The connection between mind and body is part of our everyday experience. Recall, for example, an occasion when you experienced intense fear - what was the condition of your body then? The heart was thumping away in your ears, your mouth was so dry you couldn't swallow, the breath was shallow and fast, and you broke out in cold sweat. If anyone had taken your BP reading then, it would certainly have been high. The whole body went through the experience of fear which originated in the mind. The mind was the source of the experience and the body responded to it.
Now think of a state of increasingly unpleasant physical discomfort - for example, you are on a long bus ride on a hot day, you feel the calls of nature but the bus never stops. As the minutes pass by, the physical discomfort increases and you become first tense, then anxious, then worried, irritated, agitated, angry, even aggressive. The condition of the body affects the state of the mind and your psychological condition. The body is the source of the experience and the mind responds to it.
Everything the mind experiences affects the body simultaneously, and vice versa. This connection between the mind and the body is ever present and immediate. It has been very well understood, researched and utilized by yoga, and is on its way to becoming well known to modern science also. For yogis, the existence of this connection has been a fact of life for ages, rooted in experience and the science and philosophy of yoga, tantra and samkhya. Now the scientific community is showing an interest in this subject and new knowledge about the link between body and mind is emerging, primarily in the fields of psychoneuro-immunology and psychoneuro-endocrinology. The research focuses mostly on the interface between mind and body - the brain and the nervous system, and how they affect the functions of the immune and endocrine systems. The dimension of the mind is wider then that of the brain, but the brain can be understood as a tool of the mind, and as such it serves as a link between mind and body. We can look into the connection between the nervous and immune systems, as an example of the interconnection between mind and body, by glancing into research results published in the last five years or so.
The material substance through which the link between mind and body is established are protein molecules called neuropeptides, which are secreted in the brain and transferred by the blood to receptors in target cells and organs. They are the medium through which the exchange of information between the brain and the immune system takes place. In 1985, neuropeptide-specific receptors were found on cell walls of both the brain and immune system cells.*1The discovery that neuropeptides and neurotransmitters act directly on the brain and the immune system shows their close association with the psychological states of the mind, primarily with emotions, and suggests mechanisms of their interdependence. In 1993, profound immunological changes that occur in the state of stress were outlined, including an increase in the total number of white blood cells (WBC) but a decrease in the number of B cells, cytotoxic T cells and a decrease in both the number and function of T cells and the so-called 'natural killer cells'. These changes indicate a state of alarm in the immune system and at the same time of deregulation and weakness - the immunity goes down during stress.*2
The immune system is a complex and sophisticated set-up that takes care of the defence of the body on various levels. That it works in unison with the endocrine and nervous systems has been known for decades, but recently the details about this communication are appearing, confirming the fact that the brain, the nervous system and the immune system actually 'talk to each other', and that exchange of information goes on in both directions. This is of crucial importance for maintenance of homeostasis. There are two major pathways of communication: one is the autonomic nervous system (sympathetic and parasympathetic) and the other is the hypothalamus-pituitary-adrenal axis.
The nerves of the autonomic nervous system have been found to reach immune cells and sites throughout the body, in the spleen, thymus, bone marrow, liver. When the body is exposed to microbes, or injury takes place, the innate immune cells release various chemicals called immune modulators (cytokines, interleukins, etc.) into the blood that rapidly activate neural responses which amplify local immune responses to clear pathogens and also trigger systemic neuroendocrine and regional neural responses which eventually return the system to a resting state (this is very important for maintaining homeostasis). Prolonged or inappropriate CNS counter-regulatory responses (as can occur in states of depression, tension or stress) might predispose the person to either excess inflammation (due to loss of control of the inflammatory response) or uncontrolled infection (due to excessive anti-inflammatory hormonal response).*3 In the first instance, one might get, for example, rheumatoid arthritis, and in the second chronic infection or cancer.
The sympathetic nervous system has two parts that regulate the immune system. One is the neuronal component that regulates immunity at the regional level through innervations of the immune organs and the release of transmitter noradrenalin. The effect of this neuronal component is suppression of the function of the innate immune cells; it has an inhibitory role in adaptive immunity, antibody production and regional level immunity. This mechanism has been observed in the condition of an overdose of physical exercise and in the state of prolonged psychological stress.*4 The second part of the sympathetic nervous system that regulates immunity is the hormonal component which has a systematic effect through release of the hormone adrenaline from the medulla of adrenal glands, which triggers the `flight or fight' response to deal with acute stress.
The parasympathetic nervous system (PNS) modulates immune responses at the regional level through both efferent and afferent fibres of the vagus nerve. Afferent fibres can signal the presence of peripheral inflammation to the brain (through receptors activated by the released chemicals such as interleukins, for example, during inflammation in the gut). This leads to rapid activation of the PNS regions in the brainstem and subsequent release of transmitter acetylcholine from efferent vagus nerve fibres in the gut and a resultant prevention of excessive inflammatory responses. This mechanism has been named `cholinergic anti-inflammatory pathway'.*5
The main intersection in communication between the higher brain and the immune and endocrine system is in the midbrain, in the brainstem, at the hypothalamus. The hypothalamus controls the sympathetic and parasympathetic nervous systems, and also plays a major role in control of the pituitary gland, which in turn controls all the endocrine glands in the body. Exposure to a microbe (and subsequent release into blood of cytokines and other immune mediators), as well as to a strong physical or psychological stimuli (stress) results in the secretion of corticotrophin-releasing-hormone (CRH) from the cells of the paraventricular nucleus of the hypothalamus into the hypophiseal blood supply around the pituitary gland. This stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary into the blood, which in turn stimulates the synthesis and release of glucocorticoid hormones from the cortex of the adrenal glands. This connection between the hypothalamus, the pituitary and the adrenals is called hypothalamic-pituitary-adrenal (HPA) axis or neuroendocrine or stress axis. Glucocorticoids have an anti-inflammatory effect and they also have a newly discovered physiological role in regulating multiple aspects of immune-cell functions. In physiological concentrations found in the body, they can cause significant changes in the T cells, in the innate immune response to bacterial and viral infection, increase delayed-type hypersensitivity reactions, etc., with an overall anti-inflammatory and immunosuppressive effect. The release of glucocorticoids from the adrenals in turn inhibits further production of ACTH in the pituitary and subsequently of CRH in the hypothalamus, thus establishing a physiological negative biofeedback loop through which their release is regulated. This bi-directional communication between the immune system and the central nervous system in which immune cells signal to the brain and the brain responds by regulating the immune system, in part at least, through the anti-inflammatory effects of glucocorticoids - constitutes the main hormonal negative-biofeedback loop for the central nervous system regulation of immunity.
In addition to their role in regulation of the immune system, glucocorticoids from the adrenals are also essential for maintenance of several homeostatic mechanisms in the body, including the central nervous system, the cardiovascular system, metabolic homeostasis, etc.*3 So much so that the blunted HPA axis, which is not able to maintain this fine balance of hormonal equilibrium, is seen in a wide range of autoimmune and inflammatory diseases such as rheumatoid arthritis, lupus, irritable bowel syndrome, chronic fatigue syndrome, fybromialgia, etc.*6,*7 An excess of glucocorticoids in circulation, which can occur as a result of chronic stress, is associated with increased susceptibility to viral infections, slow wound healing and decreased antibody production - indicating loss of immune power. Precise control of the glucocorticoid metabolism is needed in order to maintain immuno-homeostasis and to avoid either excessive immunosuppression or pro-inflammatory response.*26,*27
Endogenous opioids (endorphins and encephalines) which are released by the pituitary cells together with ACTH have also been found to have anti-inflammatory effects. They bind to receptors in the brain, in dorsal root ganglia in the spinal cord (clusters of cells at the rear portion of the spinal cord), in central and peripheral nerve terminals and also in lymphocytes and monocytes. They also stimulate the HPA axis and induce glucocorticoid release.*8,*9,*10
Thus new research gradually brings a clearer picture of how the nervous system, with the help of the endocrine system, regulates the function of the immune system in order to protect and maintain balance in the body. So far we have seen how the mid-brain and brain stem structures (that belong to the unconscious level of brain organization) are involved in these interactions. However, recent research points to an interesting direction: the hypothalamus as well as the sympathetic and parasympathetic nervous systems are regulated by higher brain structures that belong to the conscious level of brain organization. It has been demonstrated that the prefrontal cortex has an important role in the integration of cognitive and affective behaviour and in regulating autonomic and neuroendocrine function. Analogous to the RAM of a computer, it translates stressful experience into adaptive and manageable behaviour - it responds to stress and modulates the response through regulation of the hypothalamic paraventricular nucleus, which in turn controls the sympathetic nervous system and HPA axis activity.*11,*12,*13,*14 Here is where we actually wage battle with stress, through reasoning, understanding, adjustment and acceptance until the whole stressful experience loses its negative emotional charge and becomes just a pixel in our memory. Yoga practices of mantra repetition, yoga nidra, antar mouna and pranayama significantly aid this process. A study was published in the Harvard Mental Health Letter stating that results suggest that yoga practice modulates the stress response.*28
It is becoming evident that the higher cerebral cortex areas (that belong to the domain of consciousness) such as the insular cortex, orbital and prefrontal cortex, also control the immune system and the body's homeostatic as well as stress physiology.*15 These areas also control glandular physiological processes through the autonomic nervous system, including blood circulation, digestive and urogenital functions, pancreatic juices, respiration, etc.*16,*17
The insular cortex is part of the cerebral cortex at the side of the brain, between the temporal and parietal lobes, and it is involved in diverse functions, including homeostasis, perception, motor control, self-awareness, cognitive functioning, interpersonal experience, anxiety, emotions such as fear, anger, happiness, sadness, displeasure, and also subjective awareness of the inner body. This is where intensity of pain is judged. In fact, this area appears to be of great interest from the yogic point of view, especially considering its active role in control of the immune system. In one research study this area was found to be significantly thicker in people who meditate regularly, one of the first studies to demonstrate actual physical change in the brain as a result of meditation practice.*18,*19 The possible implications of the effects of certain yogic practices on this cortical area are wide and promising.
Yoga nidra, hridayakasha dharana, asanas performed in the yogic way with full awareness, mantra repetition - all these practices are likely to affect the functioning of the insular cortex. Research has revealed that the practice of yoga asanas increases the brain levels of GABA, a chemical whose low levels are associated with depression and anxiety disorders. The study revealed a 27% increase after a 60-minute asana session (the control group showed zero percent change).*29 Thus it is becoming evident that yoga is an effective tool in the management of depression and anxiety, and the associated negative health effects of these conditions. The neuro-physiological mechanisms of yogic kriyas are also becoming known. And there are no side effects from the yoga pill!
Most significantly, it has been seen that the immune function can be conditioned through yoga. In probably the most impressive demonstration of brain-to-immune system interaction, healthy people in a double-blind, placebo-controlled study were conditioned in four sessions over three consecutive days by being given the immunosuppressive drug cyclosporine A (as unconditioned stimulus), paired with a distinctly flavoured drink (as conditioned stimulus) every 12 hours. Of course, the immune function went down under the influence of the drug. The following week, re-exposure to conditioned stimulus (the drink), but now paired with placebo capsules again induced suppression of immune functions as proved by a decrease in circulating levels of interleukin 2 and other immune mediators, decreased lymphocyte count and decline in cytokine gene proliferation.*20 This proved that bodily function can be conditioned by using a sensory stimulus. Even the mechanism of this response has been discovered: the conditioned response originates in the brain. The ventromedial nucleus of the hypothalamus provides the output pathway to the immune system; the amygdala area provides input of visceral information necessary at the time; and the insular cortex is essential for acquiring and evoking this conditioned response of the immune system.*21
Other changes in the body can also occur as conditioned response, both in the immune system and in other functions such as antibody levels, serum iron levels, levels of oxidative DNA damage, insulin secretion, blood glucose levels, etc. Results also suggest involvement of the central nervous system and psychological stress in the pathogenesis of cancer via oxidative DNA damage by free radicals.*22
The proof that conditioning of the mind/brain/body can be achieved using sensory input (taste in the mentioned study) as the conditioned stimulus mirrors the yogic perspective. This means we can use other sensorial inputs to create new conditionings, or by clearing them or cutting them off we can un-condition the mind/brain/body of negative responses that might have been accumulated over time and associated with emotional charge in the form of complexes, compulsions, fears, phobias and a wide variety of other negative conditionings of the mind that can seriously affect the body. For this purpose we can use the practices of chidakasha and hridayakasha dharana, antar mouna, trataka, yoga nidra, kirtan, karma yoga, mantra yoga, and so on. In yoga nidra, for example, we use images and symbols that trigger deeply suppressed contents in the subconscious mind. By bringing them to the conscious level, they lose their energy charge and are dissolved. For example, the image of a lake can trigger the fear of water caused by a long-forgotten boat accident in early childhood. Once brought to the surface of consciousness, this negative conditioning is eradicated from the mind forever. Also, through the use of sankalpa in yoga nidra, we can achieve very deep and strong positive conditioning of the mind.
The synchronicity between the ancient knowledge of yoga physiology and modern research is also indicated by findings about lateralization of the functions of the left and the right cortex in terms of immune system control. Immunosuppression was found to be stimulated by the right cortex and immunopotention by the left cortex.*23 Electrical stimulation of left temporo-parieto-occipital cortex (practically one whole side of the brain surface) in rats increased circulating levels of T lymphocytes, while stimulation on the right side decreased levels of the same cells. These effects were mediated by sympathetic nervous system fibres. Also, the right prefrontal cortex has been found to control the sympathetic nervous system while the left cortex controls the parasympathetic counterpart.*25 These new scientific facts exactly match the ancient yogic physiological knowledge about ida and pingala flows of prana or energy and their influence on the body and mind, and give new scientific credibility to several yogic practices such as neti, kunjal kriya and shankhaprakshalana, trataka, nadi shodhana, bhastrika, surya bheda and chandra bheda pranayamas, surya namaskara, yoga nidra, etc. where the primary physiological mode of action lies in balancing the functions of the two brain hemispheres and the two counterparts of the autonomic nervous system (sympathetic and parasympathetic), thereby establishing new equilibrium between the vital and mental energies in the body (prana and chitta), and in the specific case of immunity - optimizing immune response by establishing a new level of equilibrium in the sympathetic and parasympathetic nervous systems and the HPA hormonal axis.
A brief summary of these new research findings would be:
We have seen how fine a balance is needed between various levels of brain organization, the endocrine glands and immune organs in order to maintain the homeostasis in the body and optimal immunity. This is possible as long as the mind and the body work in unison as a unit, as modern research shows that they are so closely interrelated that changes in one will immediately affect the other and vice versa. So much so that the term `bodymind' is now being used in common parlance, denoting the two as one indivisible whole. As long as this is the case, inner balance and the state of wellbeing is maintained. Problems arise when the body goes its own way and the mind chooses a different path and they fail to function as one unit. The body goes cooking, shopping, driving, eating, and the mind does worrying, remembering, planning, gossiping, liking or disliking, and suddenly the balance is lost and a state of imbalance or stress takes over. The connection between the mind and body is disrupted; physical, mental and emotional tensions accumulate and the flow of vital energy becomes jagged. Research proves the extent of physiological changes that take place as a result of this loss of balance within the mind and body. Hormonal and autonomic nervous changes affect the immune system, and the higher cortical areas are thrown out of balance. In such a condition, only a rung separates us from disorder or disease. However, there is a way out.
Many faculties of the insular cortex such as motor control, self-awareness, emotions, subjective awareness of the inner body perception, anxiety, etc. can be positively influenced by certain yogic practices. Even in the simplest of asanas, yoga brings together body and mind through awareness of the movement and the breath, with the mind knowing what the body is doing. For many people this awareness is a revelation in itself. Thus even the simplest of asanas can stimulate the insular cortex and through it affect and possibly condition the immune system in a positive way. During the practice, neuronal impulses travel from the motor cortex (triggered by the mental intention to perform the asana) and through sub-cortical associated areas, through motor neuronal pathways in the spinal cord and to the muscles of the body which perform the movement.
At the same time, as the movement is done with awareness, a whole new array of neuronal impulses travel back from nerve endings around the joints and through sensorial nerve pathways of proprioception and deep sensibility in the spinal cord (they give us the sense of the position of the body in space and of its individual parts relative to one another and are activated by awareness of the position), and then back to the brain, and stimulate the insular cortex (since awareness of the inner body and self-awareness is modulated here). In this way an energy loop is created, a sort of positive physiological feedback circuit, which has a charging and rejuvenating effect on the brain, the central and autonomous nervous systems and through them on the whole body. Almost as a by-product, the resultant stimulation of the insular cortex will have a positive influence in optimizing the immune response also. In fact, body awareness and breath awareness are very tangible experiences - they are based on neuronal impulses that run through the somato-sensorial neural pathways and create actual changes in the system. Thus with regular practice of even the simplest of yoga practices, we achieve tangible changes in homeostatic systems of the body, as well as higher levels of energy and wellbeing.
Modern scientific discoveries are echoing the ancient themes of the yogic scriptures - that the mind plays a central role in maintaining equilibrium in the body.