Dopamine Hypothesis + Evaluation

( Neural explanation )

Dopamine Hypothesis - Davis and Kahn

Theory linking dopamine levels to schizophrenia symptoms.

Positive Symptoms

caused by an excess of dopamine found in the sub cortex. e.g. Broca's area

Negative Symptoms

caused by low levels of dopamine found in the pre frontal cortex.

D2 Receptors

Dopamine receptors associated with increased neuron firing.

D1 Receptors

Dopamine receptors associated with decreased neuron activity/neurone firing.

PET Scans

Showed that there were higher neuron activity levels in D2 receptors.

fMRI Scans

Showed that there were lower neuron activity levels in D1 receptors.

Broca's Area

Region linked to speech production, affected in schizophrenia.

Other Theories - Post mortem and live scanning studies (McCutcheon et al. 2020)

• These have consistently found raised levels of the neurotransmitter glutamate in several brain regions of schizophrenic people.

• several candidate genes for Sz are believed to be involved in glutamate production or processing

Other drugs - Dépatie and Lal 2001

• Other drugs that increase DA levels do not cause schizophrenic-like symptoms. e.g apomorphine

Garson 2017

• Challenged the idea that amphetamine psychosis closely mimics schizophrenia

Other drugs - Curran et al 2004

Amphetamines increase DA, WORSENING symptoms in people with schizophrenia and INDUCING symptoms in people without it.

Other Drugs - Tauscher et al 2014

Antipsychotic drugs reduce DA activity and also reduce the intensity of symptoms .

Real Life Application - Rats and Schizophrenia (Catherine Tenn et al. 2003)

Relieved schizophrenic-like symptoms in rats using drugs that reduce DA action.