Methodology

PET and MRI scanning

SCANNING SCANNING TECHNIQUETECHNIQUE

SS

How do we investigate the brain?

How can we study the brain?

With a partner Identify at least 3 methods used to study the brain.

List the types of scanning techniques you have heard of?

Come up with one reason why brain scanning could be a useful research method for psychologists?

Lesson Outcome

All Students will be able to describe both PETPET and MRIMRI scanning techniques using appropriate terminology

COMPUTED TOMOGRAPHY SCAN(CT SCAN)

CT scans use a series of X-ray beams

passed through the scull and brain.

These create cross-sectional images of the brain showing

the structure, but not the function.

What is the difference between function and structure?

ELECTROENCEPHALOGRAM (EEG)

Multiple electrodes are placed on the scalp.

EEGs record electrical activity along the scalp produced by the firing of neurons within the brain

It takes 20–40 minutes

EEG READ OUT

(link) POSITRON EMISSION TOMOGRAPHY

PET

PET scanning involves producing computer-generated coloured pictures of the brain.

A radioactive tracer is injected into the body. It is usually attached to glucose. As it breaks down it emits radioactivity that can be picked up by the scanner.

The picture that is created shows the area of the brain that is active.

The PET scan can measure blood flow and oxygen use

POSITRON EMISSION TOMOGRAPHYTHE SCIENCE BIT

The scanner detects radioactive material.

Oxygen and glucose accumulate in brain areas that are metabolically active.

As the glucose is used in the active parts of the brain, the radioactive material breaks down and gives off a

neutron and a positron.

•When a positron hits an electron, both are destroyed and two gamma rays are released.

Gamma ray detectors record the brain area where the gamma rays are emitted.

This method provides a functional view of the brain.

Psychologists use PET scanning to compare brains.They can also watch the brain during activity – like doing maths or reading a book

POSITRON EMISSION TOMOGRAPHY(PET)

AdvantagesProvides an active image of

brain.Less invasive then surgeryIt is valid, can be used to

check things like the language area of the brain

It is reliable – consistent findings

Disadvantages

Expensive to useNot portable

Radioactive material used.

Can be difficult to interpret.

MAGNETIC RESONANCE (link) IMAGING

MRIMRI uses magnetic and radio waves.

The person lies in a large cylinder magnet and radio waves are then sent through the body, affecting the body’s atoms.

The scanner picks up signals as the atoms move back into position and the computer turns the signals into pictures

(LINK) MAGNETIC RESONANCE IMAGING(MRI)

Put another way

MRI detects signals produced by displaced radio waves in a

magnetic field.

It provides a detailed

anatomical (structural) view of the brain.

MRI scanning uses a strong magnetic field which affects some atoms.

ProtonsProtons (positively charged particles) in hydrogen atoms in water behave like compass needles.

The scanner’s electromagnet causes the protons to ‘point’ in the same direction.

When radio waves are passed through the head the protons return to their original positions and this is detected by the scanner.

Parts of the brain with more hydrogen atoms appear paler; those with fewer hydrogen atoms look darker.

ANOTHER USE

Functional Magnetic Resonance Imaging

(fMRI)

fMRI detects changes in blood flow to particular areas of the brain. It provides both an anatomical and a

functional view of the brain.

MAGNETIC RESONANCE IMAGING(MRI)

Advantages

No X-rays or radioactive material is used.

Provides detailed view of the brain in different

dimensions. Safe, painless, non-

invasive. No special preparation

(except removal of all metal) is required from the patient.

Disadvantages

Expensive to use. Cannot be used in

patients with metallic devices, like pacemakers.

Cannot be used with uncooperative (or claustrophobic)

patients because the patient must lie still.

You can find out more information about scanning

using your text book.Brain p240-243

MRI AND PET SCANS

Complete the worksheet plus the gap fill page 6 & 7 of your pack

LINK TASK

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