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Biological Explanation 2: The role of the amygdala

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Victoria Varney

on 27 May 2017

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Transcript of Biological Explanation 2: The role of the amygdala

Tasks
Complete the cut and stick for the evaluation of the role of the amygdala.
Practice Questions

Choose a question (or 2) to answer:
Describe one biological explanation for criminal behaviour. [5]
Describe two biological explanations of criminal behaviour. [10]
Evaluate two biological explanations of criminal behaviour. [15]
Analyse and evaluate the biological explanations for criminal behaviour. [10]
Outline how one method of modifying behaviour can be applied to the characteristics of criminal behaviour. [5]

Final activity
A choice of tasks:
Create a poster to summarise the two biological explanations.

Create flashcards for the biological explanations.

Create a plan for the possible questions in this section.

Create a podcast to help you revise.

Look online for current and new research for the topic.
Structure and function of the amygdala
The amygdala is made up of 'grey matter', a collection of neuron cell bodies densely packed together in a cluster of 13 nuclei. It is found in the
medial temporal lobe
. It is a part of the brain structure called the
limbic system
. There are two amygdalae, one per brain hemisphere.
It is neurally linked to the hypothalamus, hippocampus and prefrontal cortex. It has a widespread influence on emotion, motivation and social interaction in humans and non-human animals. It plays a major role in perception of threat and is important in determining aggressive behaviour.
Amygdala and aggression
Coccaro et al. (2007) investigated the effects of the amygdala on aggression by studying people with intermittent explosive disorder (IED).

IED has a set of symptoms, one of which is reactive aggression.

Participants were shown a set of facial expressions while in an fMRI scanner.









The participants with IED had an increase in amygdala activity when shown photos of angry faces.

This study has high realism because an angry face is an everyday signal of threat.
Amygdala and fear conditioning
Gao et al. (2010) investigated why the amygdala leads to aggression and ultimately criminal behaviour.The amygdala is involved in processing fear and fear conditioning.

As children we learn aggression and antisocial behaviour through fear conditioning. We learn that aggressive behaviour leads to punishment (or other negative outcomes, e.g. loss of friendships).

A dysfunction in the amygdala means the child cannot identify the social cues that indicate a threat (e.g. angry faces) and therefore do not associate the punishment to their own aggressive behaviour.

Fear conditioning is disrupted – the outcome for the child with amygdala dysfunction is fearlessness, and overly aggressive and antisocial behaviour.

It was a longitudinal study with 1795 participants, they were tested for fear conditioning at the age of 3. The measure used was sweating (physiological arousal) in response to a painful noise. 20 years later the researchers found out which participants were involved in criminal behaviour. Those who had committed crimes at 23 showed no fear conditioning at 3 - they were fearless. This shows that there is a causal relationship between amygdala dysfunction and antisocial/criminal behaviour.
Outline
Evaluation
Learning Objective:
To understand and evaluate the biological explanations of criminal behaviour (role of the amygdala).

Success Criteria
Use an iPad to find the amygdala and outline its structure and function.
Make notes about the role of the amygdala.
Evaluate the role of the amygdala.
Challenge: Compare the two biological
explanations of criminal behaviour.
Biological Explanation 2: The role of the amygdala
Homework
Watch the video on Eysenck's personality theory in preparation for next lesson. You should also read and highlight Factsheet 151: Criminal Personality
Criminal Behaviour
Starter
Use the iPad 3D brain app to find the amygdala of the brain. Read all about its function.

Using the textbook, answer the question in the booklet about the structure and function of the amygdala.
Answers
Support from longitudinal studies
Pardini et al. (2014) selected 503 males who had taken part in an earlier study in 1986-87 when they were 6 or 7 years old. 20 years later the researchers selected a subgroup of 56 men who had shown aggressive behaviour since childhood (including serious crime such as rape, robbery, gang fighting). fMRI scans were used to measure amygdala volume in these men. Analyses examined the association between amygdala volume and levels of aggression and psychopathic features of participants measured in childhood and adolescence. Analyses also examined whether amygdala volume was associated with violence and psychopathic traits assessed at a 3-year follow-up. The results showed that men with lower amygdala volume exhibited higher levels of aggression and psychopathic features from childhood to adulthood. Lower amygdala volume was also associated with aggression, violence, and psychopathic traits at a 3-year follow-up, even after controlling for earlier levels of these features. This represents the first prospective study to demonstrate that men with lower amygdala volume have a longstanding history of aggression and psychopathic features and are at increased risk for committing future violence giving high predictive validity.
Other areas of the brain are important
The amygdala is part of a wider system of connected structures and doesn’t operate on its own to determine criminal behaviour. It works together with the orbitofrontal cortex which is located in the prefrontal cortex (which is thought to influence self-control, regulate impulsive behaviour, and inhibit aggression).
Raine et al. (1997) investigated murderers who had used a high level of reactive (‘hot-blooded’) aggression. These individuals had higher glucose metabolism in their amygdala, but abnormally low metabolism in their prefrontal cortex. This demonstrates the complexity of aggressive criminal behaviour.
Using research to support behaviour change
In order for people to accept the biological explanation there has to be an element of behavioural change. One method is to reverse the amygdala dysfunction or lessening its effects. It has been possible to moderate the effects through diet. Gesch et al. (2002) conducted a placebo-controlled, randomised, double-blind study with 231 adult British prisoners. Half of the prisoners were given vitamin capsules, the other half received a placebo. 2 weeks later the vitamin group has committed 26% fewer offences than the placebo group.
Effects of the amygdala are indirect
Damage to the amygdala affects the ability to process fear and anxiety, which also influences social functioning (e.g. reducing empathy). This makes aggressive behaviour more likely but not inevitable. Therefore amygdala dysfunction is not necessarily a direct cause of aggressive behaviour, but it is a risk factor (and depends on biological and environmental factors too).
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