Historical methods of studying brain structure and behaviour

Before the advent of advanced technology, understanding the link between brain structure and behaviour was challenging. Early psychologists relied on specific methods to draw connections between brain areas and their functions.

Early approaches to brain research - case studies of brain injury

• Observations of individuals with brain damage provided insights into brain function:
  • For instance, a notable case from 1848 involved Phineas Gage who suffered frontal lobe damage from a workplace accident involving an iron bar.
  • Post-injury, he displayed increased impulsivity, disorganisation, and aggression, suggesting the frontal lobe's role in regulating these behaviours.
• Limitations:
  • These studies often focused on single individuals, making it difficult to generalise findings to the wider population.
  • They lacked controlled conditions, reducing their scientific validity.
• Ethical constraints:
  • Deliberately causing brain injury in humans for study purposes was not permissible, restricting the scope of experimental research.

Early approaches to brain research - animal studies

Non-human animals were used to investigate brain-behaviour links, but differences between animal and human brain structures limited the applicability of results.

Modern brain scanning techniques and their applications

The development of brain scanning technologies has revolutionised the study of brain structure and function. These non-invasive methods allow psychologists to observe brain activity and anatomy in detail.

Types of brain scanning techniques

• Positron Emission Tomography (PET scans) - These scans reveal active brain areas during specific tasks by tracking metabolic activity over a short period, typically around 60 seconds. They help link particular brain regions to functions but do not capture moment-to-moment changes.
• Computerised Axial Tomography (CAT scans) - Used to identify structural abnormalities such as tumours or blood clots, focusing on brain anatomy rather than activity.
• Magnetic Resonance Imaging (MRI scans) - Offer detailed structural images, capable of detecting small abnormalities in brain tissue.
• Functional MRI (fMRI scans) - Combine structural and functional data, showing both brain anatomy and areas of activity during tasks.
• Superconducting Quantum Interference Device (SQUID magnetometry) - Measures magnetic fields produced by neuronal activity for precise imaging of brain function, though measurements can be disrupted by external magnetic sources.

Key research on brain structure changes

Research using modern scanning techniques has demonstrated that brain structures can physically change in response to specific demands or experiences.

Maguire et al (2000) study on taxi drivers

• Method - A natural experiment involving MRI scans of 16 licensed male London taxi drivers, compared with a control group of non-taxi drivers. Participants were healthy, with an average age of 44, and taxi drivers had at least 18 months of experience.
• Results - The taxi drivers showed a significantly larger right posterior hippocampus compared to the control group. The size increase correlated with the duration of their driving career, with longer-serving drivers having a more pronounced enlargement.
• Conclusions - The hippocampus appears to play a key role in spatial memory and navigation. The increased size in taxi drivers suggests that consistent use of navigational skills can lead to structural brain changes.
• Evaluation:
  • This study highlights brain plasticity, and potential for tailored rehabilitation strategies for brain injury patients.
  • Its controlled design enhances reliability and replicability.
  • However, the small sample size and focus on male London taxi drivers limit generalisation.
  • Findings are also specific to the hippocampus and may not apply to other brain regions.

Brain structure links to specific behaviours and disorders

Investigations into brain structure have identified connections between specific brain regions and various psychological functions or disorders.

Brain regions and associated functions

• Aggression and brain areas - Research from 1948 involving cats with damaged brain regions indicated that the hypothalamus and amygdala are involved in controlling aggression levels.
• Memory and the hippocampus - A 1957 case study of a patient unable to form long-term memories after brain surgery pointed to the hippocampus as crucial for memory storage and retrieval.
• Psychopathology and structural differences - Studies from 1995 revealed variations in the prefrontal cortex between individuals with schizophrenia and those without, indicating a potential link between brain structure and this mental health disorder.

Neurochemistry and its influence on behaviour

Beyond brain structure, the biological approach also examines neurochemistry, focusing on the role of neurotransmitters in the nervous system. Biological psychologists can study how neurotransmitter activity influences behaviours.

Neurotransmitters and psychological effects

• An excess or deficiency of certain neurotransmitters can contribute to psychological conditions.
• For example, elevated dopamine levels are associated with schizophrenia, and drugs that increase dopamine, such as cocaine, can mimic schizophrenia-like symptoms.

Advantages and limitations of the biological approach

The biological approach offers a scientific perspective on behaviour but is not without limitations.

Advantages of the biological approach

• Scientific evidence - Utilises empirical methods like brain scans to support or refute theories, enhancing the credibility of findings.
• Treatment development - Identifying biological causes for mental health issues or problematic behaviours enables the creation of effective biological interventions, such as medication.

Limitations of the biological approach

• Neglect of environmental factors - Fails to consider the impact of upbringing, social context, or personal experiences, which other psychological approaches view as critical to behaviour.
• Avoidance of responsibility - Attributing negative behaviours solely to biology may allow individuals or groups to evade accountability for their actions.