Biological: The Dopamine Hypothesis Flashcards
What is the dopamine hypothesis?
-Brain is composed of millions of neurons which make up main anatomical structures of brain. Neurotransmitters are chemical messengers that transmit impulses across synapses between neurons.
-States messages from neurons that transmit dopamine fire too easily or too often, leading to symptoms of schizophrenia.
-Schizophrenics are thought to have abnormally high numbers of D2 receptors on receiving, resulting in more dopamine binding and therefore more neurons firing.
-Dopamine plays key role in guiding attention, so disturbances to this process may lead to problems relating to attention + perception.
Explain hyperdopaminergia in the subcortex
-Original version of hypothesis focused on possible role of high levels or activity of dopamine in subcortex i.e. central areas of brain.
-e.g. an excess of dopamine receptors in Broca’s area may be associate with poverty of speech and/or experience of auditory hallucinations.
Explain hypodopaminergia in the cortex
-More recent version of hypothesis have focused on abnormal dopamine systems in brain’s cortex.
-Goldman-Rakic et al (2004) have identified a role for low levels of dopamine in prefrontal cortex in negative symptoms.
Identify and describe the role of dopamine in schizophrenia in 3 sources
Amphetamines:
-A drug with special relevance for understanding of schizophrenia.
-Stimulant drugs that act by increasing availability of dopamine and noradrenaline in brain.
-A dopamine agonist, stimulating nerve cells containing dopamine causing synapse to be flooded with this neurotransmitter.
-Large doses can cause characteristic hallucinations and delusions of an episode. It can induce symptoms of acute paranoid schizophrenia in previously unaffected individuals and increase severity of symptoms in previously diagnosed cases.
Antipsychotic drugs:
-Blocks activity of dopamine in brain.
-By reducing stimulation of dopamine system, drugs eliminate symptoms such as hallucinations + delusions.
-Fact that these drugs alleviated may of symptoms strengthened case for dopamine being a significant contributory factor.
Parkinson’s disease:
-Low levels of dopamine activity found in people who suffer this disease.
-Found some people who were taking the drug L-dopa to raise levels of dopamine were developing schizophrenic-type symptoms.
What are 2 strengths of the dopamine hypothesis?
Based on Objective techniques:
-Research conducted in to this area carried out using valid and objective methods.
-e.g. PET scans have allowed researchers to investigate dopamine activity precisely by measuring waste products (metabolites).
-Post-mortems have also been used to look at differences between those with and without schizophrenia.
Gives huge advantage over other explanations like cognitive and family approaches as rely on subjective methods like observations and interviews -subjective and lack validity.
Focussing role on dopamine has led to development of anti-psychotic drugs:
-Reductionist approach has led to effective form of treatment for schizophrenia.
-By identifying and focusing on role of dopamine we have been able to successfully treat disorder with drugs that decrease levels.
Reduction of symptoms of patients taking drugs to rebalance levels of dopamine in turn supports dopamine hypothesis.
What are 2 limitations of the dopamine hypothesis
Ignores environmental factors:
-Criticised due to reductionism and failure to consider other factors e.g. environmental.
-Cognitive approach and family models propose that faulty thoughts and family dynamics contribute.
-Dopamine hypothesis assumes chemical imbalance is sole reason.
Environmental factors cannot be ignored as studies such as Tarrier show participants are more likely to suffer if from a home environment high in expressed emotion.
Ignores role of serotonin:
-Development of new types such as clozapine known as anti-psychotic drugs.
-Blocks fewer dopamine receptors for neurotransmitter serotonin. they appear particularly effective in reducing negative symptoms.
Research suggests schizophrenia may result from interaction of serotonin and dopamine rather than dopamine alone.
What can be concluded from the dopamine hypothesis?
Diathesis-stress model may be a better alternative:
-Considers both biological and social factors.
-e.g. Tienari et al (1987) looked at how childrearing skills affected those at risk from schizophrenia. Found high genetic risk children adopted into homes with healthy rearing patterns were at less risk of developing than those integrated into families with ‘adverse’ parenting. Children classified at lower risk in adverse group did not develop, which shows schizophrenia is developed in response to a number of social factors.
