Limbic system, serotonin and testosterone Flashcards
What is the limbic system?
Subcortical structures in the brain thought to be closely involved in regulating emotional behaviour including aggression.
Name the 2 psychologists who attempted to link the limbic system with emotional structures.
Papez initially.
Later revised by Maclean.
Why is the amygdala key?
Plays a key role in how an organism assesses and responds to environmental threats and challenges.
What are the features that combine to make the limbic system?
- amygdala
- hypothalamus
- fornix
- parts of the hippocampus and thalamus
Why is over-reactivity of the amygdala linked to aggression?
Over-reactivity of the amygdala is linked to aggression because it plays a role in how we interpret and respond to environmental stimuli (i.e. as threats).
Who conducted a study to test the link between aggressive behaviour and the amygdala?
Gospic et al.
What was the procedure of the ‘ultimatum game’?
- Featured 2 players: the proposer offers to split the 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 players receive nothing.
- Participants in this study played as responders whilst having their brains scanned by an FMRI.
What did the researchers find as a result of the ‘ultimatum game’?
- The researchers found that when the responder rejected unfair offers (an aggressive action to social provocation), scans revealed a fast and heightened reaction by the amygdala.
- They also found that a benzodiazepine drug (used to decrease the arousal of the autonomic system) taken before the game had 2 effects on responses to unfair offers.
- It halved the number of rejections (e.g. reduced aggression) and decreased the activity of the amygdala.
- Strong evidence of an association between reactive aggression and amygdala activity.
What is serotonin?
A neurotransmitter with widespread inhibitory effects throughout the brain. It has a key role in aggressive behaviour.
What are abnormally low levels of serotonin associated with?
Abnormally low level associated with lower self-control and an increase in impulsive behaviours including reactive aggression.
What is testosterone?
A hormone from the androgen group that is produced mainly in the male testes and is associated with aggressiveness.
Name 2 studies which support the role of testosterone in aggressive behaviour.
- Dolan found a positive correlation between testosterone levels and aggressive behaviours in a sample of 60 male offenders in UK maximum security hospitals. These men mostly suffered from personality disorder and had histories of violent behaviour.
- Poll et al. showed that female rats that were injected with testosterone became significantly more physically and sexually aggressive.
State a criticism of the limbic system’s involvement in aggression.
Other brain structures - evidence that the orbitofrontal cortex, which is not part of the limbic system. The OFC is thought to be involved in self control, impulse regulation and inhibition of aggressive behaviour.
Gospic at al. suggested that this indicates that the regulation of aggression is highly complex and involves at least 3 neural structures: the amygdala, the OFC and the connection between the 2.
State a positive of serotonin’s role in aggression.
Effects of drugs on serotonin - drugs that increase serotonin levels also reduce levels of aggressive behaviour.
Berman et al. gave their participants either a placebo or paroxetine (enhances serotonin levels). Participants then took part in a lab-based study in which electric shocks of varying intensity were given and received in response to provocation.
The paroxetine participants consistently gave fewer and less intense shocks. However, this was only true of participants who had a prior history of aggressive behaviour.
State a positive of testosterones involvement in aggressive behaviour.
Biosocial model of status (Mazur) - a study carried out measured changes in their male participants’ testosterone levels before and after a game (which they all lost). Once the 2nd sample was taken the participants were then given a choice, to either challenge their victorious opponent or complete an unrelated task. Of the losers whose testosterone levels increased, 73% chose to rechallenge. Of the losers who’s testosterone levels decreased, only 22% rechallenged. Therefore, after a loss of status, individuals behaved aggressively but only when their testosterone increased.
These findings confirm Mazur’s BMoS, increasing its validity as a plausible explanation of how testosterone may exert its effects on aggression.
