The Biology of Personality Traits

EEG

Electrical activity in the brain recorded through the scalp. Good at measuring when activity happens but not where.

Neural communication

Electrical to chemical.

Electrical communication

The dendrites receive input from other neurons, electrical impulse travels through the neuron along its axon, impulse reaches end of the axon where it can signal the next neuron.

Chemical communication

It triggers the release of neurotransmitters (chemical messengers). Neurotransmitters cross the tiny gap between neurons, called the synaptic cleft. They bind to receptors on the receiving neuron. This changes the activity of the receiving neuron, making it more or less likely to generate an action potential.

fMRI

Estimates activity in the brain through blood-oxygen changes. Good at measuring where activity occurs.

Nucleus accumbens involved in

Reward processing; linked to Extraversion

Amygdala involve in

Responding to emotionally relevant stimuli.

Prefrontal cortex involved in

Higher-level processes such as decision-making and other cognitive functions.

Dopamine neuron: Reward-value neurons

Increases in response to experiences that are better than expected, and shuts down in response to experiences that are worse than expected. Linked to Extraversion.

Dopamine nueron: Salience/novelty-related neurons

Respond to relevant, new information, whether it is better or worse than expected. Curiosity. Linked to Openness/Intellect.

Ascending reticular activating system (ARAS)

Helps regulate overall brain arousal, wakefulness, and alertness.

Genes and the environment influence on personality

Both influence the brain, which generates patterns of behavior+experience that we describe as personality

Personality neuroscience

The study of how personality traits relate to the brain

Hans Eysneck

Early major figure in personality nueroscience. Focused on ARAS.

Eysenck's original theory of Extraversion

Extraverts have lower baseline cortical arousal than introverts, so they seek more stimulation.

Eysenck's revised theory of extraversion

Introverts may be more easily aroused and become overstimulated with less stimulation.

Synapse

Space between neurons across which neurotransmitters travel

Gray's explanation of Extraversion

Extraversion is related to the Behavioral Activation System (BAS), dopamine, and sensitivity to rewards.

Behavioral Activation System (BAS)

Encourages you to take action when you think something positive or rewarding might happen.

Three types of evidence support the dopamine theory of Extraversion?

Dopamine-related drug studies, EEG responses to reward feedback, and fMRI activity during reward anticipation.

Lower latent inhibition (LI)

Automatic process that filters irrelevant details out of consciousness.

Dopamine and openness/intellect

Receiving information one is curious about activates the reward system. Dopamine (salience subsystem) facilitates working memory - (ability to maintain information in short-term memory and mentally manipulate it).

Dopamigenic system. (Four brain regions dopamine neurons extend to)

Amygdala, Nucleus accumbens, Dorsolateral Prefrontal Cortex (DLPFC), Ventromedial Prefrontal Cortex (VMPFC).

Openness vs Intellect

Openness: seeing beauty in things that others might not notice, believe in the importance of art, daydreaming. Intellect: Likes solving problems, can understand abstract problems easily, think quickly

Personality associated with activity in the Anterior Prefrontal Cortex (aPFC) and Medial Frontal Cortex (MFC) in the working memory study

Intellect

Neuroticism

Sensitivity to threat and punishment, avoidance and withdrawal from threat, both with negative emotions.

Gray’s theory: Behavioral Inhibition System (BIS)

Responsible for anxiety: passive avoidance which happens in the hippocampus and amygdala. (Withdrawal)

Gray’s theory: Fight-Flight System (FFS)

Responds to immediate danger with panic or defensive anger. Happens in the hypothalamus. (Volatility)

Larger brain structure size associated with higher Neuroticism

Amygdala and hippocampus

Higher Neuroticism and cortisol

Higher baseline cortisol and a relatively smaller cortisol increase in response to specific stressors.

Serotonin supports

Emotional regulation, motivation, and self-control. Associated with Stability.

Conscientiousness

The ability to control impulses in favor of longer-term goals or rules. Associated with frontal lobe, particularly the Lateral PFC.

Parts of PFC

• DLPFC: Working memory and complex cognitive operations.

• aPFC: Integrating cognitive operations and reasoning.

• Medial PFC: Emotion regulation.

• Lateral PFC: Maintaining goals and controlling behavior

Agreeableness

Brain regions involved in social information processing. Empathy and theory of mind; control of selfish or aggressive impulses.