Neural & Hormonal Influences Flashcards
The limbic system
A system of structures lying beneath the cortex including the amygdala, hippocampus, and hypothalamus. The region is associated with emotional behaviour. The limbic system helps to coordinate behaviours that satisfy motivational and emotional urges, such as aggression and fear.
The amygdala
This is responsible for quickly evaluating the emotional importance of sensory information and prompting an appropriate response. If certain areas of the amygdala are electrically stimulated, an animal responds with aggression. If the same areas are surgically removed, the animal no longer responds to stimuli that would have previously led to rage. Kluver & Bucy discovered that the destruction of the amygdala in a monkey who was dominant in a social group caused it to lose its dominant place in the group.
The hippocampus
This is involved with the formation of long-term memories, and so allows animals to compare the conditions of a current threat with similar past experienced. For example, if an animal has previously been attacked by another animal, the next time they encounter that animal, they are likely to respond with aggression or fear - whichever is more appropriate. Impaired hippocampus function prevents the nervous system from putting theming into relevant context, and so may cause the amygdala to respond inappropriately, resulting in aggression. Boccardi found that habitually violent offenders exhibited abnormalities of hippocampul functioning.
Serotonin
A neurotransmitter implicated in many different behaviours and physiological processes, including aggression, eating behaviour, sleep, and depression. Low levels of serotonin remove this inhibitory effect, with the consequence that individuals are less able to control impulsive and aggressive behaviour. As a result, when the amygdala is stimulated by external events, it becomes more active, causing a person to act on their impulses, making aggression more likely. Mann gave 35 healthy ppts dexfenfluramine treatment, which is known to deplete serotonin. Using a questionnaire to assess hostility and aggression levels, they found that the treatment in males was associated with an increase in hostility and aggression scores.
