Neuronal and hormonal mechanisms Flashcards
What is the limbic system?
The limbic system is a network of structures which processes and responds to environmental stimuli.
What structures make up the limbic system?
The hypothalamus, the amygdala, parts of the hippocampus.
What is the amygdala’s role?
The amygdala assesses and responds to environmental threats and challenges. In the presence of a perceived threat, the amygdala sends a stress signal to the hypothalamus, which activates the sympathetic branch of the autonomic nervous system. The reactivity of the amygdala in humans has proven to be an important predictor of aggressive behaviour.
What is the ultimatum game?
Lab-setting. The proposer offers to split money in a certain way with the responder. If the responder accepts, the money is split as proposed. But if the responder rejects the offer, both receive nothing. Participants in this study played as responders while having their brains scanned by fMRI, which highlights activity in different areas of the brain.
What were the results of the ultimatum game?
When responders rejected unfair offers (an aggressive reaction to social provocation), scans revealed a fast and heightened response by the amygdala.
What were the results of the ultimatum game when the drug benzodiazepine was taken?
It halved the number of rejections and decreased the activity of the amygdala.
What is the role of serotonin?
Serotonin is a neurotransmitter involved in the communication of neurons. It has an inhibitory effect on the brain which makes neurones more negatively charged and so therefore less likely to fire. This is associated with a greater degree of behavioural self-control.
What does it mean if someone has less serotonin?
Decreased serotonin in the pre-frontal cortex will reduce self-control and lead to an increase in impulse behaviour including aggression.
What is the breakdown product of serotonin called?
5-HIAA.
What is the role of testosterone?
Regulating social behaviour via its influence on certain areas of the brain implicated in aggression. Animal studies have demonstrated aggressive behaviour in several species and there is similar human evidence such as male prison studies have found positive correlations between testosterone and levels of aggressive behaviours. For example, Dolan found a positive correlation between testosterone levels and aggressive behaviour in male offenders in UK maximum security hospitals.
Limitation of hormonal mechanisms of aggression. (other hormones)
Evidence of the link between testosterone and aggression in humans is mixed. For example, Career and Mehta’s dual-hormone hypothesis attempts to explain why as it claims that high levels of testosterone lead to aggressie behaviour only when levels of cortisol are low. When cortisol levels are high, testosterones influence on aggression is blocked. This means that there must be hormones involved other than testosterone.
Limitation of hormonal mechanisms (issues of cause and effect).
Most research into both neural and hormonal influences on aggression is correlational. There are good ethical reasons for this, because opportunities to experimentally manipulate brain structures and hormones are very limited. But when two variables are correlated, it is impossible to establish which one is the cause of the other or if there is a third variable involved.
Limitation of neuronal mechanisms for aggression. (other brain structures)
One limitation of the limbic explanation is more recent research showing that non-limbic brain structures are also involved in aggression. For example, the Orbitofrontal cortex. The OFC is thought to be involved in self-control, impulse regulation and inhibition of aggressive behaviour. According to Coccaro, in people with psychiatric disorders that feature aggression, activity in the OFC is reduced which disrupts its impulsive-control function and thus leading to increased aggression. Combined with Gospic, this indicates that the regulation of aggression is highly complex and involves at least two neural structures.
Strength of neuronal mechanisms in aggression (effect of drugs on serotonin).
One strength of the serotonin explanation is research into the effects of drugs. Drugs that increase serotonin have been found to also reduce levels of aggressive behaviour.Berman gave participants either a placebo or a dose of paroxetine and then the participants took place in a lab-based game that involved giving and receiving electric shocks in response to provocation. The paroxetine drug consistently gave fewer and less intense shocks than the placebo group.
Strength of genetic factors in aggression. (research support for MAOA gene).
Martins studied participants with low-activity and high-activity variants of the MAOA gene in a money-distributing game. Participants had to make decisions about whether or not to contribute money for the good of the group. It was found that males with the high-activity variant were more co-operative and made fewer aggressive moves than the lower-activity participants.
