A long time ago yogis discovered, understood and implemented in practice the knowledge of the existence of the two kinds of energies in the human being, the vital and the mental energy. Together they govern the whole of our being and, when in balance, they provide for smooth functioning of our body, all its systems and of our mind as well. When in harmony, they ensure the state in which a natural and balanced evolution becomes possible. Yogis have discovered that the vital and mental energy, energy and consciousness, permeate the whole of our being through the network of energy flows, the nadis. They converge into two main nadis, ida and pingala, which flow along and intersect with each other six times within the spinal column. The mental energy flows through ida, and the vital energy through pingala, and they flow upward towards ajna chakra, the governing centre in the brain. When the flow of energy in ida and pingala is in harmony with each other, a third channel opens within the spinal canal in the centre of the spinal cord, called sushumna nadi, manifesting as an equal flow in both nostrils. An active sushumna expresses itself as a state of deep harmony in body, mind and spirit.
At the same time, the flow of ida and pingala nadis is represented by the airflow through the left and right nostrils respectively, and yogis discovered that through this physical junction the activity of ida and pingala, the mental and vital energies in the body, can be influenced and fine-tuned in order to awaken sushumna. They devised practical means for this, and this knowledge is the subject matter of swara yoga. There are various techniques to balance the swara, but the principal one is nadi shodhana pranayama, which means purification of the fine energy network of nadis within the body, and which is also known today as alternate nostril breathing. In this pranayama, we systematically establish the pattern of breathing through the left and the right nostril alternately, and focus on the flow of air through the nostrils. There are many stages of this technique, from simple to very sophisticated ones, but the essence remains the same - the alternate nostril breathing pattern that purifies, tones and balances the energies of our body and mind, or the flow of ida and pingala. Other, more specific pranayamas are surya bheda in which we stimulate pingala nadi by breathing through the right nostril only, and chandra bheda in which we breathe through the left nostril only and stimulate ida nadi.
Ida and pingala nadis are responsible for our existence in this world. Yogis and sages have seen and realized this. In Swami Niranjanananda's words, "The entire universe is comprised of two forces, consciousness and energy, which are interdependent and opposite, yet complementary. The universe hangs as a kind of web of interacting energies, suspended and functioning within the framework of tensions developed by this fundamental polarity. Wherever one looks, within nature, within the body and within the mind, this polarity can be seen as light and dark, positive and negative, male and female and so on. At every level, these two great principles are at work, creating and motivating the universe. . . When this cosmic polarity of prana and consciousness manifests in the microcosmic unit of the human body, it takes the form of chitta shakti and prana shakti, which correspond to ida nadi and pingala nadi. These two mental and physical channels within the body apply to all levels of being from gross to subtle, forming the basis for every perception, activity and experience. They represent two distinct forces within the human environment - the ebb and flow of human existence."50
Pingala regulates energy in the body, and ida regulates consciousness. These two nadis nourish the two hemispheres of our brain, which then control each and every activity of the body and mind. When the right nostril flows more freely, representing the activity of pingala, our left hemisphere is dominant and we are extroverted, active, physically fitter and we feel warmer because our metabolism is in a dynamic state - exhibiting the solar qualities of our nature. When the left nostril flows more freely, representing the activity of ida, our right hemisphere is dominant and we become more introverted, passive, fitter for mental and artistic work, and we feel colder because our metabolism slows down - exhibiting the lunar side of our nature. The purpose of yoga is to awaken and balance ida and pingala, to enable pranic energy to flow and illumine the dark and sleepy areas of consciousness so that we wake up and realize our full potential as human beings.
Scientific research supports the physiological concepts of swara yoga, and provides insight into some of the mechanisms by which the effects of pranayama practices are mediated.
Our brain is composed of two hemispheres, the right and the left, and together they are responsible for thousands of functions in the body. Most of these functions are the same and symmetrical in both hemispheres, but some are specific to or predominant in one hemisphere only. The centre for speech, Broca's Area, for example, is exclusively found in the frontal lobe of the left hemisphere. Also, understanding words, language and their meaning is primarily achieved through Wernicke's Area, which is also located in this hemisphere of pingala activity. When our pingala is sluggish, we slide deeper into the introversion of ida and encounter difficulties in communication with other people, not being able to express our thoughts clearly, though they may seem very clear to us. People may wonder, "What has happened to him?" On the other hand, the right hemisphere in the majority of the population is responsible for perceiving the emotional connotation of words and language, an ida activity. Hence, when we are too pingala or extroverted, we tend to miss fine aspects of non-verbal communication, not giving importance to the way some things are said and just paying attention to what has been said.
The right hemisphere is also dominant in perceiving the space around us, the patterns within it, the notion of direction and distance, depth and position (Joseph, 1988).*1 The left hemisphere perceives the environment in a positive and optimistic way (pingala - the sun is shining!), while the right hemisphere perceives it in a much more sombre and pessimistic manner (ida - in moonlight our visual clarity is limited so we are more cautious!). Positive, relaxed, friendly, supportive situations activate the left hemisphere, while negative, anxious, dangerous, threatening situations activate the right hemisphere.*2 In positive and friendly circumstances, we embrace the world through pingala, and in times of anxiety or threat we withdraw into the inner world of ida.
Recognition of facial expressions is the function of the right hemisphere exclusively.*3 The left hemisphere predominantly deals with logical, verbal, mathematical and analytical thinking, guiding our actions in the outer world of pingala, while the right hemisphere governs intuitive, integrative thinking that recognizes patterns in the world around us, leading us into the inner world and deeper understanding of ida. EEG studies done during aptitude testing of volunteers showed increased activity of the left hemisphere (pingala) during verbal tasks, and increased activity of the right hemisphere (ida) during spatial tasks.*4,*5
Therefore, we can conclude that scientific research findings so far support the yogic concept of ida and pingala as the two main lines on the switchboard of our mind that handle very specific aspects of our perception, thinking, emotions and behaviour. In the integrated evolution of human beings, the right hemisphere or ida, the mental energy domain, takes care of music and art awareness, three-dimensional perception, creativity and imagination, insight and intuition. The left side, the domain of vital energy or pingala, takes care of written and spoken language, dealing with numbers and abstract problems, rational decision-making, accurate judgement and discrimination. (Vivekananda Saraswati, 2008).*6 To live life fully and evolve in a harmonious way we need both kinds of abilities. Therefore, achieving and maintaining balance between the right and left brain, between ida and pingala, has very real implications in our daily life, in the way we function, interact, grow and evolve. And here swara yoga does come in the picture.
So far we have looked mainly into how the activity of two cerebral hemispheres, nourished by ida and pingala nadis, influence the domain of the human mind. However, the growing body of research data shows that they influence our body too. Yogis investigating the science of swara yoga have discovered that the activity of ida nadi, the right brain, correlates to the airflow in the left nostril, and that pingala activity correlates to the airflow in the left nostril. They also found that for most of the time one nostril flows more freely than the other and that this alternate dominance of one nostril over the other and the switch between the two happens in regular cycles of approximately 90 minutes, throughout the day and throughout life. Only during the brief periods of change do both nostrils flow equally, indicating the flow of prana through sushumna.
In scientific terms, the nasal cycle is defined as a side-to-side fluctuation in nasal engorgement and airflow, or as alternating congestion and decongestion of the nasal turbinates, the bony prominences within the nasal cavity covered with mucosal lining, very rich in blood and nerve supply. It has been found that this happens in periods ranging from approximately one to five hours. This cycle is produced by alterations in the autonomic tone of the nasal blood vessels. The nasal cycle is of considerable interest to ENT specialists and neurobiologists and it has been found to strongly correlate with a number of modifications of bodily functions, such as the relative EEG predominance of the contra lateral brain hemisphere,*7,*8 rapid eye movement (REM) and non-REM sleep patterns*9, verbal and spatial cognitive processing*10 and the release of endocrine agents such as noradrenalin, a potent stimulator of the sympathetic nervous system.*11 The pacemaker for this cycle is believed to be located at the base of the hypothalamus, in a densely packed cellular structure called the suprachiasmatic nucleus, which is involved in the control of a number of circardian and ultradian rhythms in the body, and is often referred to as `the principal biological clock' or `the mind's clock'.*12,*13
One of the earliest recorded scientific researches into the nasal cycle was done by Heetderks as early as 1927,*14 demonstrating that, based on clinical inspection of the nose, 80% of the adult population exhibit alternate nasal predominance. Hence, research data confirms the basic postulate of swara yoga that the airflow through the nostrils alternates in regular intervals and reflects the activities of the left and right hemispheres of the brain, of ida and pingala, the mental and vital energy in the body.
The medium through which the nasal cycle affects numerous bodily functions is the autonomic nervous system (ANS), which has a direct influence on all sense organs as well as inner organs and systems, including the brain and the cortex. It is composed of two divisions, and most of the organs in our body receive fibres from both divisions exhibiting opposing effects. One division is the sympathetic nervous system (SNS) which prepares us for an increased level of activity and the fight or flight response, which includes an increase in heart rate, blood pressure, cardiac output, a diversion of blood flow from the skin and splanchnic vessels of the internal organs to those supplying the skeletal muscles, increased pupil size, bronchiolar dilation, contraction of sphincters in the digestive system, and metabolic changes utilizing fat and glycogen. In other words, the sum total of these changes is to enable us to be maximally physically fit, to see and perceive most clearly and be ready for an explosive muscular action with a reduced tendency to bleeding in case of injury, with one purpose in mind - to fight or to flee, and save our skin.
In contrast, the influences of the other division, the parasympathetic nervous system (PNS), lead to rest, conservation and restoration of energy and thus to a reduction in heart rate (HR) and blood pressure, a facilitation of digestive processes and the elimination of waste products.*15 It is an opportunity to rest, repair and consolidate. As a whole, the autonomic nervous system is understood as a 'housekeeping' system which ensures our smooth functioning and adaptative responses to different situations in the outer and inner environment, and it is controlled primarily by the hypothalamus.*16,*17
A unique feature of the ANS, which is often overlooked, is that it shows an ultradian rhythm, the regular pattern that repeats itself several times within the period of 24 hours. The sympathetic nervous system, for example, dominates one side of the body and at the same time the parasympathetic nervous system dominates the opposite side. As Shannahoff-Khalsa found, *18,*19 after approximately every 90 minutes these systems switch dominance. This process is mediated by the biological clock in the hypothalamus, and affects all the organs that receive fibres from the SNS and PNS, including the cerebral hemispheres. Studies performed by Shanahoff-Khalsa from 1997 to 2000 have shown that the nasal breathing pattern correlates to the alternating cerebral hemispheric activity, both in the waking state*20,*21 and in sleep.*22,*23 Research has also shown that this alternating endogenous rhythm within the autonomic nervous system and its two divisions, the SNS and PNS, is clearly connected to the daily rhythms of the neuroendocrine, cardiovascular and insulin systems,*20,*21 as well as to the secretion of stress hormones, cateholamines, which also show an alternate dominance in the left and right side of the body, and that this left-right pattern is also tightly coupled with the natural rhythm of the nasal cycle.*24
These research studies affirm the claim of swara yoga, indicating that the nasal rhythm within which the airflow through the nostrils alternates in dominance in approximately a 90-minute cycle is in fact a unique marker of corresponding alternate dominance of the sympathetic and parasympathetic nervous systems in the left and the right sides of the body, with far reaching physiological influence.
If we look at these scientific findings from the other direction, we can see how by manipulating the nasal breathing pattern with pranayama practices, we can actually induce substantial changes in the body, using the medium of the autonomous nervous system.
In the research community, to describe and define the alternate nostril breathing technique as it is used in nadi shodhana pranayama, the term commonly used is unilateral forced nostril breathing (ULNB).
From 1980 to 1987, Werntz *26-*28 was probably the first to demonstrate, using the EEG device, that alternate nostril breathing, as it is used in nadi shodhana, stimulates the contra-lateral brain hemisphere, i.e. that breathing through the left nostril stimulates the right hemisphere, and breathing through the right nostril stimulates the left hemisphere. In this study, young healthy subjects were first asked to breathe only through the more congested nostril (expecting it to start to flow more freely) for 11 to 20 minutes, and then to breathe through alternate nostrils. Results showed that the nadi shodhana breathing pattern increased EEG power in the opposite hemisphere regardless of the phase of the nasal cycle. The authors concluded that these results suggest the possibility of a non-invasive approach in the treatment of states of psychopathology where lateralized cerebral dysfunction has been shown to occur. A pilot study in 2002,*34 using a whole-head 148 channel magnetoencephalography, explored the effects of exclusive left or right nostril breathing that correspond to chandra and surya bheda pranayamas, at one breath per minute for 31 minutes, and showed similar patterns of contra-lateral brain activation.
An interesting study by Servit and colleagues*29 proposes a possible neurophysiologic mechanism through which nadi shodhana activates the brain hemispheres. It states that increased EEG activity in the brain, specifically in the limbic system, is generated by a neural mechanism in the superior nasal meatus, the upper nasal canal located in the nasal cavity and which is connected to the sympathetic and parasympathetic branches of the maxillary nerve. They also evoked the same kind of EEG response by gently blowing air directly into the upper nasal cavity, without inflating the lungs. Furthermore, local anaesthesia of the nasal mucosal membrane suppressed the EEG changes in the opposite hemisphere. These findings throw new scientific light on the process of perfecting nadi shodhana and the importance of refining breath awareness and sensitising the nasal mucous membrane through diligent and sustained practice.
On the level of the physical body, nadi shodhana pranayama is used in yoga to increase vitality and oxygenation of tissues. This is mediated through the naso-pulmonary reflex that is triggered by unilateral nostril breathing. As early as 1939,*37 and later in 1960*38 and 1970*39, researchers demonstrated that breathing through one nostril causes increased inflation and ventilation of the same-side lung, and greater blood flow in it. Samzelius-Lejdstrom*37 showed on a sample of 182 subjects a one-sided continual nasal breathing pattern, which corresponds effectively to surya or chandra bheda pranayamas, leads to significantly wider expansion of the same-side of the chest, bringing about increased lung ventilation on the same side. This response was recorded in 94% of tested subjects. This finding throws new light on the vitalizing yet gentle and harmonious effects of nadi shodhana, in which through steady and rhythmic alternation of breath through one and the other nostril one effortlessly achieves greater expansion of one and the other side of the lungs. Coupled with greater blood flow through the lungs, this leads to better oxygenation of all tissues and increased vitality of the body.
In 2002, a six-month project undertaken by the Yoga Research Foundation (YRF), Munger, India, analysed the effects of nadi shodhana pranayama in the ratio 1:1 and 1:2 on healthy subjects. Results showed improvement in speed in repetitive mathematical tasks, as well as in breath-holding time and peak expiratory flow. These changes indicate positive changes in mental abilities and an increase in vitality. Also, the time periods in which both nostrils flowed equally increased significantly, indicating the purifying effects of nadi shodhana on the network of pranic energy channels, the nadis, and consequently a more balanced state of the autonomic nervous system.*50
On the psychological level, there are studies that show a correlation between breathing predominantly through one nostril and the corresponding increase in brain activity in the opposite hemisphere, leading to increased cognitive performance specific to that hemisphere.*30-*32 Right-nasal dominance related to relatively greater verbal performance, stimulating pingala, left brain activity. Left-nasal dominance was coupled to relatively greater spatial skills, stimulating ida, right brain activity.
In a 2007 study, Telles*33 compared the effects of continual breathing through the right nostril, through the left nostril, and through both nostrils alternately, using simple breath awareness as a control, for their effects on the letter-cancellation task, which is a psychological test that assesses the performance of the left brain or pingala domain. Twenty male volunteers performed breathing patterns that effectively demonstrated surya bheda, chandra bheda and nadi shodhana pranayama techniques for 30 minutes, with a breath awareness technique as a control. They were tested before and after each of these four techniques, on four consecutive days, with daily variations in the order in which they performed them. The results showed that letter-cancellation task scores significantly improved (i.e. there were fewer errors) following right and alternate nostril breathing, indicating that surya bheda and nadi shodhana pranayama stimulate left brain performance (pingala nadi). One could expect that nadi shodhana would also improve the right brain cognitive performance of ida, if such a corresponding and relevant task had also been included in this study.
Two clinical trials,*35,*36 one clinical case report and one randomised controlled trial, used specific L-UFNB pattern, meaning left-unilateral-forced-nostril-breathing which is in fact chandra bheda pranayama, for the treatment of obsessive-compulsive disorder (OCD), with substantial and significant clinical reductions in obsessions and compulsions when measured with the Yale-Brown Obsessive-Compulsive Scale, along with significant reductions in other psychological symptoms using other scales, resulting in reduction and in some cases elimination of medications.