Biological explanations description 

the initial hypothesis

individuals had too much dopamine

• griffith et al: induced psychosis in volunteers with dextro-amphetamine
• participants showed abrupt paranoid delusions and cold detached responses

this initial hypothesis was seen as too simple- administering drugs reducing dopamine had little/ no effect on negative symptoms

Dopamine Receptor sites

suggested the hypotheiss was over-simplified as subtypes of dopamine receptor sites had been found: D1-D5

widely found in the Cerebral Cortex and subcortically in the **Limbic System: (**Amygdala, Hypothalamus, Hippocampus)

Seeman and Lee: research shows the impact of antipsychotic drugs on D2 receptor

→ as D2 receptors found mainly in subcortical reigons of the limbic system, D2 became main focus of dopamine hypothesis

D1= -ve symptoms

D2= +ve symptoms

Revised Dopamine Hypothesis

limbic system contains subcortical structures. functions:

• Emotions
• memory formation
• arousal

nerve pathways leave the limbic system to the cerebral cortex (and other subcortical structures). 2 main pathways associated with schizophrenia - Mesocortical/ mesolimbic

Mesocortical Pathway

carries signals from the ==ventral tegmental area to the frontal lobe==

vital in :

• emotional responses
• motivation
• cognition

Davis et al: too little dopamine in D1 receptors of the frontal lobe of those with -ve symptoms snd cognitive impairments