Schizophrenia Research (OCR GCSE Psychology): Revision Note

Schizophrenia core study: Daniel, Weinberger, Jones et al. (1991)

Background

• Previous research found low activity in the prefrontal cortex of people with schizophrenia

  • This brain region is associated with planning, decision-making, and control of behaviour

• Reduced activity in the frontal lobes has been linked to a lack of dopamine, a neurotransmitter which affects attention and perception

• Researchers aimed to test whether dopamine activity influences blood flow and cognitive performance in schizophrenia

Aim

• To investigate the effect of amphetamine (a dopamine agonist) on regional cerebral blood flow (rCBF) in the brains of people with schizophrenia.

• To see whether increasing dopamine would alter brain activity during a cognitive task

Method

• Type of study:

  • Laboratory experiment using Single Photon Emission-Computed Tomography (SPECT) brain scans

• Independent variable (IV):

  • Whether participants were given amphetamine or a placebo

• Dependent variable (DV):

  • Regional cerebral blood flow and performance on the Wisconsin Card Sorting Test

• Sample:

  • 10 inpatients from the National Institute of Mental Health, Washington, USA

  • All had chronic schizophrenia and were clinically stable for at least 6 weeks on a fixed dose of an antipsychotic drug

  • All were free from any illness that could affect blood flow and free of alcohol or drug use

• Procedure:

  • Brain activity was recorded using SPECT scans while participants performed two computer-based tasks:

    • BAR task: a simple sensorimotor task where participants matched bars based on orientation.

    • WCST: a complex cognitive task testing prefrontal cortex activation.

  • Five participants completed the BAR task first, and five completed the WCST first (counterbalanced)

  • Each participant completed both tasks twice: either after taking an amphetamine or after a placebo, with 2–4 days between sessions

  • Both tasks required similar motor responses to ensure a fair comparison

Results

• Amphetamine caused a small general increase in prefrontal cortex activity overall

• Significant differences in blood flow were found in the frontal cortex, occipital cortex, and anterior cingulate cortex during the WCST

• Cognitive performance improved after amphetamine:

  • Participants made more correct responses compared to the placebo condition

• Behavioural effects varied:

  • Some became more alert and motivated

  • Others became irritable or experienced low mood (dysphoria)

• Placebos had no significant effect on brain activity or performance

Conclusion

• Amphetamine increased dopamine levels in the prefrontal cortex activity

  • Activity in this brain area was higher during cognitive tasks, despite a reduction in overall blood flow in that region

• The findings support the biological theory of schizophrenia, showing a link between a lack of dopamine in the prefrontal cortex and schizophrenia

• The study also indicates that some cognitive deficits may be reversible through dopamine-related neural activity

Criticisms

• Small sample size:

  • Only 10 participants were included, meaning that the results may not generalise to all people with schizophrenia

• Cultural bias

  • All participants were from a small region of the USA, mostly White, limiting representativeness

  • Since schizophrenia rates differ across ethnic groups, generalisations about the brain–schizophrenia relationship should be made cautiously

• Lack of temporal validity

  • The study used older diagnostic systems for schizophrenia, which differ from those used today, so results may not reflect current classifications

• Ethical concerns:

  • Participants were exposed to SPECT brain scans and amphetamine, with unclear long-term effects

  • Some were scanned after receiving only a placebo, meaning there was no therapeutic benefit to justify potential risks

• Extraneous variables

  • Participants had previously received haloperidol (an antipsychotic), which may have influenced brain activity

  • This makes it harder to establish cause and effect between dopamine levels and brain function