Overview of Techniques Used to Study the Brain
students, when psychologists study behaviour, they do not only ask what people do. They also ask how the brain makes that behaviour possible 🧠. This lesson explores the main techniques used to study the brain in IB Psychology HL. By the end of this lesson, you should be able to explain key methods, compare their strengths and weaknesses, apply them to research situations, and connect them to the wider biological approach to understanding behaviour.
Introduction: Why Study the Brain?
The biological approach assumes that behaviour can be explained partly through brain structure, brain activity, and the nervous system. That means if researchers want to understand memory, emotion, learning, stress, or mental disorders, they often need ways to look inside the brain or measure how it works.
A major challenge is that the brain is protected by the skull and is extremely complex. Scientists therefore use different techniques for different purposes. Some methods show the structure of the brain, while others show its activity or chemical processes. No single technique answers every question, so psychologists and neuroscientists usually choose a method based on the research aim.
Key idea
The main question is not just “What is in the brain?” but also “Which parts are active, when are they active, and how does that relate to behaviour?” ✅
Structural Techniques: Looking at Brain Anatomy
Structural techniques help researchers see the shape, size, and physical condition of the brain. These methods are important when studying injury, disease, or differences between brain areas.
CT scans
A computed tomography scan, or $CT$ scan, uses X-rays taken from many angles to create a cross-sectional image of the brain. These images can be combined to show brain structure in detail.
CT scans are useful for detecting problems such as bleeding, tumors, or swelling after a head injury. For example, if a person is in a car accident and doctors suspect brain damage, a $CT$ scan can quickly show whether there is internal injury.
However, $CT$ scans are mainly structural. They show anatomy, not real-time brain activity. They also expose the person to radiation, which is a limitation compared with some other methods.
MRI scans
Magnetic resonance imaging, or $MRI$, uses a strong magnetic field and radio waves to produce detailed images of brain structure. Unlike $CT$, it does not use X-rays, so it does not expose the person to ionizing radiation.
$MRI$ scans are especially helpful for seeing soft tissue clearly. They can reveal differences in brain size or abnormalities in areas such as the hippocampus or corpus callosum. Because the images are highly detailed, researchers use $MRI$ in studies of development, aging, and neurological conditions.
A limitation is that $MRI$ only shows structure. It does not directly measure neural activity. Also, the person must stay still inside a loud scanner, which can be uncomfortable 😵.
Functional Techniques: Measuring Brain Activity
Functional techniques are used to study what the brain is doing while a person performs a task, feels an emotion, or responds to a stimulus. These methods are central to modern biological psychology because they help link behaviour to brain function.
fMRI
Functional magnetic resonance imaging, or $fMRI$, measures changes in blood oxygenation in the brain. When a brain area becomes more active, it needs more oxygen, so blood flow changes. $fMRI$ detects these changes and creates a map of active regions.
This technique is widely used in psychology because it helps identify which brain areas are involved in language, attention, decision-making, memory, and emotion. For example, researchers might ask participants to complete a memory task while in the scanner and then compare activity in the hippocampus during different conditions.
A key point is that $fMRI$ does not directly measure neurons firing. It measures blood flow changes, which are an indirect sign of activity. This means researchers must be careful when making conclusions. Also, an image showing activity does not prove that one area causes the behaviour; it only shows that the area is associated with it.
PET scans
Positron emission tomography, or $PET$, uses a small amount of radioactive material called a tracer. The tracer is usually attached to a substance such as glucose, which is used by active brain cells. The scan shows which brain areas are using more of the tracer, giving information about metabolic activity.
$PET$ scans have been useful in studying disorders such as Alzheimer’s disease and Parkinson’s disease, as well as the effects of drugs on the brain. They can show how brain chemistry changes during different tasks or illness states.
A limitation is that $PET$ scans involve radiation and are therefore less commonly used when safer alternatives exist. They also give less detail about fine structure than $MRI$.
EEG
Electroencephalography, or $EEG$, records the brain’s electrical activity using electrodes placed on the scalp. It is especially useful for measuring brain waves and tracking changes over time.
$EEG$ has excellent temporal resolution, which means it can detect changes in brain activity very quickly. This makes it useful when studying sleep, attention, and response timing. For example, researchers may use $EEG$ to compare brain wave patterns during different sleep stages.
However, $EEG$ has weaker spatial resolution than $MRI$ or $fMRI$, meaning it is harder to pinpoint exactly where the activity is coming from. It tells us when activity occurs better than where it occurs.
fNIRS
Functional near-infrared spectroscopy, or $fNIRS$, is another method that measures blood flow changes near the surface of the brain using infrared light. It is less expensive and more portable than $fMRI$, which makes it useful in studies with infants, children, or participants who cannot easily stay still in a scanner.
It is often used in educational or developmental research because it is more comfortable than some other techniques. A drawback is that it only measures activity near the surface of the brain, so it cannot detect deeper structures well.
Recording and Stimulating the Brain
Some techniques are not only about observing the brain. Others allow researchers to influence brain activity and examine how behaviour changes. These methods can help identify whether a brain region has a role in a particular function.
Lesion studies
A lesion is damage to a brain area caused by injury, surgery, stroke, or disease. In lesion studies, researchers examine how damage to a specific area affects behaviour.
This method has been important in understanding localization of function, the idea that different parts of the brain are responsible for different tasks. For example, if damage to the left hemisphere affects language, this suggests that language is linked to that region.
Lesion studies can provide strong evidence because they connect damage to changes in behaviour. However, real brain injuries are often messy and affect more than one area, so it is difficult to make precise conclusions.
Electrical stimulation
Researchers can also stimulate a brain area using electrical methods and observe the effects. This is done carefully, often in clinical or animal research. If stimulating one region changes movement or perception, that gives clues about what the region does.
A related method in clinical neuroscience is deep brain stimulation, where implanted electrodes deliver electrical pulses to targeted areas. It is used in some medical treatments, such as for symptoms of Parkinson’s disease.
Electrical stimulation can help show causation more directly than observation alone, but it is invasive and not usually used in healthy human participants for research purposes.
Comparing the Techniques
students, one of the most important skills in IB Psychology HL is comparison. Each technique has strengths and weaknesses, and the best method depends on the research question.
If a researcher wants to know about brain structure, $MRI$ or $CT$ may be appropriate. If the aim is to study activity while a participant is doing a task, $fMRI$, $PET$, $EEG$, or $fNIRS$ may be better. If the goal is to understand the effects of damage, lesion studies are useful. If the aim is to test whether a region plays a role in a function, stimulation methods may help.
Quick comparison example
Imagine a study on memory. A structural scan such as $MRI$ could show whether the hippocampus is smaller than normal. An $fMRI$ scan could show whether the hippocampus becomes active during recall. A lesion study could examine whether people with hippocampal damage struggle to form new memories. Each technique answers a different part of the same broad question.
This is why biological psychology often uses multiple methods together. Combining evidence gives a more complete picture than relying on one technique alone 🔍.
Ethical and Practical Considerations
Studying the brain involves important ethical and practical issues. Some methods are non-invasive, such as $EEG$ and many forms of $fMRI$, while others are invasive or involve radiation, such as $PET$ and some lesion or stimulation methods.
Researchers must consider participant safety, informed consent, comfort, and confidentiality. They also need to think about cost, availability, and how easy the method is to use with different age groups. For example, a child may find a noisy scanner stressful, which could affect the quality of the data.
Another important issue is interpretation. Brain images can be impressive, but a bright area on a scan does not automatically mean a behaviour has been fully explained. Behaviour is produced by networks of brain regions, not just a single “spot” in the brain.
Conclusion
The techniques used to study the brain are central to the biological approach to understanding behaviour. Structural methods such as $CT$ and $MRI$ help researchers examine anatomy. Functional methods such as $fMRI$, $PET$, $EEG$, and $fNIRS$ show activity. Lesion studies and stimulation methods help researchers understand the role of specific areas in behaviour.
Together, these methods allow psychologists to build evidence about how the brain supports thought, emotion, and action. For IB Psychology HL, the key is not only remembering the names of the techniques, but also knowing what each one measures, what it is best used for, and what its limitations are.
Study Notes
- The biological approach explains behaviour through brain structure, brain activity, and nervous system function.
- $CT$ scans show brain structure using X-rays, but they do not show activity and involve radiation.
- $MRI$ scans show detailed brain anatomy using magnetic fields and radio waves, with no ionizing radiation.
- $fMRI$ measures blood oxygen changes and is used to study brain activity during tasks.
- $PET$ scans use radioactive tracers to measure brain metabolism and activity.
- $EEG$ records electrical activity from the scalp and has excellent temporal resolution.
- $fNIRS$ measures surface-level blood flow changes and is useful in child and developmental research.
- Lesion studies examine how brain damage affects behaviour and support the idea of localization of function.
- Electrical stimulation can test whether a brain region plays a role in a specific behaviour.
- No single method is perfect; researchers often combine techniques for a fuller understanding.
- A scan can show association between activity and behaviour, but not always direct causation.
- Ethical issues include safety, consent, comfort, radiation exposure, and invasiveness.