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PSYB30 CH 7.odt

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Connie Boudens

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CHAPTER 7: THE NEUROSCIENCE OF PERSONALITY WHAT IS NEUROSCIENCEAND HOW DO WE STUDY IT? -the nervous system is made up of the central nervous system and the peripheral nervous system >the central nervous system include the brain and the spinal cord whereas the peripheral nervous system includes the somatic nervous system (controls movements of the muscles), >the autonomic nervous system (regulates smooth muscles i.e., inner organs); it is further divided into the: • sympathetic division: which mobilizes energy (e.., for fight or flight) • parasympathetic division: supports systems that replenish the body's energy stores (e.g., salivation, digestion) -the brain is protected by the cerebral spinal fluid (CSF) that cushions the brain and flows through the spaces in the brain called ventricles—continually produced, circulated, and reabsorbed through the brain & ventricles -researchers hypothesize that differences in bodily responses, brain structure, brain activity, and biochemistry activity are all related to individual differences in personality Bodily Responses -autonomic system responsible for body's responding to arousing events -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): a measure of skin conductance or how quickly a slight electrical current passes through two points on the skin-the faster the current, the more moisture -muscle activity is measured by electromyography (EMG) or myoelectric activity: estimated the electrical impulses of the muscles during contraction and relaxation—used in biofeedback to monitor muscle contraction Brain Structure -researchers have looked for differences among people in the relative size and weight of specific parts of the brain, or even in the kinds and number of cells found in various parts of the nervous system -computerized tomography (CT scan) (known as computer axial tomography (CAT scan)): take a high- resolution x-ray picture of the brain—by looking at thin cross-sections of the brain (often less than a mm) we can detect abnormalities or differences in brain tissue -magnetic resonance imaging (MRI): 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 -both techniques only capture a picture of the brain at one moment in time BrainActivity -measures of brain activity are ways of looking for differences in brain structures while the brain is stimulated -one early technique was called the cortical stimulation—using either electrodes implanted in the brain or direct electrical stimulation of parts of the brain, the patient is awake and reported on sensations as various parts of the brain are being stimulated -electroencephalogram (EEG) electrodes are placed on the scalp to monitor electrical activity of the brain >when electrical activity of the brain or other parts of the nervous system is measured in response to a specific stimulus, this is called an evoked potential (EP)--both EEG & EP indicate amount of brain activity in response to a stimulus -in positron emission tomography (PET scan), a slightly radioactive glucose-like substance with a very short life is injected into brain and person is placed in a scanner.Active regions of brain use up more glucose than inactive regions and scans of these regions appear in different colours related to their activity level -the most detailed view of brain activity at a cellular level comes from functional magnetic resonance imaging (fMRI)-works the same as MRI except brain activity levels are monitored over time by tracing blood oxygen levels in the brain (more active areas use more oxygen and this activity is translated into diff colour scans of the brain) >a few problems occur w/ this technique: 1) timing of response: when viewing a stimulus, our thoughts react w/in milliseconds whereas blood flow takes about 2 seconds—makes it difficult to pinpoint the precise areas that fired at the exact moment of a thought or reaction 2) procedure is time-intensive and equipment is expensive so that often experiments use only a small number of participants (small sizes make it diff to find a reliable & sign effect) 3) nonindependence error: researchers may unintentionally bias their results by not independently selecting which brain areas to correlate w, say, personality characteristics or other variables 4) confounds such as time of day and nervousness of participants can also affect the results of neuroimaging studies -newest technique for studying brain activity: transcranial magnetic stimulation (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 w greater accuracy the exact areas that are affected >essentially, TMS mimics a brain lesion, which allows researchers to draw inferences about cause and effect BiochemicalActivity -physiological differences may appear as differences in how the brain and body process various chemicals including neurotransmitters, hormones, and drugs >researchers analyze CSF, saliva, blood, or urine to monitor levels of these chemical substances -neurotransmitters are chemicals released by neurons to inhibit or excite the next neuron into action >some imp neurotransmitters are norepinephrine, epinephrine (norepinephrine & epinephrine considered stress hormones as well (noradrenaline and adrenaline)), dopamine, and serotonin >norepinephrine and epinephrine help 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 body processes serotonin) >the enzyme, monoamine oxidase (MAO) regulates, to some degree, the availability of dopamine, norepinephrine, and epinephrine in the system -challenge test: researchers administer a drug that is known to either increase or decrease a neurotransmitter's functioning and monitor the impact of this new substance on reactions to presumed to be related to the neurotransmitter Research Methods Illustrated: Correlational Designs II: Scatterplots, Correlations, and theAlleged “Voodoo Science of the fMRI Studies: -scatterplot is a v useful graphic, it can tell us at least three things about a set of data: 1) it can alert us to outliers in one or both of variables understudy 2) can tell us the direction of the correlation: whether it's positive or negative 3) the thickness of the cloud or scatter of the dots tells us the strength of the correlation • the more the scatterplot looks like a circle, the less the two variables are related • the more the scatterplot looks like an oval, the more strongly the two variables are related • a perfect correlatin will look like a straight line NEUROLOGICALTHEORIES OF PERSONALITY -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 -temperament is 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 -when it comes to basic physiological temperaments, the evidence from many theoretical backgrounds and diff kinds of research methods converges on these three • to understand both the logic and the evidence supporting this assertion, let's take a close look at two imp biological theories of personality: Hans Eysenck's PEN model and Jeffrey Gray's reinforcement sensitivity theory Overview of Eysenck's Three Dimensions -extroversion: sociable, popular, optimistic, and somewhat unreliable (introversion: quiet, introspective, reserved, and reliable and have a few close friends) -neuroticism: contrast with em otional stability—ppl 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 -psychoticism: loners, egocentric, troublesome, manipulative, impulsive, uncooperative, hostile, withdrawn, and do not fit anywhere -Eysenck drew on at least three pieces of evidence to support his view that these differences in personality are genetic and biological 1) cross-cultural universality in traits implies a strong biological component 2) ppl 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. This consistency suggests a strong biological component to these traits 3) PEN each have moderate heritability Neurology of Extraversion -Eysenck thought that the main difference between introverts and extroverts had to do with arousal ascending reticular activating system (ARAS), a pathway transmitting signals from the limbic system and hypothalamus to the cortex >his hypothesis was not proven to hold true -there is a sign difference in how extraverts and introverts respond to moderate stimulation, suggesting that the key difference between them is in there arousability or sensor reactivity -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 neuroticism had to do with stability or instability of the sympathetic nervous system -the vulnerability of ppl high in neuroticism to negative emotions such as fear and anxiety was due to an extrasensitive 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 -ppl high in neuroticism and introversion show an increase in heart rate in response to an intense stimulus -ppl high in neuroticism but not introversion show greater startle response to fearful pictures -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) -for Jeffrey Gray, personality IS the variation in the functioning of brain systems -the very essence of what makes ppl unique is differences in their responses to stimuli in the world -Gray's idea was to 1) identify brain-behaviour systems that accounted for imp differences among ind's and 2) link these systems to standard measures of personality Overview of Three Neurological Systems -according to the Reinforcement Sensitivity Theory, there are three hypothetical brain-behaviour systems—these systems are presumed to exist based on evidence from neurology, physiology, behaviour, and personality -rather than identify isolated parts of the brain working separately, we can look for interconnected areas that function similarly and work together in accord w one of these hypothesized systems -Gray's great contribution was in recognizing that everything in the brain is interconnected -think of these systems as a kind of shorthand for a whole set of neural networks 1) Fight-flight-freeze system (FFFS): system assoc'd with emotion of fear • responsible for orchestrating our reactions to aversive stimuli • we may opt to confront or fight the stimulus, avoid or escape it, or to remain frozen in place hoping the danger passes • personality factor that matches this biological system is fearfulness and avoidance 2) Behavioural Approach System (BAS): this syste
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