Characteristics of the disorder;

Positive symptoms;

  • 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.

Negative symptoms;

  • 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

Disordered thinking;

  • 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.

Measuring metabolites;

  • 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 

Enlarged ventricles;

  • 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.

Cortical atrophy:

  • 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.



No comments have yet been made