Rewire Your Brain: Think Your Way to a Better Life
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Central
Nervous Neurotransmitters Brain Structures System Oxytocin OFC Vagus nerve Dopamine Amygdala Vasopressin Insula Cingulate cortex Mirror neurons Spindle cells These systems provide you with the opportunity to form rich and multidimentional social relationships. Consequently, there are many forms of social communication. One of the most basic is based on touch. Touch The skin is the largest organ in the human body. It contains two dif- ferent types of receptors: (1) those that help you to locate, identify, and manipulate objects, and (2) those that help you to connect with other people through emotion. This second, socially connective function has been shown to facilitate mental and physical health and longevity. Touching and being touched have many important evolutionary functions. In other primates, for example, mutual grooming promotes social cohesiveness and bonding. Touching expresses reassurance and affection. Partly for this reason, being touched by someone else is more pleasurable than touching yourself. Not only does it rep resent bonding and/or sensuality, it also feels better because it is unpredictable. Touching and being touched promote biochemical changes in the brain. The secretion of the neurotransmitters dopamine, oxytocin, and endorphins occurs with caressing, comforting, and soft touch- ing; this promotes closeness with a person as well as feelings of well - being. Touching has also been associated with lower levels of stress hormones and enhanced brain cell survival. c07.indd 147 c07.indd 147 1/29/10 10:27:37 AM 1/29/10 10:27:37 AM 148 Rew i r e Yo u r B r a i n Touching has been shown to enhance the immune systems of peo- ple who are suffering from various illnesses as well as the immune systems of the people who are caring for them. For example, thera- peutic back massage has been shown to enhance the immune func- tions of people who have cancer. Touch has been shown to positively affect the aberrant behavior of people of all ages. Depressed and/ or aggressive adolescents have benefi ted from touch, and agitated elderly people in nursing homes are calmed by hand massages. Touching is therefore an important way to connect with other people and produce changes in their brains as well as in your own brain. President Obama must intuitively know this, for he often adds warmth to a handshake by placing his left hand on the shoul- der of the person with whom he is shaking hands. The Effects of Nurturance and Its Deprivation Caring for others and being cared for by others have powerful effects on the brain from the moment of birth. A graphic example of how the lack of nurturance can affect the brain occurred in Romania. After the repressive regime of Nicolae Ceausescu was overthrown in 1989, more than 150,000 children were found lan- guishing in Romanian orphanages. They were malnourished and neglected, and many were dying of infectious diseases. Typically, one person cared for thirty or more children. The children were fed and kept clean but otherwise received minimal care. The orphans often resorted to such primitive methods of self - stimulation as head-banging, incessant rocking, and hand-fl apping. They exhibited multiple developmental delays because they missed human contact during critical developmental periods. Infants less than a year old who were placed in Romanian orphanages for more than eight months had higher cortisol blood levels (an indica- tor of signifi cant stress) than orphans who were adopted within the fi rst four months of their lives. The cortisol levels of children who were institutionalized beyond eight months continued to increase. This means that the longer they were deprived of nurturance, the greater were their stress levels during childhood. c07.indd 148 c07.indd 148 1/29/10 10:27:37 AM 1/29/10 10:27:37 AM S o c i a l M e d i c i n e 149 As middle - class European, Canadian, and U.S. couples began to adopt some of these children, they were faced with the daunting problem of managing the tragic effects of early neglect. Several stud- ies have examined how these children have adapted to their adoptive families and how they have fared in school. For example, British psychologist Michael Rutter compared 156 Romanian orphans who were adopted by age three and a half and compared them to fi fty nondeprived children who were adopted before six months of age. All the children were followed longitudinally and were examined for a variety of behavioral problems. The Romanian adoptees were more likely to exhibit behavior problems such as ADHD, autistic - like problems, and cognitive impairment. These problems were more likely to occur among children who left the Romanian orphanage after their second birthday. The children who left Romania prior to six months of age resembled the nondeprived children adopted in Britain. The risk of developing behavioral problems increased for the children who were adopted after six months of age from a Romanian orphanage. The risk was greatest if they were adopted after age two. This study shows that during the fi rst year of life, a baby thrives on nurturance or is stunted by the lack of it. The effects on the brain have a profound bearing on how successfully the children will adapt to the world later in life. The British study was not the only one to illustrate the powerful effects of being deprived of nurturing, especially early in life. A similar story occurred in Canada, where children from Romanian orphan- ages were adopted by parents in British Columbia. The Canadian researchers found that the Romanian children who had spent at least eight months in a Romanian orphanage had signifi cant devel- opmental problems, whereas those who spent less than four months there did not suffer the same degree of impairment. Similarly, the Romanian orphans who were adopted by U.S. fami- lies continue to show many of the same symptoms of their early social deprivation. They have been described as being stoic, being uninterested in playing, tending to hoard food, and having diffi culty crying or expressing pain. Brain scans revealed that key parts of their social brain, such as the OFC, were underactive. c07.indd 149 c07.indd 149 1/29/10 10:27:38 AM 1/29/10 10:27:38 AM 150 Rew i r e Yo u r B r a i n A deprivation of nurturing can also cause signifi cant neurochemi- cal abnormalities. Research on adult animals separated at birth from their mothers revealed persistent abnormalities in the production and normal functioning of neurotransmitters, including alterations in the following: • The expression of dopamine transporter genes • The dopamine - mediated stress response • The expression of serotonin receptors • The expression of benzodiazepine receptors • The infant ’ s sensitivity to morphine • The cortisol receptors related to stress response The extremes of deprivation described above are not common. It is far more common for mothers to be less than attentive to their babies. What if your mother was distracted and preoccupied with her own problems? The research on babies of depressed mothers has shown that these infants behave as if they too are depressed, even in the presence of nondepressed adults. Maternal depression causes multiple defi cits and developmental problems in children, including not only behavior problems but also neurological and biological problems. For more than twenty years, Tiffany Field and her colleagues have demonstrated that infants of depressed mothers have a wide range of problems. For example, infants of depressed mothers have displayed increased aversion and helplessness and have vocalized less. They have had higher heart rates, decreased vagal tone and developmental delays at one year old. Just as a deprivation of nurturing can damage the brain, a grow- ing body of research shows that nurturance has a protective effect on the brain and on psychological development. For example, one series of studies showed that rat pups that were handled became more resistant to stress and lived longer. Among the brain systems that benefi t from nurturance are the hippocampus and its receptor sites for stress hormones such as cor- tisol. Excessive stress can damage the hippocampus through exces- sive exposure to cortisol, causing dendrites in the hippocampus to c07.indd 150 c07.indd 150 1/29/10 10:27:38 AM 1/29/10 10:27:38 AM S o c i a l M e d i c i n e 151 shrivel up, but with early nurturance, the cortisol receptors actually multiply. These receptors provide a negative feedback loop, like a thermostat. When stress hormones fi lter into the brain, the recep- tors in the hippocampus are triggered and the production of cortisol is shut down, as if to say, “ I ’ ve had enough of that stress hormone; no more is needed. ” However, when there are too few receptors, a different response is triggered, as if to say, “ Make more stress hormones! ” The negative feedback loop thus keeps stress low and comfort high when you are provided with nurturance. When you are nurtured, you are better able to nurture others. For example, the research on rat pups showed that the rats that were cared for with licking and grooming grew up to do the same for their offspring, but the rat pups that were not nurtured in this way grew up to neglect their pups. To factor out any genetic infl uence, the researchers had less attentive mothers raise the offspring of nurtur- ing mothers, and vice versa. The rat pups born to the inattentive mothers but raised by attentive mothers grew up to be indistinguish- able from the biological offspring of the nurturing mothers. They were signifi cantly less fearful when put in unfamiliar surroundings, just like those who were born of and raised by nurturing mothers. The opposite occurred when the biological offspring of nurturing mothers were raised by inattentive mothers: they grew up to be neurotic and fearful adults. Thus, the genes that you were born with have less effect on you than nurturing does. Researchers have also found that the gene that produces the glucocorticoid receptor (cortisol in humans) in the hippocampus is twice as active in rat pups raised by nurturing mothers as in those raised by inattentive mothers. It appears that receiving nurtur- ance causes an increase in a molecule that increases production of the glucocorticoid receptors in the hippocampus (Weaver, Cervoni, Champagne, D ’ Alessio, Sharma, Seckl, et al., 2004). That gene produces more receptors, which provide an enhanced thermostat and resistance to stress. In other words, nurturance turns your genes on or off. This means that if you were lucky enough to be nurtured, your brain went through structural changes that helps you manage stress. This doesn ’ t mean that you won ’ t experience stress, of course. c07.indd 151 c07.indd 151 1/29/10 10:27:38 AM 1/29/10 10:27:38 AM 152 Rew i r e Yo u r B r a i n It just means that you are better prepared for it than people who did not receive as much nurturance. Despite the importance of early nurturance, you can still gain brain - based benefi ts from nurturance throughout your lifetime. If you were lucky to receive enhanced nurturance early in your life, it gives you a head start in gaining from all the benefi ts of social medi- cine. Through the power of neuroplasticity, you can either enhance or enjoy the benefi ts of the positive nurturance or, like Marc, repair the limitations you ’ ve acquired from poor nurturance. In the next section I ’ ll explain how having a secure relationship with your parents helps you to develop secure relationships with others. Secure relationships form the basis for good mental and physical health. If you haven ’ t experienced those types of relation- ships yet, there ’ s still time. If you are fortunate to have experienced secure relationships, you can build on them. Bonding and Attachment Since the beginning of your life, your emotions have functioned as a means of communication with your caregivers. Your emotions can be understood as feelings, reactions, and behaviors that arise in response to personally signifi cant situations or events. Bonding begins at birth, then becomes the foundation for your communication skills. Psychologists refer to these bondings as attachment relationships because they represent the degree to which you were attached to your caregivers. Early bonding begins before the development of language, and many of the basic attachment patterns are formed during the period of right hemispheric domi- nance, which is during the fi rst two years. The right hemisphere continues to play a dominant role in appraising, contextualizing, and establishing the meaning of your interpersonal experiences. The amygdala, too, plays an important role in mediating early attachment relationships. Highly connected with other brain areas, the amygdala stamps the incoming stimuli with emotional value in a very quick, black - and - white, good - and - bad manner. The amygdala c07.indd 152 c07.indd 152 1/29/10 10:27:38 AM 1/29/10 10:27:38 AM S o c i a l M e d i c i n e 153 does this with stimuli coming from within you as well as with the external stimuli that come in through your ears, eyes, and skin. Like the right hemisphere, the amygdala is important in appraising the meaning of facial expressions and other emotional communications that you received fi rst from your caregivers and now in your relation- ships with others. Developmental psychologists have used a variety of methods to explore how early attachment relationships play a signifi cant role in the type and quality of your relationships later in life. For example, Mary Ainsworth devised an experimental situation called the Yüklə 1,07 Mb. Dostları ilə paylaş:
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