(1)
Department of Psychiatry, Cooper University Hospital, and Cooper Medical School of Rowan University, Camden, NJ, USA
Penetrative insight joined with calm abiding utterly eradicates afflicted states.
–Shantideva (1997)
8.1 Yoga and Meditation: Rationale and Feasibility in Health care
Although heterogeneous and complex with respect to its scope and meaning, Yoga and meditation can be broadly conceptualized as self-management strategies for gaining insight into the principles of the human mind that explain the nature of its thoughts and experiences. These insights help us realize how to reaccess a natural and positive state of mind, how to experience calmness in sustained manner regardless of the circumstances we encounter in our daily life, and how to translate these for our well-being. Yoga is based on the humanitarian philosophy that the basic ingredients of happiness, though present inside everybody, remain untapped and thus inaccessible to many. It draws upon people’s innate wisdom and proposes utilization of the healthy perspectives available to everyone. In Yoga, health is just a preliminary preparation for achieving higher goals. Health is rather a very important side effect of the practice of Yoga (Iyengar 2001). In the all-encompassing and multidimensional aspects of Yoga, as evident in the Eight-limbed Yoga or the Noble Eightfold Path, one sees the balanced combination of the following: a healthy Yogic lifestyle (including the Middle Way, moral behavior, natural environment, and healthy diet), adequate bodywork through Yogic postures (asanas) and procedures (Sans. bandhas, mudras, and kriyas), breath work (pranayama), and techniques of mental development including concentration and mindfulness that lead to elevation of one’s consciousness to deeper meditative states (samadhis/samapattis) in the path of self-realization. Being mother to Ayurveda, the therapeutic system of ancient India (equivalent to the allopathic system of medicine), one can clearly see that Yoga doesn’t negate the use of medications and other methods of modern medicine (Frawley 1999).
Yoga is a technology to upgrade one’s internal infrastructure which is the source of all human experience. Therapeutic rationale of Yoga and meditation lies in the following three facts (this author calls it a trilogy):
(i)
All our experiences are created in the inside of us, but because of the projective (Sans. vikshepa) mechanisms, the mind is constantly running away from this inner locus.
(ii)
Because of this projective and centrifugal mechanisms of the mind, the experiencer (i.e., the self), the things experienced (i.e., the world with all its objects), and the medium/interface we use to experience (i.e., the mind and the associated sense organs) are not able to work in a harmonious manner. This internal disharmony leads to the distortion of our experience, leading to a state of cognitive–emotive dissonance. Modern science calls it stress; Yogic and meditative philosophies call it dvanda [Sans.] or klesha [Pali]. The stress, as we know, leads to poor health.
(iii)
Cognitive neuroscience informs us that our memories of things are the neural representation of information, which is nothing but internal representations in our brain and mind. Memory serves as a crucial parameter in shaping our experience. Memory is state dependent in the sense that there exists a relationship between encoding cues and retrieval cues in this process. Retrieval is a reconstructive process, not an actual replica of experience (Pally 1997, 2005). Meditative wisdom including those of Buddha and Patanjali informs us that amelioration of stress is possible by modification and reappraisal of our internal representations: this is done by the meditative insight about nature of these representations. As one can see here, these models are akin to the cognitive therapy models. Actually these models are broader in approach and more extensive in their applications, as we see from utility of mindfulness models like MBCT, DBT, Y-MBCT, etc. In addition, potential utility of these lies not only in illnesses but also in health. Over the millennia, Yoga and meditation have been advocated as a way of life as well as a kind of psychosomatic preparation for spiritual elevation. In these, one can see that Yoga reflects the basic human goal to transcend the pain, suffering, and uncertainty of human life. As a matter of fact, health has never been the main goal of Yoga; it is rather an important side effect of the practice of Yoga (Iyengar 2001). Patanjalian Yoga and Buddhist meditation have been handed down to millions of practitioners as tools for appreciably improving the health of a person physically, mentally, and socially. As reflected in a recent study (Prasad et al. 2011) conducted at the Mayo clinic, authors note that even 15 min of daily meditation practice can reduce stress and improve quality of life of the health care professionals. However, as elaborated later, the current methodology employed for the evidence-based study of Yogic interventions is not optimal. Yoga, a module of many do’s and don’ts, influences almost all aspects of our life that include but not limited to the diet, nutrition, metabolism, physical and social habits, emotional attitudes, and so on. This broad range of scope makes it rather difficult for researchers to experimentally determine the cause and effects of Yoga’s Dos and the Don’ts. So one important fact could be that these interventions are effective, but when we design a trial, we simply don’t have adequate methods to measure these experiential parameters. Despite these difficulties in measurements of the effects, Yoga–mindfulness–based interventions is feasible not only for treatment of psychotic illnesses like schizophrenia (Vancampfort et al. 2012) but also severe impulsivity like ADHD (Zylowska et al. 2008).
8.1.1 Why Yoga–Meditation if There Is a Pill?
The straight answer to this question is simple: there is no pill that can effectively address all our healthcare concerns. There are many good reasons for using Yoga- and meditation-based psychotherapy. It can be used alone or in combination with medication and both for illness and for optimizing wellness. Used for thousands of years, studies indicate these cost-effective interventions are effective not just in amelioration of psychiatric symptoms but also greatly useful in terminal illnesses like cancer. Another relatively untapped utility of Yoga- and meditation-based interventions is their great potentials in preventive medicine. Also the effects of these tools are not just on a particular body part or system or on a particular symptom. Rather, they influence the person and the life as a whole. If carefully performed under supervision, there are no side effects and even people with severe psychotic illnesses like schizophrenia could tolerate these interventions (Vancampfort et al. 2012). Yoga–meditation combines humanistic models with positive psychology and self-help models of care. Thus, they promote the autonomy of the individual which could decrease the burden of care not only in the caregivers but also in the healthcare providers. These therapeutic methods don’t negate the utility of appropriate pharmacological interventions, rather supplement them. These interventions could provide respite in circumventing some of the difficulties with the health care access in this managed care era.
8.2 Specific Effects of Yoga and Meditation on Brain and Body
Meditation, being a deeply contemplative and experiential phenomenon, affects multiple regions of the brain. In addition to the key structures (frontal circuits, thalamus, amygdala, insula, and other limbic areas) already described in Chap. 3, its most notable effects are on the brain structures associated with parasympathetic activity. Parasympathetic activities provide recovery from stress and general restoration of the organism. During meditation, activity of the right parietal lobe may decrease, which can induce dissolution of the sense of self in space and time (Newberg et al. 2002). This is apparently contributory to reduction in the self–other dichotomy, a crucial factor in creation of empathy. As has been shown in studies (Brefczynski-Lewis et al. 2007), extensive training in concentrative meditation (focused attentive: FA type) improves the ability to sustain attentional focus on a particular object. The study mentioned above involved investigation of the neural correlates of FA meditation in expert meditators (in Tibetan Buddhist traditions) and novices, using f-MRI scans of brain. FA meditation in this study increased activation in multiple brain regions involved in self-monitoring (the dorsolateral prefrontal cortex, DLPFC), attentional orienting (the superior frontal sulcus and intraparietal sulcus), and engaging attention (the visual cortex). As predicted, the meditation-related activation patterns depended on the level of expertise of the practitioner.
Some recent studies indicate that Yoga and meditation interventions induce not only functional changes in the brain but structural changes as well. Some of these changes are (i) increased gray matter in the insula (Lazar et al. 2005; Holzel et al. 2008), hippocampus (Holzel et al. 2008; Luders et al. 2009), and prefrontal cortex (Lazar et al. 2005; Luders et al. 2009); (ii) increased neural fiber density in the anterior cingulum (Tang et al. 2010); (iii) reductions in the thinning of the prefrontal cortex region due to aging (Lazar et al. 2005); (iv) improved psychological functioning associated with these key brain areas including attention (Tang et al. 2007; Carter et al. 2005), compassion, and empathy (Lutz et al. 2008); (v) decreased stress-related cortisol (Tang et al. 2007); (vi) strengthened immune response (Davidson et al. 2003; Tang et al. 2007); (vii) improvement of a variety of medical conditions including cardiovascular disease, asthma, type II diabetes, and chronic pain (Walsh and Shapiro 2006); (viii) improvement of many psychological conditions including insomnia, anxiety, phobias, and eating disorders (Walsh and Shapiro 2006); (ix) increased thalamic GABA levels, decreased anxiety, and improvement of mood (Streeter et al. 2007, 2010); and (x) positive effects on stress-induced changes in cognitive functions (Mohan et al. 2011).
8.3 The Basic Dilemma of a Researcher When Testing the Efficacy of Mind–Body Interventions
Wide-ranged applications and roles of Yoga and meditation in treatment and maintenance of psychophysical health are being proven in increasing manner and in the rigorous ways of evidence-based research in modern medicine. The studies are too many and actually overwhelming to be mentioned in a book chapter like this. It is worth mentioning here the difficulties inherent in conducting research in experiential disciplines in general and Yoga and meditation, in particular. In randomized controlled trials involving complex interventions like Yoga and meditation, the researcher is always faced with one basic dilemma of whether to design a trial with a single modality that does not reflect the true Yoga and meditation practice accurately or alternatively, to undertake a multifaceted Yoga intervention trial that complicates interpretations from a conventional evidence-based perspective. Historically, conventional medicine follows a reductionist or linear Cartesian framework. In this approach, complex problems such as chronic diseases are typically divided into smaller, simpler, and thus tractable units. Yoga and meditation interventions are experiential and holistic, encouraging integration and gestalt (the whole) over reductionism (the parts). Yogic concepts of the complex and ever-changing mind are nonlinear and dynamic. In terms of modern science, these theories are systems (nonlinear) models or complexity models. In a system, nonlinearity or complexity is said to exist when the amount of output is not proportional to its input, i.e., the system response to a sum of inputs is not simply the sum of their separate responses. Because Yoga operates on a global systems level that involves human mind and its numerous complexities, research into its use should assess numerous factors at many time points and/or spatial conditions and identify patterns that reflect global behavior rather than singular, distinguishing markers or variables. The concrete and linear reductionist approach to conventional randomized control trials cannot capture experiential changes and dynamism of complex mind–body interventions like mindfulness. The reductionist approach tends to reduce the evaluated system into individual parts and thus risks missing the therapeutically active elements of Yoga and meditation. The reductionist approach can sometimes make these elements appear nonobjective.
The other challenge in Yoga research is that while there is a strong need for examining utility in the evidence-based medicine format, being exclusively experiential and subjective in nature, transcendental experiences cannot be verified well by traditional experimental techniques. One really needs to be equipped with experiential measures for documenting the changes that follow the researcher’s direct meditative experience. For understandable reasons, many researchers do not have an authentic experience of Yoga and meditation. Apart from the experiential abstractness and heterogeneous use of yoga, there is a paradigmatic mismatch between the fundamental principles espoused by Yogic theory and many of the analytical tools and methods generally applied in clinical research. Also despite all the standardizations described earlier, there is an utter scarcity of good books describing standardized protocols for conducting clinical and research work on Yoga and meditation in homogenous and standardized manner. All these issues make interpretation of research on the efficacy of the interventions in Yoga and meditation very difficult. Similar difficulties are inherent in the studies that examine the efficacy of non-behavioral psychotherapies (e.g., psychoanalysis) as well.
Yoga deals mostly with the inner life, the facts of which are based upon experience no less than the facts of science. However, it may not be possible or even desirable to demonstrate them. The self-investigative spirits of Yoga to find the fundamental one have attracted not only philosophers and mystics but also scientists to the likes of Albert Einstein, Julius Oppenheimer, and Fritjof Capra. One can see that despite the seemingly unrelatedness, the common ground between modern science and mystic science is the basic interest to know the roots or the origins: the fundamental unity among all the diversities of life. As Capra (1975, p. 106) says: “The unity and inter-relation of all things and events is not only the very essence of the Eastern world view, but also one of the basic elements of the world view emerging from modern physics. This concept of unity among diversity is the key principle which explains how the Hindus can cope with presence of so many Gods (330 million!). The basic attitude of Hinduism is that in substance, all these divinities are identical. They are all manifestations of the same divine reality, reflecting different aspects of the infinite, omnipresent, and the ultimately incomprehensible Brahman.” The ultimate aim of all branches of science is discovery of the Fundamental One, the Unity, the one appearing as many out of which the manifold is manufactured. Yoga as a science has similar aims, and it proposes to start from the internal world (the subtle, the locus of experience) and, through that, to achieve control over the whole—both internal and external (the gross, the effect of the subtle).
8.3.1 Methodologically Sound Clinical Trial of Mindfulness Interventions: Essentials
A recent meta-analysis regarding the use of mindfulness interventions for insomnia (Kanen et al. 2014; accepted for publication) conducted by this writer and colleagues further illustrates these points and describes what a proper (scriptural) methodology for mindfulness-based trial could entail. These points are based on the following rationale taken from the scriptures. Buddha called mindfulness as one way to achieve the end of suffering. Essentially a proper methodology for a clinical trial to test the efficacy of mindfulness-based intervention should consist of the actual methodology of meditation as they have been described in the original scriptures. When designing a research trial on Yoga and meditation, some of the methodological shortcomings could be avoided by adhering to the outstanding texts, both classical and modern, that describe these interventions in more authentic manner. These include but not limited to Buddhaghosha (430 CE) (trans. Nyanamoli, 1976; this whole book is devoted to description of meditation and its methodology), Nyanaponika (1965, p. 85–107), Eliade (1969, p. 162–199), Vivekananda (1956), Taimni (1961), Kabat-Zinn (1990), Santina (1997, p. 333–339, 341–347), and Segal et al. (2002, 2013). The human mind is graded with respect to its ability to perceive reality, and mindfulness is the process of cultivating one’s attention (concentration) that produces the higher grades of mind. Like we sharpen a pencil for a purpose, i.e., to write, similarly, by means of meditation we sharpen the mind for a definite and higher purpose—in this case, the wisdom in order to attain freedom from suffering or distress. Because meditation by itself is not enough, it must be combined with the wisdom (Pali. panna) or meditative insight (vipassana), the purpose being its generalization to daily life, to ameliorate the sufferings. In mindfulness trials, therefore, interventions should include both elements of meditation, concentration and mindfulness, as the concentrated state of mind is a prerequisite for achieving mindfulness. In addition, there needs to be a standardized way to implement the meditative wisdom into one’s daily life. Middle Way is such a meditative lifestyle but has not been used that much in the published Yoga–meditation efficacy trials.
In the light of above discussion, let’s examine the clinical situation insomnia and what a sound design of clinical protocol of mindfulness interventions could entail. For insomnia, clearly the target areas for interventions include the suffering or symptoms of insomnia and the attending dysfunctions. In original scriptural traditions, combining concentration, meditation, and wisdom in a methodical manner for amelioration of distress is necessary. In the traditions of developing Right Mindfulness (sati patthana), the original method of meditation described by the Buddha, the cultivation of stable and focused attention (concentration/bare attention) is prerequisite for the subsequent stage of mindfulness (this involves using bare statements in the four stations of mindfulness) in which uniformly hovering attention provides mindful observation of present mental contents with a nonjudgmental and detached attitude. Cultivating mindfulness involves two processes: (a) development of bare attention/concentration and (b) cultivation of mindfulness, a purely receptive and detached state of awareness, while still maintaining the bare attention. Sequential use of both (a) and (b) in one’s daily life results in amelioration of symptoms and sufferings. This merger of daily life with Right Mindfulness (bare attention/concentration + detached and receptive awareness of mindfulness resulting in clear comprehension/vipassana) is the hallmark of sati patthana. The bare attention is clear, single-minded awareness of the bare facts of perception of an object, the simple registering of the facts about that object without elaboration from subjectivity/self-referencing. Simply said, it is just registering the bare event as it is and moving on to the next moment without sinking into the store house of memory, preventing distortion of the facts. Bare attention about an object allows the object to speak for itself and thus keeps the narrowing and leveling effects of habitual judgment at bay; it sees the objects ever anew, as if for the first time. The Right Mindfulness needs to be practiced with respect to its four stations: (i) mindfulness toward body and breathing, (ii) mindfulness toward state of mind, (iii) mindfulness toward feelings, and (iv) mindfulness toward mental contents (i.e., one’s thoughts, feelings, perceptions, memory, and will/desire about the object in one’s awareness at that particular moment). These four stations of mindfulness are basically the four specific applications of mindfulness in a symptom-specific manner. In the case of insomnia, the essential elements in the intervention could be meditation on insomnia and its attending dysfunctions (sufferings in Buddha’s terms) using the four station of mindfulness. With respect to insomnia, these four contemplations are, respectively, as follows: (a) contemplating upon bodily sensations (lethargy, etc. pain) associated with insomnia, using the mindfulness breathing to ameliorate and transcend these bodily sensations. This is followed by the three contemplations on mind using the bare attention and bare statements: (b) contemplating upon the state of mind (the bare statement in this case is the mind at this moment is unpleasant), (c) contemplating upon the feelings (the bare statement here is the mind at this moment is filled with anger/frustration), and (d) contemplating upon the contents of mind in a detached and uniformly attentive manner, rather than clinging to the mental contents, building a personal story of suffering, and losing the mindfulness state. As mentioned before, in this station, one sees the mental objects as they are, i.e., seeing thoughts objectively as just thoughts, feelings as just feelings, and perceptions as just perceptions at that moment without identifying them. This in itself will provide the mindful practitioner the wisdom about insomnia, which will guide him/her in carrying out the actions needed to alleviate this suffering, i.e., the symptom of insomnia and its attending dysfunctions.
8.3.2 Efficacy of Yoga and Meditation: Empirical Evidence
Despite the abovementioned difficulties in interpreting the research on Yoga and meditation, in a recent meta-analysis (Goyal et al. 2014) that included 47 trials with 3,515 participants, evidence suggested that meditation programs help reduce anxiety, depression, and pain in some clinical populations. The author concluded that “clinicians should be prepared to talk with their patients about the role that a meditation program could have in addressing psychological stress. Future research in meditation would benefit by addressing the remaining methodological and conceptual issues.” In another recent article published by researchers from Columbia University, New York (Miller et al. 2014, p. 1–8), a 5-year longitudinal study assessed whether high-risk adults who reported high importance of religion or spirituality had thicker cortices than those who reported moderate or low importance of religion or spirituality and whether this effect varied with family risk status. This prospective study, which involved 103 adults who were at familial risk for depression, strongly suggests that religion and spirituality may build resilience against depression by toughening the brain. The researchers found that the brain cortices of subjects who placed a high importance on religion or spirituality were thicker than the brain cortices of those who did not. In addition, the brain cortices were especially strong in those individuals who placed a high importance on religion or spirituality and who had a high risk of depression. The authors of this study conclude that a thicker brain cortex associated with spirituality may confer resilience to the development of depressive illness in individuals with high familial risk for major depression, possibly by expanding a cortical reserve that counters the vulnerability that cortical thinning poses for developing familial depression. They further add: “This study points to measurable, beneficial effects of presumably healthy spirituality, especially for individuals with biological predispositions to depression, and adds to substantial and growing evidence that psychiatrists should support healthy development in that sphere of patients’ lives.” These findings are consistent with the general impressions form other researchers regarding the efficacy of Yoga- and mindfulness-based interventions (Segal et al. 2002, 2013); Kabat-Zinn et al. 1992). The preliminary data from this author’s outpatient clinic at the Cooper University Hospital, Camden, New Jersey (September 2012-May 2014; unpublished), reflect the methodology described earlier and concur with the findings mentioned above with respect to the efficacy of interventions using Yoga and meditation.
8.4 Yoga in Maintenance of Psychophysical Health: Attention and Memory Are the Main Tools
Because of shortcomings of conventional methodology in interpreting Yoga and meditation interventions and relative scarcity of access to standardized manuals on Yoga and meditation in an evidence-based format, it will not be that useful to quote the numerous research studies that examine the efficacy of Yoga and meditation in health and illness. Instead, discussion of a conceptual paradigm on the rationale and the evidence-based ways to use Yoga and meditation in health and illness could serve the purpose better, i.e., to foster further development of standardized and integrated protocols for both clinical and research use of these invaluable therapeutic interventions. The three main reasons for the use of Yoga–meditation in maintenance of one’s psychophysical health are:
(a)
Yoga is a profound psychosomatic science.
(b)
Meditation is a science of attention.
(c)
Yoga and meditation interventions are essentially models of self-care not only for stress reduction and improvement of productivity and quality of life but also can be used in targeted and symptom-specific manner in illnesses.
All meditation practices involve stilling the mind (concentration) whereby all content-laden thoughts (e.g., fantasies, daydreams, plans) cease and the mind enters a state of mindfulness, i.e., open and detached awareness, formlessness, clarity, and bliss. This cultivation of stable attention (and memory) during the meditative process is a key parameter in its use for stress reduction, increasing productivity in daily life as well as for optimization and maintenance of psychophysical health. This understanding has great therapeutic potential in the treatment of disorders of attention and memory including ADHD, dyslexia, and other cognitive disorders in which use of Yoga and meditation is relatively untapped until recently. Some of these are elaborated in the previous chapters of this book. As emphasized in the Chaps. 2, 3, and 4, meditation (mindfulness) is the main step of Yoga; attention (and memory) is its main tool: they deserve more discussion here. This understanding is quite pertinent in order to understand the full scope of the utility of Yoga and meditation in psychophysical health.
8.4.1 Meditation, Attention, and the Default Mode Network of the Brain
The various brain areas involved in meditation are already described in Chap. 3. Meditation is the science of cultivation of attention in which a major task is to observe and regulate our internally generated thoughts. The classic definition of attention by James (1890, p. 403–404) is “the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.” During meditation we close our eyes, focus on our internal train of thoughts, and try to block/uncouple the mind (internal analyzing system) from the external sensory/perceptual inputs. During periods of internally guided thought, perceptual decoupling occurs temporarily, i.e., processing of perceptual information (external distractions) is neglected. However, the internally and externally driven streams may compete and attention can be rapidly recoupled to perceptual events if salient external events occur.
The default mode network is a network of brain regions that are active when the individual is not focused on the outside world; rather, it is involved in internal train of thoughts (day dreaming is an example of this), and the brain is at wakeful rest. The ability to generate and sustain these internal trains of thoughts (internally driven cognitions) unrelated to external reality frees one from the constraints of acting on immediate, environmentally triggered events alone. Smallwood et al. (2011) propose that such thoughts are produced as a result of cooperation between the default mode network and a frontal–parietal control network. The default mode network provides the autobiographical information of the individual that acts like a scaffold for the frontal–parietal network to further sustain the internal trains of thought and buffer them from the disturbances of the external world. In the process, the attention generated by the frontoparietal network suppresses the irrelevant external (perceptual) information. The engagement of the internally guided trains of depends mainly upon the perceptually guided cognition and less upon external physical referents for cognition. Because access to the top-down attentional control system (from cerebral cortex downward) is generally a prerequisite of conscious experience, during periods of internally guided thoughts (like in meditation), activation of top-down attentional control system and the default mode activity often operate simultaneously. On the other hand, the bottom up system (neural pathways from the peripheral sense organs to the cerebral cortex; see Chap. 3) feeds the cerebral cortex, the highest center for information processing.
8.4.2 The Basic Mechanisms Involved in Attention
Attention, memory, and intelligence are closely interdependent processes. In a connectionist view of how the brain processes information, O’Reilly and Munakata (2000) identified three kinds of processing performed by neural networks of the human brain: (i) a slow learning type involving learning the overlapping and distributed representations of the environment (related to semantic memory and crystallized intelligence) that is performed by the posterior cortex, (ii) active maintenance of limited amounts of information over short time intervals enabling the problem-solving functions of the prefrontal cortex (related to concepts like working memory, executive functions, and fluid intelligence), and (iii) rapid acquisition of novel information by the hippocampus (this concept is related to episodic memory). Fluid intelligence refers to global problem-solving proficiency, and crystallized intelligence is characterized by collected and primarily verbal knowledge.
Attention
William James, one of the first modern experimental psychologists and the author of the lengthy textbook The Principles of Psychology (1890), provides a complete description of the phenomenon of attention. The immediate effects of attention allow us: (a) to perceive, (b) to conceive, (c) to distinguish, (d) to remember things more clearly, and (e) to shorten our reaction time in response to a task. From this, one can easily see the connection between one’s attention and memory. As mentioned before, memory is closely related to intelligence. Smart individuals are of two kinds: those in the first category know a lot but are not proficient problem solvers, whereas people in the second category know less but are skilled at problem solving. Neuropsychologists conceptualize these two types of intelligence as: (a) crystallized intelligence, which is involved in the first type of smartness, i.e., knows a lot category (this intelligence increases at least into middle age), and (b) fluid intelligence, which is involved in the second type of smartness, i.e., the good problem solver category. This intelligence reaches its zenith in late adolescence and slowly declines thereafter. Fluid intelligence is more vulnerable to brain damage and aging.
Dual Attentional Systems in the Human Brain
Cognitive neuroscience research has found that the human brain employs dual systems of attention that consists of a posterior/dorsal system and an anterior/ventral system (Fox et al. 2006). The posterior system orients and engages novel stimuli in order to achieve a task and consists of the superior parietal cortex, superior colliculus, and the pulvinar. It receives dense norepinephrine (NE) innervations from a key brain area called the locus ceruleus. NE inhibits the spontaneous activity of postsynaptic neurons (in this case, the parietal cortex) and thus allows us for better orientation by increasing the signal-to-noise ratio of target neurons. Localized in the prefrontal cortex (PFC) and the anterior cingulate cortex (ACC), the anterior system subserves the executive functions (problem-solving abilities) and helps maintain a focus. It is modulated by ascending dopamine (DA) fibers from the ventral tegmental area (VTA). DA suppresses spontaneous activity of target neurons (in this case, the PFC) and reduces their responsiveness to new inputs thus allowing us to better focus. Any severely challenging task puts extreme pressure on both these attentional systems. Performance declines as the attention is fatigued and careless mistakes are made. Anxiety develops in response to too much arousal, further exacerbating the poor performance, and even more mistakes are made. Here, it is worth mentioning the work of Diamond et al. (2007) on the Yerkes–Dodson law (1908) that stipulates that one’s performance increases with physiological or mental arousal eventually reaching a plateau. When levels of arousal become too high, performance decreases. Graphically, this is represented as an inverted U-curve where arousal is in the x-axis and performance is in the y-axis. The upward part of the inverted U represents the energizing effect of arousal and the downward part represents the negative effects of arousal (or stress) on cognitive processes like attention, memory, and problem solving.
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