An Introduction to Neuropsychology
What Is Cognitive Neuroscience?
Cognitive neuroscience is a field of study that bridges biology and psychology. It asks: how do physical structures in the brain produce thoughts, memories and behaviours? Thanks to advances in brain scanning technology, researchers can observe the living brain in action and link patterns of neural activity to specific psychological functions.
Brain Scanning Techniques
Before modern scanning, the only way to study the brain was through case studies of people with brain injuries or through post-mortem examination. Today, three main scanning methods allow researchers to study the brain non-invasively.
A CT scan (Computed Tomography) uses a series of X-rays from different angles to create detailed cross-sectional images of the brain’s structure. CT scans are fast and widely available, making them useful in medical emergencies such as identifying a stroke or a tumour. However, they show structure only — not which areas are active.
A PET scan (Positron Emission Tomography) works differently. The patient is injected with a small amount of radioactive glucose. As the brain uses glucose for energy, the most active areas absorb the most glucose and produce the most radioactive emissions. The scanner detects these emissions and creates a colour-coded map showing brain activity. PET scans show function, but the resolution is lower than MRI and the participant must be injected with a radioactive substance.
An fMRI scan (Functional Magnetic Resonance Imaging) detects changes in blood oxygenation. When a brain area is active, it receives more oxygenated blood. The fMRI detects this and produces detailed, real-time images of which areas are working during a given task. fMRI has high spatial resolution, involves no radiation, and is currently the most widely used technique in cognitive neuroscience research.
Three scanning techniques: CT (X-rays, structure only, fast), PET (radioactive tracer, shows activity, lower resolution), fMRI (blood oxygen, real-time activity, high resolution, no radiation). CT and PET are older; fMRI is currently the most precise for research.
Aim: Endel Tulving aimed to use brain scanning to investigate whether episodic memory (personal memories) and semantic memory (general knowledge) are stored in different areas of the brain.
Method: Tulving used PET scanning while participants recalled either episodic memories (personal, experienced events) or semantic memories (general facts). He observed which brain areas showed increased activity during each type of recall.
Results: Episodic memory recall was associated with greater activity in the right prefrontal cortex, while semantic memory recall was associated with greater activity in the left prefrontal cortex. This pattern was consistent across participants.
Conclusion: The two types of long-term memory are supported by different, lateralised brain regions. This was important evidence that memory is not a single, unified function but is neurologically divided — supporting the idea of distinct memory systems and the principle of localisation of function.
Tulving’s gold memory study used PET scans to show that episodic memory recall activates the right prefrontal cortex and semantic memory recall activates the left prefrontal cortex — demonstrating that different memory types are neurologically distinct.
Neurological Damage: Stroke and Injury
Understanding what happens when the brain is damaged provides powerful evidence for localisation of function. A stroke occurs when the blood supply to part of the brain is cut off, causing neurons in that region to die due to oxygen deprivation. Because neurons cannot regenerate, the damage is often permanent.
The effects of a stroke depend entirely on which area of the brain is affected. A stroke in the motor cortex may cause paralysis or weakness on one side of the body (the opposite side to the damage, because the brain’s motor pathways cross over). A stroke affecting Broca’s area in the left frontal lobe may cause difficulty producing speech, while a stroke affecting Wernicke’s area in the temporal lobe may disrupt language comprehension.
A strength of brain scanning is that it provides objective, non-invasive evidence about brain function in living people, moving beyond the limitations of post-mortem case studies. This has greatly expanded our understanding of where psychological functions are located.
However, brain scans have weaknesses. They show correlation, not causation — an area lighting up during a task does not prove that area causes that function. Scans also measure activity across thousands of neurons at once, so fine-grained detail is limited. PET scans involve radioactive tracers, raising ethical concerns about exposing participants to radiation. All scans also require participants to lie still in an artificial laboratory setting, which may not reflect real-world brain activity.