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Chapter 7


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Kira A Borden

Chapter 7 THE NEUROSCIENCE OF PERSONALITY - Meditation is a way that you could be healthier and happier. Although some religious and cultural traditions embrace meditation as a powerful spiritual practice, modern medical research has traditionally scoffed at alternative treatments. - Overall, the data suggest that regular meditation fundamentally changes how our brains work and that its activation is related both to the emotions we feel and to how we respond to stressful events. The researchers surmised that meditation makes people more open to experiencing positive emotions and less reactive to negative emotions with the overall effect of decreasing their anxiety and improving immune functioning- all of this without drugs! - When it comes to understanding our biological functioning and personality, it’s like the question of which came first, the chicken or the egg: Does your physiology determine our personality, or does our personality determine our physiology? - We may be born with a certain physiology that may cause us to develop certain traits, but the environment can modify aspects of our personality. Perhaps the best way to think of our physiology is as a package of potentialities for personality traits that may be devekoped, discouraged, or even modified by our experiences. - However, at the same time research such as the meditation study suggests that our behavior also affects our physiology. What is Neuroscience and How Do We study it? - Researchers who explore the neuroscience behind personality focus on the brain and the nervous systems. - The nervous system is made up of the central nervous system and the peripheral nervous system. - The central nervous system includes the brain and the spinal cord whereas the peripheral nervous system includes the somatic nervous system (outside), which controls movements of the muscles, and the autonomic nervous system (inside- controls the inner body) which regulates smooth muscles (inner movement) ( eye blinking) (e.g., inner organs), cardiac muscle, and glands. - The autonomic nervous system is further divided into the sympathetic division and the parasympathetic division. - The sympathetic division mobilizes energy (e.g., for fight or flight) { nervous , stores the energy }, whereas the parasympathetic division supports systems that replenish the body’s energy stores (e.g., salivation, digestion, ect). (opposite)- try to make your body normal - The brain is protected by a bath of cerebrospinal fluid (CSF) that cushions the delicate brain and also flows through spaces in the brain called ventricles. CSF is similar to blood plasma, and is continually produced, circulated and reabsorbed through the brain and the ventricles. - The brain contains a number of structures and systems that control everything from thinking, reasoning, learning, and memory, to breathing, sleeping and eating , to movement and the processing of sensory information, to the experience of emotions. Because all of these parts are crucial for basic functioning, we should not expect to see large differences among people. - However, individual can vary in all kinds of ways, from how they may respond to stress (e.g., heart palpitations, sweating) to what they think is happy or sad, to how they respond to hormones and drugs. - Researchers hypothesize that differences in bodily responses, brain structure, brain activity and biochemical activity are all related to individual differences in personality. Bodily Responses - When our body responds to arousing events in the environment it is the autonomic nervous system that responds. When aroused, the sympathetic division responds by increasing heart rate, blood pressure, blood flow to the extremities, respiration, sweating, and muscle activity. - Sweating is measured by galvanic skin response (GSR) which is a measure of skin conductance or how quickly a slight electrical current passes through two points on the skin. The faster the conductance of the current, the more moisture is present that indicates greater arousal. - Muscle activity is measured by electromyography (EMG) or myoelectric activity, which estimates the electrical impulses of the muscles during contraction and relaxation. EMG is often used in biofeedback to train people to perceive muscle contractions so that they can learn to relax their muscles. Brain Structure - In the past, the only way of studying differences in brain structure and cells was through dissecting the brain after death. During an autopsy the brain may be removed and sections of tissues preserved for cytological (cell) study. - Today, through the advent of more sophisticated techniques we can study the structure of a living human brain through noninvasive procedures. - For example, computerized tomography (CT), called a CT scan, takes a high-resolution x-ray picture of the brain By looking at thin cross sections of the brain- often less than a millimeter!- details we can detect abnormalities or differences in the brain tissue. (This same technique was once called computer axial tomography [CAT] or CAT scan). - Bone injuries , used for cancer , short time - Magnetic resonance imaging (MRI): a high-resolution three-dimensional picture of the brain tissue obtained by the use of radio frequency waves. First, a strong magnetic field causes the nuclei of some atoms to resonate. Then radio frequency waves are used to detect the activity of these atoms. Because hydrogen atoms are present in all tissues but in varying concentrations, the pattern of resonance formed by the hydrogen atoms forms a multidimensional picture of the brain. Soft tissues , a lot of time Brain Activity - Both CT scans and MRIs can detect only static pictures of the brain- that is, pictures of brain structure at one moment in time. - Measures of brain activity are ways of looking for differences in brain structures while the brain is stimulated. Often, participants are given a mental task to work on or other stimuli to react to while measures of brain activity are taken. - One early technique of studying brain activity is cortical stimulation. Using either electrodes implanted in the brain or direct electrical stimulation of parts of the brain, the patient is awake and can report on sensations as various parts of the brain are being stimulated. - Today, we are able to sue less invasive procedures. - For instance, in an electroencephalogram (EEG) electrodes are placed on the scalp to monitor electrical activity of the brain. - When electrical activity of the brain or other part of the nervous system is measured in response to a specific stimulus, this is called an evoked potential (EP). - Both EEGs and EPs indicate amount of brain activity in response to a stimulus. However, the newer techniques identify the exact location of brain activity. - In positron emission tomography (PET), called a PET scan, a slightly radioactive glucose like substance with a very short half-life (rate of breakdown) is injected into the brain and the person is placed in a scanner similar to a CT scanner. Active regions of the brain use up more glucose than inactive regions and, with the aid of computer enhancement, scans of these rgions appear in different colors related to their activity level. - The most detailed view of brain activity at a cellular level comes from functional magnetic resonance imaging (fMRI) - Functional magnetic resonance imaging (fMRI): a high-resolution three-dimensional picture of brain activity over time using blood oxygen levels. Color enhancement is used to identify amount of activity across many regions of the brain. - Though the use of fMRI for personality research is on the rise, there are some notable problems with fMRI research. One problem is timing of response. When viewing a stimulus, our thoughts react within milliseconds whereas blood flow takes about 2 seconds. This makes it difficult to pinpoint the precise area that fired at the exact moment of a thought or reaction. - Another problem is that the procedure is time-intensive and the equipment expensive so that often experiments use only a small number of participants Small sample sizes make it difficult to find a reliable and significant effect. - A third problem called the nonindependence error is that researchers may unintentionally bias their results by not independently selecting which brain areas to correlate wit, say, personality characteristics or other variables. - Lastly, confounds such as time of day and nervousness of participants can also affect the results of neuroimaging studies. - One of the newest techniques for studying brain activity is transcranial magnetic stimulation (TMS). - Transcranial magnetic stimulation (TMS): using an electrical current to disrupt or enhance neuron functioning to pinpoint with greater accuracy than other techniques an exact area of brain function. - With TMS a brief electrical current passes through a coil placed on the head. The magnetic field disrupts the regular activity of the neurons, sometimes impairing and sometimes enhancing function. By carefully mapping parts of the brain that are stimulated and noting what kind of functioning is disrupted, researchers are able to pinpoint with greater accuracy than cortical stimulation or EP the exact area affected. - There is one major problem with interpreting the results of brain scan research: what exactly does it mean when an area reacts in response to certain stimuli? According to critics of brain localization techniques, it could mean a number of things. he area is center for tht characteristic or response. o PET: area might hve glucose cuz tht is working less sufficient needin more glucose. Biochemical Activity Neurotransmitters are chemicals released by neurons to inhibit or excite the next neuron into action. - Neurotransmitter help transmit signals through the nervous system. Some important neurotransmitters are norepinephrine, epinephrine, dopamine, and serotonin. - These all have a similar molecular structure, so that drugs that affect one tend to affect all of them. Norepinephrine (noradrenaline) and epinephrine (adrenaline) are also considered stress hormones. - They help the body deal with threat by increasing blood flow to the muscles which increases heart rate and blood pressure. - Dopamine is related to feelings of pleasure and helps regulate movement, learning, attention, and rewards. - Serotonin is involved with mood regulation, arousal, the control of sleeping and eating and pain regulation. Depression, anxiety and other mood disorders are related to how the body processes serotonin. - The enzyme monoamine oxidase (MAO) regulates, to some degree, the availability of dopamine, norepinephrine, and epinephrine in the system. - Norepinephrine and serotonin may also be related to symptoms of depression. - Antianxiety drugs work by mimicking another neurotransmitter, gamma-aminobutryric acid (GABA), an inhibitory neurotransmitter. - Researchers may study neurotransmitters and the systems that process them by having participants engage in a task or activity and monitor the fluctuations in these chemicals. - When it is impossible to directly measure the level of neurotransmitters- as with norepinephrine, for example- researchers indirectly monitor how the neurotransmitter is being used by measuring known byproducts of neurotransmitter metabolism. - Another way is through a challenge test in which researchers administer a drug that is known to either increase or decrease a neurotransmitter’s functioning and monitoring the impact of this new substance on reactions presumed to be related to the neurotransmitters. Research Methods Illustrated: Correlational Designs II: Scatterplots, Correlations, and the Alleged ‘Voodoo Science” of fMRI Studies. Scatterplots or scattergram: a two-dimensional graph that shows the relationship between two variables. - They show the scatter or spread of the data. - Many brain-imaging studies will use scatterplots to illustrate their results. Each point represents a participant in the study. - The line through the clouds of points is called a linear regression line and it estimates our best guess of how we can predict y-values from x-values. Neurological Theories of Personality - Hans Eysenck noted that even as we recognize that a substaintial portion of our personality is inherited ‘there must be biological intermediaries between DNA and personality, and these intermediaries should be specified by theory and investigated’. These biological intermediaries, what Eysenck’s technology was not sufficiently advanced in 1947 to detect, are physiological differences. - Despite bigger and better and less invasive techniques and even with the ability to decode the smallest gene, protein, and neurotransmitter, scientists are not able to find consistent physiological differences that relate in a clear way to differences in personality characteristics. - It may be that our techniques are not up to the task or it may be that aspects of the human nervous system interact in complicated ways that we have yet to untangle. - Maybe biology has the biggest impact at a broader, more general level of personality, called temperament. - Temperament: a set of personality characteristics that are 1. Relatively stable across the life span 2. Expressed through general energy level 3. Present from early childhood 4. Similar in other species of animals 5. Present at birth, at least in a general way 6. Determined by genetic factors 7. Changeable with maturation and experience In their search for the biological basis of personality nearly all major personality typologies converge on three primary temperaments, or clusters of related personality traits:  Extraversion: Positive emotion, reward sensitivity, social rewards, sociability, approach.  Neuroticism: Negative emotion, anxiety, punishment sensitivity, withdrawal.  Impulsivity: Psychoticism, lack of constraint, sensation seeking, novelty seeking, lack of conscientiousness, lack of agreeableness. - There has been striking similarity in the various models that researchers have proposed. For example, Eysenck’s Psychoticism, Extraversion , and Neuroticism model (PEN model), the five- factor model, the Big Five, Grays RST and Cloninger all posit at least two of these three dimensions as part of their theories. - However, both the FFM and the Big Five split Eysenck’s Psychoticism factor into Agreeableness and Conscientiousness. Table 7.2 Correspondence Among Three Personality Clusters and Major Trait Theories Theory Extraversion Neuroticism Impulsivity Eysenck Extraversion Neuroticism Psychoticism Gray Behavioural Approach Behavioral Inhibition System System Five Factor Extraversion Neuroticism Low Conscientiousness Cloninger Reward Dependence Harm Avoidance Novelty Seeking Eysenck’s PEN Model - When Eysenck first started working in the 1940s, he was unusual in his desire to build a personality theory based on experimental findings. Further, he believed that a comprehensive theory should explain how people developed their personalities as well as predict consequences and outcomes of various personalities. - The three dimensions—Psychoticism, Extraversion, and Neuroticism—form the PEN model. This model is used to describe personality. People can be high or low on each of the three factors. Overview of Eysenck’s Three Dimensions 1. Extraversion  People who are high in this factor, extroverts, tend to be sociable, popular, optimistic, and somewhat unreliable.  Those low in extroversion- introverts- tend to be quite, introspective, reserved and reliable, and to have a few close friends.  Essentially, extraversion refers to how outgoing people are, to both the social and the physical environments. 2. Neuroticism  Neuroticism is contrasted with emotional stability.  People high in this factor tend to be distressed, insecure, and upset in many areas of life.  They are chronically worried, nervous and moody, hold a low opinion of themselves, and find it difficult to get back on an even keel after an upsetting experience.  In contrast, emotionally stable people are even-tempted, calm, relaxed, carefree, unworried and somewhat unemotional and return to their natural state quickly after an emotional experience. 3. Psychoticism  We think of Psychoticism as being antisocial and contrast it with ego control  People high in Psychoticism tend to be loners, egocentric, troublesome, manipulative, impulsive, uncooperative, hostile and withdrawn and do not fit in anywhere.  In contrast, people low in Psychoticism tends to be altruistic, socialized, empathetic and conventional. They care about others and are able to control their impulses to a greater extent than those high in psychoticism. - Eysenck drew on at least three pieces of evidence to support his view that these differences in personality are genetic and biological. 1. First, cross-cultural universality in traits implies a strong biological component. After all, we would expect that large differences in culture and environment would produce different kinds of personality factors. The fact that three factors of Psychoticism, Extraversion and Neuroticism occur in such diverse culture suggests a biological, rather than cultural explanation. 2. Second, people show tremendous consistency in these three traits over time, despite changing environments. Responses and habits might change over time and situations, but traits do not. 3. The third piece of evidence is that robust finding that Extraversion, Neuroticism and Psychoticism each have moderate heritability. As Eysenck state, “genetic factors cannot directly influence behavior or cognitions, of course and the intervening variables must inevitably be physiological, neurological, biochemical or hormonal in nature”. - Although Eysenck suspected that arousal and attention were involved with all three of his factors, he admitted that the research evidence did not suggest a clear hypothesis for a biological explanation of psychoticism. Neurology of Extraversion - Eysenck thought that the main difference between introverts and extraverts had to do with arousal and on that score he was right. He considered two possibilities: that introverts and extraverts differed in arousal level or in arousability. - Eysenck thought that introverts had greater cortical arousal than extraverts, particularly in the ascending reticular activating system (ARAS), a pathway transmitting signals from the limbic system and hypothalamus to the cortex. The ARAS processes the more cerebral aspects of arousal or emotion. Activation in the ARAS can make a person alert and mentally sharp or sluggish and mentally dull. - Because of their hypothesized overaroused baseline conditions, introverts act more restrained and inhibited. They avoid conditions that would aggravate their already overstimulated conditions, preferring to stay to themselves and engaging in more quite activities. - In contrast, the system of extraverts, Eysenck reasoned, lets in too little stimulation so that their underaroused condition leads them toward more stimulating and unrestrained behaviors. - Basically, extraverts are more outgoing and engaged with the world to raise their naturally low level of arousal. In this way, both extraverts and introverts attempt to regulate their own arousal striving to find their comfort zone: an optimal level of arousal. - Over 1000 studies have been conducted testing Eysenck’s theory of arousal with no success, claiming that his hypothesis in not true. - However, there is a significance difference in how extraverts and introverts respond to moderate stimulation, suggesting that the key difference between them is in their arousability or sensory reactivity. - Arousability: in physiology, how reactive people are to stimulation; an important difference between extraverts and introverts. - One study found that people studying in the quite study spaces of their college library- spaces with individual carrels, small tables- tended to be introverted. Extraverted preferred to study in the noisy but highly sociable areas of the library. - People’s noise preferences and performance outcomes depend on their optimal level of arousal as determined by their personality. Neurology of Neuroticism - Eysenck hypothesized that physiological arousal could also account for individual differences in Neuroticism. - he thought that Neuroticism had to do with stability or instability of the sympathetic nervous system (i.e. those parts of the brain that are involved in emotional regulation such as the hippocampus, amygdala, cingulum, septum and hypothalamus) - Basically, the vulnerability of people high in Neuroticism to negative emotions such as fear and anxiety was due to an extra sensitive emotional or drive system. - Extraversion and Neuroticism are similar in that both involve arousal; however, the big difference is in the valence or quality of that arousal. - Extraversion is marked by positive arousal such as excitement and energy, whereas Neuroticism is marked by negative arousal such as fear and anxiety. - People high in Neuroticism show an increase in heart rate in response to an intense stimulus. So do introverts. However, people high in Neuroticism but not introverts show greater startle response to fearful pictures. - These findings suggest that people high in Neuroticism may be more sensitive to negative emotions in particular and not to arousing situations in general, the way that introverts are. - All in all, there is no support for Eysenck’s hypothesis that Neuroticism is related to activation in the sympathetic nervous system. Reinforcement Sensitivity Theory (RST) - An alternative
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