Download Functional Magnetic Resonance Imaging

Description of Functional Magnetic Resonance Imaging
(fMRI)
Background Information
fMRIs are a modification of a regular MRI
machine. Whereas MRIs simply show the structure
of the brain, fMRIs can record ongoing brain
activity. They are also more accurate and display
results in a higher resolution than PET scans. They
are very common in a range of modern
neuropsychological research studies.
An fMRI machine
So how do they work? When the brain
performs a task (like playing the piano, thinking,
looking at pictures, etc.) neurons are “activated”. As
you should already know, 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.1
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.
What happens in an fMRI?2
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.
In one study the researchers investigated what was happening in the
brains of people who were in love when they saw images of their loved one.3
While the participant was lying in the fMRI machine, they showed each
participant a photo of the person they were in love with, and then showed a
picture of an acquaintance.4 The results showed that different areas of the brain
were activated depending on the person the subject was looking at. A part of
the brain involved in motivation (the VTA) with high levels of dopamine was
activated when the subject saw their “beloved”. The researchers were able to
use the fMRI in this study to investigate the relationship between the brain,
love, and motivation.
An image from Fisher’s study
1
Check out the blog for links for more scientific and technical information on exactly how an fMRI works, but this is
only if you’re particularly interested in the specific biology of it all (which I’m not!)
2
Make sure to check out the blog for a video of how an fMRI works.
3
This is in the “Key Study Description: Dopamine and Motivation” handout.
4
An acquaintance is someone you know but isn’t quite a friend.
fMRIs are 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 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:
 Dopamine and Romantic Love (See Key Study Description)
 PTSD and fMRI studies (see above)
 Mirror Neurons (Course Companion, p48)
Key Questions
1.
2.
3.
4.
What correlation does an fMRI show?
fMRIs measure “dynamic rather than static” information. What does this mean?
What are the strengths and limitations of using an fMRI?
What is the relationship between brain activity and behaviour as shown in the results of one
study using fMRI?
Extension Critical Thinking Questions
 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? (Evaluation)
References
Hannibal, Jette. Crane, John. Psychology. Course Companion. Oxford Press. UK. 2009
Law, Alan et al. Psychology: Developed Specifically for the IB Diploma. 2010.