Biological explanation: The dopamine hypothesis

Biochemical explanation

• Caused by elevated levels of dopamine at key synaptic sites in subcortical regions of the brain

• Excess DA leads to too many impulses being transmitted triggering positive symptoms of schizophrenia

• Can be caused by numerous factors, including presynaptic neurons releasing too much DA

• Post synaptic there may not be enough dopamine being broken down, leaving too much dopamine in surrounding cells

• Reuptake processes may be impaired leaving too much dopamine in the synapse

Revised dopamine hypothesis

Davis et al (1991) pointed out that in the prefrontal cortex there are no D2 receptors so there may be a deficiency of dopamine in the region

Hyperdopaminergia

When there are overactive D2 receptors firing along the mesolimbic pathway from the ventral tegmental area to the nucleus accumbens, this leads to increased positive symptoms

hypodopaminergia

Caused by underactive D2 receptors in the mesocortical pathway from the ventral tegmental area to the prefrontal cortex, leading to negative symptoms

Evaluation points

• Research support: Randrup and Munkvad

• Alternative explanations

• Biologically reductionist

• Practical applications through drug treatments

• Cause and effect

• Can be compared to the diathesis stress model