J. Walter and W.G. Walter. The central effects of rhythmic sensory stimulation.Clinical Neurophysiology, 1(1):57–86, 1949.

[2] G. de Niet, B. Tiemens, B. Lendemeijer, and G. Hutschemaekers. Music-assistedrelaxation to improve sleep quality: meta-analysis. Journal of Advanced Nursing,65(7):1356–1364, July 2009.

[3] D. Vernon. Human Potential: Exploring Techniques Used to Enhance Human Per-formance. Routledge, 2009. ISBN978-0415457705.

[4] C. Huang. A comprehensive review of the psychological effects of brainwave en-trainment. Journal of alternative therapies, 14(5), Sep./Oct. 2008.

[5] W. G. Walter, V. J. Dovey, and H. Shipton. Analysis of the electrical response ofthe human cortex to photic stimulation. Nature, 158(4016):540–541, 1946.

[6] J. Toman. Flicker potentials and the alpha rhythm in man. Journal of Neurophys-iology, 4:51–61, 1941.

[7] S. H. Nystrom. Effects of photic stimulation on neuronal activity and subjectiveexperience in man. Acta Neurol Scand., 42(5):505–514, 1966.

[8] G. Moruzzi and H. W. Magoun. Brain stem reticular formation and activation ofthe EEG. Electroencephalogr Clin Neurophysiol., 1(4):455–474, 1949.

[9] L. J. Rogers and D. O. Walter. Methods for finding single generators, with ap-plication to auditory driving of the human EEG by complex stimuli. J NeurosciMethods, 4(3):257–265, 1981.

[10] J.H. Williams. Frequency-specific effects of flicker on recognition memory. Neuro-science, 104:283–286, 2001.

[11] K. Schwab, C. Ligges, T. Jungmann, B. Hilgenfeld, J. Haueisen, and H. Witte.Alpha entrainment in human electroencephalogram and magnetoencephalogramrecordings. NeuroReport, 17:1829–1833, 2006.

[12] G. Oster. Auditory beats in the brain. Scientific American, 229(4):94–102, October1973.

[13] S. Karino, M. Yumoto, K. Itoh, A. Uno, K. Yamakawa, S. Sekimoto, and K. Kaga.Neuromagnetic responses to binaural beat in human cerebral cortex. J Neurophysiol,96:1927–1938, 2006.



[14] R. Kennerly. QEEG analysis of binaural beat audio entrainment: A pilot study. Jof Neurotherapy, 8:122, 2004.

[15] D. W. F. Schwarz and P. Taylor. Human auditory steady state responses to binauraland monaural beats. Clinical Neurophysiology, 116:658–668, 2005.

[16] H. Pratt, A. Starr, H. Michalewski, A. Dimitrijevic, N. Bleich, and N. Mittelman.Cortical evoked potentials to an auditory illusion: Binaural beats. Clinical Neuro-physiology, 120(8):1514–1524, 2009.

[17] R. M. Aarts. Overview of Binaural Beats to evoke brainwave entrainment. Technicalreport, Philips Research Labs, 2009. Nat.Lab. Technical Note PR-TN 2009/00555,March 2010.

[18] V. Mihajlovic and G. G. Molina. D3.1 BRAIN Initial prototype of advancedSSVEP signal processing tools, Technical Note PR-TN 2009/00182. Technical re-port, Philips Research Eindhoven, 2009.

[19] E. D. Adrian and B. H. C. Matthews. The Berger rhythm: potential changes fromthe occipital lobes in man. Brain, 57 (Part 4):355–384, 1934.

[20] C. S. Herrmann. Human EEG responses to 1–100 Hz flicker: resonance phenomenain visual cortex and their potential correlation to cognitive phenomena. Experimen-tal Brain Research, 137(3):346–353, 2001.

[21] R. W. Lansing and J. S. Barlow. Rhythmic after-activity to flashes in relation to thebackground alpha which precedes and follows the photic stimuli. Electroencephalog-raphy and Clinical Neurophysiology, 32(2):149–160, 1972.

[22] D. Regan. Steady-state evoked potentials. Journal of the Optical Society of America,67(11):1475–1489, 1977.

[23] D. Zhu, J. Bieger, G. Garcia Molina, and R. M. Aarts. A survey of stimulationmethods used in SSVEP-based BCIs manuscript accepted for publication in Com-putational Intelligence and Neuroscience, December 2009.

[24] J. A. Frederick, J. F. Lubar, H. W. Rasey, S. A. Brim, and J. Blackburn. Effectsof 18.5 Hz auditory and visual stimulation on EEG amplitude at the vertex. J ofNeurotherapy, 3:23–28, 1999.

[25] J. P. Rosenfeld, A. M. Reinhart, and S. Srivastava. The effects of alpha (10-Hz)and beta (22-Hz)entrainment stimulation on the alpha and beta EEG bands: Indi-vidual differences are critical to prediction of effects. Applied psychophysiology andbiofeedback, 22(1):3–20, 1997.

[26] Y. Wang, X. Gao, B. Hong, C. Jia, and S. Gao. Brain-computer interfaces basedon visual evoked potentials. IEEE Engineering in Medicine and Biology Magazine,27(5):64–71, 2008.

[27] M. Middendorf, G. McMillan, G. Calhoun, and K. S. Jones. Brain-computer in-terfaces based on the steady-state visual-evoked response. IEEE Transactions onRehabilitation Engineering, 8(2):211–214, June 2000.



[28] B. Allison, B. Graimann, and A. Graser. Why Use A BCI If You Are Healthy?,BRAINPLAY 07 Brain-Computer Interfaces and Games Workshop at ACE (Ad-vances in Computer Entertainment), p.7, 2007.

[29] D. Ibanez, G. G. Molina, and D. Chestakov. Detection of steady-state visual evokedpotentials in the EEG, technical note pr-tn 2009/00150. Technical report, PhilipsResearch Eindhoven, 2009.

[30] W. Klimesch. EEG alpha and theta oscillations reflect cognitive and memory per-formance: a review and analysis. Brain Research Reviews, 29(2-3):169–195, 1999.

[31] J. A. Frederick, D. A. L. Timmermann, H. L. Russell, and J. F. Lubar. EEGcoherence effects of audio-visual stimulation (AVS) at dominant and twice dominantalpha frequency. Journal of Neurotherapy, 8(4):25–42, 2005.

[32] S. T. Morgan, J. C. Hansen, and S. A. Hillyard. Selective attention to stimuluslocation modulates the steady-state visual evoked potential. Proceedings of theNational Academy of Sciences of the United States of America, 93(10):4770, 1996.

[33] D. A. L. Timmermann, J. F. Lubar, H. W. Rasey, and J. A. Frederick. Effects of20-min audio-visual stimulation (AVS) at dominant alpha frequency and twice dom-inant alpha frequency on the cortical EEG. International Journal of Psychophysi-ology, 32(1):55–61, 1999.

[34] R. B. Silberstein, J. Ciorciari, and A. Pipingas. Steady-state visually evoked poten-tial topography during the wisconsin card sorting test. Electroencephalography andClinical Neurophysiology/Evoked Potentials Section, 96(1):24–35, 1995.

[35] R. B. Silberstein, P. L. Nunez, A. Pipingas, P. Harris, and F. Danieli. Steady statevisually evoked potential (ssvep) topography in a graded working memory task.International Journal of Psychophysiology, 42(2):219–232, 2001.

[36] A. H. Kemp, M. A. Gray, P. Eide, R. B. Silberstein, and P. J. Nathan. Steady-state visually evoked potential topography during processing of emotional valencein healthy subjects. NeuroImage, 17(4):1684–1692, 2002.

[37] Z. Wu and D. Yao. The influence of cognitive tasks on different frequencies steady-state visual evoked potentials. Brain Topography, 20(2):97–104, 2007.

[38] J. Lane, S. J. Kasian, J. E. Owens, and G. R. Marsh. Binaural auditory beats affectvigilance performance and mood. Physiology & Behavior, 63(2):249–252, 1998.

[39] M. D. Joyce, D. Siever, and M. Twittey. Audio-visual entrainment program as atreatment for behavior disorders in a school setting. In Abstracts of Papers Presentedat the 30th Annual Meeting of the Association for Applied Psychophysiology andBiofeedback, volume 24 (2), pages 136–136, June 1999.

[40] H. Wahbeh, C. Calabrese, H. Zwickey, and D. Zajdel. Binaural beat technologyin humans: a pilot study to assess neuropsychologic, physiologic, and electroen-cephalographic effects. J Altern Complement Med, 13(2):199–206, March 2007.



[41] H. Wahbeh, C. Calabrese, and H. Zwickey. Binaural beat technology in humans:a pilot study to assess psychologic and physiologic effects. J Altern ComplementMed, 13(1):25–32, Jan./Feb. 2007.

[42] R. P. Le Scouarnec, R. M. Poirier, J. E. Owens, J. Gauthier, A. G. Taylor, andP. A. Foresman. Use of binaural beat tapes for treatment of anxiety: a pilot studyof tape preference and outcomes. Altern Ther Health Med., 7(1):58–63, January2001.

[43] R. Padmanabhan, A. J. Hildreth, and D. Laws. A prospective, randomised, con-trolled study examining binaural beat audio and pre-operative anxiety in patientsundergoing general anaesthesia for day case surgery. Anaesthesia, 60(9):874–7,September 2005.

[44] A. Manns, R. Miralles, and H. Adrian. The application of audiostimulation and elec-tromyographic biofeedback to bruxism and myofascial pain-dysfunction syndrome.Oral Surg Oral Med Oral Pathol., 52(3):247–52, September 1981.

[45] A. Richardson and F. McAndrew. The effects of photic stimulation and privateself-consciousness on the complexity of visual imagination imagery. British journalof psychology (London, England: 1953), 81:381, 1990.

[46] H. von Gizycki, G. Jean-Louis, M. Snyder, F. Zizi, H. Green, S. Franconeri,J. Gaglio, S. Troia, A. Spielman, J. Nunes, and H. Taub. Photic stimulation pro-duces a hypnagogic state. Sleep Research, 26:269, 1997.

[47] H. von Gizycki, G. Jean-Louis, M. Snyder, F. Zizi, H. Green, V. Giuliano, A. Spiel-man, and H. Taub. The effects of photic driving on mood states. Journal ofpsychosomatic research, 44(5):599–604, 1998.

[48] M. Doppelmayr, W. Klimesch, K. Hodlmoser, P. Sauseng, and W. Gruber. Intel-ligence related upper alpha desynchronization in a semantic memory task. BrainResearch Bulletin, 66(2):171–177, 2005.

[49] J. Williams, D. Ramaswamy, and A. Oulhaj. 10 Hz flicker improves recognitionmemory in older people. BMC neuroscience, 7(1):21, 2006.

[50] R. Olmstead. Use of auditory and visual stimulation to improve cognitive abilitiesin learning-disabled children. Journal of Neurotherapy, 9(2):49–61, September 2005.

[51] D. R. Morse and E. Chow. The effect of the relaxodont brain wave synchronizeron endodontic anxiety: evaluation by galvanic skin resistance, pulse rate, physicalreactions, and questionnaire responses. Int J Psychosom., 40(1-4):68–76, 1993.

[52] H. C. Ossebaard. Stress reduction by technology? An experimental study into theeffects of brainmachines on burnout and state anxiety. Applied Psychophysiologyand Biofeedback, 25(2):93–101, October 2000.

[53] M. C. Haytac, K. Aslan, O. Ozcelik, and H. Bozdemir. Epileptic seizures triggeredby the use of a powered toothbrush. Seizure, 17(3):288–91, April 2008.



[54] R. S. Fisher, G. Harding, G. Erba, G. L. Barkley, and A. Wilkins. Photic-andpattern-induced seizures: a review for the epilepsy foundation of America workinggroup. Epilepsia, 46:1426–1441, 2005.

[55] http://en.wikipedia.org/wiki/Photosensitive epilepsy, 2009 Dec. 9.


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