Rhythmic Entrainment

Rhythmic Entrainment Intervention: A Theoretical Perspective

By Jeff Strong
REI Institute Director



originally published in Open Ear Journal, 2/98

Rhythmic Entrainment Intervention (REI) is a Music Medicine therapy program utilizing recorded hand drumming rhythms to stimulate the central nervous system and improve brain function.(1) REI is designed to facilitate both short-term and long-term improvement in a variety of symptoms common to neurobiological disorders. The REI Program consists of two twenty-minute recordings played as background music which contain complex, unusual percussion rhythms chosen to address specific behavioral and cognitive areas. Each client receives a custom-made REI Program designed specifically for his/her needs based on a comprehensive intake questionnaire and interview process.

REI was derived from two ancient rhythmic drumming techniques which have been used to treat psychological and physical illnesses for thousands of years. These two healing techniques, called shamanic drumming and rhythm healing, both use specific rhythmic drumming patterns to influence the body to bring about healing.

Shamanic drumming is estimated to be between 20,000 and 30,000 years old and is considered one of the oldest organized systems for healing. Practiced in nearly all parts of the world, this technique is "...strikingly similar the world over, even for peoples whose cultures are quite different in other respects, and who have been separated by oceans and continents for tens of thousands of years."(2)

Shamanic drumming uses a single, repetitive rhythm played between three and four beats per second which can last from less than ten minutes to well over an hour. The rhythm played at this speed will induce a trance state in the listener and, when accompanied by specific visualizations, has been observed to facilitate healing of a variety of illnesses, both physical and psychological.

In contrast, rhythm-healing uses numerous rhythms which are dependent on either the symptoms or the cause of the illness. In Rhythm healing it is believed that certain rhythmic drumming patterns can influence the internal rhythmic patterns of the individual and correct those which are thought to be causing the illness. This technique is used to treat a variety of psychological conditions and seems to have originated in West Africa, having spread to parts of Central America, North America, South America, and the Caribbean.

The rhythm healer goes through considerable training in order to be able to choose and perform the correct rhythms for his patient. The rhythms are based upon the behavioral and psychological characteristics of that person and are often unique to each particular individual. "The Minianka musician who heals does not necessarily fall back on a repertory of established rhythms," says Malian drummer Yaya Diallo. "Determining the right music in each case is a highly individual matter. No predetermined formulas are given. He needs to create a dialogue between the sounds he produces and the responses of the person heís treating. Through his trained observation, he discovers the right rhythm for his patient. It may be a new rhythm, uniquely indicated for the case before him."(3)

As in rhythm healing, REI uses specific rhythms to address particular behaviors and combines these rhythms with the steady rhythmic pulse practiced in shamanic drumming. It is the use of specific, complex rhythms played at eight beats per second which distinguishes REI from other drumming techniques.

Drumming rhythms can influence the human body because of a phenomenon of nature called entrainment. Entrainment is defined as a synchronization of two or more rhythmic cycles and was first discovered by Dutch scientist Christian Huygens in 1665. While working on the design of the pendulum clock, Huygens found that when he placed two of them on a wall near each other and started them at different times, they would eventually end up ticking in unison. Entrainment has been found to be a universal force in nature and will act on any two or more vibrating bodies as long as they have similar rhythmic cycles.

Entrainment of biological rhythms has been documented in many areas. For example, respiration and heart-rates have been shown to be entrained by sound;(4) motor movements can be entrained by an auditory stimulus;(5,6,7,8,9) subtle body movements of people in conversation will synchronize;(10) and brain waves can be entrained by listening to an auditory rhythm.(11,12,13)

The ability of an auditory stimulus, such as the shamanic drumming rhythm, to entrain internal brain wave frequencies is known as auditory driving. Auditory driving research has found that there is a direct relationship between the speed of the rhythm played and the brain wave state created. Its not necessary for the rhythm be repetitive and unvarying in order to have this effect. It's been found that a varying rhythm could also produce an altered state of consciousness. Maxfield used a technique where a simple variable rhythm was played at 4 beats per second and found that the same theta state was created as when the steady, non-varying 4 beat-per-second rhythm was used.(14)

Variable rhythms, such as those used in REI, have shown additional benefits for the nervous system. For example, listening to a variable rhythm for just ten minutes can improve spatial abilities by 15% in normal children over those who listened to silence, a simple melody or a continuous tone.(15) In fact the use of a variable rhythm alone seems to be more effective at improving spatial task abilities than listening to Mozart's baroque music.(16)

Rhythm also acts as an energizer of the nervous system, increasing neuronal activity and exciting the entire brain region even in people with severe neurological disorders.(17,18,19,20,21,22) An unpredictable or varying rhythm causes the nervous system to activate in an effort to decipher it and find a pattern. This can a have an enhancing effect on learning and creativity.(23) It seems that a varying or unusual rhythm both alters consciousness as well as activates the brain in a way in which increased learning capability and heightened overall neuronal activity has been observed.

REI's eight-beat-per-second rhythms target the alpha frequency, which has been found to be beneficial in improving overall brain function as well as heightening learning and sensory processing.(24) It has also been documented that many people with neurobiological disorders have a difficult time producing and maintaining alpha waves in their brains. Current research also suggests that increasing the production of alpha waves may improve some of the symptoms of these conditions especially in attention deficit disorder and learning disabilities.
Beyond stimulating the entire brain and producing an alpha frequency, REI uses specific rhythms which correspond to certain behavioral and cognitive characteristics. For instance, a rhythm in 21/16 appears to be especially effective at calming most individuals with autism, while a rhythm in 47/16 has been found useful for reducing self-stimulatory behaviors. Not only are these rhythms in odd time signatures, but the accent patterns are such that it is very difficult to find the downbeat in the rhythm.

Brainwave Entrainment refers to the brain's electrical response to rhythmic sensory stimulation, such as pulses of sound or light.

When the brain is given a stimulus, through the ears, eyes or other senses, it emits an electrical charge in response, called a Cortical Evoked Response (shown below). These electrical responses travel throughout the brain to become what you "see and hear". This activity can be measured using sensitive electrodes attached to the scalp.

When the brain is presented with a rhythmic stimulus, such as a drum beat for example, the rhythm is reproduced in the brain in the form of these electrical impulses. If the rhythm becomes fast and consistent enough, it can start to resemble the natural internal rhythms of the brain, called brainwaves. When this happens, the brain responds by synchronizing its own electric cycles to the same rhythm. This is commonly called the Frequency Following Response (or FFR ):

FFR can be useful because brainwaves are very much related to mental state. For example, a 4 Hz brainwave is associated with sleep, so a 4 Hz sound pattern would help reproduce the sleep state in your brain. The same concept can be applied to nearly all mental states, including concentration, creativity and many others. It can even act as a gateway to exotic or extraordinary experiences, such as deep meditation or "lucid dreaming" type states.

If you listen closely to most NP2 Audio/Visual Sessions, you will hear small, rapid pulses of sound. These pulses may be harder to detect if you turn off Tones, but Noise and Background Sounds are also embedded within them. As the session progresses, the frequency rate of these pulses is changed slowly, thereby changing your brainwave patterns and guiding your mind to various useful mental states.