Dendrites: projections on nerve cells that typically receive stimulation
Axons: pass on stimulation from the nerve cell
Afferent nerves: messages travel along these nerves from the body to the brain
Efferent nerves: messages travel along these nerves from the brain to the body (muscles, glands, organs)
Interneurons: organize and regulate transmission between nerve cells; the biggest bundle of these is the brain
Figure 8.1 Personality and the Brain
Hypothalamus – connected to just about everything else; secretes several hormones
Amygdala – important role in emotion (this is discussed more later)
Hippocampus – important in processing memories
Cortex – outer layer of the brain
Neocortex – outermost layer of the cortex – most distinctive part of the human brain
Frontal cortex – large size; crucial for uniquely human aspects of cognition such as planning ahead, anticipating consequences, and emotional experience
Brain damage: track problems caused by damage to different parts of the brain
Phineas Gage: more will be said about him later in this chapter
Lesions: mostly on animals
Brain stimulation: stimulate the brain directly to see what happens; this is difficult and rare
People while conscious: stimulating an area deep in the middle of the brain (substantia nigra) of one woman caused an acute episode of depression (Figure 8.2 on p. 252 on next slide)
Transcranial magnetic stimulation and transcranial direct current stimulation: used to create “virtual lesions” by turning off parts of the brain to see how psychological processes are affected
Figure 8.2
EEG: electrodes on the scalp pick up electrical signals
MEG: detects magnetic indications of brain activity
CT scans: can examine small structures
PET: map brain activity based on blood flow
fMRI: map brain activity based on magnetic impulses generated by oxygen in the blood
Canli article from the reader – Functional Brain Mapping of Extraversion and Neuroticism
Blood oxygenation may indicate inhibitory activity, not just excitatory activity (footnote on p. 254)
BOLD signals and perfusion imaging: look at how activation differs from neutral or a control group or across brain regions in individuals
Just because an area of the brain is active in response to a stimulus does not mean the same psychological process occurs every time that area is active (example in book: emotion)
Most researchers only look at small areas of the brain: other important areas may be missed
Difficult to detect the neural context effect: activity in one area may depend on what is going on in another area(s)
The technology is difficult to use: for participants and researchers; the statistics used to summarize data are complex, and possibly inaccurate and may lead to misleading or exaggerated results
Figure 8.6 graphic summary of data from fMRI scans of participants who viewed happy faces
Introverts are chronically overaroused (too much information is let in) and extraverts are underaroused (not enough information is let in)
Lemon juice test: introverts salivated more
Supportive recent research: extraverts had less activity in three areas of the brain while working on a memorization task
Unsupportive research: different parts of the brain can show different levels of arousal (so the ARAS does not control everything)
Whitman: had a malignant tumor next to the amygdala, which may have caused his motivation to murder his wife, mother, himself, and 14 others without understanding why he wanted to do this
Discussion question: What if Whitman had survived? Would it have been fair to prosecute him for murder?
Activity 8-2. Charles Whitman’s tumor
Word in parentheses indicates which side is more active
Brain asymmetry: the degree to which the two sides of the brain respond differently; may be an individual difference associated with emotional sensitivity
Phineas Gage (1848): personality changed in a negative way (fitful, irreverent, impatient, obstinate), less emotional, could not hold a job, made unwise decisions (figure 8.8 on p. 262 on next slide)
Others with brain damage to this area: unable to understand others’ emotions or regulate own impulses and feelings, unable to make appropriate decisions
Somatic marker hypothesis: idea that the bodily (or somatic), emotional component of thought is a necessary part of problem solving and decision making
Figure 8.8
Negative emotions and cooperativeness: people prone to negative emotions have an especially high level of activity in the prefrontal cortex; People who are cooperative have high activity when interacting with others
May play a role in self-enhancement: when this area was temporarily shut-off, self-descriptions were less positive than in a control condition
Capgras syndrome: believe loved ones have been replaced; follows injury to right frontal lobe; possible explanation is that people fail to respond emotionally to their loved ones and therefore conclude they must not be the same people
Both (cognition and emotion) are needed for each to function fully
Activity 8-1. Capgras Syndome
Important for experiencing emotion; inhibits the amygdala
Charles Whitman (tumor interfered with the anterior cingulate-amygdala circuit)
Possible implications for extraversion and neuroticism: stronger response to positive and neutral words among extraverts than introverts; more activity among neurotics when a stimuli did not match an expectation (mismatches may trigger negative emotions associated with neuroticism)
Prefrontal leucotomy: damages small areas of white matter behind each frontal lobe with intention of decreasing pathological levels of agitation and emotional arousal
Lobotomy: remove whole sectors of the frontal lobes
Observations of patients consistent with brain damage: frontal lobes play a role in anticipating the future, including negative outcomes, and in planning and decision making
Replaced with drugs: drugs are now more commonly used to treat similar mental problems
Activity 8-3. The lobotomist
“Nearly everything in the brain is connected to everything else”: systems and circuits may be more important than areas
Persistence: two areas of frontal cortex and part of the striatum
C-system: lateral prefrontal cortex, hippocampus, medial temporal lobe, and posterior parietal cortex
Neural context effect: it’s important to look at more than one area of the brain to understand complex processes
People differ in average levels of neurotransmitters and enzymes that break them down, and differences are associated with personality traits
Behavioral activation: reward seeking; strong BAS related to being energetic and impulsive
Individual difference: more cells related to motivation to seek rewards and enjoy them; related to extraversion (esp. assertive, dominant, and outgoing)
Related to plasticity (combination of extraversion and openness): increases motivation to seek rewards and impulsivity
Role in inhibition of behavioral impulses: benefits of avoiding excessive worrying, being too quick to anger, and being oversensitive
Serotonin depletion syndrome: Low serotonin levels
About 22 million Americans (or 10%) had taken the drug by 1999
Positive effects: stops needless worry, decreases sensitivity to minor stresses, increases cheerfulness, increases work productivity
Hormone definition: a biological chemical that affects the body in a location different from where the chemical is produced
Epinephrine (mostly in the body) and norepinephrine (mostly in the brain)
creates the fight-or-flight response: the brain is fully alert and concentrated on the threat
Anxiety, neuroticism: this response is a problem if it is too easily triggered; may be the result of an overactive norepinephrine system
tend-and-befriend: calm others down and get people to work together to deal with the threat
Importance of oxytocin: promotes nurturant and sociable behaviors, relaxation and reduction of fear
Based on evolutionary theory, women also had to protect their children, so fight-or-flight may not have worked for them
Fight-or-flight and tend-and-befriend are only the initial response to stress
Link with aggression is complex: some studies have found that high levels of testosterone (T) are related to aggression and behavioral control problems and criminal behaviors such as assault and drug use, but men with high T are not always aggressive
Related to many other behaviors in men (sociability, self-acceptance, dominance, frustration when things don’t get done, sexual experience) and women (unprovoked violent crime, sexual interest and desire, sociability, impulsivity, lower inhibition and conformity)
Role in control and inhibition of aggression and sexuality (based on steroid users)
Unknown causal direction between T and behavior: T increased among fans of winning soccer team and decreased among fans of losing team; sexual activity may increase T, not the other way around
Dabbs et al. article in the reader – Testosterone differences among college fraternities
Released in response to stress (physical or psychological): helps prepare body for action
Chronically high levels in people with severe stress, anxiety, and depression: probably an effect rather than a cause; Increases the risk of heart disease and may make the brain smaller
Low levels: sensation seeking (impulsivity, not following the rules of society); possibly due to abnormal responding to danger signals
Definition: using drugs to change personality to something more desirable
Also see Figure 8.12 on p. 288 – Regions of the brain associated with the Big Five
Correct answer: c
A – highlight the importance of technological advances to studying the brain
B – even with this technology, some findings are still unreliable because of the (over)sensitivity of the technology, based on subjective interpretations of the researchers, and disputed by researchers
Correct answer: d – emphasize the important of the frontal lobes for personality and social and cognitive functioning
