Specification

  • The structure of the brain, different brain areas including the pre-frontal cortex and limbic system and brain functioning as an explanation of aggression as a human behaviour.

Brain Areas & Aggression

Aggression is a complex behaviour that is influenced by a variety of different brain areas.

The Limbic System

The amygdala is a key structure in the limbic system that is involved in aggression. The amygdala is responsible for processing emotional information, particularly fear and anxiety, and is activated when an individual perceives a threat. This activation can lead to an aggressive response. Research has shown that the amygdala is particularly active in individuals who are prone to aggressive behavior, and that damage to the amygdala can lead to a reduction in aggression.

The hypothalamus, which is also part of the limbic system, plays a critical role in regulating aggression by controlling the release of hormones, such as testosterone and cortisol, which are associated with aggressive behaviour. The hypothalamus is also involved in the regulation of the HPA axis, which can lead to increased aggression when activated.

The hippocampus, which is responsible for memory and spatial navigation, plays a critical role in the regulation of aggression. Research has shown that the hippocampus is active during aggressive behaviour, and that damage to the hippocampus can lead to difficulties in the regulation of aggressive behaviour.

The cingulate gyrus is involved in the regulation of emotional processing and is thought to play a role in the regulation of aggression. Research has shown that the cingulate gyrus is active during aggressive behaviour, and that damage to the cingulate gyrus can lead to difficulties in the regulation of aggressive behaviour.

Pre-Frontal Cortex

The prefrontal cortex (PFC) is a region of the brain located at the front of the cerebral hemispheres that plays a critical role in a wide range of cognitive and emotional processes, including decision making, impulse control, and emotion regulation. Studies in both animals and humans have shown that the PFC is involved in the regulation of aggression.

Damage to the PFC has been found to lead to increased aggression in both humans and animals. For example, studies of patients with brain injuries to the PFC have shown that they are more prone to aggressive behavior compared to healthy individuals. Similarly, studies in animals have shown that lesions to the PFC can lead to increased aggressive behavior.

Additionally, research has found that the PFC is involved in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis, which is a system in the body that is activated in response to stress. Studies have shown that when the HPA axis is activated, it can lead to increased aggression. The PFC plays a role in regulating the HPA axis, and research has found that people with low activity in the PFC are more likely to be aggressive when the HPA axis is activated.

Evaluation

Kluver and Bucy’s (1939)

Kluver and Bucy’s (1939) research provides evidence for the role of the limbic system in regulating aggressive responses. The researchers performed bilateral removal of the temporal lobes, which contain the limbic structures such as the amygdala, in rhesus monkeys.

After the surgery, the monkeys exhibited a number of behavioral changes, including a marked increase in aggressive behavior. The researchers observed that the monkeys would engage in unprovoked attacks on other animals and objects, and that they were less afraid of novel or potentially threatening stimuli. These findings suggest that the limbic structures, particularly the amygdala, play a critical role in regulating aggressive behavior.

Additionally, the monkeys also showed a phenomenon known as “psychic blindness,” which is characterized by a lack of fear or interest in visual stimuli. This suggests that the limbic structures may also play a role in the processing of emotional information.

Kluver and Bucy’s research demonstrates that the limbic system, and specifically the amygdala, play a critical role in the regulation of aggression and emotional processing.

Phineas Gage

The case of Phineas Gage is a famous example in neuroscience that has been used to demonstrate the relationship between brain structures and aggression. Phineas Gage was a railroad construction worker who, in 1848, had an iron rod accidentally pierce through his skull, damaging his brain. The rod entered through his cheek and exited through the top of his skull, damaging the frontal lobes, specifically the ventromedial prefrontal cortex (vmPFC) of his brain.

Surprisingly, Gage survived the accident and initially had no significant physical impairments. However, his personality underwent a dramatic change. Before the accident, Gage was described as a hardworking, responsible, and well-liked individual. After the accident, he became impulsive, irresponsible, and aggressive. His behaviour became so extreme that he was unable to hold down a job or maintain relationships.

This case study supports the role of brain structures in aggression because it demonstrates that specific regions of the brain, in this case the vmPFC, play a critical role in regulating aggressive behavior. The vmPFC is involved in decision making, impulse control, and emotional regulation, and it’s thought that the damage to Gage’s vmPFC led to the changes in his behavior.

This study also highlights the importance of the vmPFC in the regulation of emotions, including aggression. It shows that changes in the brain structures can lead to changes in behaviour, specifically in this case, increased aggression

Wong et al. (1997)

The study by Wong et al. (1997) provides evidence for the role of the amygdala in aggression by investigating the neural mechanisms underlying aggression in rats. The researchers used a rat model of aggression called resident-intruder paradigm, in which a resident rat is placed in a cage with a smaller intruder rat. The resident rat will often attack the intruder rat, displaying aggressive behaviour.

The researchers found that when they electrically stimulated the central nucleus of the amygdala (CeA), a region of the amygdala known to be involved in the regulation of aggressive behaviour, it increased aggressive behaviour in the resident rats. Conversely, when they inactivated the CeA with a chemical called muscimol, it decreased aggressive behaviour.

Additionally, the researchers found that the increased aggressive behavior was accompanied by increased activity in the CeA and increased release of the neurotransmitter norepinephrine in the CeA. This suggests that the CeA plays a critical role in the regulation of aggression by modulating the activity of neural circuits that control aggressive behavior.

The study by Wong et al. (1997) provides evidence for the role of the amygdala in aggression by showing that electrical stimulation of the CeA, a specific region of the amygdala, can increase aggressive behaviour in rats. The study also showed that the CeA is involved in the regulation of aggression by modulating the activity of neural circuits that control aggressive behaviour.

Raine et al. (1997)

One study by Raine et al. (1997) used MRI scans to investigate the brain structures of 19 violent males. The researchers found that the violent offenders had significantly larger amygdala volumes compared to a control group. These findings suggest that the amygdala may be involved in the regulation of aggressive behavior in humans as well.

Past Paper Questions

  • Identify two areas of the brain that are thought to influence aggression in humans. (2) June 2017
  • Explain one weakness of the structure of the brain as an explanation of human aggression. (2) October 2020
  • Describe the role of the pre-frontal cortex as an explanation of aggression. (3) January 2020
  • Anastacia had an accident where she slipped on a wet floor, banged her head and was unconscious for a short time. Since then she has become more aggressive, getting angry quickly and often shouting at her friends if she thinks they are wrong. Anastacia recently hit another person who accidently pushed her in a crowded room. Describe brain functioning as an explanation for Anastacia’s aggression. (4) June 2018
  • Describe how damage to the limbic system may cause the increase in aggression shown by Petal. (4) October 2019
  • Explain one strength and one weakness of brain functioning as an explanation of aggression in humans. (4) June 2017
  • Explain one strength and one weakness of brain functioning as an explanation for Anastacia’s aggression. (4) June 2018
  • Explain one strength and one weakness of damage to the limbic system as an explanation of Petal’s aggression. (4) October 2019
  • Discuss how different brain areas and brain functioning could account for Grei’s aggressive behaviour. (8) June 2019
  • The structure of the brain, different brain areas and brain functioning have been put forward as an explanation of human aggression. To what extent do you agree that this is a complete explanation of human aggression? (12) January 2017