The Dopamine Hypothesis

Question 1

What neurotransmitter has been implicated in the symptoms of schizophrenia?

Answer 1

Dopamine

Question 2

What activities does dopamine play a key role in?

Answer 2

Guiding attention, so disturbances with dopamine levels may lead to problems relating to attention, perception and thought, found in people with schizophrenia.

Question 3

What did the ORIGINAL dopamine hypothesis claim?

Answer 3

The original dopamine hypothesis claimed that an excess of the neurotransmitter dopamine in certain areas of the brain was responsible for schizophrenia.

Question 4

The original dopamine hypothesis thought schizophrenics had abnormally high levels of what?

Answer 4

D2 receptors on receiving neurons

Resulting in more dopamine binding and then more neurons firing

Question 5

The key role that the dopamine hypothesis plays is highlighted by what 2 key sources of evidence?

Answer 5

• Drugs that increase dopaminergic activity

* Drugs that decrease dopaminergic activity

Question 6

Give an example of a drug which is a dopamine agonist

Answer 6

• Amphetamine
• Cocaine
• Speed

Question 7

What does a dopamine agonist do?

Answer 7

It stimulates nerve cells containing dopamine causing the synapse to be flooded with this neurotransmitter.

‘Normal’ individuals who are exposed to large spears of dopamine releasing drugs can develop hallucinations and delusions characteristic of a schizophrenic episode. This generally disappears with abstinence from the drug.

Question 8

What drugs are dopamine antagonists?

Answer 8

Antipsychotic drugs

Question 9

What do dopamine antagonists do?

Answer 9

They block the activity of dopamine in the brain by blocking receptors to stop excess dopamine in the synapse binding and overstimulating the neuron. By reducing activity in the neural pathways of the brain, they eliminate symptoms such as hallucinations and delusions.

Question 10

What do these two sources of evidence (dopamine agonists and antagonists) suggest about the role of dopamine in schizophrenia?

Answer 10

It suggests that too much leads to positive symptoms such as hallucinations and delusions.

Question 11

What does the revised dopamine hypothesis say?

Answer 11

The most recent explanation focuses on the role of excess levels of dopamine in positive symptoms and low levels in negative symptoms.

Question 12

What is the word for too much dopamine?

Answer 12

Hyperdopaminergia

Question 13

In the revised hypothesis model, what part of the brain does it suggest has hyperdopaminergia?

Answer 13

There are high levels of dopamine in the sub-cortex (central) areas of the brain, including the Broca’s area (associated with speech production)

Question 14

What does hyperdopaminergia in the sub cortex of the brain suggest?

Answer 14

It suggests that the speech problems associated with schizophrenia such as poverty of speech and the experience of auditory hallucinations may be the result of too much dopamine.

Question 15

What is the word for low levels of dopamine?

Answer 15

Hypodopaminergia

Question 16

In the revised dopamine hypothesis, what part of the brain does it suggest has hypodopaminergia?

Answer 16

The prefrontal cortex (responsible for thinking and decision making)

Question 17

What type of symptoms of schizophrenia is caused by hypodopaminergia in the prefrontal cortex?

Answer 17

Low levels of dopamine found in the prefrontal cortex may be associated with the negative symptoms of schizophrenia.

Question 18

What does hyperdopaminergia and hypodopaminergia in the brain suggest?

Answer 18

It may be then that both explanations are correct - both low and high levels in different brain regions may be involved in schizophrenia.

High levels for positive symptoms and low levels for negative symptoms.

Question 19

EVALUATION

Does the role of dopamine have any practical applications?

Answer 19

The role of dopamine had led to an important practical application.

Knowledge of the role of neurotransmitters has benefitted psychiatry by allowing the development of antipsychotic drugs which are the primary course of treatment for schizophrenia. These drugs act to reduce dopamine levels and are now the primary course of treatment for the disorder.

These drugs are now an indispensable treatment for schizophrenia and the fact that they have dramatically improved the life of schizophrenics and their families is a real strength of the dopamine hypothesis.

Question 20

EVALUATION

Describe the study that provides support for drug treatments and why it supports abnormal dopamine functioning in schizophrenia

Answer 20

The success of drug treatments provides support for abnormal dopamine functioning in schizophrenia.

Much of the evidence for the role of dopamine comes from the success of drug treatments that attempt to change levels of dopamine activity in the brain. Antipsychotic drugs reduce the effects of dopamine and in doing so reduce the symptoms of schizophrenia.

Leucht et al carried out a meta-analysis of 212 studies that had analysed the effectiveness of different antipsychotic drugs compared with a placebo. They found that all the drugs tested were significantly more effective than placebo in the treatment of positive and negative symptoms.

The effectiveness of these drugs suggest that dopamine does play an important role in the development of schizophrenia. Therefore, this supports the dopamine hypothesis because it suggests that too much dopamine causes the positive symptoms.

Question 21

EVALUATION

Give one criticism of the dopamine hypothesis

Answer 21

A criticism of the dopamine hypothesis is that it does not provide a complete explanation for schizophrenia.

Antipsychotic drugs do not alleviate hallucinations and delusions (positive symptoms) in about one-third of patients. Also, in some patients, hallucinations and delusions are present despite levels of dopamine being normal.

This suggests that rather than dopamine being the sole cause of positive symptoms, other neurotransmitter systems, acting independently of the dopaminergic system, may also produce the positive symptoms of schizophrenia. Current research is focusing on the role of the neurotransmitter glutamate.

This suggests that evidence for the dopamine hypothesis can at best be described as mixed.