In the first part of this series we explained what Yoga Nidra really is, how it works and the process behind it.
What is the science behind yoga nidra?
There is a science behind it that influences our brain activity, autonomic nervous system and subsequently, our overall well-being. The withdrawing of our senses, increased activity of the auditory center and rotation of awareness has a deep impact on the brain.
Controlling centers of the brain
During a Yoga Nidra practice, we heighten the awareness of the parts of the body to stimulate the brain. There is an integrated response by the hypothalamus, the region serving as the control centre for the whole autonomic nervous system. The hypothalamus receives input from the external environment via the sensory/motor areas of the cerebral cortex. The hypothalamus also forms a part of the ascending reticular activating system (RAS), the part of the brain stem responsible for patterns of sleep, arousal and wakefulness. Through this mechanism, the altered sleeping patterns observed in practitioners of yoga nidra appear to be mediated.
The pituitary gland also exhibits behaviour and secretion patterns that are directly influenced by levels of mental and emotional activity modulated in the hypothalamus. Pituitary hormones are involved in every aspect of life in the physical body. In yoga, there is a lot of emphasis placed upon the psychophysiology of this gland. The functions of the pituitary gland are recognized to be that of the eyebrow center (the agna chakra). Yoga nidra is one of the most powerful means devised to awaken this psychic centre. Regular practice helps reach these heightened parts, stimulates and controls activity. Let’s relook at the results from a study that found incorporated PET scans observed an increase in dopamine levels in the ventral striatum of participants during practice of Yoga Nidra, Dopamine being a neurotransmitter that is commonly associated with reward-motivated behavior and social anxiety. This is a clear indication of how the brain stimulation has an impact on mood, and thus, our state of relaxation.
Our subconscious memory stores impressions based on experiences and knowledge that we consume. This may be positive, negative or neutral impressions, but these impressions define our mood, stress levels, behaviour and attitude, thus influencing our well-being in a large way.
Yoga Nidra is a method that can be used to correct any such negative habits, attitudes, disorders and diseases, and impressions of the mind. How does this work? During the practice, we reach a borderline state between sleep and awakening, which means that any messages or voices we hear during this time directly affect our subconscious. This gradually, over a period of time, overwrites previous habits, impressions and attitudes. An important step in Yoga Nidra is Sankalpa or resolve. A teacher, at the beginning of the practice, asks us to make a resolution - it could be generic such as ‘I am peaceful and happy’ or specific to a disorder or challenge, such as addictions, stress, pain, or even eating habits. There is also a visualization stage where you are guided through visualizing yourself after accomplishing your resolve. The powerful words along with the usage of only the auditory channel, during the practice, penetrate through the mind, to the subconscious, creating new thoughts, feelings and impressions. This is also a powerful way to purge fears and phobias from one’s subconscious. The words penetrate to the subconscious during this borderline state, overwriting any previous impressions that have settled as fears or phobias. The teacher has to take care in the selection of visualization to ensure it does not awaken fears, but rather helps one overcome them.
The brain’s electrical activity and yoga nidra
Yogis, psychologists and physiologists, all recognize the existence of these three distinct states of the individual human consciousness - waking, dream and deep sleep states. Each of these states of consciousness, as well as the borderline state of yoga nidra, has been correlated with distinct patterns of electrical activity in the brain.
In the wakeful state of awareness, the conscious mind is actively engaged with the external environment through the sensory channels of experience. During this period, fast rhythm beta waves predominate. Before the dreaming state, is the state of Yoga Nidra, the borderline state. Here the subconscious mind is active in the alpha brainwave patterns, inducing deep relaxation and a conscious dreaming state. During the dreaming state, when the subconscious mind becomes predominant, the suppressed desires, fears, inhibitions and deep-seated impressions (samskaras) are actively expressed. This is characterized by theta waves. In the deep sleep state, the unconscious mind, source of instincts, drives deeply buried experiences of earlier
As this occurs, the consciousness passes from being awake to dreaming and then to being asleep. In Yoga Nidra, however, the process of descent is different. Here beta waves are superseded by alpha waves, and the period of alpha predominance is greatly extended. Since increased alpha activity is characteristic of relaxation, this finding implies that yoga nidra promotes a much more relaxed state of sleep than is otherwise obtained.
Researchers have proposed that if the underlying witness consciousness can be maintained during the experiences of sleep and dreaming, a fundamental evolutionary change in the central nervous system and its operation occurs. This change along with the experience of a distinct fourth state of consciousness, in which dream states of perception, including the astral, psychic and causal dimensions, are experienced.
From a neurophysiological point of view, this fourth state of heightened consciousness is mirrored in the electrophysiological operation of the brain as the enhanced operation of the higher cortex - known as the witnessing of ‘conscious brain’ - together with heightened control and reduced arousability of the limbic centres of the ‘emotional brain’. Yoga Nidra, thus, indicates an ongoing process of increasing self-awareness, which is accompanied by a resetting of the inbuilt controlling and regulatory mechanisms of consciousness in the brain and is reflected in greater autonomic stability, enhanced emotional control and an increasingly conscious being.
How yoga nidra Influences memory function
There are two factors involved in the process o f memory. The first is the brain’s ability to absorb information and the second is its ability to recall the information later on. Yoga Nidra works on both of these levels by establishing a state of maximum receptivity in the subconscious mind, along with a simultaneous state of awareness. Like a passive witness, the brain makes a continual recording of all the events and perceptions of our daily lives as they occur, even those of which we are not consciously aware.
For example, unknown to us, the auditory faculty is making a continual recording of every sound that reaches it. These impressions are stored in the vast memory banks of our grey matter computer, the cerebral cortex. Here they are destined to remain latent and inaccessible, unless we can find a way to recall them. The method of recalling these dormant records into consciousness is to present an appropriate stimulus during the ordinary waking state.
Yoga Nidra balances the brain hemispheres
Researchers propose that yoga nidra is an appropriate state in which to learn something new because it employs both hemispheres of the brain in the task: the logical, conscious left and the non-logical, subconscious right. In a traditional classroom, students are encouraged to pay attention (a left hemisphere function), but while trying to absorb what the teacher is saying, their subconscious mind (right hemisphere) is continually recording signals that have nothing to do with the learning task at hand. However, in Yoga Nidra, the signals which are being received by the subconscious are reorganized in such a way that the whole mind is receptive to them. Thus, far more of the total brain is focused effortlessly on learning.
The science behind this art of guided relaxation is, thus, deep and profound. With regular practice, it’s impact is far greater than we can assume. Far from being tangible, the practice and the outcome is one we have to commit to and trust in our teachers for the best experience. To many of us, the science of this sounds complex. And that’s where a teacher’s guidance to the practice is our answer.
Have you experienced this before? Or are you curious to experience it? Tell us about it in the comments.