Nidra in Sanskrit means sleep. But it’s not a nap or a guided relaxation. It’s a secret door to liberation and equilibrium. During Yoga Nidra you are not sleeping but through my guidance you relax and reduce brain waves to the level of deepest relaxation, which allow you to heal your physical and mental body, bringing energy and restoration to your body and mind. We all know the importance of sleep. When we sleep our body rejuvenates. Meditation reaches deeper and relaxes our mind while we are awake. Yoga Nidra silences the mind and allows our body to repair itself. Yoga Nidra is calming the waves of the mind. Ancient yogis realized that when we consciously descend into the state of “awakened” sleep or “meditative awareness,” our bodies can very effectively repair themselves. In Yoga Nidra, some thoughts are present, but they do not disturb us. In the space between our thoughts, we can settle into eternal consciousness beyond the mind and heal ourselves. I will try to explain it a bit more scientifically. The information below draws heavily from Kamini Desai, PhD, Yoga Nidra: The Art of Transformational Sleep. There are five major brainwave states: 1. Beta, associated with the normal awake state (personality clashes, power struggles, and many other emotional dramas can bring Beta brainwaves to 13-100 cycles per second. We can really be fired up! Feeling, emotions, reactions and thoughts are rushing through our head non-stop. 2. Gamma, 40-70 cycles per second. Researchers have found that mentally-challenged and learning-disabled individuals tend to have lower Gamma brainwave activities than average. Gamma waves are important for learning, memory and information processing. Meditation increase Gamma brainwave activity, which are usually experienced while awake but interestingly can also be experienced in REM sleep. 3. Alpha waves are associated with relaxed wakefulness all the way into dreaming or REM sleep. Dr. Hammond reports in the Journal of Neuropathy that: “Alpha brainwaves (8-12 cycles per second) are slower and larger. They are associated with a state of relaxation and correspond with the brain shifting into [relaxed gear]. If someone merely closes their eyes and begins picturing something peaceful, in less that half a minute there begins to be an increase in Alpha brainwaves.” This is why most meditation techniques involves closing the eyes. My students also know that I encourage them to close their eyes during many asanas. The Alpha waves are a bridge from wakefulness into sleeping and a DEEPER STATE OF CONSCIOUSNESS. If one has difficulty dropping from Beta to Alpha brainwaves, it will be difficult to fall asleep. Studies have shown that those with insomnia, excessive stress and anxiety have less Alpha brainwave activity while awake. In these cases, Yoga Nidra can actually be a good “exercise” for teaching the body how to let go of thought and fall asleep. Yoga Nidra helps to create more Alpha waves, allowing a person to be more relaxed and better able to cope with life. 4. Theta waves. Entering Alpha and Theta brainwave states accelerates memory retention and enhances learning. Compared to adults, children have much greater Alpha and Theta brainwave activity which allows them to digest and assimilate information from their surroundings at an astonishing rate. As we enter the Alpha brainwave state, we experience relaxation and ease. The body is often overcome with an overwhelming feeling of well-being associated with the release of serotonin into the system. In this state, the immune system is boosted enabling us to better fight off and recover from infections and disease. Here, we also begin to gain access to the subconscious mind. Dreaming occurs in the deep Alpha and high Theta brainwave states. We cross these same states in Yoga Nidra, but consciously so. In the dream state, identification with one concrete reality becomes much more changeable and malleable. When crossing the Alpha brainwave state in Yoga Nidra, you may feel as if you are hearing the guidance of a teacher while simultaneously participating in a semi-dream state. Images, thoughts, and events may come and go, but in a disengaged way—as if observing these thoughts and images on a screen. Even though thoughts may be moving through in this state, they are more like background static as opposed to a foreground disturbance. 5. Delta waves. As we enter deeper states of meditation, we pass into Theta brainwave states. The brainwaves and movement of the mind slow down to the equivalent of a deep sleep state. Deep Theta and Delta brainwave states are associated with shusbupti. The brain, cycling from 8-12 cycles per second in the dream state moves to a deeper state of silence at just 4-7 cps. Literally, Yoga Nidra is stilling the fluctuations of mind down to almost nil. This is a big shift from up to 100 cps in a waking state! Theta brainwave states are associated with increased creativity, feeling relaxed and carefree. Artists, inventors and children often have more Theta brainwave activity, even in the waking state. This is also the state out of which creative solutions, inspirations and answers will often arise. If you have ever fallen asleep and awoken with an answer or solution to a problem, this a result of entry into the Theta state. Along with the Alpha brainwave state, the Theta brainwave state is associated with increased retention of learned material and long-term memory. From early childhood to puberty, Alpha frequency increases but then starts to decrease with age. This can be prevented with mental training and is not age-related per se. People who can sustain a Theta brainwave state absorb information and learn very quickly. This is why children learn and retain information so easily. In the Theta brainwave state, memories are consolidated and “filed” in logical order so that information can be retrieved when needed. The Delta brainwave state preserves cognitive abilities after trauma. It seems that slow-wave sleep induced immediately after a brain injury helps prevent damage and helps the brain retain normal brain function. Even though the diagnosis of brain injury is increasing, very few effective, non-invasive and accessible treatments exist to prevent or even reverse compromised cognitive function. Yoga Nidra could be an important tool to enhance recovery from traumatic brain injury because of the slow-wave Delta brainwave state it induces. In Theta brainwave states, we gain access to unconscious patterns and behaviors that, unbeknownst to us, guide our conscious actions, thoughts and behaviors. Thus, in this brainwave state, we can make potential changes in these behaviors. It is also the place where incomplete experiences can be integrated and completed at the deepest level, without even necessarily knowing what those experiences were or what changes happened. It has been determined that integration of emotional memories is, “significantly correlated with the amount of REM sleep and also with right-dominant prefrontal Theta power during REM.” This same effect can happen consciously as we cross it during Yoga Nidra. You may have thoughts in Yoga Nidra, but you are not interacting with them in the same way. They are distant from you, like a radio in another room. Though the voice of the mind is still there, it is not disturbing in any way; nor are you participating in what it says in the way you would in the waking state. It is just there, talking away—just as the radio does, but you are not talking back. Often, at this level of Yoga Nidra, you may have dream-like images, thoughts, or feelings moving through. These often blend with the voice and guidance of the Yoga Nidra facilitator, creating a kind of wakeful dream. This is because the first level of Yoga Nidra crosses the dream state and can be experienced a dream-like way. Deeper states of Yoga Nidra happen in the Theta brainwave state. Experiences here can include drifting in and out of hearing the guidance of the Yoga Nidra. You may experience hypnagogic imagery such as colors, shapes, and lights or enter trance-like states. You may hear words, but you may not make sense of them in the usual way. The words are no longer being processed through the mind. However, the body is still responding directly and non-mentally to the directions given. As Yoga Nidra takes you even deeper into Theta and Delta states, you may enter a gap of nothingness. It may feel like biological sleep, but when you are asked to come back at the end, you do. This is how you know you were, in fact, not sleeping in the same way you do at night. Your body is still receiving outside information while in the deepest and most profound of Yoga Nidra states. This is the distinction between biological and Yogic sleep. While the mind is silent as in sleep, awareness still abides. In Yoga Nidra, most people arrive at this deeper level of letting go within the first few times of practicing. Both meditation and meditation-based Yoga Nidra will take you there, but many find Yoga Nidra to be a very powerful and more accessible means to enter this space. Thereafter, the ability to enter this zone grows and people find their seated meditations are also imbued with these same qualities. The deepest sleep states and Yoga Nidra states happen in the Delta brainwave frequency. Here, amazingly, brainwave activity can slow all the way down to 0.5 cycles per second. The fluctuations of mind slow down to only the most basic survival functions. Since all other activity is shut off, this is the most restorative state for the body. When under anesthesia, when knocked unconscious or in a coma, the body is in a Delta brainwave state. The body, if injured severely enough, goes into a coma because this is the best state from which to heal. Medical professionals, as a last resort, now induce a coma with certain traumatic injuries in hopes of allowing the body to heal itself. Every time we go to Delta brainwave states in Yoga Nidra we are profoundly healing and restoring the body. Ultimately many people ask me: How often is it recommended to do Yoga Nidra? Sick people should do it twice a day. Healthy people will find significant benefits when they do it at least 3-5 times per a week. Every night, we cycle through the brainwave states several times. When we get a good amount of Delta brainwave sleep, we awake feeling particularly refreshed, alert and rejuvenated. It has been repeatedly shown that Theta and Delta activity tend to decrease as we age, and the tendency to stay in the upper Alpha state increases. Yoga Nidra can help reverse this tendency and the sleep problems that can result. In Delta states of Yoga Nidra, human growth hormone is released. As we get older, growth hormone levels decline. Human growth hormone is essential to maintain proper metabolism and regulate the proportion of body fat to muscle. It influences the storage ratios of good to bad cholesterol and it is vital for proper heart muscle functioning. Growth hormone also maintains and corrects bone density and enables the growth and regeneration of all the organs of the body, including the brain. In adults, low or absent growth hormone can cause emotional symptoms, such as tiredness and lack of motivation. All of this can be counteracted in the Delta brainwave state in which growth hormone is released. Delta brainwave states also reduce the amount of cortisol, a stress hormone, in the system. Cortisol accelerates the process and can be highly detrimental to the system. Cortisol reduction reduces the rate at which we age. Imagine that each time you practice Yoga Nidra, you move from the wave (the body/mind) to the ocean of formless consciousness. This is why one of the instructions in Yoga Nidra is to stay awake. This should not be a stressful task, but simply an intent put forth to your subconscious mind. Then let go and allow whatever happens to happen. In the beginning, some people have difficulty staying awake because the body is accustomed to being asleep in deeper brainwave states. Eventually, however, we train ourselves to be awake but as deeply relaxed and we can distance from the mind as in sleep. As you practice Yoga Nidra, situations that used to bother you simply don’t irritate you as much. You will find yourself less reactive to things that used to trigger you. Habits that seemed to have negative effects on your life simply disappear. You will find yourself calmer and steadier in the midst of things that would have shaken your foundation. In Ayurveda, the sister science to Yoga, turiya is known as the place where spontaneous and miraculous healing occurs. When we are identified with the mind, the body is affected by what the mind thinks and feels. Repeated thoughts and emotions to which we attach and believe, create chemical effects in the body and can contribute to disease. Turiya is evidenced by a complete release of identification with mind—including the subtle patterns that cause disease in the body. The body’s healing energy (prana), which is usually consumed by our thoughts and emotions, is now free to operate at its most accelerated and restorative level. This is why, in Ayurveda, the definition of health is swasthya—to be seated in the Self. Turiya is where this happens. Even in medical science, a doctor intuitively knows the body will heal itself best when the mind and body are less active. This is why a doctor will always tell you to get plenty of rest when you are sick. Yoga Nidra is the most profound rest there is—not only for the body but also for the mind, which is usually holding the body’s energy hostage. When released from the captivity of the mind, the body’s natural energy can focus on healing. For more see: Kamini Desai, PhD, Yoga Nidra: The Art of Transformational Sleep Pierre Bonnasse, Yoga Nidra Meditation: The Sleep of the Sages