biological - dopamine hypothesis
- Created by: Elyseee
- Created on: 15-01-21 14:00
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- dopamine hypothesis
- limbic system
- Mesolimbic - carries signals from ventral tegmental area to nucleus accumbens. Too much dopamine can cause overstimulation and positive symptoms. Antipsychotic drugs reduce dopaminergic transmission, reduce dopamine activity in pathway and thus positive symptoms
- Mesocortical - carries signals from ventral tegmental area to frontal lobe. Pathway vital in emotional responses, motivation and cognition. Davies et al 1991 - too little dopamine evident in D1 receptors of those with cognitive impairments and negative symptoms
- Consists of variety of subcortical structures engaged in many functions, notably emotions, memory for mind and arousal
- Nerve pathway leave limbic system to other subcortical structures and cerebral cortex
- Two main pathways -mesolimbic and mesocortical (dopamine is major neurotransmitter for both)
- initial hypothesis
- Proposed that individuals with schizophrenia had too much of neurotransmitter dopamine as they demonstrated symptoms related to high dopamine levels
- Griffith et al 1968 - induced psychosis in non-schizophrenic volunteers by administering dexto-amphetamine (increase amount of dopamine in brain), found volunteers exhibited generally abrupt onset of paranoid delusions, and cold and detached emotional response
- Initial hypothesis identified as too simple, confirmed by fact that administering drugs to reduce dopamine levels had little to no effect on those who mainly suffered with negative symptoms
- dopamine receptor sites
- Situation complicated by discovery of several types of dopamine receptors, D1-D5 - widely distributed in cerebral cortex and subcortically in limbic system
- D2 receptor, Seeman and Lee 1975 - research shows impact of antipsychotic drugs on this receptor, found primarily subcortically, limbic system became main focus of dopamine hypothesis
- limbic system
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