A quick summary…

The time is right, it seems, with so many of the perennial questions recurring, for me to attempt to summarise what I think I know about AVS/entrainment (in no particular order)…

  • Any repetitive light or sound signal is likely to cause a corresponding EEG signal over the visual or auditory cortex respectively. This effect is easily demonstrable over the frequency range 4-20Hz. Above and below this range, response is less predictable.
  • Responses can be seen on rising or falling edges. The steeper the edge, the sharper the response. Square waves sound nasty. The most compelling waveform that sounds okay in the MWS presets is the semi-sine.
  • I have not seen cortical evoked response from any modulation type other than amplitude, however the presence of other types of modulation does not diminish the effectiveness of the main beat and can provide some very interesting sounds.
  • Isochronic beats are more likely to show a response than monaural beats.
  • High pitches are more likely to elicit a response than low pitches. Low pitches are more conducive to theta and delta rhythms, however below 100Hz (approx., unknown) the pitch also becomes a gamma beat, which may or may not be useful for the session’s intended purpose. My impression of binaural based sessions using low pitches is that they benefit more from the added gamma stimulation than from the lowered pitch.
  • Binaural beats do not cause corresponding signals over the sensory cortex.
  • Binaural beats at low frequencies (<4Hz) seem particularly effective in encouraging the brain to settle into lower frequency rhythms, even though there appears to be no mechanism of entrainment.
  • Binaural beats are most effective alone, or with intermittent background (bells or chimes).
  • Binaural beats can be used alongside isochronics to make them sound nicer – interesting sounds can be created by having the binaural at multiples of the isochronic beat, or the binaural pitch forming a pleasing chord with the iso pitch – the binaural will have no direct effect, and the effect of the isochronic will not be diminished.
  • Isochronic and monaural beats are more likely to result in non-sensory parts of the brain showing a corresponding rhythm than binaural beats.
  • White noise is effective both as a beat (pulsed) or continuous. As a beat noise is at least as effective as tone-filled isochronic. Continuous noise dampens activity at non-target frequencies. Pink and brown noise are not as effective as white noise.
  • Apart from hospital conducted trials on the Laxman, which verified its usefulness as a relaxation device, I am unaware of any formal trials conducted using complex sessions. All of the research I am aware of has used single stimuli.
  • Information on neurotransmitter release has typically been based on studies where release was shown to occur when particular brain rhythms were present. Direction of causality has not been established as far as I know.
  • A great deal of the information that AVS draws upon comes from neurofeedback research and practice. Neurofeedback has shown us that some conditions respond favorably to feedback training to change brain rhythms. It would appear that encouraging the same rhythms using AVS/entrainment can have similar effects to feedback training.
  • If you do with your brain what you want AVS to help you do, the expected rhythms will be seen in the expected places. AVS encourages the brain to settle into a rhythm, it does not cause your mind to do the particular thing, i.e. presence of delta rhythm does not imply meditation, however delta will be seen when meditating, with or without AVS (AVS makes it easier).
  • More is not better – if pure EEG response is desired, anything more than an isochronic track will diminish effectiveness.
  • More might be better – if you want to engage the brain so that “other things” don’t impinge upon the desired task, complexity is the most effective tool – long period patterns, wave interactions, complex waveforms, non-repeating sequences, chords, accented beats, etc. Complexity does not mean clutter – lots of extra sounds or instruments will diminish effectiveness. When adding anything that isn’t directly reinforcing the beat, I always ask myself, “How will I think when I hear this?” – if it’s going to cause me to think in a manner contrary to the intent of that part of the session, it should not be added.
  • Perceived spacial placement and motion matters. A single moving sound source will tend to grab and hold attention. Multiple moving sound sources will tend to lead to dissociation, increased inter-hemispheric activity and trance-like states. Sounds perceived as being to the side or behind the listener are more likely to trigger a startle response.
  • Recognizable music or vocals will usually diminish the effectiveness of alpha, theta or delta sessions by triggering SMR/beta/gamma activity. This is used to good effect with spoken words during alpha and high theta.
  • Multiple beats can be distinguished if they are carried on tones at least one octave apart.
  • Light can deliver two distinct flash rates, differentiated by amplitude with a single colour. Red and blue stimulus can be distinguished, green appears as both.
  • Light is best above 7Hz, and is excellent above 20Hz.
  • Audio is more effective than visual for asymmetrical stimulation even with specifically designed hemispheric stimulus glasses.
  • If the session is designed to facilitate rather than entrain, sound and light is usually more compelling.
  • If the session is designed to entrain, then either sound or light will probably be more effective than both, except with a very simple sessions where the light and sound are completely synchronous.
  • I have seen no evidence that beta is trainable, it can be stimulated, but the effect is short-term.
  • I have seen no evidence that gamma can be trained or entrained, however gamma stimulus increases gamma activity.
  • Alpha and theta can be both entrained and trained.
  • Delta is rarely entrained, but the mind readily drifts into the delta rhythm in the presence of delta beats.
  • Ramped beat frequencies don’t work – I have seen no evidence of entrainment following a ramp – EEG over the sensory cortex shows a loss of correspondence for the duration of the ramp. Steps of at least 6 seconds work at least as far as keeping a corresponding evoked response over the auditory cortex.
  • Pitch is a powerful tool in evoking mood. While I have no evidence that pitch is significant of itself, the intent of a session can be reinforced with appropriately rising and falling pitch.
  • Using standard note frequencies for pitches enhances musicality of the session.
  • Binaurals are highly conducive to the states sought for meditation and hypnosis, NLP or other suggestion based practices.
  • Isochronics are best for therapeutic applications, or for self-guided therapies and focused contemplation.
  • For therapeutic applications (depression, anxiety, ADD/ADHD, chronic pain, etc.), keep it very simple – the research is all based on simple stimulus and I have seen nothing to lead me to believe that results are improved by anything more than a pleasant background to keep the subject amused. Masking the beat will definitely reduce effectiveness – therapies are specifically based on the entrainment effect. Proper diagnosis is also very helpful in achieving good therapeutic results – depression, for example, has diverse manifestation and etiology, with each variation and individual responding best to a unique therapeutic blend.
  • Any variety of sessions and session styles will benefit overall mental acuity, with random and other non-frequency specific sessions being particularly good general brain exercise. The Mind Art sessions on the Procyon are a very enjoyable example.
  • Nobody has sufficiently broad or deep research data to satisfactorily support, or refute, most of the claims made for AVS/Entrainment. From my own experience and experimentation, every application that I have been able test has benefited from AVS, although not necessarily due to pure entrainment. All of the commercial content I have encountered has contained sufficient recognizable stimulus for it to be potentially psychoactive – the particular style being mostly a matter of aesthetics, with few openly exposing the stimulus for maximum effect. The basic principles of brain rhythm and entrainment response appear to be quite sound, but the brain isn’t a simple clockwork mechanism, and so there is a great deal more to AVS than a beat.

Feel free to prompt me to address any other favorites I’ve missed.

Cheers,
Craig

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Comments

  • Robert  On June 1, 2010 at 7:01 pm

    Great post Craig!

  • faith  On June 2, 2010 at 3:58 pm

    I must say I have good experiences with binaural beats. Its amazing how that technology actually affects our brain and make improvements to our lives. Mind power is an area that I am deeply interested in, look forward to more of your posts. Thank you.

    • CraigT  On June 3, 2010 at 10:14 am

      Yup, binaurals are a funny animal – no doubt that they have an effect, but exactly how as yet escapes me. I guess it’s more the mind that is a funny animal – getting to know what it does and does not do under any given circumstances is quite an adventure.
      Thanks for your interest.
      Cheers,
      Craig

  • Carl Preyer  On June 9, 2012 at 6:23 am

    Thank you for the compilation of information. It is very helpful. I don’t know anywhere else that there is such a collection of helpful tips. Please update your list if you have more. Thanks again.

    • CraigT  On June 9, 2012 at 2:26 pm

      You’re welcome, thanks.

      You can subscribe to the blog and it tweets when I put up a new post.

      Cheers,
      Craig

  • Andy Owings  On September 13, 2012 at 3:08 pm

    Hi Craig. I currently use binaurals and agree that they seem to work pretty well. However, they seem to flare up my tinnitus for some reason. I am going to buy either the Laxman or Mindlights for consciousness exploration….do you think the light stimulation alone with a pleasant soundtrack that doesnt have binaurals will be nearly as effective as one with binaurals? Also, is there another beat you would suggest for consciousness exploration…isochronic perhaps? Thanks, Andy

    • CraigT  On September 14, 2012 at 9:20 am

      Hi Andy,

      I have had success with my own tinnitus using short, sharp clicks created with a program of my own, BrainForm ( https://craigtavs.wordpress.com/2009/08/23/very-powerful-session/ and https://craigtavs.wordpress.com/2009/11/08/frequency-independent-session/ ). BrainForm was only ever experimental and is totally unsupported, can’t even guarantee it will work on some machines, but I’m happy to send you a copy if you wish.

      The MindLights includes a session specifically for tinnitus based on the work of Prof. Toennies ( http://www1.uni-hamburg.de/psych-3/seminar/toennies/Homepage/HNO.pdf – in German).

      Most of my personal AVS use is aimed at altered-states/enhanced consciousness. For me variety is the key to keep the mind finding and exploring new corners of consciousness. Writing my own sessions has several benefits – the act of creation is always good for the mind, the session will be constructed according to my best understanding of AVS in general and my own mind in particular, and, with this belief in the session, I will be more inclined to let the session have its way with me.

      As for binaurals, I am convinced that binaurals don’t work at all in the purest sense of brainwave entrainment. EEG will rarely show anything over the auditory cortex. That said, binaurals do improve the quality of meditation/contemplation and, under such circumstances, the stimulation frequency will be seen by EEG over non-sensory regions. Binaurals are most useful for delta, not at all above 10Hz.

      Light stimulation works well standalone. NeuroProgrammer includes a sensory modality test that will give an indication of your sight/sound response.

      Cheers,
      Craig

  • Andy Owings  On September 14, 2012 at 4:43 pm

    HI Craig. First off, I have to say that you are the nicest guy for taking time out of your life and helping me (and all the rest of us like you are doing)…I cant tell you how much I appreciate what you are helping me with here as this is all very important to me. So really, thank you again. It would be absolutely wonderfuul if you could send me the Brain Form program so that I might try it for my tinnitus. You have my email so perhaps you could shoot it over via email? Also, that is great to know about the noise cancellation headphones…I am going to do a test on my headphones on the site you recommended to see if the sounds are feeding through properly. Also, really interesting on your take re binaurals in general…so is what you are saying above about binaurals…is that also your opinion for isochronic, etc? I assume so because its all very similar but just wanted to check. Finally, this is great info re altered states of consciousness. That is my primary interest with all of this as well. I see what you mean about writing your own sessions, etc. Unfortunately I am not the most patient person to sit and compose my own stuff…but maybe over time I can learn how to do it and become more interested in it. Although personally, I feel like leaving the composition up to the pros while I just use it and focus on my altered states of consciousness…but thats just me. I understand where you are coming from when you say you are more inclined to let the session have its way with you if you have composed the track. Thanks again, Craig. Cheers, Andy

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