Attack and Escape Behaviors

• Attack behaviors are associated with increased activity in the corticomedial area of the amygdala.

• An initial attack behavior increases the probability of a second attack behavior.

Violence

• Violence is particularly enhanced with both a genetic predisposition and an early troubled environment.– Example: Interaction

between MAOA levels and childhood maltreatment

Research shows that men with the highest rates of violent behavior also have slightly higher testosterone levels.

Testosterone

Prenatal Testosterone Contributes to Aggression

Androgens Influence Biting Attacks in Mice

Injecting women with testosterone decreases their ability to identify angry expressions.

Testosterone

Homicide Rates in Selected Cities (1998-2000)

Serotonin

• Studies also suggest a connection between aggressive behavior and low serotonin turnover.• Turnover is the amount of a neurotransmitter

that is released and resynthesized by neurons.• E.g., social isolation of male juvenile mice

decreased serotonin turnover and increased aggressive behavior.

Serotonin

• 5-hydroxyindoleacetic acid (5-HIAA) is a serotonin metabolite found in the blood, cerebrospinal fluid, and urine that allows researchers to infer turnover rate.– High levels of 5-HIAA imply much serotonin

release and turnover.– Research with monkeys has demonstrated that

low levels of 5-HIAA increases the probability of attack on larger monkey• few survived past age 6.

Serotonin

• In human studies, low serotonin turnover has been linked to: – People with a history of

violent behavior and violent crime.

– People who attempt suicide by violent means.

– Recurrent violent behaviors.

Serotonin

• Serotonin activity can also be influenced by genetics.

• Genes control the production of tryptophan hydroxylase.

• People with less active form of this enzyme are more likely than others to report frequent anger and aggression.

Amygdala and Fear

Amygdala & Fear

Amygdala & the eyes

Major Facial Expressions of Emotions Are Easily Recognized Around the World

Facial Expression• Volitional facial paresis– difficulty in voluntary facial

movement, natural movement is fine

– damage to motor cortex and subcortical connections

• Emotional facial paresis– voluntary movement is fine;

natural movement impaired– damage to PFC, thalamus,

white matter of the frontal lobe