neuroscience of personality

Eyesenck’s PEN model

• theory of extraversion

  • introverts had greater cortical arousal than extroverts

  • RAS(reticular activation system) transmits signals from limbic system and hypothalamus to cortex

  • introverts higher in baseline arousal, act more restrained and inhibited

  • extroverts low in baseline arousal, seek more stimulating and unrestrained behaviors

• brain scans show no difference between groups at rest

Extraversion

• differences between arousability and sensory reactivity

• study of I/E groups learning rules of word pairs while listening to white noise

  • control group: white noise matched to group and could be personally adjusted in volume

  • no control matched: could not adjust volume but matched to group type

  • no control unmatched: could not adjust volume and was matched to opposite group type

  • results: arousal

    • I/E showed similar measures of arousal in matched condition and choiced condition

    • opposite condition showed greater arousal for introverts and lower arousal for extroverts

  • results: performance

    • choice and match conditions performed similarly

    • opposite condition requried more learning trials

    • worse for introverts than extroverts

Neuroticism

• Eysenck thought stability of sympathetic nervous system was responsible for neuroticism

  • sends warning signals for things most people deem unimportant

• high neuroticism linked to increased heart rate to intense stimuli and increased startle reflex

  • high sensitivity to negative emotions

• sympathetic responses widely vary however…

Reinforcement sensitivity theory (RST)

• 3 overarching systems that interact with personality and biology, which play into how we interact with our environment

• Fight-Flight-Freeze system (FFS):

  • emotion of fear, gets us to respond to aversive stimuli

• Behavioral Approach System (BAS):

  • responses to “appetitive stimulus” or things that are rewarding

  • makes a person more sensitive to reward

• Behavioral Inhibition System (BIS):

  • helps resolve conflicts within one of the other systems

  • may cause anxiety, worry, vigilance

  • may clinically lead to OCD or GAD

RST

RST the research

• support for theory

• brain areas related to reward: ventral striatum, amygdala, orbitofrontal cortex, ventral pallidum, midbrain

• BAS scored high in the difference between appealing foods and gross foods

  • strongest reaction when looking at areas related to food regulation

• people learn through:

• Strong BAS = reward sensitive learning

  • learn more quickly by going for it

• Strong BIS = punishment sentitive learning

  • trying to avoid punishment

• uneven spread in award/conflict/punishment sensitivity

Neurological correlates

• two main areas in relation to extroversion and neuroticism: frontal/prefrontal cortex and amygdala

• cortex:

  • greater right cortex cortical thickness in introverts than extroverts(less inhibition)

    • extroverts may have more efficient processing in that case

  • neuroticism negatively correlated with left cortex

    • higher meant less grey matter compared to low neuroticism

    • stronger in males than females

• amygdala:

  • extroverts have higher gray matter in left amygdala compared to introverts

  • higher neuroticism had lower concentration of gray matter in right amygdala than low neuroticim

    • fear and negative-base emotions cause more activation in this area

Left-right asymmetry

• Right and left hemisphere are specialized

  • left = linguistic processes for most people

  • right = spatial processes for most people

• cortex responds to emotions differently 

  • right frontal and prefrontal cortex is more active than left during negative emotions

    • people differ in how large the relative differences are

• right asymmetry = shy, inhibited children and depressed adults

• extroverts = more positive emotions at rest and in response

  • meditation = greater left brain symmetry at rest and response

Neuroscience is…?

The study of both structure and function of the nervous system and brain.

How do we study it?

• we have:

  • neurons

  • nerves (pituitary, adrenal, thyroid, etc.)

  • glands

  • hormones

  • physiological responses

  • psychological responses

• study via:

  • brain activity

  • brain structure

  • biochemical reactions

  • body reactions

Body reactions

• typically measuring the downstream effects of a biological x physiological interaction

  • e.g. fear, anger, reactivity, serenity, etc.

• measurments:

  • heart rate

  • GSR galvanic skin response

    • measures how quickly a slight electrical current passes through two points on the skin

  • EMG electromyography

    • estimates electrical impulses of muscles during contraction and relaxation

Brain structure

• looking at structural features of the brain

  • size of certain areas

• computerized tomography

  • x-ray for brain

  • detects abnormalities through brain “slices”

• Magnetic Resonance Imaging MRI

  • strong magnetic field and radio frequency used to measure electromagnetic energy given off by hydrogen atoms

• Electroencephalography EEG

  • electrodes placed on scalp, monitor electrical activity in the brain

• Functional magnetic resonance imaging fMRI

  • monitors brain activity over time

  • measures blood oxygen levels, more oxygen used up = greater color difference

  • idea on a specific area of the brain being used during certain activities

• Positron Emission Tomography PET

  • radioactive glucose is injected and person placed in CT scanner

  • amount of metabolism is changed to different colors, showing where work is getting done