Key Studies Using fMRI and PET 🧠📊

students, in this lesson you will learn how scientists use brain-imaging methods to study behaviour and mental processes. The focus is on two major techniques: functional magnetic resonance imaging ($fMRI$) and positron emission tomography ($PET$). These methods are important in the biological approach because they help researchers connect what people do, think, and feel with activity in the brain. By the end of this lesson, you should be able to explain how the methods work, describe key studies, and use them to support biological explanations of behaviour.

Why brain scans matter in psychology

The biological approach asks how the brain, nervous system, hormones, and genes influence behaviour. Brain-imaging methods are valuable because they let researchers observe the living brain in action. Instead of studying the brain only after death, scientists can look at which areas are active while a person remembers, moves, reads, listens, or feels emotion.

This is useful because behaviour is not controlled by one single brain spot. Different tasks often involve networks of regions working together. For example, reading a word may involve visual areas, language areas, and memory systems. A scan can help show which parts of the brain are linked with a task and whether certain groups, such as people with depression or schizophrenia, show different patterns of activity compared with healthy participants.

However, brain scans do not directly show thoughts. They show patterns of activity related to brain function. That means psychologists must be careful when interpreting results. A scan can suggest that a brain area is involved in a task, but it does not prove that the area alone causes the behaviour. This is an important IB idea when evaluating biological evidence.

How $fMRI$ works

$fMRI$ stands for functional magnetic resonance imaging. It measures changes in blood oxygen levels in the brain. When a region of the brain is working harder, it uses more oxygen. The body responds by increasing blood flow to that area. The scanner detects these changes and creates a picture of brain activity.

A common term connected to $fMRI$ is the $BOLD$ signal, which means blood oxygenation level dependent signal. Areas with more oxygen-rich blood usually appear more active. The method is popular because it is non-invasive and does not use radiation. It also gives detailed images of the brain’s structure and function.

A simple example can help. Imagine students is doing a memory task in a scanner. If the scan shows increased activity in the hippocampus, a brain area involved in memory formation, researchers may conclude that this region plays a role in remembering information. This kind of evidence supports the biological approach by linking a mental process to a physical brain system.

Still, $fMRI$ has limits. It is very good at showing where activity happens, but it is less precise about when it happens. Brain activity changes quickly, while the blood response is slower. Also, activity in a scan may reflect many processes at once, not just one simple function.

How $PET$ works

$PET$ stands for positron emission tomography. It uses a radioactive tracer, usually attached to a substance such as glucose. Glucose is important because brain cells need energy. When the tracer is injected or inhaled, it travels through the body and collects in active brain areas. The scanner detects the radiation and builds an image of activity.

Because active brain regions use more glucose, $PET$ can show which areas are working during a task. It has been used to study language, memory, movement, and disorders such as Alzheimer’s disease. Compared with $fMRI$, $PET$ is less commonly used today because it involves exposure to radioactive material and has lower spatial and temporal detail. However, it remains important in biological psychology and medicine.

A useful real-world example is studying glucose use in the brains of people with Alzheimer’s disease. If scans show reduced activity in certain regions, this can help explain the memory and thinking problems seen in the disorder. In this way, $PET$ supports biological explanations by linking changes in brain metabolism to changes in behaviour.

Key study example: Raichle et al. and brain activity during language

One important example of brain-imaging research is the work of Raichle and colleagues, who used $PET$ to examine how the brain processes language. In these studies, participants completed tasks that required listening to words, speaking, or reading. The scan showed that different language tasks activated different areas, especially in the left hemisphere, which is often dominant for language in most right-handed people.

This kind of study matters because it showed that language is not controlled by one tiny centre. Instead, multiple brain areas work together. The results supported earlier neuropsychological ideas but also gave stronger evidence because the researchers could observe living brain activity during real tasks.

For IB Psychology, the main takeaway is that imaging studies can identify patterns of activation that support a theory about brain function. If a task consistently activates a certain area, that area may be involved in the behaviour. But students should also remember that the presence of activation does not prove a simple one-to-one relationship between a brain area and a behaviour.

Key study example: PET and the study of addiction

$PET$ has also been used to study addiction. For example, researchers have examined the brains of people with substance dependence to see how drugs change reward pathways. These studies often focus on the dopamine system, especially areas such as the striatum. Dopamine is a neurotransmitter linked with reward, motivation, and reinforcement.

In addiction research, $PET$ can show lower levels of dopamine receptor availability or changes in glucose metabolism after drug use. This helps psychologists understand why addictive substances can be so powerful: they alter brain chemistry in ways that affect motivation and self-control.

This supports the biological approach because it shows that behaviour such as drug-seeking is not just a moral issue or a matter of weak will. It has a measurable biological basis. At the same time, psychologists also recognize that environment matters. Stress, peer pressure, and learning history can all influence addiction. The strongest IB answers usually explain both biological and environmental factors.

Key study example: fMRI and decision-making

$fMRI$ is widely used to study decision-making, especially in tasks involving reward and self-control. A classic type of study asks participants to make choices between immediate and delayed rewards. When people choose a smaller reward now instead of a bigger reward later, certain brain areas linked to impulse control and reward processing show activity.

For example, researchers have found that the prefrontal cortex is important for planning, self-control, and weighing consequences, while the reward system, including the ventral striatum, responds strongly to immediate rewards. This helps explain why teenagers may sometimes take risks even when they know the possible consequences. Their brains are still developing, especially in systems related to control and judgment.

For students, the exam-style link is this: if a study using $fMRI$ shows that a region becomes active during a task, it provides evidence that the region is involved in the behaviour. If the study compares groups, such as adolescents and adults, it may also show developmental differences in brain function. That makes $fMRI$ very useful for understanding behaviour across the lifespan.

How to use these studies in IB answers

When answering an IB question about biological explanations, use brain-imaging studies to provide evidence. A strong response usually includes four parts:

1. Name the method, such as $fMRI$ or $PET$.
2. State what it measures.
3. Give a study or example.
4. Explain what the findings mean for behaviour.

For example, you might write that $fMRI$ measures blood oxygen changes and has shown that the prefrontal cortex is active during self-control tasks. This supports the idea that self-control has a biological basis. Or you could say that $PET$ has shown changes in dopamine-related activity in addiction, suggesting that drug dependence involves brain systems tied to reward.

It is also important to evaluate the methods. $fMRI$ has better detail and no radiation, but it is expensive and can be noisy and uncomfortable. $PET$ can show metabolism and neurotransmitter activity, but it requires radioactive tracers and provides less detail than $fMRI$. Both methods are correlational, so they cannot on their own prove cause and effect.

Conclusion

$fMRI$ and $PET$ are key tools in biological psychology because they help scientists study the living brain while people are thinking and behaving. $fMRI$ measures blood oxygen changes, while $PET$ uses radioactive tracers to measure glucose use and other aspects of brain activity. Studies using these methods have improved understanding of language, memory, addiction, and decision-making.

For IB Psychology HL, the main idea is not just memorizing scan names. students should understand what the methods measure, what the findings suggest, and how the evidence supports biological explanations of behaviour. These studies show that behaviour is connected to brain function, while also reminding us that interpretation must be careful and scientifically grounded. 🧠✨

Study Notes

• $fMRI$ stands for functional magnetic resonance imaging.
• $PET$ stands for positron emission tomography.
• $fMRI$ measures changes in blood oxygen levels, often described by the $BOLD$ signal.
• $PET$ uses a radioactive tracer, often linked to glucose, to show brain metabolism and activity.
• Both methods help psychologists study the living brain during tasks.
• Brain scans show correlation between activity and behaviour, not direct proof of cause.
• Key areas often studied include the prefrontal cortex, hippocampus, striatum, and language regions.
• $fMRI$ is non-invasive and has strong spatial detail, but it is slower in timing.
• $PET$ can measure metabolic activity and some neurotransmitter-related processes, but it uses radiation.
• These methods are useful in studying language, memory, addiction, emotion, and decision-making.
• In IB answers, always explain what the method measures, give a study example, and connect it to the biological approach.