Describe and evaluate two biological explanations of schizophrenia. (10+15)
The biological approach explains schizophrenia in terms of the dopamine hypothesis, a key principle in the biological approach. Dopamine was first looked at in the 1950s in relation to Parkinson’s disease and has since been the first stepping stone towards further understanding of many mental and physiological illnesses. The drug, L-DOPA was found to increase the levels of dopamine in the brain and has been key in improving the conditions of many people with Parkinson’s Disease. The dopamine hypothesis suggests that by manipulating dopamine in particular areas of the brain, we can reduce the symptoms of schizophrenia.
Initially, as a basic concept it was suggested that individuals with schizophrenia had too much dopamine and therefore demonstrated symptoms which reflected high levels of dopamine. This idea was supported by research and we’ve since gained further understanding from J.J. Griffith’s 1968 research conducted on non-schizophrenic volunteers which used a drug, dextro-ampthetamine, to induce psychosis, which ultimately led to schizophrenic symptoms such as paranoid delusions and a cold, detached emotional response. Therefore, this suggests that there is a link between dopamine and both positive and negative symptoms of schizophrenia.
However, the initial dopamine hypothesis was identified as being too simple, confirmed by the fact that administering drugs that reduce the levels of dopamine had little or no effect on those individuals who suffered mainly with the negative symptoms of schizophrenia.
Further elaboration on the dopamine hypothesis came with the discovery of several subtypes of dopamine receptor sites. This discovery allowed scientists to pinpoint areas of the brain to administer an increase or decrease of dopamine using drugs; dopamine receptor sites, D1-D5, which are widely distributed in the cerebral cortex and also subcortically in the limbic system. The D2 receptor site was of particular interest and research conducted by Seeman and Lee in 1975 showed the impact of antipsychotic drugs on this specific type of receptor. As D2 receptors are found primarily in subcortical regions, the limbic system became the main focus of the dopamine hypothesis.
The revised dopamine hypothesis is a further expansion upon what was known about receptor sites, with the main focus being on the limbic system. The limbic system consists of a variety of subcortical structures that are engaged in many functions, but most notably emotions, memory formation and arousal. Nerve pathways leave from the limbic system to many other subcortical structures and also to the cerebral cortex; two of the main pathways associated with schizophrenia in particular include the mesolimbic and mesocortical pathways.
Dopamine is a major neurotransmitter in the mesolimbic pathway. This pathway carries signals from the ventral tegmental area to the nucleus...