Neural And Hormonal Mechanisms Flashcards
(18 cards)
What is the limbic system
Part of the brain that includes the:
- amygdala
- hypothalamus
- hippocampus
What is the role of the limbic system
It plays a key role in the way that an organism responds to environmental threats and challenges
- key factor in whether we respond aggressively or not
The amygdala
Centre for emotions, emotional behaviour and motivation
- involved with instinctive feelings and reactions to environmental stimuli, which includes aggression
Research support for the role of the amygdala in aggression
Gospic et al
-Ultimatum study
Gospic et al
- lab method, assessing aggressive behaviour using a game ‘the Ultimatum game’
- 2 players, the proposer and the responder
Proposer offers to split money in a certain way w the responder - if responder agrees, money is split how stated, if rejected, no one gets money
- ppts had their brains scanned w fMRI’s while playing
- found heightened response in the amygdala when responders rejected unfair offers
Gospic additional findings
when benzodiazepine was taken before playing (drug that reduces arousal of ANS):
1. Number of rejections were halved (reduced aggression)
2. Decreased activity in amygdala
- strong evidence of an association between reactive aggression and amygdala activity
Serotonin
key hormone that stabilises our mood, feelings of well-being and happiness
- has widely inhibitory effects in the brain, slows and dampens neuronal activity
Findings about serotonin
- Denson - found when S was present at normal concentration in orb frontal cortex, it was associated w reduced firing of neurons = greater behavioural self control
- Virkkunen compared levels of S in cerebrospinal fluid of violent impulsive and violent non-impulsive offenders
- found levels were lower in impulsive, they also suffered more sleep irregularities
Hormones
Chemical messengers in the body which scan change behaviour and cause physical changes in the body
Hormones involved in aggression
- oxytocin
- testosterone
pre natal exposure to testosterone
has an organising effect on the developing brain
- increased spatial ability + competitive aggression
- immediately after birth, T cells stimulate growth in areas on the hypothalamus and amygdala
Testosterone research
- Giammanco
- Dolan
Giammanco
Animal study
- showed increases in T have produced aggressive behaviour in several species
- and vice versa, less T = decreased aggressive behaviour
Dolan
Found positive correlation between T and aggressive behaviour
- sample of 60 male offenders in max security hospitals
- most suffered from personality disorders, and had history of impulsively violent behaviour
Supporting evaluation for neural and hormonal mechanisms
- Berman et al study (placebo or no)
- Mazurs MBoS and Mehta and Joseph
Berman et al
Gave pots a placebo or a dose of paoxetine (serotonin booster)
- lab study where they could give shocks of varying intensity as a response to provocation
- ppts w drug gave fewer and less intense shocks
CA - only true for those who had a history of aggression
Mazurs MBoS, Mehta and Joseph
Mazurs model suggests that human T levels change rapidly throughout the day esp in response to social interactions related to status
- eg. falling from 1st to 2nd = change in T and affects post-comp aggression
Mehta and Joseph, study w competitive game and measured changes in T before and after comp, given choice to re-challenge, or complete an unrelated test
- found 73% of the losers (whose T rose) decided to re-challenge their opponent but only 22% of the losers (whose T fell) decided to do so
- supports Mazurs theory that T changes based on status, improves validity
Opposing evaluation for neural and hormonal mechanisms
- Mixed evidence for T
-Carre and Mehta, high levels of T only produce aggression when cortisol levels are low
- when cortisol levels are high, T fuelled aggression is blocked
Popma, confirmed this belief in a study of direct physical aggression in adolescent males
- C and T may be a better predictor of aggression
