dopamine hypothesis Flashcards
what is dopamine
a neurotransmitter that helps control the brains reward and pleasure centres. also helps regulate movement and emotional responses, and it enables us to see rewards but to take action to move toward them.
what is hyperdopaminergia
schizophrenics suffer from an excessive amount of dopamine in subcortical areas. this causes the neuron’s that use dopamine to fire too often and too many messages. High dopamine activity leads to acute episodes and positive symptoms.
associated with mesolyombic pathway.
what is hypodopaminergia
an argument for low levels of dopamine in the prefrontal cortex which is associated with negative symptoms of schizophrenia.
associated with mesocortical pathway.
what is the association between glutamate and dopamine levels
low glutamate levels associated with high levels of dopamine.
imbalance of glutamate levels in the cerebral cortex may create negative symptoms, whereas glutamate imbalance in basal ganglia could contribute to pos symptoms.
evidence supporting dopamine hypothesis
brain scans:
PET scans have found higher densistities of dopamine receptors and higher levels of dopamine production in schizophrenic brains.
there were found to be more than twice as many dopamine receptors than normal brains.
this could make their brains more sensitive to effects of dopamine.
MRI:
Walter 2009 found that dopamine overactivity in mesolimbic pathways of schizophrenics.
evaluation of brain scans
Strength = scientific
weakness: pet and mri scans are unable to distinguish between the brains orf people who do and do not have schizophrenia and therefore lacks predictive validity.
weakness: abnormal dopamine receptor activity may be a consequence rather than a cause.
evidence supporting dopamine hypothesis: drug studies
amphetamines
. amphetamines increase dopamine levels, producing delusions and hallucinations. amphetamines given to schizophrenic patients make their symptoms worse. supports the role of dopamine in schizophrenia.
PCP
(angel dust) inhibits glutamate and produces psychotic symptoms(even more of an effect on psychotic symptoms than amphetamines.
supports that glutamate is linked
however, hallucinations and delusions are a characteristic of other mental disorders, including bipolar.
anti psychotic drugs
such as chlorpromazine that reduce the symptoms schizophrenia reduce dopamine activity by temporarily blocking d2 receptors.
strengths/weaknessesn of dopamine hypothesis
S= neurotransmitters levels and receptor activity can be measured objectively so empirical evidence can be generated.
however neurotransmitters theories describes how neurotransmitter levels in schizophrenia are unusual but do not explain how they give rise to the symptoms.
evidence conclusion
although criticisms can be made of each piece of evidence, support for the role of neurotransmitters comes from a variety of sources which collectively give good support to the theory.
strengths/weakness - nurture
ignores nurture….family dysfunction schizophrenic mother, expressed emotion, double blind theory
alternative theory
other theories have focused on genetic and social factors.
it is difficult to ignore these other factors so neurotransmitter theories may be reductionist in focusing purely on neurotransmitter activity.
current thinking is that schizophrenic will only develop if bio factors such as neurochemical imbalance come together with significant psychological stressors.
this is known as the diathesis stress model.
