- Created by: isystedman
- Created on: 31-05-18 16:40
Characteristics of the disorder;
- Symptoms or behaviours that are shown in addition to normal behaviour.
- Hallucinations are perceptions that aren't real, they are usually sounds, voices or tactile.
- Delusions are beliefs that aren't real, are usually in the form of persecution or grandiosity.
- Symptoms or behaviours that inhibit normal behaviour.
- Alogia - poverty of speech
- Avolition - unconcerned with the goings on in their environment
- Anhedonia - does not act appropriately in desirable situations
- The flatness of affect - no emotion
- Catatonic behaviour - fast repetitive movement or none at all
- The person's thoughts jump from one topic to another.
- Some will say the thoughts are not their own, this is called insertion.
Biological Explanation 1 - The Dopamine Hypothesis
The limbic system;
- The receptor site D2 is of most interest in research. This is found in the subcortical regions in the limbic system.
- The limbic system has nerve pathways that lead to subcortical regions and the cerebral cortex.
- The mesolimbic pathway carries signals from the ventral tegmental area to the nucleus accumbens. Too much dopamine in this pathway can cause positive symptoms.
- The mesocortical pathway carries signals from the ventral tegmental area to the frontal lobe.
- Davis found that too little dopamine is evident in D1 receptors of patients who show negative symptoms.
Evaluation of biological explanation 1;
Dopamine imbalances may be caused by genes;
- If dopamine imbalances are responsible, what causes them
- Gottesman found that as genetic similarity increased, so did the probability of both having schizophrenia.
- Scientists have found 108 genes associated with schizophrenia so it is a complex matter.
- To measure neurotransmitters, we measure what they are broken down into (metabolites)
- Metabolites are found in the cerebrospinal fluid which requires a lumbar puncture (painful)
- Can be difficult to measure so should be cautious when looking at neurotransmitter levels
The role of serotonin;
- Conventional antipsychotics worked by only blocking D2 but that didn't always work.
- Atypical antipsychotics like clozapine block D2 but also the serotonin receptor
- Shows dopamine cannot explain the disorder on its own
Dopamine, cause or effect?
- As well as dopamine being the cause, it could be an effect
- Cook used PET scans and could find no dopamine activity differences between those with and those without schizophrenia.
Biological Explanation 2 - Structural Abnormalities
- In some individuals with the disorder, their ventricles seem to be larger than those without.
- Weinberger used CAT scans and reported that a group of 58 patients with schizophrenia had larger ventricles than his control group of 56 normal individuals.
- Andreasen used MRI scans and found that schizophrenic individuals had ventricles that were 20-50% larger than normal individuals.
- Means the loss of neurons in the cerebral cortex making the brain look shrunken
- Atrophy results in the widening of the groves covering the cerebral cortex and are said to be shown in 20-35% of patients.
- Vita et al used CAT scans found 33% of the schizophrenic group showed atrophy.
- Is specifically related to males.