Aggression & The Nervous System Flashcards
What links to aggression?
emotional behaviour
how should we logically approach aggression research?
start with the brain areas dealing with emotions as hostile aggression is due to the intention to do so as a result of provocation
What does the prefrontal cortex do in terms of aggression?
doesn’t ‘make’ emotions but has a big role in regulating emotions - the ventromedial prefrontal cortex deals with choices
what does the ventromedial prefrontal cortex do in terms of choices and aggression?
if another area releases anger hormones, this area decides whether or not to act on these impulses
What does damaging the prefrontal cortex, or existing damage in the prefrontal cortex do in terms of aggression?
Aggression could be seen in some people as an impairment on this region of the brain, so they’d have a harder time preventing themselves from not following through on their impulses.
What study and explanation can help support the idea that deficiencies in the PFC leads to impulsive aggression?
Raine et al (1997) compared guilty parties stating themselves to be not guilty by reason of insanity (NGRI) with some non-offenders (control group). All participants had a 30 minute PET scan during cognitive tasks. Results found NGRIs have lower brain activity in certain areas such as the prefrontal cortex and amygdala - the regulators of emotion.
What does Raine et al. 1998 look for?
Raine et al. (1998) carried out another study to see if different crimes have different activity patterns in their brain functioning. There were three groups:
Violent offenders with impulsivity and emotionally driven
Violent offenders with planned and predatory crimes
Control group (non violent)
Results found that with PET scanning evidence, there was lower prefrontal cortex activity in those who were emotionally driven and impulse based, in comparison to those who planned and were consistently predatory as well as the control group.
Why is aggression present in the limbic system?
Aggression may therefore be present in the limbic system, as these structures are linked with self preservation instincts: this can include homeostatic responses, but also behavioural functions. It can contain structures like the amygdala and hypothalamus.
What role does the amygdala have in aggression?
The amygdala is very involved in perceiving threats and retaliation of said threats. Upon removal of this, animals tend to be more passive and irresponsible, but also more aggressive when it is stimulated: damage may reduce responses to threats, perception of emotions as well as a marked diminished fear response.
What studies can be used to show brain structure and functioning to be linked to aggression?
Downer 1961 ; Swanje 2012; Gorka et al. 2013 ; Anay and Veimati 1978
How can Downer 1961 be used to show Brain structure and functioning to be linked to aggression?
Downer (1961) surgically altered monkeys brains to alter visual transmissions to the amygdala by removing one of them in their brain. Upon the transmission of people reaching the amygdala, they behaved more aggressively (their normal response) but were more docile and calm when this signal wasn’t received.
How can Swanje 2012 be used to show brain structure and functioning to be linked to aggression?
Swanje (2012) used 20 healthy female volunteers for an MRI scan to calculate the size of the amygdala. They also took a self-report questionnaire (Life History of Aggression Assessment → LHAA) and used this to calculate their aggression scores. There was a negative correlation between the amygdala volumes and their aggression scores
How can Gorka et al. 2013 be used to show brain structure and functioning to be linked to aggression?
Gorka et al. (2013) used FMRI scans to compare brain responses to emotional stimuli between people who were and weren’t drinking → alcohol is known as a factor in a large number of violent crimes and scenes of aggression. Results found participants who had drunk alcohol had less brain activity between the left orbitofrontal cortex, and the amygdala when presented with angry or fearful stimuli
How is the hypothalamus involved within aggression?
The hypothalamus is involved in homeostatic responses such as hunger or seeking out food, but also in prey hunting animals, It also has a role in the attack behaviours i.e. a cat pounce on a rat due their hypothalamus’ electrical impulse. Parasites in rates make the loss of innate fear of cats through their suppression of the hypothalamus.
How can Anay and Veimati 1978 be used to show brain structure and functioning to be linked to aggression?
Anay and Veimati (1978) altered the activity in the hypothalamus and basal ganglia of cats by using catecholamine neurotransmitters. If you decrease this, the cats would become more aggressive (hissing, scratching, biting etc.) but increasing it has the opposite effect
What research methods are used in aggression and brain structure?
Laboratory Experiments
Correlational Analysis
Studies Using Animal Models
Brain Scanning
define limbic system
a set of brain structures that includes the amygdala. It is important in the generation and regulation of emotional responses
define amygdala
a brain structure that is important for experiencing fear in response to threats and also in recognising fear in other people. There are two amygdalae, one in each cerebral hemisphere.
define hypothalamus
a brain structure involved in many homeostatic functions like eating. In predatory animals the hypothalamus is involved in generating predatory aggression and hunting responses
define prefrontal cortex
the frontmost, outermost area of the brain. One of its functions is to decide whether or not to act on impulses generated elsewhere in the brain.
What does damage to the corpus callosum do in terms of aggression?
inability to think through the consequences of their actions
What were the aims of Raine et al. 1997?
To find out if there’s a difference in the structure of brain activity between people who have committed murder (NGRIs) and non-murderers - in particular the roles of the prefrontal cortex, the corpus callosum, the amygdala, the medial temporal lobe (MTL)/hippocampus and the thalamus in predisposing people towards aggression
To find out if the findings of studies linking brain structure to aggression in animals could be generalised to humans
What was the independent variable for Raine et al. 1997?
whether the participant in an offender pleading NGRI or a non-murderer in the Control group
What was the dependent variable for Raine et al. 1997?
relative glucose levels in the prefrontal cortex, the other lobes of the brain, the corpus callosum, the amygdala, the MTL/hippocampus and thalamus as revealed by the PET scan
What were the participants like for Raine et al. 1997?
41 offenders pleading NGRI to the crime of murder (an opportunity sample) and 41 Controls.
Within the offenders, there were 39 men and 2 women (with a mean age of 34.3) - 23 had a history of brain damage, 3 had a history of drug abuse, 6 schizophrenia sufferers, 2 epileptic and 7 with other emotional/learning disorders.
The Controls were people of the same age and sex with no history of crime or mental illness, except 6 schizophrenic
What was the procedure like for Raine et al. 1997?
They were tested at the University of California. Each was injected with a glucose tracer and performed a continuous performance task (CPT) for 32 minutes before the PET scan was carried out.
What were the controls Raine et al. 1997 used in his study?
The participants were allowed to practise the CPT 10 minutes before the glucose tracer was injected to make sure they were all equally familiar with it
He made sure none of the participants from both conditions was on medication - the NGRIs were kept free of medication for 2 weeks before the PET scan
How did Raine et al. 1997 conduct a PET scan to effectively look at the different areas of the brain?
The PET scan was broken into slices and boxes, enabling Raine to measure the relative amount of tracer in each of the brain’s four main cortical regions and the 4 subcortical regions.
What did Raine et al. 1997 find that was expected?
As expected, the NGRIs showed less activity in the frontal lobe, especially the prefrontal cortex which is associated with rational thinking, self-restraint and memory. There was also less activity in the parietal lobe which is associated with abstract thinking e.g. morality or justice, however there was more activity in the occipital lobe
What did Raine et al. 1997 find in the subcortical regions/ hemispheres?
In the subcortical regions, the NGRIs had less activity in the corpus callosum which is associated with long-term planning. There was also an imbalance of activity in the right and left hemispheres in the limbic system - there was less activity on the left and more on the right, in the amygdala and MTL/hippocampus, and more activity on the right side of the thalamus - these are areas of the brain that are associated with aggression in animals.
What did Raine et al. 1997 conclude in terms of brain abnormalities and anti-social behaviour/violence?
Prefrontal deficits may make someone more impulsive and emotional
Deficits in the limbic system may make someone aggressive, as observed in cats: the amygdala controls urges and desires, the thalamus processes information and the hippocampus processes information → deficits may make it hard for someone to learn from their mistakes or understand their emotions
Deficits in the corpus callosum make it harder for the hemispheres to communicate, making it harder to think through long term consequences and make decisions
Areas such as the parietal lobe, the amygdala and hippocampus have a role in recognition - deficits here make it harder for someone to judge social situations, leading to overreaction
What did Raine et al. 1997 conclude in terms of generalisation of animal studies?
He concludes that animal findings can be generalised to humans, and that there is a link between brain structure and aggression but he is optimistic that they can be prevented, if they’re identified earlier.
What did Raine et al. 1997 warn about generalising his findings?
The finding only apply to this group of murderers pleading NGRI, not all voilence. He also claims that he isn’t claiming that violence is purely biological in nature, as he believes social and situational factors e.g. culture and upbringing also play a role. His results don’t show that the NGRIs had no freewill or they “couldn’t help themselves;” a brain structure only gives us a predisposition towards acting a certain way.
What was a limitation in terms of the PET scan used in Raine et al. 1997?
They admit that this is the largest sample of the time looking at different areas of the brain with a control group however they admit that the PET images weren’t particularly clear and limited in how accurately they could be measured.
What doesn’t Raine et al. 1997’s study show?
The study doesn’t show the causes of these brain deficits, nor that brain deficits can be linked to violence as not all NGRIs were accused of violent murders
What was the generalisability like for Raine et al. 1997?
Large sample (82) which was the largest of its time - anomalies should not skew the data too much and thus making the results generalisable to the target population however NGRIs are unusual offenders, who aren’t representative of the target population - not all NGRIs commit violent murders.
What was the reliability like for Raine et al. 1997?
PET scanning has been a reliable technique since the 1970s, producing objective and replicable results that can be tested and retested to check its reliability.
The CPT ensures all participants were concentrating on the same thing, ensuring similar types of brain activity - standardised procedures
But Raine admits of problems in the reliability of PET scans in the 1990s as results were sometimes unclear and had to be interpreted, which introduces subjectivity and low reliability.
What was the objectivity/application like for Raine et al. 1997?
He suggests that if damage causing brain deficits can be prevented, people would not develop a murderous disposition - this involves early intervention with at-rish children in schools, programmes to steer young people away from drugs and monitoring those with brain damage.
It may be possible to treat those with brain deficits as if these regions could be stimulated (drug therapy or counselling), they might be less likely to engage in impulsive, aggressive behaviour.
