Role of the amygdala

Question 1

Structure of the amygdala

Answer 1

Two amygdalae.
Each amygdala is located close to the hippocampus, in the temporal lobe.
It’s part of the limbic system.

Question 2

Functions of the amygdala

Answer 2

Essential to your ability to feel certain emotions and to perceive them in others.
This includes fear.

Question 3

Raine et al (1997)

Answer 3

Used PET scans to compare the brain activity og 39 males, 2 females, convicted murderers with a control group.
They found that the murderers did have different brain functioning compared to the control group in some areas.
The murderers had reduced activity in the prefrontal cortex and abnormal activity in the amygdala.

Question 4

IED

Answer 4

Intermittent explosive disorder.
Involves repeated and sudden episodes of impulsive, aggressive, violent behaviour or angry verbal outbursts in which you react out of proportion to the situation.
These outbursts cause significant distress, negatively impact relationships, work and school.

Question 5

IED - treatment

Answer 5

IED is a chronic disorder that can continue for years, although the severity of outbursts may decrease with age.
Treatment involves medications and psychotherapy to help control aggressive impulses.

Question 6

Coccaro et al (2007)

Answer 6

Investigated the effects of the amygdala on aggression by studying people with IED.
A common symptom of IED is outbursts of reactive aggression.
Each participant viewed images of faces at the same time of having an fMRI scan of their brain.
There was a key difference between these participants and non-IED controls.
The participants with IED showed high levels of amygdala activity when they viewed angry faces.
This finding demonstrates an association between amygdala activity and processing of aggressive emotions - and the study had high realism because an angry facial expression is an everyday signal of threat.

Question 7

fMRI

Answer 7

Functional Magnetic Resonance Imaging.
A method used used to scan brain activity while a person is performing a task.
Repeated MRI scans are made so that a series of images can be put together to show activity.

Question 8

Yu Gao and colleagues (2010) - background

Answer 8

We learn as children to inhibit our aggressive behaviour and antisocial behaviours through fear conditioning.
We learn that aggressive behaviour leads to punishment or other negative outcomes.
We know that the amygdala is involved in processing fear information and fear conditioning.
A dysfunction of the amygdala means the child can’t identify the social cues that indicate threat and therefore doesn’t link punishment to their aggressive behaviour.
Fear conditioning is disrupted and the outcome is that individuals with amygdala dysfunction seems fearless, overly aggressive and antisocial.

Question 9

Yu Gao and colleagues (2010) - methodology, procedures, findings and conclusions

Answer 9

Longitudinal study.
1,795 participants.
Tested for fear conditioning at the age of 3.
The measure used was physiological arousal (indicated by sweating) in response to a painful noise.
Twenty years later, the researchers found out which participants were involved in criminal behaviour.
Those who had committed crimes at the age of 23 years had shown no fear conditioning when they were 3.
They were “fearless”.
This suggests there may be a casual relationship between amygdala dysfunction and antisocial / criminal behaviour.

Question 10

Feinstein et al (2012)

Answer 10

Investigated the rare case of a woman named SM who had lesions to both amygdala. This caused her to be unable to experience fear.

Question 11

Feinstein et al (2012) - procedures

Answer 11

To provoke fear in SM, she was exposed to live snakes and spiders, taken on a tour of a haunted house, and shown emotionally evocative films.

Question 12

Feinstein et al (2012) - findings

Answer 12

On no occasion did SM exhibit fear, and she never endorsed feeling more than minimal levels of fear.
Across a large amount of self-report questionnaires, 3 months of real-life experience sampling, and a life history replete with traumatic events, SM repeatedly demonstrated an absence of overt fear manifestations and an overall impoverished experience of fear.
Despite her lack of fear, SM is able to exhibit other basic emotions and experience the respective feelings.

Question 13

Feinstein et al (2012) - conclusion

Answer 13

The findings support the conclusion that the human amygdala plays a pivotal role in triggering a state of fear and that the absence of such a state precludes the experience of fear itself.

Question 14

Pardini

Answer 14

Identified 56 aggressive men in a sample of 503 males studied from when they were about 6 years old.
They had shown aggressive behaviours since childhood and has since been involved in crimes such as robbery and gang fighting.
fMRI brain scans showed that high levels of aggression over the 20 year period were associated with low amygdala volume.
This is support of the role of the amygdala.
Important confounding variables like IQ, ethnicity and substance abuse were controlled in the study.

Question 15

Gospic et al (2011)

Answer 15

Used the Ultimatum Game, a laboratory based method of measuring aggressive behaviour.
It involves two players, the Proposer and the Responded, and a sum of money.
The Prosper offers to split the money in a “fair” or “unfair” way.
An unfair offer is considered to be a social provocation or threat.
If the Responder accepts then the money is split accordingly.
However, if the Responder refuses the offer then both get nothing.
A rejection of an offer is considered aggressive behaviour.
The study’s participants played the role of Responder while undergoing fMRI brain scans.

Question 16

Gospic et al (2011) - findings and conclusions

Answer 16

Found that when Responders rejected unfair offers, amygdala activity was heightened and quicker.
Furthermore, a sedative drug given before the game had two effects:
It reduced aggression (by halving the number of rejections) and at the same time reduced amygdala activity.
This is strong evidence of an association between reactive (“hot-blooded”) aggression and increased amygdala activity.

Question 17

Raine et al (1997) - regulation of aggressive criminal behaviour

Answer 17

Investigated murderers who had used an overwhelming degree of reactive (“hot-blooded”) aggression in their crimes.
These individuals had higher glucose metabolism in the their amygdala.
They also had abnormally low metabolism in the prefrontal cortex (which includes the OFC).
This finding demonstrates just how complex the regulation of aggressive criminal behaviour is.
It involves at least three important brain structures:
The amygdala
The OFC
The neural connection between them
Therefore, dysfunctions of the amygdala may not be enough on their own to account for criminal behaviour.
The neurology of aggressive crime is complex and risks being oversimplified by a focus on just the amygdala.

Question 18

Effects of the amygdala are indirect

Answer 18

The amygdala has a role in regulating fear and anxiety-related behaviours.
For example -
The physiological arousal that accompanies the fight-or-flight response.
Damage to the amygdala affects the ability to process fear and anxiety-related information normally, which in turn affects social functioning.
This makes aggressive behaviour more likely but not inevitable.
Therefore amygdala dysfunction isn’t necessarily a direct cause of aggressive criminal behaviour, but it’s instead a risk factor for it.
Whether an individual becomes involved in criminal behaviour depends on other biological and environmental factors.
This is a more complex explanation than the conventional amygdala dysfunction theory.

Question 19

Gesch et al (2002) - methodology and procedures

Answer 19

Conducted a placebo-controlled, randomised, double-blind study with 231 adult British prisoners.
Some of the prisoners were given capsules containing nutrients such as vitamins, minerals and omega-3 fatty acids.
The other participants received a placebo.

Question 20

Gesch et al (2002) - findings

Answer 20

After taking supplements for two weeks, the active intervention group committed 35% fewer disciplinary offences on average than they had before the trial began.
They also committed 26% fewer offences on average than the placebo control group.

Question 21

Derntl et al (2009)

Answer 21

Used MRI scans to investigate the effect of testosterone on amygdala activity in healthy male participants.
She found that increased testosterone improved the amygdala’s ability to process threat-related stimuli (fearful and angry facial expressions).
She argued that “when confronted with human facial expressions, testosterone prepares females and males for further behavioural activation.”
This could explain why violent crime is more common amongst males, as they have a higher concentration of testosterone than women.