What does functional magnetic resonance imaging measure?

It measures changes in blood flow and in the oxygenation of the blood, which reveal which regions of the brain are most active.

Give one strength and one weakness of functional magnetic resonance imaging.

It locates activity to within a few millimetres, but the blood flow response lags several seconds behind the nerve activity, so its timing is poor.

How is functional magnetic resonance imaging used to find out what a region of cortex does?

The person carries out a chosen task in the scanner and the pattern of activity is compared with that during rest or a control task, so the areas that become more active can be identified.

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Neurobiology and Behaviour: Neuroscience

Functional imaging: fMRI, PET and EEG

3 things to know
Component 3

Overview

Recall questions on what each technique measures, the trade-off between spatial and temporal resolution, the use of a radioactive tracer, what an electroencephalogram records, and what functional imaging can and cannot establish about function.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why does the blood supply reveal neural activity?

Key term

How does a magnetic resonance scanner detect a change in the oxygenation of the blood?

Key term

What is injected into a patient before a positron emission tomography scan?

Questions from this subtopic

Each one with the model answer underneath.

1
What does functional magnetic resonance imaging measure?
Model answer
It measures changes in blood flow and in the oxygenation of the blood, which reveal which regions of the brain are most active.
2
Why does the blood supply reveal neural activity?
Model answer
Active neurones use more oxygen and glucose, and the blood flow to that region increases within a second or two of the activity beginning.
3
How does a magnetic resonance scanner detect a change in the oxygenation of the blood?
Model answer
Oxygenated and deoxygenated haemoglobin have different magnetic properties, so the signal coming from a region alters as the proportion of oxygenated blood in it changes.
4
Give one strength and one weakness of functional magnetic resonance imaging.
Model answer
It locates activity to within a few millimetres, but the blood flow response lags several seconds behind the nerve activity, so its timing is poor.
5
How is functional magnetic resonance imaging used to find out what a region of cortex does?
Model answer
The person carries out a chosen task in the scanner and the pattern of activity is compared with that during rest or a control task, so the areas that become more active can be identified.
6
What is injected into a patient before a positron emission tomography scan?
Model answer
A tracer is injected, usually a glucose analogue labelled with a short-lived radioactive isotope that emits positrons.

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