The invention of functional magnetic resonance imaging (fMRI) has rapidly advanced our knowledge and understanding of the human brain. In the IB Psychology course, fMRIs are a good example of a “technique used to study the brain in relation to behaviour.”
fMRIs are a modification of a regular MRI machine. Whereas MRIs simply show the structure of the brain, fMRIs can record ongoing brain activity.
So how do they work? When the brain performs a task (like playing the piano, thinking, looking at pictures, etc.) neurons are “activated” and different areas of the brain have different functions. So with each task a particular part of the brain is functioning. This means that those neurons are “firing” and neurotransmission is occurring in that area of the brain. During this neurotransmission, there is an increased blood flow between the neurons. The fMRI uses magnetic fields and radio waves to detect these changes in blood flow in the brain.
The fMRI can project on the computer which parts of the brain have the increased blood flow, which allows researchers to see which parts of the brain are functioning during different tasks. Different colours show the different levels of activation in areas of the brain.
Participants have to lie completely still while in an fMRI. This is actually one major limitation. In the future, fMRI scanning will be able to conducted while people walk and act as normal. Can you think how this might improve our understanding of the brain and how it relates to behaviour?
For this reason, fMRIs are used in studies to help show localization of brain function – the fact that particular areas of the brain are associated with specific tasks.
They are also used to see how certain factors can affect this function. Researchers do this by manipulating an independent variable (e.g. serotonin levels) and then seeing how this affects function of the brain during certain tasks, like reacting to other people.
What happens in an fMRI?
When researchers are using an fMRI they ask participants to lay in the machine and perform certain tasks. Often there is a screen that appears in the fMRI and it has the relevant information that the participants use to complete the task the researchers are asking of them. There is also a hand held remote that has various buttons, one of these being the button they can push if they want to stop the process.
How & why fMRIs are used.
A common procedure is to have participants view images of faces on the screen while they lay in the fMRI. The computer can tell which parts of the brain are activated as the participant sees a happy face, or a sad, angry, fearful face or neutral face. This procedure is often used when studying emotions and reaction. In particular, they can be useful when researchers are trying to see how chemical messengers (e.g. neurotransmitters or hormones) affect brain activity when processing emotion.
For example, in Passamonti et al.’s study (read more here) the researchers were able to see how reduced serotonin affects the PFC and amygdala when we’re perceiving a threatening face. The results showed that low serotonin reduces PFC activity when participants are viewing an angry face and also the connections with the amygdala are reduced. This could help explain why low serotonin is linked with aggression – the PFC helps us stop acting impulsively, like if we’re threatened, so if someone is threatened (as was mimicked with the angry face) and the have low serotonin, their PFC might not function properly to stop them reacting aggressively.
fMRIs are also often used in research investigating the biological factors affected in people with psychological disorders. One study compared war-vetereans who had been diagnosed with PTSD and war-veterans who did not have PTSD (the control group). They flashed images of happy face and angry faces while in the fMRI and the participants simply had to look at the photographs and the fMRI recorded what areas of the brain were activated. The results showed that in the PTSD subjects, there was an increase in activation in the amygdala when seeing the angry faces. There was also less activity in their frontal lobes than in the control groups. The amygdala is known to have a role in processing emotional memories and as mentioned earlier, the frontal lobe helps to control our behaviour and our emotional impulses. Other research studies using fMRI have also shown a correlation between a hyper-responsive amygdala, reduced activity in the frontal cortex and PTSD symptoms.
So does this mean that a hyper-responsive amygdala may be the cause of PTSD symptoms? If you can answer this question you will have figured out a major limitation in using fMRI in psychological research.
Examples of Research using fMRI:
- Serotonin and impulsive, reactive aggression (Passamonti et al) (Link)
- Cognitive etiologies of PTSD (Urry et al.) (Link)
- Testosterone and impulsive, reactive aggression (Radke et al.)
Critical Thinking Considerations
- How did one study use an fMRI to investigate (and demonstrate) relationships between the brain and behaviour? (Application)
- What are the fundamental differences between an MRI and an fMRI? (Analysis)
- What are the strengths and limitations of using fMRIs to investigate relationships between the brain and our behaviour? Do you think it’s limited by ecological validity? For example, do you think there are reasons why (Evaluation)