Aggression revision
Biological explanations of aggression: Neural and hormonal
What is aggression
Aggression is behaviour that is threatening and intends to harm someone
- It can be physical or non physical
- Dan be directed at people and objects
Aggression and the hypothalamus
The hypothalamus is involved in activating the SNS and controls the flight or fight
response
- When the hypothalamus detects a potential threat or danger it triggers the
production of aggression behaviour, e.g. sends action potentials to motor neurons
to clunch fits ready to punch
The Role of the Amygdala in Aggression
The Amygdala helps the hypothalamus in detecting potential danger by seeing if the
situation is good or bad
- Therefore it detects the emotional meaning of events
- If the events are bad or dangerous, then the amygdala sends action potentials to
the hypothalamus, causing it to produce aggressive behaviour
MIR studies support the role of the amygdala in aggression. Sumer et al conducted a case
study on a 14 year old girl who had started to display excessive rage and anger even in
situations that were not suitable to display aggression in. Sumer et al did a MRI scan and
found that there was a tumour pressing into her amygdala. He concluded that this tumour
was causing the abnormal levels of aggression. This was because the amygdala
determines the emotional meaning of events and decides when a person needs to be
aggressive. This meant that as the tumour was pressing onto her amygdala there was
increased activity in the amygdala which leads to more aggression as the neurons are
sending more action potentials to the hypothalamus.
Mpakopoulou provides support for the role of the amygdala in aggression. She reviewed
13 studies of patients with extreme seizures due to abnormal activity in their amygdala. To
treat these seizures the patients had brain surgery to disconnect their amygdala from the
rest of their brain called an amygdalotomy. Before the surgery, patients had too much
,activity in their amygdala meaning they displayed increased aggression. After the surgery,
neurons in the amygdala could no longer send electrical signals to the hypothalamus
meaning their levels of aggression decreased. When Mpakopoulou reviewed all the studies
with the amygdalotomy, she found that it caused a decrease in aggressive behaviour that
ranged from 33% to 100%. This meant that for some patients the amygdalotomy fully
prevented aggressive behaviour which provides strong evidence for the role of the
amygdala in producing aggression.
One limitation of studies investigating the role of amygdala in aggression is that the
results aren't consistent across studies. For example, if neurons in the amygdala are
damaged, so that there is less neural activity in the amygdala, then there should be less
action potentials sent to the hypothalamus, causing a decrease in aggression. Some
studies have shown this but not all studies have. One study had found that damage in the
amygdala in cats had led to increased aggression alongside the same with monkeys.
However, all of these studies have shown that damage to the amygdala leads to a change
in aggression and therefore the amygdala is involved in aggression but the effects are not
consistent across studies. This suggests that the role of the amygdala in aggression may
be more complicated than thought. Recent research has found that the amygdala is split
up into subregions and each subregion performs a slightly different function. This means
that the role of the amygdala might differ depending on the sub-region of the amygdala.
The role of the hippocampus in aggression
Sometimes to determine the emotional meaning of an event we need to rely on our
memories
- When determining whether the events in the environment are good or bad the
amygdala also gets help from the hippocampus (as it stores our LTMs)
- The hippocampus sends action potentials to the amygdala which gives it
information about any relevant memories which helps the amygdala decide the
emotional meanings of events
- If the event is bad or treating then the amygdala will send action potentials to the
hypothalamus to produce aggression
The limbic system
Amygdala, hippocampus and hypothalamus are called the limbic system and they work
together to produce aggressive behaviour
The role of the frontal cortex in Aggression
, When we want to behave aggressively in an inappropriate situation, the frontal cortex
sends electrical signals that inhibit neurons in the amygdala which causes the neurons in
the amygdala to generate fewer action potentials to the hypothalamus which stops
aggressive behaviour
- If a person's frontal cortex is damaged and the neurons they cannot generate
electrical signals then the amygdala will not be inhibited meaning signals will
continue to be sent to the hypothalamus and are more likely to display aggression
The role of neurotransmitters: Serotonin
As well as the limbic system and frontal cortex, there are other brain mechanisms that can
help control aggression by increasing or decreasing aggressive behaviour
- Serotonin is one of the main neurotransmitters released in the limbic system and
plays a role in controlling our mood and how we feel about things
- When serotonin is released at synapses in the amygdala it causes negative
electrical charge to flow into neurons so the neurons are inhibited and are less
likely to generate action potentials meaning that the amygdala sends less action
potentials to the hypothalamus
- Serotonin then reduces aggressive behaviour and the more serotonin we have, the
less likely we are to be aggressive and the more serotonin we have, the more likely
we are to be aggressive
Support for the role of serotonin in aggression comes from Crocketts investigation. She
recruited a group of participants and split them into two groups, one was given a drug
which decreased their level of serotonin whilst the other was given a drug to increase their
level of serotonin. According to the biological approach it should be expected that
participants with increased serotonin levels to become less aggressive and participants
with decreased serotonin levels to become more aggressive. To test this prediction she
asked participants to take part in a social decision making game where she measured
their aggression levels. Crockett found that the participants who were given drugs to
increase their level of serotonin became more likely to make fair decisions and did not get
aggressive. On the other hand, if participants were given drugs that reduced their levels of
serotonin they were more likely to display aggression and anger if their appointment
made an unfair decision. This supports the idea that serotonin plays a role in controlling
aggression by reducing the level of aggression.
The role of neurotransmitters: Testosterone
Hormones are also involved in controlling levels of aggression
- Hormones are chemical messengers released by glands into the bloodstream
- Testosterone is a hormone that increases our tendency to be aggressive
Biological explanations of aggression: Neural and hormonal
What is aggression
Aggression is behaviour that is threatening and intends to harm someone
- It can be physical or non physical
- Dan be directed at people and objects
Aggression and the hypothalamus
The hypothalamus is involved in activating the SNS and controls the flight or fight
response
- When the hypothalamus detects a potential threat or danger it triggers the
production of aggression behaviour, e.g. sends action potentials to motor neurons
to clunch fits ready to punch
The Role of the Amygdala in Aggression
The Amygdala helps the hypothalamus in detecting potential danger by seeing if the
situation is good or bad
- Therefore it detects the emotional meaning of events
- If the events are bad or dangerous, then the amygdala sends action potentials to
the hypothalamus, causing it to produce aggressive behaviour
MIR studies support the role of the amygdala in aggression. Sumer et al conducted a case
study on a 14 year old girl who had started to display excessive rage and anger even in
situations that were not suitable to display aggression in. Sumer et al did a MRI scan and
found that there was a tumour pressing into her amygdala. He concluded that this tumour
was causing the abnormal levels of aggression. This was because the amygdala
determines the emotional meaning of events and decides when a person needs to be
aggressive. This meant that as the tumour was pressing onto her amygdala there was
increased activity in the amygdala which leads to more aggression as the neurons are
sending more action potentials to the hypothalamus.
Mpakopoulou provides support for the role of the amygdala in aggression. She reviewed
13 studies of patients with extreme seizures due to abnormal activity in their amygdala. To
treat these seizures the patients had brain surgery to disconnect their amygdala from the
rest of their brain called an amygdalotomy. Before the surgery, patients had too much
,activity in their amygdala meaning they displayed increased aggression. After the surgery,
neurons in the amygdala could no longer send electrical signals to the hypothalamus
meaning their levels of aggression decreased. When Mpakopoulou reviewed all the studies
with the amygdalotomy, she found that it caused a decrease in aggressive behaviour that
ranged from 33% to 100%. This meant that for some patients the amygdalotomy fully
prevented aggressive behaviour which provides strong evidence for the role of the
amygdala in producing aggression.
One limitation of studies investigating the role of amygdala in aggression is that the
results aren't consistent across studies. For example, if neurons in the amygdala are
damaged, so that there is less neural activity in the amygdala, then there should be less
action potentials sent to the hypothalamus, causing a decrease in aggression. Some
studies have shown this but not all studies have. One study had found that damage in the
amygdala in cats had led to increased aggression alongside the same with monkeys.
However, all of these studies have shown that damage to the amygdala leads to a change
in aggression and therefore the amygdala is involved in aggression but the effects are not
consistent across studies. This suggests that the role of the amygdala in aggression may
be more complicated than thought. Recent research has found that the amygdala is split
up into subregions and each subregion performs a slightly different function. This means
that the role of the amygdala might differ depending on the sub-region of the amygdala.
The role of the hippocampus in aggression
Sometimes to determine the emotional meaning of an event we need to rely on our
memories
- When determining whether the events in the environment are good or bad the
amygdala also gets help from the hippocampus (as it stores our LTMs)
- The hippocampus sends action potentials to the amygdala which gives it
information about any relevant memories which helps the amygdala decide the
emotional meanings of events
- If the event is bad or treating then the amygdala will send action potentials to the
hypothalamus to produce aggression
The limbic system
Amygdala, hippocampus and hypothalamus are called the limbic system and they work
together to produce aggressive behaviour
The role of the frontal cortex in Aggression
, When we want to behave aggressively in an inappropriate situation, the frontal cortex
sends electrical signals that inhibit neurons in the amygdala which causes the neurons in
the amygdala to generate fewer action potentials to the hypothalamus which stops
aggressive behaviour
- If a person's frontal cortex is damaged and the neurons they cannot generate
electrical signals then the amygdala will not be inhibited meaning signals will
continue to be sent to the hypothalamus and are more likely to display aggression
The role of neurotransmitters: Serotonin
As well as the limbic system and frontal cortex, there are other brain mechanisms that can
help control aggression by increasing or decreasing aggressive behaviour
- Serotonin is one of the main neurotransmitters released in the limbic system and
plays a role in controlling our mood and how we feel about things
- When serotonin is released at synapses in the amygdala it causes negative
electrical charge to flow into neurons so the neurons are inhibited and are less
likely to generate action potentials meaning that the amygdala sends less action
potentials to the hypothalamus
- Serotonin then reduces aggressive behaviour and the more serotonin we have, the
less likely we are to be aggressive and the more serotonin we have, the more likely
we are to be aggressive
Support for the role of serotonin in aggression comes from Crocketts investigation. She
recruited a group of participants and split them into two groups, one was given a drug
which decreased their level of serotonin whilst the other was given a drug to increase their
level of serotonin. According to the biological approach it should be expected that
participants with increased serotonin levels to become less aggressive and participants
with decreased serotonin levels to become more aggressive. To test this prediction she
asked participants to take part in a social decision making game where she measured
their aggression levels. Crockett found that the participants who were given drugs to
increase their level of serotonin became more likely to make fair decisions and did not get
aggressive. On the other hand, if participants were given drugs that reduced their levels of
serotonin they were more likely to display aggression and anger if their appointment
made an unfair decision. This supports the idea that serotonin plays a role in controlling
aggression by reducing the level of aggression.
The role of neurotransmitters: Testosterone
Hormones are also involved in controlling levels of aggression
- Hormones are chemical messengers released by glands into the bloodstream
- Testosterone is a hormone that increases our tendency to be aggressive
