What is entrainment?
Brainwaves are measured by the brain’s electrical activity. Entrainment is a phenomenon by which an organism in some way synchronizes with an external rhythm. When the brain experiences a stimulus, it emits an electrical signal in response called a cortical evoked response (CEO). These responses go through your brain and interprets them into something you can understand, such as sound, smell, touch, etc. If presented with a sufficiently consistent and fast rhythm, the CEOs eventually synchronize to the beat’s frequency, thus changing your brainwave pattern. As this would imply, this would change your dominant mental state.
In other words, each beat produces an electrical response in the brain. After some time, these responses resemble the beats heard by the listener. Thus, the listener’s brainwaves synchronize to the same beat as the stimulus. For example: if someone is listening to beats with a frequency of 10 hertz (Hz), that person’s brainwaves will synchronize over time to that same frequency. Sounds crazy, doesn’t it? Using an example of beta wave entrainment, Mental Health Daily makes an important point:
Not all of your electrical activity would shift, but the dominant state of awareness would shift to that characterized by beta waves.
Before brushing this off as pseudoscience, take note that multiple studies have been done not only proving this phenomenon, but utilizing it in various therapies including pain reduction, focus, and sleep. Doctor Thomas Budzynski, one of the pioneers in the area of biofeedback, managed a private biofeedback clinic for 16 years. One of his publications is a guide and survey of the clinical use of brainwave entrainment (PDF).
Types of brainwave entrainment (BE)
Imagine you are wearing headphones: in one ear, there is a 200 Hz tone playing, and in the other, there is a 210 Hz tone playing. Hearing these different tones, your brain would perceive a beat of 10 Hz. The beat in and of itself doesn’t exist, but your brain hears the difference in frequencies and perceives it as a beat. Over time, your brain’s dominant state shifts to that mental state (alpha in this case). Beats work up to a difference of 30 Hz because the brain perceives the tones as completely separate. Binaural beats do not work without headphones and are not as effective as other options: however, they are still effective and easy to use.
The difference between monaural beats and binaural beats is that the beat is produced in a single ear, whereas binaural beats need two: no headphones required! Monaural beats are more effective because they stimulate more of the cortex (specifically, the basilar membrane).
These can be described as pulsations. A single tone is being turned on and off quickly, matching the frequency one wishes to entrain to. So if a tone is being switched on and off at a frequency of 20 Hz, the brain will synchronize to that mental state (beta in this case). It has nothing to do with the frequency of the main tone. Isochronic tones are the most effective BE tool and, like monaural beats, no headphones are required.
Though auditory BE is more common, visual BE is more highly effective. This is due to the larger size of the visual cortex than the auditory cortex. All methods involve flashing lights which are perceived by the brain through closed eyelids. After some time, the brain synchronizes to the frequency. Some methods include: flashing lights onto a wall or from a screen, goggles with LED lights, and 3D and virtual reality goggles (these goggles can be used with open eyes).
Combining the effects of auditory and visual BE enhances its effects as it stimulates both the auditory and visual cortices. The light flashes and sound pulsations are synchronized to the desired frequency.
By far the most direct method, EMBE uses electrodes placed on one’s head to generate rapid EM pulses. It is highly effective since the brain responds in milliseconds. This method is also more direct in that specific areas of the brain can be targeted whereas with other methods, the areas affected are more general.
Doctors Tina Huang and Christine Charyton published an article reviewing the effects of clinical applications of BE. 20 articles were selected for review based on their criteria. I’ll leave all of the results to the reader in this PDF of their study, but there are some I would like to note:
- When treated with photic stimulation for 30 days, 44% of the subjects who experienced frequent migraines reported a subsequent reduction in migraine frequency (source).
- Three groups were taken and examined for pre-surgical anxiety. One group listened to music with binaural beats, another with music, and another with no audio. Those treated with binaural beats before their operation showed a 26.3% reduction in anxiety (using the State-Trait Anxiety Inventory questionnaire as a guide) (source).
- Three studies were reviewed by Huang and Charyton included mood studies using binaural beats. The subjects did not show improvements but in fact worsened (source, pages 43, 45).
Word of Caution
Brainwave entrainment is an effective tool in relaxation and focus; however, there are those who tout miraculous abilities of BE that either simply do not exist or have no supporting evidence. As I said before, do not let pseudoscientific claims push you away from exploring a true science. Claims that BE (particularly auditory BE) cures depression, “heals DNA,” or heals anything, are scientifically unfounded and may unfortunately lead those who are desperate for help into frustration and disappointment.
If you decide on experimenting with them, do not expect immediate results or perhaps any results. Some people are more receptive to it than others (especially those who are sensitive to hypnotism, according to Budzynski). They can work! Keep an open mind and see what happens!