Schizophrenia - Biological Explanations Flashcards
What is the definition of genetics?
Genes consist of DNA strands. DNA produces ‘instructions’ for general physical features of an organism (such as eye colour, height) and also specific physical features. These may impact on psychological features. Genes are transmitted from parents to offspring, i.e., inherited.
What is dopamine, and how is it linked to schizophrenia?
Dopamine – A neurotransmitter that generally has an excitatory effect and is associated with the sensation of pleasure. Unusually high levels are associated with schizophrenia and unusually low levels are associated with Parkinson’s disease.
What are neural correlates?
Neural correlates – Patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience.
What is the genetic basis of schizophrenia?
Schizophrenia runs in families. There is a strong relationship between genetic similarity and shared risk of schizophrenia, as shown in studies like Gottesman’s (1991) large-scale family study. Gottesman’s graph shows a 48% risk for identical twins, 17% for siblings, and 1% for the general population. This supports a genetic basis. Candidate genes, which are specific genes associated with risk, are believed to make schizophrenia polygenic and aetiologically heterogeneous. Research such as Ripke et al. (2014) identified 108 separate genetic variations linked to schizophrenia.
What is the dopamine hypothesis?
The dopamine hypothesis suggests that dopamine plays a role in schizophrenia. Hyperdopaminergia in the subcortex involves high levels of dopamine activity, such as in Broca’s area, leading to speech poverty or auditory hallucinations. More recent versions focus on hypodopaminergia in the cortex, where low dopamine levels in the prefrontal cortex are linked to negative symptoms. Both hypotheses may be correct, as both high and low dopamine levels contribute to different symptoms of schizophrenia.
What are neural correlates of schizophrenia?
Neural correlates involve structural or functional abnormalities in the brain linked to symptoms. For example, neural correlates of negative symptoms include abnormal activity in the ventral striatum, which is involved in anticipating rewards. Juckel et al. (2006) found that lower levels of activity in this region are linked to avolition. For positive symptoms, activity in the superior temporal gyrus and anterior cingulate gyrus is associated with hallucinations, as shown by Allen et al. (2007).
What is one evaluation point for the genetic explanation of schizophrenia?
Multiple sources of evidence support the genetic explanation. Gottesman’s (1991) family study shows how genetic similarity correlates with schizophrenia risk. Adoption studies, such as Pekka Tienari et al. (2004), found children of schizophrenia sufferers had higher risk even when adopted into non-schizophrenic families. Ripke et al. (2014) provided molecular-level evidence linking genetic variations to schizophrenia, supporting the idea that schizophrenia has a genetic basis.
What is one evaluation point for the dopamine hypothesis?
Mixed evidence exists for the dopamine hypothesis. Dopamine agonists increase symptoms in people without schizophrenia, while antipsychotics reduce symptoms (Curran et al., 2004). However, some studies, such as Noll (2009), suggest that other neurotransmitters like glutamate may also play a role. This indicates the dopamine hypothesis is not a complete explanation.
What is one evaluation point regarding neural correlates?
A correlation-causation problem exists in studies of neural correlates. For example, while Juckel et al. (2006) linked lower ventral striatum activity to avolition, this does not prove causation. It is possible that negative symptoms cause the reduced activity, or a third factor affects both. Thus, neural correlates alone cannot establish cause and effect.
What is one evaluation point regarding environmental factors in schizophrenia?
The role of the psychological environment is important but unclear. Evidence suggests genetic factors are strong, but environmental factors may also play a role. For example, Morkved et al. (2017) found that 67% of people with schizophrenia reported childhood trauma compared to 38% of a matched control group. This highlights the interaction between genes and environment in schizophrenia.
