Structure of the Brain and Aggression Flashcards
Limbic System
Papez and Maclean identified limbic system as comprising a number of structures.
Key structure is the amygdala, has a role in responding to environmental threats and challenges.
Coccaro et al. 2007
Studied people with intermittent explosive disorder - outbursts of extreme reactive aggression.
Brains scanned by fMRI while they viewed images of faces.
Coccaro et al. 2007 Findings
IED PPs showed high levels of amygdala activity when viewing images of angry faces. Not found in non-IED PPs.
Evidence of association between amygdala reactivity and aggression is meaningful because angry facial expressions are an ecologically valid sign of threat.
Role of Serotonin
NT with inhibitory effects on transmission between neurons in the brain, slowing down neural activity.
Normal levels in orbitofrontal cortex associated with normal behavioural self-control.
Decreased serotonin could disturb this leading to more impulsive behaviours.
Matti Virkkunen et al
Compared levels of a serotonin breakdown product called 5-HIAA in cerebrospinal fluid of violent impulsive and non impulsive offenders.
Matti Virkkunen et al Findings
Levels were lower in impulsive offenders, who also suffered from more sleep irregularities. Interesting as serotonin helps regulate sleep patterns, this disturbance implies disruption of serotonin functioning.
Role of Prefrontal Cortex
Research indicates amygdala does not work alone in determining aggression, but with the OFC in the prefrontal cortex which has a role in higher cognitive functions like rational thinking and decision making.
OFC - Self control, impulse regulation and inhibition of aggressive behaviours.
OFC and Coccaro et al
Patients with psychiatric disorders featuring aggression, activity in OFC is reduced, disrupting impulse control functioning.
Raine et al
PET scans to study murderers.
Found greater glucose metabolism in amygdala but low metabolism in prefrontal cortex compared to a matched control group.
Role of Dopamine
Dopamine is an NT that has inhibitory effects in some areas and excitatory in others. Regulates motivating behaviour and our experience of reward.
According to Dongju Seo et al.
Serotonin underactivity stimulates dopamine overactivity.
Both linked with impulsivity and aggression.
Serotonin hyperfunction is primary cause of impulsive aggression and dopamine hyperfunction contributes.
Support Padrini
Evidence for amygdala role in aggression
Padrini et al identified 56 males who were in a study 20 years earlier when 6 or 7.
Behaved aggressively over 20 years.
Using fMRI, they found a strong negative correlation between aggression levels and amygdala volumes.
Why was Padrini support
Findings could not be explained by potential confounding variables or earlier levels of aggression because they were all controlled.
Shows explanation has predictive validity.
Against
Research into neural influences on aggression is often correlational.
Often done by finding links between high aggression levels etc perhaps by using fMRI.
Although they are ethical because experimental means the people would have to be made aggressive.
Impossible to establish whether structure, function/dysfunction is cause or effect of aggressive behaviour or a third variable involved
Competing Against
Some attempted to overcome by using drugs to increase serotonin activity like paroxetine in Berman et al which made PPs give less electric shocks.
Link between serotonin and aggression that goes beyond correlational findings.
