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Dr. Swami Mudraroopa Saraswati
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.
Yogic views
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.
SWARA YOGA AND RESEARCH
Swara and the mind
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.
The nasal cycle
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.
Nasal cycle as a marker of autonomic nervous system oscillations
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.
Nasal cycle, swara and pranayama research
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
Psychological implications of swara
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.
Swara yoga in psychiatry and neurology
Recently, interesting findings, related to swara yoga postulating the mental aspects of ida and pingala nadis emerged as a result of the study published in the International Journal of Developmental Neuroscience in 2007.*44 Hand, eye and nasal airflow dominance were studied in 37 autistic children and compared with a control group of 20 children. The autistic children showed strong left nasal dominance, breathing predominantly through the left nostril, while in the control group balanced alternate nasal dominance was present. The authors conclude that, "Autism and early language impairment may be associated with left-handedness, left-eyedness and nasal dominance . . . These results show that the patients with autism had no normal nasal cycle; they probably had almost continuous left nasal breathing."
In yoga physiology, autism is understood as a state of imbalance in which ida nadi is far too overactive and children become overly introverted. The state of imbalance presents itself as the predominant airflow through the left nostril. Implications of these scientific findings point to yogic measures that can induce the state of balance in the ida-pingala system: Surya bheda pranayama activates the breathing pattern through the right nostril, pingala. By activating the extrovert human nature, this gradually brings about a state of harmony. Also, autistic children can be taught padadhirasana with the right hand tightly pressed against the left armpit. Matsya kridasana on the left side of the body with the right knee bent would further benefit those children. Both of these asanas stimulate pingala.
Studies have been carried out on the use of surgical vagus nerve stimulation for the control of drug-resistant epileptic seizures, and the effectiveness of this method is recognized, but there are side effects to consider.*45 Experimental and human studies strongly suggest that the anti-seizure effects of vagus stimulation are mediated through the reticular activating system, the limbic system and central autonomic network. Vagus, as the principal part of the parasympathetic nervous system, is controlled by ida nadi. Therefore, the use of chandra bheda pranayama to gently stimulate the vagal nerve in a natural way, without any side effects of surgery, may help in difficult cases of epilepsy.
Swara yoga in ophthalmology
Unilateral right nostril breathing, equivalent to surya bheda pranayama and practiced for 20 minutes continuously, was shown to reduce intraocular pressure by 25% in glaucoma simplex (both open and closed angle glaucoma) in 46 out of 51 patients.*46,*48 All patients were under standard pharmacological drug treatment, and several had also undergone surgical treatment also in the past. Lowering of intraocular pressure was significant and happened in both eyes. Patients that did not respond had juvenile glaucoma and a neo-vascular type of glaucoma that seriously limit the flow of ocular liquid in the eye. This study shows fascinating autonomic nervous system regulation of ocular pressure by surya bheda pranayama. What is more, there is evidence that this reduction is of the same magnitude in both healthy people and patients suffering from glaucoma.
Yogic effects are almost immediate and in the range of up to 30-35% of reduction, while pharmacological effects take 20-30 minutes and are in the range of 15-35%. What remains to be done is to investigate the exclusive use of surya bheda without the use of drugs as a possible treatment for glaucoma. Although during this study the effects of surya bheda lasted for 2-3 hours, there is the possibility that by sustained daily practice its influence on intraocular pressure would become even more stable and prolonged. Also, there are some preliminary findings of increased right nostril obstruction by nasal polyps in patients suffering from glaucoma, indicating that insufficient right nostril flow may be a contributing factor in this disorder.
Swara yoga in cardiology
Raghuraj and Telles in 2008*47 presented the results of surya and chandra bheda and nadi shodhana pranayamas on blood pressure, compared to simple breath awareness and natural breathing. Each session of breathing practice lasted for 30 minutes, followed by 10 minutes of quiet sitting. Following surya bheda, there was a significant increase in systolic, diastolic and mean pressure. In contrast, the systolic and diastolic pressure decreased after nadi shodhana and the systolic and mean pressure were lower after chandra bheda. Hence, unilateral nostril yoga breathing practices appear to influence the blood pressure in different ways. These effects suggest possible therapeutic applications, indicating that nadi shodhana may be the best choice for long-term management of high blood pressure (HBP), and surya bheda as a tool to rectify a tendency towards low blood pressure.
In 2007, the Yoga Research Foundation conducted a study on 30 hypertensive adults and it was found that the practice of nadi shodhana pranayama for one month with the ratio 1:1 (inhalation - exhalation), without holding the breath, brought down both systolic and diastolic pressure by an average 14.5 mmHg and 4.2 mmHg respectively.*50
Yogic tools for quick change of swara: matsya kridasana, padadhirasana, and yoga danda, and nostril airflow
Research conducted by ENT specialists Haight and Cole in 1984-1986 *40-*43 and published in American journals of otorhynolaringology showed through a series of complex experiments that adopting the posture equivalent to matsyakridasana leads to significant changes in the nasal airflow, resulting in decongestion and consequent increased airflow through the upper nostril and at the same time to congestion and decreased airflow through the lower nostril. Progressive lengthening of the time spent in this asana increased the magnitude of nasal response and it endured for longer.
They reported that nasal changes occurred in 37 out of 42 subjects and concluded that the efferent pathway for these vasomotor reflex responses is via the sympathetic fibres to the erectile tissue of the nasal mucosa, and that the receptors are located deep in the subcutaneous tissue of the chest wall but superficial to thoracic organs. They concluded that the pressure-sensitive zones are located in the ventral, dorsal and lateral aspects of the pelvic and pectoral girdles and thoracic wall. They also state that, "This topographical distribution is strikingly similar to that which induces contra-lateral sweating in response to localized pressure, the 'hemi-hydrotic reflex'. Therefore, there is a possibility that these responses share a common afferent pathway."
In addition to this, researchers observed that at least in some people nasal dominance shifts due to asymmetrical weight distribution while seated. The implications are to be considered when perfecting a sitting asana for the advanced practice of pranayama. An uneven weight distribution in the asana can interfere with the natural swara rhythms.
Others studied the effects of sustained pressure in the armpit that also extends to the reflex point in the fifth inter-costal space on the frontal chest wall. This is the kind of pressure achieved through the use of a yoga danda, a wooden armrest designed by yogis to exert pressure in the described areas of the body in order to facilitate pranayama practice. Also, the same kind of pressure is applied by the hands and thumbs in padadhirasana, an asana that is used to alter the swara. A study published in the Journal of Applied Physiology *49 revealed that, "Pressure in the axilla, armpit, can induce changes that lead to decongestion and increased airflow in the contra-lateral nostril." To prove that this particular pressure in the armpit is responsible for the nasal flow change, researchers positioned subjects in such lying positions using two separate tables so as to free the lower neck, shoulder and hand from any weight or pressure, and in that position no change in the nasal airflow was found.
In addition to these findings, we can add that pressure in the armpit and more specifically at the fifth inter-costal space on the frontal wall of the chest and consequent increase in the nasal airflow in the opposite nostril can easily be understood from the point of view of Chinese acupuncture. The point of origin of the lung channel on the frontal chest wall is being stimulated by pressure, especially by the thumb in padadhirasana. The lung channels from the left and right side of the body intersect with each other above the upper lip, only to end with their last acupuncture points just near the nostril opening on the opposite side. Therefore, stimulation of the left lung channel will result in opening of the right nostril and vice versa.
SUMMARY
So far, scientific research indicates that substantial changes in the body and mind can be achieved using the techniques of swara yoga. Basic research studies directed the attention to probable mechanisms that connect the nasal breathing cycle and pranayama techniques with the limbic system and further on to the higher brain structures in the cortex. Other more pragmatic researchers demonstrated that higher cognitive faculties of the left and right brain hemisphere and the overall regulator of psychophysiological homeostasis in the body, the autonomic nervous system, can be effectively influenced by pranayama practices. Potentially far-reaching consequences of fine-tuning the sympathetic and parasympathetic nervous systems have been observed. Changes in blood chemistry, in the blood levels of stress hormones and insulin, in blood pressure, in EEG readings and in sleep patterns have been reported. They also proved that additional tools of swara yoga, postures like padadhirasana and matsya kridasana, can alter the nasal cycle, which has been shown to be a unique marker of autonomic nervous system activity.
Further on, the possible therapeutic use of pranayama in the management of various disorders in diverse fields of medicine, such as psychiatry, neurology, endocrinology, cardiology, ophthalmology and others, has been analysed and found significant. So far, autism, epilepsy, compulsive-obsessive disorder, high and low blood pressure and glaucoma have been shown to benefit from chandra bheda, surya bheda and nadi shodhana pranayamas.
There is sound scientific evidence that by adopting simple yoga postures such are matsyakridasana and padadhirasana, one can quickly and effectively manipulate the swara and through it the whole autonomic nervous system. In the course of time other yoga practices which exhibit similar effects, like the purification practices of jala and sutra neti, should receive attention from researchers.
We need both ida and pingala, and we need them awakened and in balance with each other. Then we can glide between the two domains effortlessly and naturally, adjusting to circumstances and meeting the challenges of life in a balanced way, keeping good health, mental poise and a harmonious evolution of our personality.
IDA PINGALA Left nostril Right nostril Right hemisphere Left hemisphere Introversion Extroversion Mental and artistic work Physical and dynamic work Metabolism slows down - cool Metabolism speeds up - warm Interprets emotional connotation of communication Use and meaning of words and language, both spoken and written Recognition of facial expressions Intuitive, integrative, accurate Rational decisions, thinking judgment Music and art awareness, imagination Logical, verbal, mathematical, analytical Perception of space, patterns, direction Parasympathetic Nervous System Sympathetic Nervous System Management of: Management of: - epilepsy - obsessive compulsive disorder - glaucoma - high blood pressure - low blood pressure
FOR FUTURE CONSIDERATION
Research into the field of swara yoga and pranayama encounters certain challenges. A good number of researchers think that the extent of the psychophysiological response of their subjects to pranayama techniques may significantly depend on their proficiency in yoga practice.
This observation should be taken into consideration when evaluating research data in a practical sense. Definitely, the manner in which one does pranayama greatly influences its effects on the body and on the mind. By its nature and essential mechanism, pranayama is more psychic than mental, and more mental than physical. One uses the medium of the physical body to manipulate the breath in a specific and prescribed way, but that is just a preliminary though necessary step. The main objective of pranayama is to access the psychic energy network of prana, the essential energy of our psychophysiological metabolism, and in this context we use the breath to connect our physical body with our energy and psychic bodies. The better we connect with these realms of our being in which prana flows freely, the more prana will be filtered down to the physical body, and more tangible effects on our brain and nervous system will happen. The key to unlock this process is the refinement of breath awareness in pranayama. Easy to say, but how to achieve this? This refinement of awareness spontaneously happens in the process of yoga, using various and integrated yoga practices and techniques from diverse branches of yoga, and not just pranayama. It is also a natural outcome of taking yoga with us into our life and lifestyle, as happens naturally in Satyananda Yoga. As one moves along this path, one definitely becomes more aware of subtle energies within the body and the mind, and then they wake up and the effects of pranayama reach deeper and deeper dimensions of our being.
One should not become discouraged by these facts. On the contrary, this knowledge should be used as an assurance that the right path and course of action in perfecting one's yoga can lead to deeper changes in ourselves.
Bibliography
*1. Joseph R., 'The Right Cerebral Hemisphere: Emotion, Music, Visual-spatial Skills, Body Image, Dreams and Awareness', J.Clin. Psychol, 1988, Sept 44 (5), pp 630-73.
*2. Duda P.D., Brown J., 'Lateral Asymmetry of Positive and Negative Emotions', Cortex, 1984, June 20 (2), pp 253-61.
*3. McLaren J., Bryson S.E., 'Hemispheic Asymmetries in the Perception of Emotional and Neutral Faces', Cortex, 1987, Dec 23 (4), pp 645-54.
*4. Davidson R.J., Chapman J.P., Chapman I.J., Henriques J.B., 'Asymmetrical Brain Electrical Activity Discriminates Between Psychometrically-matched Verbal and Spatial Cognitive Tasks', Psychophysiology, 1990, Sept 27 (5), pp 528-43.
*5. Klein R., Pilon D., Prosser S., Shannahoff-Khalsa D., 'Nasal Airflow Asymmetries And Human Performance', Biol. Psychol., 1986, Oct 23 (2), pp 127-37.
*6. Vivekananda, Dr. Rishi,Practical Yoga Psychology, Yoga Publications Trust, Bihar, India, 2008, pp 55-56.
*7. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Alternating cerebral hemispheric activity and the lateralization of autonomous nervous function',Hum Neurobiol. 1983; 2:39-43.
*8. Shannahoff-Khalsa D.S., Boyle M.R., Buebel M.E., 'The Effects of Unilateral Forced Nostril Breathing on Cognition', Int J Neurosci, 1991; 57:239-249.
*9. Frye R.E., Doty R.L., 'The Influence of Ultradian Autonomic Rhythms, as Indexed by the Nasal Cycle, on Unilateral Olfactory Thresholds', In: Doty R.L. ed. Chemical Signals in Vertebrates VI, New York: Plenum Press, 1992, 595-598.
*10. Klein R., Pilon D., Prosser S., et al. 'Nasal Airflow Asymmetries and Human Performance', BioI Psychol. 1986, 23:127-137.
*11. Levin B.E., Rappaport M., Natelson B.H., 'Ultradian Variations of Plasma Noradrenaline in Humans', Life Sci. 1979; 25:621-627.
*12. Klein D.C., Moore R.Y., Reppert S.M., eds. Suprachiasmatic Nucleus: The Mind's Clock, New York: Oxford University Press, 1991.
*13. Swaab D.F., Fliers E., Partiman T.S., 'The Suparchiasmatic Nucleus of the Human Brain in Relation to Sex, Age, and Senile Dementia', Brain Res. 1985; 342:37-44.
*14. Heetderks D.R., 'Observations on the Reaction of Normal Nasal Mucous Membrane", Am.J. Med. Sci. 1927; 174:231-244.
*15. Swanson L.W., 'The hypothalamus'. In: A. Bjorkland, T. Hokfelt, Swanson L eds. Handbook of Chemical Neuroanatomy, Vol. 5, Integrated Systems of the CNS. Amsterdam, The Netherlands: Elsevier Science Publishers BV; 1987:1-124.
*16. Beattie J. Hypothalamic mechanisms. Can Med Assoc J. 1932;26:400-405.
*17. Hess W.R. Diencephalon, Autonomic and Extrapyridimal Functions. New York, NY: Grune and Stratton; 1954.
*18. Shannahoff-Khalsa D. 'Lateralized Rhythms of the Central and Autonomic Nervous Systems', Int J Psychophysiol. 1991;11:225-251.
*19. Shannahoff-Khalsa D.S. 'Psychophysiological States: The Ultradian Dynamics of Mind-Body Interactions'. In: Bradley R.J., Harris R.A., Jenner P., eds. International Review of Neurobiology. vol 80. San Diego, Calif: Academic Press/Elsevier Scientific Publications; In press.
*20. Shannahoff-Khalsa D.S., Kennedy B., Yates F.E., et al. 'Ultradian Rhythms of Autonomic, Cardiovascular, and Neuroendocrine Systems are Related in Humans', Am J Physiol. 1996; 270:R873-R887.
*21. Shannahoff-Khalsa D.S., Kennedy B., Yates F.E., et al. 'Low-Frequency Ultradian Insulin Rhythms are Coupled to Cardiovascular, Autonomic, and Neuroendocrine Rhythms', Am J Physiol. 1997; 272:R962-R968.
*22. Shannahoff-Khalsa D.S., Yates F.E. 'Ultradian Sleep Rhythms of Lateral EEG, Autonomic, and Cardiovascular Activity are Coupled in Humans', Int J Neurosci. 2000; 101:21-43.
*23. Shannahoff-Khalsa D.S., Yates F.E. 'Ultradian Sleep Rhythms of Lateral EEG, Autonomic, and Cardiovascular Activity are Coupled in Humans', Int J Neurosci. 2000; 101:21-43.
*24. Kennedy B., Ziegler M.G., Shannahoff-Khalsa D.S. 'Alternating Lateralization of Plasma Catecholamines and Nasal Patency in Humans', Life Sci. 1986; 38:1203-1214.
*25. Foley J., DuBois F. 'Quantitative Studies of the Vagus Nerve in the Cat. I. The Ration of Sensory and Motor Studies', J Comp Neurol. 1937; 67:49-67.
*26. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Cerebral Hemispheric Activity and Autonomic Nervous Function', Paper presented at: 10th Annual Meeting of the Society for Neuroscience, November 9-14, 1980; Cincinnati, Oh.
*27. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Selective Cortical Activation by Altering Autonomic Function', Abstract presented at: Annual Meeting of the Western EEG Society Meeting. February 21, 1981; Reno, Nev.
*28. Werntz D.A., Bickford R.G., Shannahoff-Khalsa D. 'Selective Hemispheric Stimulation by Unilateral Forced Nostril Breathing', Hum Neurobiol. 1987;6:165-171.
*29. Servit Z., Kristof M., Strejckova A. 'Activating Effect of Nasal and Oral Hyperventilation on Epileptic Electrographic Phenomena: Reflex Mechanisms of Nasal Origin', Epilepsia. 1981; 22:321-329.
*30. Klein R., Pilon D., Prosser S., et al. 'Nasal Airflow Asymmetries and Human Performance', Biol Psychol. 1986; 23:127-137.
*31. Shannahoff-Khalsa D.S., Boyle M.R., Buebel M.E. 'The Effects of Unilateral Forced Nostril Breathing on Cognition', Int J Neurosci. 1991; 57:239-249.
*32. Jella S.A., Shannahoff-Khalsa D.S. 'The Effects of Unilateral Forced Nostril Breathing on Cognitive Performance', Int J Neurosci. 1993; 73:61-68.
*33. Telles S., Raghuraj P., Maharana S., et al. 'Immediate Effect of Three Yoga Breathing Techniques on Performance on a Letter-Cancellation Task', Percept Mot Skills. 2007; 104:1289-1296.
*34. Baglio S., Bucolo M., Fortuna L., et al. 'MEG Signals Spatial Power Distribution and Gamma Band Activity in Yoga Breathing Exercises', Paper presented at: Conference Proceedings of the IEEE Engineering in Medicine and Biology Society. October 23-26, 2002; Houston, Tex.
*35. Shannahoff-Khalsa D.S., Beckett L.R. 'Clinical Case Report: Efficacy of Yogic Techniques in the Treatment of Obsessive Compulsive Disorders', Int J Neurosci. 1996; 85:1-17.
*36. Shannahoff-Khalsa D., Ray L., Levine S., et al. 'Randomized Controlled Trial of Yogic Meditation Techniques for Patients with Obsessive Compulsive Disorders', CNS Spectr. 1999; 4:34-46.
*37. Samzelius-Lejdstrom I. 'Researches with the Bilateral Troncopneumograph on the Movements of the Respiratory Mechanisms during Breathing', Acta Otolaryng. 1939; 35 (suppl) : 3-104.
*38. Stoksted P. 'Obstructions in the Nose and their Influence on the Pulmonary Functions', Acta Otorhinolar. 1960; 158 (suppl): 110.
*39. Drettner B. 'Pathophysiological relationship between the upper and lower airways'. Ann Otol Rhinol Laryngol. 1970;79:499-505.
*40. Haight J.J., Cole P. 'Reciprocating nasal airflow resistances'. Acta Otolaryngol. 1984;97:93-98.
*41. Haight J.S., Cole P. 'Unilateral Nasal Resistance and Asymmetrical Body Pressure', J Otolaryngol Suppl. 1986;16:1-31.
*42. Cole P., Haight J. 'Posture and the Nasal Cycle', Am Otol Rhinol Laryngol. 1986;95:233-237.
*43. Cole P., Haight J.S. 'Posture and Nasal Patency', Am Rev Respir Dis. 1984; 129:351354.
*44. Dane S., Balci N. 'Handedness, Eyedness and Nasal Cycle in Children with Autism', Int J Dev Neurosci. 2007; 25:223-226
*45. Henry T.R. 'Therapeutic Mechanisms of Vagus Nerve Stimulation', Neurology. 2002; 59 (suppl 4):S3-S14.
*46. Joshua Backon, Nelson Matamoros, Manuel Alberto Brown, Uriel Ticho, 'A Functional Vagotomy Induced by Unilateral Forced Right Nostril Breathing Decreases Intraocular Pressure in Open and Closed Angle Glaucoma', British Journal of Ophthalmology, 1990, 74, 607-609
*47. Raghuraj P., Telles S., 'Immediate Effect of Specific Nostril Manipulating Yoga Breathing Practices on Autonomic and Respiratory Variables', Appl Psychophysiol Biofeedback. 2008 Jun; 33(2):65-75.
*48. Chen J.C., Brown B., Schmid K.L., 'Effect of Unilateral Forced Nostril Breathing on Tonic Accommodation and Intraocular Pressure',Clin Auton Res. 2004 Dec; 14(6):396-400.
*49. Rao S., Potdar A. 'Nasal Airflow with Body in Various Positions', J Appl Physiol. 1970; 28:162-165.
*50. Swami Niranjanananda Saraswati, Prana and Pranayama, Yoga Publications Trust, Bihar, India, 2009, p40
Correction
To page 39, lines 12-16 should read: 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 right nostril.
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.
Yogic views
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.
SWARA YOGA AND RESEARCH
Swara and the mind
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.
The nasal cycle
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.
Nasal cycle as a marker of autonomic nervous system oscillations
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.
Nasal cycle, swara and pranayama research
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
Psychological implications of swara
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.
Swara yoga in psychiatry and neurology
Recently, interesting findings, related to swara yoga postulating the mental aspects of ida and pingala nadis emerged as a result of the study published in the International Journal of Developmental Neuroscience in 2007.*44 Hand, eye and nasal airflow dominance were studied in 37 autistic children and compared with a control group of 20 children. The autistic children showed strong left nasal dominance, breathing predominantly through the left nostril, while in the control group balanced alternate nasal dominance was present. The authors conclude that, "Autism and early language impairment may be associated with left-handedness, left-eyedness and nasal dominance . . . These results show that the patients with autism had no normal nasal cycle; they probably had almost continuous left nasal breathing."
In yoga physiology, autism is understood as a state of imbalance in which ida nadi is far too overactive and children become overly introverted. The state of imbalance presents itself as the predominant airflow through the left nostril. Implications of these scientific findings point to yogic measures that can induce the state of balance in the ida-pingala system: Surya bheda pranayama activates the breathing pattern through the right nostril, pingala. By activating the extrovert human nature, this gradually brings about a state of harmony. Also, autistic children can be taught padadhirasana with the right hand tightly pressed against the left armpit. Matsya kridasana on the left side of the body with the right knee bent would further benefit those children. Both of these asanas stimulate pingala.
Studies have been carried out on the use of surgical vagus nerve stimulation for the control of drug-resistant epileptic seizures, and the effectiveness of this method is recognized, but there are side effects to consider.*45 Experimental and human studies strongly suggest that the anti-seizure effects of vagus stimulation are mediated through the reticular activating system, the limbic system and central autonomic network. Vagus, as the principal part of the parasympathetic nervous system, is controlled by ida nadi. Therefore, the use of chandra bheda pranayama to gently stimulate the vagal nerve in a natural way, without any side effects of surgery, may help in difficult cases of epilepsy.
Swara yoga in ophthalmology
Unilateral right nostril breathing, equivalent to surya bheda pranayama and practiced for 20 minutes continuously, was shown to reduce intraocular pressure by 25% in glaucoma simplex (both open and closed angle glaucoma) in 46 out of 51 patients.*46,*48 All patients were under standard pharmacological drug treatment, and several had also undergone surgical treatment also in the past. Lowering of intraocular pressure was significant and happened in both eyes. Patients that did not respond had juvenile glaucoma and a neo-vascular type of glaucoma that seriously limit the flow of ocular liquid in the eye. This study shows fascinating autonomic nervous system regulation of ocular pressure by surya bheda pranayama. What is more, there is evidence that this reduction is of the same magnitude in both healthy people and patients suffering from glaucoma.
Yogic effects are almost immediate and in the range of up to 30-35% of reduction, while pharmacological effects take 20-30 minutes and are in the range of 15-35%. What remains to be done is to investigate the exclusive use of surya bheda without the use of drugs as a possible treatment for glaucoma. Although during this study the effects of surya bheda lasted for 2-3 hours, there is the possibility that by sustained daily practice its influence on intraocular pressure would become even more stable and prolonged. Also, there are some preliminary findings of increased right nostril obstruction by nasal polyps in patients suffering from glaucoma, indicating that insufficient right nostril flow may be a contributing factor in this disorder.
Swara yoga in cardiology
Raghuraj and Telles in 2008*47 presented the results of surya and chandra bheda and nadi shodhana pranayamas on blood pressure, compared to simple breath awareness and natural breathing. Each session of breathing practice lasted for 30 minutes, followed by 10 minutes of quiet sitting. Following surya bheda, there was a significant increase in systolic, diastolic and mean pressure. In contrast, the systolic and diastolic pressure decreased after nadi shodhana and the systolic and mean pressure were lower after chandra bheda. Hence, unilateral nostril yoga breathing practices appear to influence the blood pressure in different ways. These effects suggest possible therapeutic applications, indicating that nadi shodhana may be the best choice for long-term management of high blood pressure (HBP), and surya bheda as a tool to rectify a tendency towards low blood pressure.
In 2007, the Yoga Research Foundation conducted a study on 30 hypertensive adults and it was found that the practice of nadi shodhana pranayama for one month with the ratio 1:1 (inhalation - exhalation), without holding the breath, brought down both systolic and diastolic pressure by an average 14.5 mmHg and 4.2 mmHg respectively.*50
Yogic tools for quick change of swara: matsya kridasana, padadhirasana, and yoga danda, and nostril airflow
Research conducted by ENT specialists Haight and Cole in 1984-1986 *40-*43 and published in American journals of otorhynolaringology showed through a series of complex experiments that adopting the posture equivalent to matsyakridasana leads to significant changes in the nasal airflow, resulting in decongestion and consequent increased airflow through the upper nostril and at the same time to congestion and decreased airflow through the lower nostril. Progressive lengthening of the time spent in this asana increased the magnitude of nasal response and it endured for longer.
They reported that nasal changes occurred in 37 out of 42 subjects and concluded that the efferent pathway for these vasomotor reflex responses is via the sympathetic fibres to the erectile tissue of the nasal mucosa, and that the receptors are located deep in the subcutaneous tissue of the chest wall but superficial to thoracic organs. They concluded that the pressure-sensitive zones are located in the ventral, dorsal and lateral aspects of the pelvic and pectoral girdles and thoracic wall. They also state that, "This topographical distribution is strikingly similar to that which induces contra-lateral sweating in response to localized pressure, the 'hemi-hydrotic reflex'. Therefore, there is a possibility that these responses share a common afferent pathway."
In addition to this, researchers observed that at least in some people nasal dominance shifts due to asymmetrical weight distribution while seated. The implications are to be considered when perfecting a sitting asana for the advanced practice of pranayama. An uneven weight distribution in the asana can interfere with the natural swara rhythms.
Others studied the effects of sustained pressure in the armpit that also extends to the reflex point in the fifth inter-costal space on the frontal chest wall. This is the kind of pressure achieved through the use of a yoga danda, a wooden armrest designed by yogis to exert pressure in the described areas of the body in order to facilitate pranayama practice. Also, the same kind of pressure is applied by the hands and thumbs in padadhirasana, an asana that is used to alter the swara. A study published in the Journal of Applied Physiology *49 revealed that, "Pressure in the axilla, armpit, can induce changes that lead to decongestion and increased airflow in the contra-lateral nostril." To prove that this particular pressure in the armpit is responsible for the nasal flow change, researchers positioned subjects in such lying positions using two separate tables so as to free the lower neck, shoulder and hand from any weight or pressure, and in that position no change in the nasal airflow was found.
In addition to these findings, we can add that pressure in the armpit and more specifically at the fifth inter-costal space on the frontal wall of the chest and consequent increase in the nasal airflow in the opposite nostril can easily be understood from the point of view of Chinese acupuncture. The point of origin of the lung channel on the frontal chest wall is being stimulated by pressure, especially by the thumb in padadhirasana. The lung channels from the left and right side of the body intersect with each other above the upper lip, only to end with their last acupuncture points just near the nostril opening on the opposite side. Therefore, stimulation of the left lung channel will result in opening of the right nostril and vice versa.
SUMMARY
So far, scientific research indicates that substantial changes in the body and mind can be achieved using the techniques of swara yoga. Basic research studies directed the attention to probable mechanisms that connect the nasal breathing cycle and pranayama techniques with the limbic system and further on to the higher brain structures in the cortex. Other more pragmatic researchers demonstrated that higher cognitive faculties of the left and right brain hemisphere and the overall regulator of psychophysiological homeostasis in the body, the autonomic nervous system, can be effectively influenced by pranayama practices. Potentially far-reaching consequences of fine-tuning the sympathetic and parasympathetic nervous systems have been observed. Changes in blood chemistry, in the blood levels of stress hormones and insulin, in blood pressure, in EEG readings and in sleep patterns have been reported. They also proved that additional tools of swara yoga, postures like padadhirasana and matsya kridasana, can alter the nasal cycle, which has been shown to be a unique marker of autonomic nervous system activity.
Further on, the possible therapeutic use of pranayama in the management of various disorders in diverse fields of medicine, such as psychiatry, neurology, endocrinology, cardiology, ophthalmology and others, has been analysed and found significant. So far, autism, epilepsy, compulsive-obsessive disorder, high and low blood pressure and glaucoma have been shown to benefit from chandra bheda, surya bheda and nadi shodhana pranayamas.
There is sound scientific evidence that by adopting simple yoga postures such are matsyakridasana and padadhirasana, one can quickly and effectively manipulate the swara and through it the whole autonomic nervous system. In the course of time other yoga practices which exhibit similar effects, like the purification practices of jala and sutra neti, should receive attention from researchers.
We need both ida and pingala, and we need them awakened and in balance with each other. Then we can glide between the two domains effortlessly and naturally, adjusting to circumstances and meeting the challenges of life in a balanced way, keeping good health, mental poise and a harmonious evolution of our personality.
IDA PINGALA Left nostril Right nostril Right hemisphere Left hemisphere Introversion Extroversion Mental and artistic work Physical and dynamic work Metabolism slows down - cool Metabolism speeds up - warm Interprets emotional connotation of communication Use and meaning of words and language, both spoken and written Recognition of facial expressions Intuitive, integrative, accurate Rational decisions, thinking judgment Music and art awareness, imagination Logical, verbal, mathematical, analytical Perception of space, patterns, direction Parasympathetic Nervous System Sympathetic Nervous System Management of: Management of: - epilepsy - obsessive compulsive disorder - glaucoma - high blood pressure - low blood pressure
FOR FUTURE CONSIDERATION
Research into the field of swara yoga and pranayama encounters certain challenges. A good number of researchers think that the extent of the psychophysiological response of their subjects to pranayama techniques may significantly depend on their proficiency in yoga practice.
This observation should be taken into consideration when evaluating research data in a practical sense. Definitely, the manner in which one does pranayama greatly influences its effects on the body and on the mind. By its nature and essential mechanism, pranayama is more psychic than mental, and more mental than physical. One uses the medium of the physical body to manipulate the breath in a specific and prescribed way, but that is just a preliminary though necessary step. The main objective of pranayama is to access the psychic energy network of prana, the essential energy of our psychophysiological metabolism, and in this context we use the breath to connect our physical body with our energy and psychic bodies. The better we connect with these realms of our being in which prana flows freely, the more prana will be filtered down to the physical body, and more tangible effects on our brain and nervous system will happen. The key to unlock this process is the refinement of breath awareness in pranayama. Easy to say, but how to achieve this? This refinement of awareness spontaneously happens in the process of yoga, using various and integrated yoga practices and techniques from diverse branches of yoga, and not just pranayama. It is also a natural outcome of taking yoga with us into our life and lifestyle, as happens naturally in Satyananda Yoga. As one moves along this path, one definitely becomes more aware of subtle energies within the body and the mind, and then they wake up and the effects of pranayama reach deeper and deeper dimensions of our being.
One should not become discouraged by these facts. On the contrary, this knowledge should be used as an assurance that the right path and course of action in perfecting one's yoga can lead to deeper changes in ourselves.
Bibliography
*1. Joseph R., 'The Right Cerebral Hemisphere: Emotion, Music, Visual-spatial Skills, Body Image, Dreams and Awareness', J.Clin. Psychol, 1988, Sept 44 (5), pp 630-73.
*2. Duda P.D., Brown J., 'Lateral Asymmetry of Positive and Negative Emotions', Cortex, 1984, June 20 (2), pp 253-61.
*3. McLaren J., Bryson S.E., 'Hemispheic Asymmetries in the Perception of Emotional and Neutral Faces', Cortex, 1987, Dec 23 (4), pp 645-54.
*4. Davidson R.J., Chapman J.P., Chapman I.J., Henriques J.B., 'Asymmetrical Brain Electrical Activity Discriminates Between Psychometrically-matched Verbal and Spatial Cognitive Tasks', Psychophysiology, 1990, Sept 27 (5), pp 528-43.
*5. Klein R., Pilon D., Prosser S., Shannahoff-Khalsa D., 'Nasal Airflow Asymmetries And Human Performance', Biol. Psychol., 1986, Oct 23 (2), pp 127-37.
*6. Vivekananda, Dr. Rishi,Practical Yoga Psychology, Yoga Publications Trust, Bihar, India, 2008, pp 55-56.
*7. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Alternating cerebral hemispheric activity and the lateralization of autonomous nervous function',Hum Neurobiol. 1983; 2:39-43.
*8. Shannahoff-Khalsa D.S., Boyle M.R., Buebel M.E., 'The Effects of Unilateral Forced Nostril Breathing on Cognition', Int J Neurosci, 1991; 57:239-249.
*9. Frye R.E., Doty R.L., 'The Influence of Ultradian Autonomic Rhythms, as Indexed by the Nasal Cycle, on Unilateral Olfactory Thresholds', In: Doty R.L. ed. Chemical Signals in Vertebrates VI, New York: Plenum Press, 1992, 595-598.
*10. Klein R., Pilon D., Prosser S., et al. 'Nasal Airflow Asymmetries and Human Performance', BioI Psychol. 1986, 23:127-137.
*11. Levin B.E., Rappaport M., Natelson B.H., 'Ultradian Variations of Plasma Noradrenaline in Humans', Life Sci. 1979; 25:621-627.
*12. Klein D.C., Moore R.Y., Reppert S.M., eds. Suprachiasmatic Nucleus: The Mind's Clock, New York: Oxford University Press, 1991.
*13. Swaab D.F., Fliers E., Partiman T.S., 'The Suparchiasmatic Nucleus of the Human Brain in Relation to Sex, Age, and Senile Dementia', Brain Res. 1985; 342:37-44.
*14. Heetderks D.R., 'Observations on the Reaction of Normal Nasal Mucous Membrane", Am.J. Med. Sci. 1927; 174:231-244.
*15. Swanson L.W., 'The hypothalamus'. In: A. Bjorkland, T. Hokfelt, Swanson L eds. Handbook of Chemical Neuroanatomy, Vol. 5, Integrated Systems of the CNS. Amsterdam, The Netherlands: Elsevier Science Publishers BV; 1987:1-124.
*16. Beattie J. Hypothalamic mechanisms. Can Med Assoc J. 1932;26:400-405.
*17. Hess W.R. Diencephalon, Autonomic and Extrapyridimal Functions. New York, NY: Grune and Stratton; 1954.
*18. Shannahoff-Khalsa D. 'Lateralized Rhythms of the Central and Autonomic Nervous Systems', Int J Psychophysiol. 1991;11:225-251.
*19. Shannahoff-Khalsa D.S. 'Psychophysiological States: The Ultradian Dynamics of Mind-Body Interactions'. In: Bradley R.J., Harris R.A., Jenner P., eds. International Review of Neurobiology. vol 80. San Diego, Calif: Academic Press/Elsevier Scientific Publications; In press.
*20. Shannahoff-Khalsa D.S., Kennedy B., Yates F.E., et al. 'Ultradian Rhythms of Autonomic, Cardiovascular, and Neuroendocrine Systems are Related in Humans', Am J Physiol. 1996; 270:R873-R887.
*21. Shannahoff-Khalsa D.S., Kennedy B., Yates F.E., et al. 'Low-Frequency Ultradian Insulin Rhythms are Coupled to Cardiovascular, Autonomic, and Neuroendocrine Rhythms', Am J Physiol. 1997; 272:R962-R968.
*22. Shannahoff-Khalsa D.S., Yates F.E. 'Ultradian Sleep Rhythms of Lateral EEG, Autonomic, and Cardiovascular Activity are Coupled in Humans', Int J Neurosci. 2000; 101:21-43.
*23. Shannahoff-Khalsa D.S., Yates F.E. 'Ultradian Sleep Rhythms of Lateral EEG, Autonomic, and Cardiovascular Activity are Coupled in Humans', Int J Neurosci. 2000; 101:21-43.
*24. Kennedy B., Ziegler M.G., Shannahoff-Khalsa D.S. 'Alternating Lateralization of Plasma Catecholamines and Nasal Patency in Humans', Life Sci. 1986; 38:1203-1214.
*25. Foley J., DuBois F. 'Quantitative Studies of the Vagus Nerve in the Cat. I. The Ration of Sensory and Motor Studies', J Comp Neurol. 1937; 67:49-67.
*26. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Cerebral Hemispheric Activity and Autonomic Nervous Function', Paper presented at: 10th Annual Meeting of the Society for Neuroscience, November 9-14, 1980; Cincinnati, Oh.
*27. Werntz D.A., Bickford R.G., Bloom F.E., et al. 'Selective Cortical Activation by Altering Autonomic Function', Abstract presented at: Annual Meeting of the Western EEG Society Meeting. February 21, 1981; Reno, Nev.
*28. Werntz D.A., Bickford R.G., Shannahoff-Khalsa D. 'Selective Hemispheric Stimulation by Unilateral Forced Nostril Breathing', Hum Neurobiol. 1987;6:165-171.
*29. Servit Z., Kristof M., Strejckova A. 'Activating Effect of Nasal and Oral Hyperventilation on Epileptic Electrographic Phenomena: Reflex Mechanisms of Nasal Origin', Epilepsia. 1981; 22:321-329.
*30. Klein R., Pilon D., Prosser S., et al. 'Nasal Airflow Asymmetries and Human Performance', Biol Psychol. 1986; 23:127-137.
*31. Shannahoff-Khalsa D.S., Boyle M.R., Buebel M.E. 'The Effects of Unilateral Forced Nostril Breathing on Cognition', Int J Neurosci. 1991; 57:239-249.
*32. Jella S.A., Shannahoff-Khalsa D.S. 'The Effects of Unilateral Forced Nostril Breathing on Cognitive Performance', Int J Neurosci. 1993; 73:61-68.
*33. Telles S., Raghuraj P., Maharana S., et al. 'Immediate Effect of Three Yoga Breathing Techniques on Performance on a Letter-Cancellation Task', Percept Mot Skills. 2007; 104:1289-1296.
*34. Baglio S., Bucolo M., Fortuna L., et al. 'MEG Signals Spatial Power Distribution and Gamma Band Activity in Yoga Breathing Exercises', Paper presented at: Conference Proceedings of the IEEE Engineering in Medicine and Biology Society. October 23-26, 2002; Houston, Tex.
*35. Shannahoff-Khalsa D.S., Beckett L.R. 'Clinical Case Report: Efficacy of Yogic Techniques in the Treatment of Obsessive Compulsive Disorders', Int J Neurosci. 1996; 85:1-17.
*36. Shannahoff-Khalsa D., Ray L., Levine S., et al. 'Randomized Controlled Trial of Yogic Meditation Techniques for Patients with Obsessive Compulsive Disorders', CNS Spectr. 1999; 4:34-46.
*37. Samzelius-Lejdstrom I. 'Researches with the Bilateral Troncopneumograph on the Movements of the Respiratory Mechanisms during Breathing', Acta Otolaryng. 1939; 35 (suppl) : 3-104.
*38. Stoksted P. 'Obstructions in the Nose and their Influence on the Pulmonary Functions', Acta Otorhinolar. 1960; 158 (suppl): 110.
*39. Drettner B. 'Pathophysiological relationship between the upper and lower airways'. Ann Otol Rhinol Laryngol. 1970;79:499-505.
*40. Haight J.J., Cole P. 'Reciprocating nasal airflow resistances'. Acta Otolaryngol. 1984;97:93-98.
*41. Haight J.S., Cole P. 'Unilateral Nasal Resistance and Asymmetrical Body Pressure', J Otolaryngol Suppl. 1986;16:1-31.
*42. Cole P., Haight J. 'Posture and the Nasal Cycle', Am Otol Rhinol Laryngol. 1986;95:233-237.
*43. Cole P., Haight J.S. 'Posture and Nasal Patency', Am Rev Respir Dis. 1984; 129:351354.
*44. Dane S., Balci N. 'Handedness, Eyedness and Nasal Cycle in Children with Autism', Int J Dev Neurosci. 2007; 25:223-226
*45. Henry T.R. 'Therapeutic Mechanisms of Vagus Nerve Stimulation', Neurology. 2002; 59 (suppl 4):S3-S14.
*46. Joshua Backon, Nelson Matamoros, Manuel Alberto Brown, Uriel Ticho, 'A Functional Vagotomy Induced by Unilateral Forced Right Nostril Breathing Decreases Intraocular Pressure in Open and Closed Angle Glaucoma', British Journal of Ophthalmology, 1990, 74, 607-609
*47. Raghuraj P., Telles S., 'Immediate Effect of Specific Nostril Manipulating Yoga Breathing Practices on Autonomic and Respiratory Variables', Appl Psychophysiol Biofeedback. 2008 Jun; 33(2):65-75.
*48. Chen J.C., Brown B., Schmid K.L., 'Effect of Unilateral Forced Nostril Breathing on Tonic Accommodation and Intraocular Pressure',Clin Auton Res. 2004 Dec; 14(6):396-400.
*49. Rao S., Potdar A. 'Nasal Airflow with Body in Various Positions', J Appl Physiol. 1970; 28:162-165.
*50. Swami Niranjanananda Saraswati, Prana and Pranayama, Yoga Publications Trust, Bihar, India, 2009, p40
Correction
To page 39, lines 12-16 should read: 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 right nostril.
