Key Stage4-MRI Watching the Brain at Work

Key Stage4-MRI
Watching the brain at work

Pupil worksheet

Background

An MRI scanner uses magnetic fields to take detailed pictures of the brain. Doctors use the scans to help diagnose disease. Functional Magnetic Resonance Imaging (fMRI)is a brain research technique. Scientists collect data from a grid of voxels (3D pixels) through the brain. These data show exactly which areas of the brain are associated with different activities.

There is a strong magnetic field in an fMRI scanner. This means we can detect changes in blood oxygen levels in different brain areas. This is how it works:

• If you wiggle your fingers, there is more activity in the cells in the areasof the brain that make this movement happen.
• These areas need more oxygen, which the blood delivers. The ratio of oxygenated blood: deoxygenated blood increases in these areas.
• Protons in oxygenated blood spin more slowly than protons in deoxygenated blood. This means that oxygenated blood distorts the magnetic field less than deoxygenated blood.
• Less distortion means that a higher signal is recorded.

Question to discuss

Will an increase in brain activity in a certain area of the brain cause an increase or decrease in the measured MRI signal? Why?
Your task

Stage 1

Design an experiment to find out which areas of the brain are associated with an activity, for example listening to music, watching a video clip, or singing.

• Choose your activity, and make up a scientific question to investigate.
• Identify the independent variable.
• The dependent variable is the MRI signal strength in each brain voxel.
• Identify the control variables – Which variables will you keep the same, or control, so that you can compare data from doing and not doing the activity?

If you did the experiment, a computer would compare changes in MRI signal strength across many brain voxels to find the most active areas.

Stage 2

You will need volunteers for your experiment. They will need to be in the scanner for about 45 minutes, alternately doing and not doing your activity. Write an advert to recruit volunteers. In your advert, include:

• What you want to find out, and why.
• A brief outline of what fMRI is, and how it works.
• The precautions you will take to keep volunteers safe.
• What the volunteers will have to do in the scanner, and how long it will take.

Stage 3

To make sure you can compare the data from different volunteers, you will need to give them all the same instructions. Write a script to remind you what to say.

Extension task
Plan an investigation to isolate a very specific brain function such as speaking words or perceiving another person’s emotion.

Help sheet 1

Stage 1 – experiment design

Help sheet 1

Stage 1 – experiment design

Help sheet 2

Stage 2 – Recruiting volunteers

Safety notes

An FMRI scanner includes a huge electromagnet. Objects made of magnetic materials move towards the magnet when it is switched on. If a volunteer hasany magnetic metal in their body – perhaps a tiny piece of steel in their eye – the magnetic field makes it move. The moving object may damage the body. Magnetic fields also damage heart pacemakers.

Magnetic or not?

Objects people might have on (or in) them

Questions to discuss

ADecide which objects are safe to take into the scanner.

BWhich objects inside a person may make having an fMRI scan unsafe?

Help sheet 3

Stage 3 – Script to read to volunteers

Help sheet 3

Stage 3 – Script to read to volunteers