The dopamine hypothesis

• The dopamine hypothesis states that neural correlates result in schizophrenia specifically an excess of dopamine in certain regions of the brain leads to positive symptoms of schizophrenia.

  This is because messages fire too easily and too often leading to hallucinations and delusions.

  Increased numbers of D2 receptors leads to more dopamine binding and more neurons firing and it's these neurons that cause the positive symptoms.
• The original hypothesis outlined hyperdopaminergia which is the heightened levels of dopamine in the sub-cortex.

  This is due to increased numbers of dopamine receptors in Broca's which lead to speech poverty and auditory hallucinations.
• The updated hypothesis proposes the idea of hypodopaminergia which is lower levels of dopamine in the cortex.

  Goldman and Rakic stated that low levels of dopamine in the pre frontal cortex where thinking and decision making occurs leads to negative symptoms of schizophrenia.
• AO3

  :)

  Pet scans support the dopamine hypothesis and neural correlates.

  This is because the number of D2 receptors measured in the brains of schizophrenics were more than those in a 'normal' brain.

  This suggests that there may be more dopaminergic activity andf thus supports the original dopamine hypothesis, increasing its validity.
• AO3

  :)

  Research to support the dopamine hypothesis comes from Curran who found that dopamine agonists (amphetamine and cocaine) increase the levels of dopamine within individuals, making symptoms worse and producing more schizophrenic like symptoms in non sufferers.

  He also found that patients with Parkinson's who have low dopamine and take L-Dopa, have an increase in dopamine levels which can cause hallucinations.

  Therefore this supports the hyperdopaminergic explanation and the idea that positive symptoms are the result of high dopamine and this increases its validity.
• AO3

  :(

  However, there are issues with causality for the dopamine hypothesis as it can't easily explain differing abnormalities which occur from the dopamine system.

  This is because it's unlikely that there is just one neurotransmitter at play as researchers have investigated how serotonin and glutamate also interact with dopamine regarding schizophrenia.

  McCutcheon found post mortem studies and live scanning showed increased levels of glutamate in several areas of the brains of Sz patients.

  This reinforces the idea that dopamine may not be the only neurotransmitter at play.