aggression😡 (neural and hormonal mechanisms) Flashcards
what is the limbic system?
network of structures in brain thought to be involved in regulating emotional behaviour including aggression.
what is the amygdala?
linked to the production of aggressive behaviour, FMRI’S show increased activity during aggressive responses..
how something respond an assesses environmental threats and challenges.
what is the hypothalamus?
responsible for the regulation of the autonomic nervous system, which in turn regulates responses to emotional circumstances. Therefore, damage to this area can result in an inappropriate aggressive response to a perceived threat.
what is the orbitofrontal cortex? (OFC)?
controls executive function (decision making) which attempts to control aggression produced by the limbic system.
what study did eggar and flan demonstrate in 1963?
not key
demonstrated electrically stimulating an area of the hypothalamus would cause cats to show aggression towards a rat.
Also showed stimulating different parts of amygdala would either increase of suppress aggressive behaviour.
suggests hypothalamus has a role in producing aggressive behaviour and different areas in amygdala have separate roles in regulating aggression.
However, study was conducted on cats so findings may not be generalised to aggressive behaviour in humans
what did gossip et al study?
what type of study?
lab method known as ultimatum game. proposer offers to split money in certain way with responder. If responder accepts then money is split but if they reject both receive nothing.
ppts in study were responders whilst having FMRI brain scans. researchers found that when responders rejected unfair offers, scans revealed a fast and heightened response by the amygdala.
Also found that a benzodiazepine drug taken before game had 2 effects to responses with unfair offers. It halted the number of rejections and decreased activity of amygdala.
Shows strong evidence of association between reactive aggression and amygdala activity.
what is serotonin?
neurotransmitter involved in communication of impulses between neurons
what does normal lvls of serotonin do?
linked with w reduced firing of neurons in OFC. this is associated w greater degree of self-control, meaning ppl aren’t aggressive.
what may decreases serotonin do?
disturb this mechanism, reducing self control and leading to an increase in impulsive behaviour including aggression
what did passamonti study in serotonin?
not key
tryptophan in food is needed by the body to produce serotonin. Study used a technique called acute tryptophan deletion (avoiding foods containing tryptophan) to reduce amount of serotonin in brains of the experimental group. researchers measured brains response to seeing angry/ neural faces using FMRI. result showed reduced communication between amygdala and frontal cortex when deprived of serotonin. ppts also scored highly on an aggression questionnaire. suggests lack of serotonin reduces frontal Cortex’s ability to control aggressive impulses in the amygdala.
study used randomised, double blind placebo controlled method. data analysed was FMRI readings. Use of such careful scientific measurements suggests that findings on aggression from study has very high validity. However use of an aggression questionnaire could one seen as not truly measuring aggression lvls.
what did virkkunen et al (1994) discover?
compared serotonin breakdown product in the cerebrospinal fluid of violent impulsive and violent non-impulsive offenders. levels were lower in impulse offenders and they also suffered more sleep irregularities.
Significant bc serotonin regulars sleep patterns. disturbance of this pattern strongly implies some disruption of serotonin functioning, further supporting the role of serotonin in reactive aggression
what do males tend to be?
what is testosterone?
what does it control?
more aggressive than women
male sex hormone
controls development of male sex characteristics. lvls around 8X higher than in females. has a role in regulating social behaviour via its influence on certain areas of the brain implicated in aggression
What did Dolan et al find?
found positive correlation between testosterone lvls and aggressive behaviour in a sample of 60 male offender in the uk maximum security hospitals.
these men have suffered from a personality disorder such as psychopathy and had histories of impulsively violent behaviour.
what did wagner research into aggression?
not key
measured aggression in mice by now often they bit a target. it was found that males were more frequent than females, however this sex difference disappeared after castration. this sex difference in biting frequency was restored when the male mice were injected with testosterone. Injections also increased female bite frequency. suggesting that lvl of testosterone hormone in body of the mice is directly connected to the expression aggressive behaviour.
AO3
❌Weakness of limbic system
there’s the role of other brain structures. studies show that amygdala does not operate in isolation in determining aggression.
it appears to function in tandem w OFC which isn’t apart of limbic system.
the OFC is thought to be involved in self control, impulse regulation and inhibition of aggressive behaviour.
according to coccaro, ppl w psychiatric disorders that feature aggression have reduces activity in OFC, disrupting its impulse control function and thus leading to increased aggression. combined with gossips findings it indicates that aggression is complex and involves 3 neural structures + in the brain; amygdala, OFC, and connection between the 2
