The Brain (structure and functions) Flashcards
identify all the LOBES and its location in the brain
- frontal lobe (left side of brain)
- parietal lobe (to the right of frontal lobe)
- optical lobe (down a bit then tiny right of parietal lobe)
- temporal lobe (down a bit then 2x tiny left of optical lobe)
- corpus collosum (the middle of the brain - connects both hemispheres)
identify the individual parts of the limbic system and their role
- hippocampus:
takes short-term memories and converting them into long-term memories. - hypothalamus:
production of many of the body’s essential hormones, chemical substances that help control different cells and organs.
The hormones from the hypothalamus govern physiologic functions such as temperature regulation, thirst, hunger, sleep, mood, sex drive, and the release of other hormones within the body.
houses the pituitary gland and other glands in the body. - amygdala:
responsible for the perception of emotions (anger, fear, sadness) as well as controlling aggression.
helps to store memories of events and emotions so that an individual may be able to recognize similar events in the future.
describe pre-frontal cortex/lobe
involved in movement, decision-making, problem solving, and planning
responsible for personality expression and the planning of complex cognitive behaviours.
contains our personalities and have an input to our emotional responses and control our social inhibitions.
It is also shows in depression and regulating our emotions.
How does the hypothalamus (area) explain aggression
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Alpers (1937) studied a well-liked, mild-mannered, middle-aged lawyer who was later shown to have a tumour in the medial hypothalamus, began to display uncharacteristic outbursts of aggressive behaviour that were shocking to all that knew him. This localized tumour was said to be the cause of his uncharacteristic violence. - HUMAN REASEARCH
Hess (1928) demonstrated an ability to induce aggressive behaviour in cats by electrical stimulation of the hypothalamus. Electrical stimulation of the hypothalamic attack area (HAA), in the medio-basal hypothalamus, in rats and cats elicited ‘biting attacks’. The densest projection to the HAA originated in the pre-frontal cortex; damage to this area is implicated in human aggression. It was also found that brain stem stimulation in the central gray area produces hissing and characteristic vocalisations. - ANIMAL RESEARCH
: ) The HAA plays a key role in the control of aggressive behaviours; similar hypothalamic structures exist in all species studied so far, including humans.
: ( Generalisation from animal experimentation; is aggression in animals more evolutionary/ to aid survival than in humans where knowledge may be more powerful than an evolutionary predisposition.
How does the amygdala (area) explain aggression
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Kluver & Bucy (1939) found that lesions to the medial temporal lobe in monkeys abolished aggressive behaviours; this gave rise to the condition Kluver- Bucy syndrome). Follow up studies also demonstrate how various male species can be tamed with lesions to the amygdala.
Downer (1961) also did studies with monkeys. The monkeys had part of their amygdala removed and the optic nerve cut. The monkey received visual signals that either went to the intact amygdala or signals that went to the ablated (removed) amygdala. If the monkeys had visual input that connected to the intact amygdala, they reacted in their normal way to humans- which was to be aggressive. If their visual input had no amygdala to reach then the monkeys were much calmer and placid- this did not reflect their usual reactions. This provides evidence for the amygdala being involved in an aggressive response to perceived threat.
: ) Animal experimentation has greatly improved our knowledge of aggression and the underlying neurobiology.
: ) There are similarities between animals and humans in terms of brain structure making generalisation possible, especially monkeys where there is evolutionary continuity.
: ( Generalisation issues (as before)
How does the pre-frontal cortex (area) explain aggression
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Phineas Gage suffered from an accident in which an iron rod was driven through his head and damaged the frontal cortex of the brain. Whilst laying new railway tracks some gunpowder exploded, launching a 3cm thick 90cm long iron bar through his face, skull and brain and out the other side. Gage survived, but remained a changed man.
afterwards the gage that was generous, etiquette manners, respectful and hard working transformed into the man that was impulsive, rude, obscene language, anti-social etc
This gave insight into particular regions of the brain as controlling aspects of our personality. Gage’s behavioural problems following his accident concurs with several other individuals with damage to the same brain region (Damasio, 1994).
– In the pre-frontal cortex, murderers had lower levels of glucose metabolism in the left and right relative to controls. Damage to this area of the brain can result in impulsivity, loss of self-control, immaturity, altered emotionality and the inability to modify behaviour, which can all in turn facilitate aggressive acts (Damasio, 1985). The researchers concluded that the offenders who had shown emotional impulsive aggression had not been able to regulate their behaviour due to this low level of functioning.
: ( There is an assumption with case study evidence that damage to an area of the brain results in the impairment we see in the individual. However, it is possible that how we study the brain is not precise or sophisticated enough to draw such conclusions.
Describe serotonin
low serotonin = highly aggressive (vice versa)
how does serotonin (brain functioning) explain aggression
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Low levels of serotonin and high levels of dopamine have been linked to aggression; psychologists believe that low levels of serotonin, known as the body’s natural ‘happy drug’, can lead to an increase in aggression levels. This is because serotonin is thought to inhibit our response to emotional stimuli that might otherwise lead to aggressive behaviour, so low levels of serotonin mean we will respond aggressively more often.
Serotonin is a neurotransmitter that has an important role in social decision-making by inhibiting aggressive social responses. Serotonin usually reduces aggression by preventing stimulation of the amygdala, a structure in the brain’s limbic system. Stimulation of the amygdala increases aggressive behaviour but serotonin prevents stimulation, thereby reducing aggression.
If there are low levels of serotonin in the brain, there is less inhibition of the amygdala. As a result it becomes more active when stimulated by external events, causing the person to act on their impulses and making aggression more likely. Therefore, low levels of serotonin have been associated with an increased susceptibility to impulsive and aggressive behaviour.
Mann et al.. gave participants the drug dexfenfluramine, which depletes levels of serotonin in the brain, to participants. The researchers then used a questionnaire to assess hostility and aggression levels, which were raised after taking dexfenfluramine in males but not in females.
Popova et al. found that among dogs that have been selectively bred for domestication and for increasingly docile temperament, there has been a corresponding increase (over generations) of brain serotonin. This suggests that there is a link between low levels of serotonin and high levels of aggression.
Further evidence comes from the use of drugs that raise levels of serotonin in the brain, such as antidepressants. In clinical studies, antidepressant drugs which elevate serotonin levels (e.g. SSRIs) also tend to reduce irritability and impulsive aggression. This suggests that increased serotonin levels do lead to reduced aggression. However, this relationship may not be causal.
: ( However results from animal research may not apply to humans due to the differences between our brain structures and dogs, for example. Animals are studied in artificial environments and show different social behaviour to humans. Aggression in humans might be far more complex than aggression shown in animals.
: ( There may be a gender bias in this research. Although a link was found between low levels of serotonin and aggression, this was not evident for the female participants. This suggests that the role of serotonin in aggression may be different for female compared to males, and therefore there is a gender bias in human studies in this area.
Describe dopamine
higher dopamine = more aggressive (vice versa)
how does dopamine (brain functioning) explain
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There also appears to be a link between the neurotransmitter dopamine and aggression, in that increased dopamine levels can produce increased levels of aggressive behaviour. For example, the increased rates of aggressive behaviour found in the schizophrenic population are believed to be due to the raised levels of dopamine in the brain.
Lavine (1997) found that an increase in dopamine levels through the use of amphetamines was associated with an increase in aggressive behaviour, suggesting that higher levels of dopamine correlate with higher levels of aggression.
The role of dopamine in aggression have also been demonstrated in studies which have used amphetamines, which increase levels of dopamine. Studies have found that when participants are given amphetamines, there is a corresponding increase in their levels of aggression.
: ) Evidence supporting the importance of dopamine in aggression comes from studies using antipsychotics, which reduce dopamine levels in the brain. These studies have generally found that the use of antipsychotics reduces the incidence of aggression, thus suggesting that decreased dopamine levels lead to decreased aggression.
: ( It is not clear whether there is a causal link between dopamine and aggression, however research has found a relationship between the two.
: ( A criticism of these links between neurotransmitters and aggression is that they can be described as reductionist. The complexity of human behaviour means that biological explanations are insufficient on their own to explain the many different aspects of human aggression. For example, research by Bandura found that social learning can be a powerful influence on the aggressive behaviour of children.
