Computerised axial tomography (CAT) scans

Computerised axial tomography (CAT) scans, also known as CT scans, produce detailed three-dimensional images of the brain's structure. This technique combines multiple X-ray images to reveal internal features layer by layer.

How CAT scans work

1. The machine rotates around the body, capturing X-ray images from various angles and at different depths.
2. These images represent thin "slices" through the brain, similar to cross-sections.
3. A computer processes the data to construct a complete 3D model, allowing users to see inside the brain 'slice by slice'.

Positron emission tomography (PET) scans

Positron emission tomography (PET) scans produce coloured images that indicate levels of functioning in different brain regions during tasks. These images show which areas are active when performing physical or mental activities.

How PET scans work

1. A radioactive tracer, often attached to compounds like glucose or oxygen, is injected or inhaled.
2. This tracer is detected by a scanner in the brain. As brain cells use the labelled glucose or oxygen in active parts of the brain, the tracer decays, releasing positrons.
3. When a positron collides with an electron, gamma rays are produced.
4. Detectors around the head capture these gamma rays.
5. A computer then maps their origins to create images showing activity levels, building up pictures of the brain with different levels of radioactivity, indicating cortical activity.

Functional magnetic resonance imaging (fMRI) scans

Functional magnetic resonance imaging (fMRI) scans monitor brain activity through blood flow changes. They detect variations in blood oxygenation, which correlate with neural activity.

How fMRI scans work

1. The scanner uses a strong magnetic field and radio waves to create detailed images of the body.
2. When neural activity rises in a brain area, it consumes more oxygen, prompting increased blood flow to deliver oxygenated blood.
3. Oxygenated blood differs in its properties from oxygen-poor blood, creating detectable signals.
4. The scanner captures these signals and a computer converts them into detailed images, highlighting active regions.
5. Monitoring these changes enables researchers to determine which parts of the brain are most active.

Applications and evaluation in studying human behaviour

Brain scanning techniques are applied in neuroscience to explore links between brain structures and behaviours. They can reveal how damage or activity in specific areas influences actions, such as after brain damage or to identify brain regions involved in cognitive activities. Brain-imaging technology is a promising way to investigate the possible relationship between biological factors and behaviour.

Evaluation of brain scanning techniques

Brain scans are a promising way to investigate the possible relationship between biological factors and behaviour. However, scanning can merely register structures and activity in the brain, and it is not possible to determine cause-effect relationships at this point.