Early on I found myself uncomfortable with “Brainwave Entrainment” as the umbrella term for the use of sound and light to affect mental states. Entrainment is but one of a yet unknown number of responses to audiovisual stimulation.

BWE is specifically the use of repetitive rhythms, emulating the brain rhythms measurable at the scalp, to induce matching rhythms over the auditory and/or visual cortices, in the hope that other functional regions of the brain will synchronise to that rhythm. The frequencies chosen for BWE are those which have been observed to be present in “model” cases. It is supposed that if one can persuade the brain to exhibit these rhythms, then the mental state will be equivalent to that of one who is exhibiting these rhythms while expertly performing the desired task (typically meditation). The therapeutic line of reasoning is precisely the same – take EEG readings from a “healthy” subject, then induce similar readings in the patient. The therapeutic connection is far more robust than the “spiritual” connection.

Every individual is different and optimum results will only be achieved by measurement (bio/neuro-feedback) or diligent trial and error. The starting point can be pretty much anywhere in the range of interest, but can be refined to high, mid or low within any range by remembering that they are not discrete bands, but regions of a continuum of frequencies. For example, if you’re wanting quiet contemplation, then alpha is the correct choice. If you want to introduce an “intuitive” element then you can either intersperse some theta, or use a frequency lower in the alpha range, closer to theta. Most importantly, the numbers don’t matter.

AVS includes BWE, but also accommodates the many other modes of audiovisual manipulation of the brain/mind.

Once you move from BWE, waveform becomes as important as frequency.

The raw efficiency of BWE is affected by the waveform, but for pure BWE you will be using a simple waveform – one uninterrupted up and one uninterrupted  down per cycle. As soon as your waveform deviates from a sine, non-BWE effects are introduced, until you arrive at a true square (as opposed to the optimised squares used in NP2/MWS) which has many characteristics of a two-pulse stimulus, due to the harmonics associated with its leading and trailing edges.

Next we have complex waveforms. These can be deliberately engineered using the waveform editor in MWS, or with a bit of clever mixing, can be synthesised from NP2 or MWS tone tracks. To use these effectively requires intuitive trial and error – find an observed phenomena in research abstracts, contemplate the mechanisms involved, and then start trying waveforms and frequencies until something happens or not.

Noise is where it gets really interesting. I’ve done a whole post on noise (A noisy noise annoys an oyster), so I won’t do this one to death. Those who are interested in “extreme” experiences will find experimentation with noise most rewarding. It is the basis of a number of “secret” protocols. Generally AVS is safe, however there are things that can be done with noise that are not safe, so experimentation should be accompanied with reasonable theoretical consideration. It would be irresponsible for me to provide greater detail. Noise, as used in NP2 and MWS , and any variant on its use that you are likely to encounter or accidentally produce is safe.

The way I see it, “recreational” embraces any use of AVS that has no specific intent other than to pleasurably pass time. Incorporation of conventional brain rhythms into any musical piece can affect mood, so a clever designer can reinforce the emotive of the music itself with direct stimulus. Quite specific neurotransmitter responses can be triggered with AVS, making it possible to emulate feelings associated with love, fear, joy, etc. I have had sufficient unpleasant experiences exploring this to be unwilling to provide detail.

A rule I have come to accept is that psychoactivity is inversely proportional to how pleasant an audio stimulus sounds, or how pretty a lightshow looks. Truly mind bending sessions sound horrible and look boring.

Its probably a good idea to seriously consider whether you really want to take AVS to its extremes. It is frighteningly effective and facilitates access to parts of the mind that may well be better left alone. There’s a lot of pleasure and rewarding results that can be enjoyed with sessions no more complex than those included with NP2/MWS or the mind machines.

I end almost every day by launching either the sub-delta or sleep induction (white noise) sessions from MWS. I’ve extended them to two hours and I start them half an hour before I want to sleep and use the session end options to shut the computer down when done.

This probably exhausts the generalisations I can make on the subject. To provide more detail I would need to know of the specific application – feel free to ask. (And also remember – anything I can tell you beyond what is readily available is the result of n=1 research – highly unreliable!)


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  • Dave siever  On February 12, 2010 at 6:00 am

    The concept of brain wave entrainment was founded in 1932 by /Adrian & Matthews. In those days it was termed cortical driving and frequency-following response. Well over a thousand studies have been published on the effects of BWE or AVE. The definition of BWE/AVE as published in my chapter in “Quantitive EEG and Neurofeedback,” is as follows:

    Audio-visual entrainment (AVE), a subset of brainwave entrainment, uses flashes of lights and pulses of tones to guide the brain into various states of brain wave activity.

    Auditory or visual stimulation (AVS) can take a wide variety of forms, generating different subjective and clinical effects. The simplest form of AV stimulation is to present a series of random light flashes and/or sound pulses to a subject such as from watching TV or cars drive by, and investigate the resulting subjective experiences or electroencephalography (EEG) effects.

    Audio-visual entrainment (AVE) on the other-hand, involves organized, repetitive stimulation at a particular frequency for a specific period of time, and the frequency of stimulation is reflected within the EEG. The stimulation doesn’t effect the cortex by spilling-off the auditory or visual areas, it does so by activating the thalamus vian the geniculate bodies (Collura & Siever, 2009). Rhythmic photic entrainment (PE) therefore affects the whole brain with the exception of the temporal lobes (Siever, 2007). Auditory entrainment (AE) has a much smaller effect throughout the main cortex, but has some effect in the temporal lobes in the auditory processing areas (Ten-20 electrode sites T3 & T4). A recent study by Frederick, et. al, 2004, found that 18 Hz PE increased the EEG at the vertex (top of head) by 49%, while auditory entrainment increased EEG by 21%. Plain AVS won’t affect EEG like this.

    In 1956, W. Gray Walter published the first results on thousands of test subjects comparing flicker stimulation with the subjective emotional feelings it produced. Test subjects reported all types of visual illusions and in particular the “whirling spiral,” which was significant with alpha production (Walter, 1956). In the late 1950s, as a result of Kroger’s observations as to why US military radar operators often drifted into trance, Kroger teamed up with Sidney Schneider of the Schneider Instrument Company, and produced the world’s first electronic clinical photic stimulator – the “Brainwave Synchronizer.” It had powerful hypnotic qualities and soon studies on hypnotic induction were published (Kroger & Schneider, 1959; Lewerenz, 1963; Sadove, 1963; Margolis, 1966).

    So far as waveforms go, square waves make nicer imagery, but also generate a 3rd harmonic in the brain. Therefore, even when stimulating at 10 Hz (alpha), a person may experience an anxiety reaction from the 30 Hz harmonic. Risk of seizure also increases. Almost all AVE devices use square-wave photic generation. Sine wave PE doesn’t generate harmonics, so a 10 Hz sine wave only makes 10 Hz, and the user will relax. As far as auditory waveforms go, clicks have the most prominent impact on the brain. But clicks are generally aggravating and ruin their own experience. A pure tone such as a monaural beat or isochronic tones produce AE. The waveform affects the listening experience, but due to the logarithmic nature of hearing (which involves the stapedius reflex), the EEG response is much the same with most waveforms (excluding clicks).

    AVE doesn’t just increase the frequency of stimulation, it inhibits the 1/2 of stimulation. There a frequency of 14 Hz will inhibit the excessive (bad) theta in ADHD children (Siever, 2000). A left hemisphere induced frequency (by stimulating the right-fields of both eyes (Mind Alive patent, 1995)) of 20 Hz will inhibit the excessive and “bad” alpha in the left frontal lobe and help reduce depression (Siever, 2007 & 2009).

    Dave Siever,
    Mind Alive Inc.

    • CraigT  On February 12, 2010 at 7:11 am

      Thanks for taking the time to provide some great information!

  • Steve  On February 14, 2010 at 10:19 am

    Hi Craig,

    This post is a great read. I’ve said this once before, but it doesn’t hurt to say again that I really appreciate the fairness with which you treat this subject. What a relief not to hear the same pseudoscientific BS that you get from most other sources on the topic of entrainment/avs/ave/whatever.

    Not to say that your approach is all that scientific, but at least you’re up front about that. You have your own goals in mind as you set about your ‘research’, and you don’t make grandiose announcements about your ‘discoveries’ – just a few tantalizing hints about what works and doesn’t work for you. Sometimes they seem pretty esoteric and aggravating to me (like your statement about how irresponsible you would be to elaborate further on unsafe uses of noise), but that beats the hell out of saying something like: “Here is the recipe for buddha consciousness”.

    Anyway, as a new Procyon user, I just wanted to share some of my experiences with this fascinating machine and entrainment in general. I was tempted to post on the mindplace forums (esteband is my handle over there), but your blog seems a more appropriate venue, since I want to talk about more than just the hardware, and really (after reading so many of your blog posts), it’s your opinions that I value most.

    I recieved my procyon 2 weeks ago, and am just starting to get to know the preset sessions. I’ve written and posted one synchromuse session. I wrote it primarily because I wanted to “see” my own musical compositions. It works well to get me into a very relaxed state before falling asleep; I would say that it sets me up pretty well for a night of sweet dreams.

    That’s primarily why I bought the procyon. A little background: I am almost 1 year into the sometimes uncomfortable path of sobriety. It has been hard for me to get to sleep, and I found myself becoming a little dependent on sleeping pills. That doesn’t fit too well with my new life plan, so I started thinking of non-chemical ways I could overcome this hurdle. I thought back to almost 15 years ago, when I started making “brainwave” music with a little windows program from Syntrillium Software called “Cool Wave” – the precursor to Cool Edit, and later Adobe Audition. This basic little audio editor had a fairly robust tool for modulating audio to create binaural beats. It totally worked for me back then, but somehow over the years, I forgot all about it. Luckily, a few weeks ago, I remembered how well it worked as a relaxation aid, and I figured there must be much more software available by now. So in my searches, I discovered Gnaural and NP2. Sure enough, these new tools worked just fine.

    Further research led me to this blog, and then to mindplace. Your reviews convinced me that the Procyon would be a great purchase for me – not only for its effectiveness, but also for its programmability. Effective? Yes. Programmable? Yes, but certainly not very easily so. It’s a poor musician who blames his instrument, but damn, this is going to be one hard instrument to learn.

    Anyway, my experiences with the procyon have been all over the place. As I said, I bought it primarily as a relaxation aid, but I would also welcome any “consciousness altering” or psychedelic effects as bonuses. I’m finding that indeed, procyon sessions can be psychedelic (or dissociative, or sleep-inducing, or fill-in-the-blank), but that the process seems not to be automatic. Instead, results depend largely on my focus – that the only thing that “happens” if I’m totally passive is that a 15, 30, or 60 minute chunk of time just disappears from my day. But if I do apply some measure of focus, I can observe some things ‘happening’ to my mental state, my vision, my hearing, and even my body. So it occurred to me that this may be an excellent way for me to practice my mental focus, and that through this, I have essentially discovered meditation.

    I am not, by any means, a student of meditation. In my teens and twenties, I was fascinated by it, and somewhat taken in by a lot of new-age mumbo jumbo. I dabbled a little bit, but found it too difficult and gave up in discouragement. As I matured, I somehow came to detest the whole new-age movement, including its jargon, and especially its imagery. It was hard for me to separate the concept of meditation from all this contempt. Still, I can’t deny that meditation, in general, is almost universally recognized as a very healthy practice. I concede that it has improved the lives of countless people. Now that I have had some little glimpse of what it may be about for me and me alone – not as part of any dogma or doctrine or philosophy – I’m excited about what I have stumbled upon.

    But at this stage, I’m clueless. I don’t know where to apply this focus I have just discovered. I admire what I percieve as your scientific approach to this phenomenon, and would like to pursue something similar.

    As I delve into these procyon sessions, I’m finding that I have a lot of mental chatter. The most common topic of my mental monologue is just a running commentary on the visual and audio patterns I am experiencing. My brain concocts a lot of math to explain the patterns I’m seeing. I imagine the phase relationships between waveforms, I imagine the ratios of R to G to B. I start to think of systems to compose these patterns more intuitively. This is a fun trip. But it gets a little old, because I know that I will probably never flesh out all these ideas.

    I have also tried focusing on “Letting Go”. This is hard, but I find I can maintain it for short periods of time. Instead of trying to analyze the patterns I’m seeing, instead of trying to anticipate their movements or to guess at how they were composed – I just sit back and observe them as they’re happening. I believe this letting go is accelerating the actual entrainment, which contributes to even more trippy and beautiful visuals, which makes it even harder to let go. But I’m finding the key point is that this is not passive. It takes an exercise of my will NOT to comment, NOT to hold on. And what happens when I do this is unexplainable. I find it puts me almost in a dream state. I drift away to some memory, or some strange experience that becomes very real for a brief moment. Sometimes, it’s so real that my body will jerk awake. It’s really strange. Anyway, at this point, I obviously have a very loose definition of meditation. But I’m glad that entrainment or whatever has allowed me to glimpse it.

    I’m very curious about what you focus on when you do this activity. Specifically, I want to know if, for you,there’s more to it than “letting go”. Can you guide this experience? Do you start out with a goal, and how do you know (aside from neurofeedback) whether you have reached it? These questions are probably too general. I don’t expect you to write a tome like I just did. I’m sorry. I just feel like a kid who got an erector set for christmas. I want to build a huge rocketship, but maybe I need to build the simple tower in the instruction booklet first.

    Thanks again for a consistently interesting blog.


    • CraigT  On February 14, 2010 at 10:51 am

      Congrats on the alcohol! If you can get away from those sleeping pills, you’ll be in great form. You may wish to consider such herbals as valerian or scullcap.
      You’re right that the Procyon isn’t the most user-friendly beasty on the planet, although there isn’t a mind machine that can do what it does that is any easier. To be honest, I rarely program the Procyon now, preferring to use it with AS from NP2 or MWS. Tricolour doesn’t seem to have any significance beyond looking pretty, so I find the ability to set AS colour mapping sufficient to meet my needs for different stimulus colours. There are things that AS can’t do as well as native Procyon, and when you want to do those things, only a Procyon will do.
      Sorry for going vague and evasive on some subjects. The reasons are severalfold. First, not everyone thinks before they act – too much information can be a dangerous thing. Second, it wouldn’t be easy to describe the techniques in words, and I am not going to post examples. And finally, some techniques are what might be called “proprietary” – they are my signature sounds.
      One thing that I have found to be an indicator that I’m in the right place is that I lose the sense of two discrete visual fields and the perceived field of vision expands to a single peripheral-to-peripheral oval, that has its apparent location within, or just behind, the head. I find that recalling that it is not with my eyes that I “see” under these circumstances, but with my visual cortex. Once my vision is in this state, I can then engage in whatever thought processes I wish, knowing that if I lose focus, my vision will also revert to ordinary. A similar phenomenon occurs with audio – the sense of listening with two ears gives way to an internal representation of the sounds, often with high selectivity, awareness of some components of the sound heightened and others diminished.
      As you seem to be undertaking this with intensity and purpose similar to my own, I would be happy to venture further by private email.

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