Brain Imaging Techniques

Question 1

Types of brain imaging techniques (structural imaging)

Answer 1

Allow us to see brain structures
* CT: computerized tomography
* MRI: magnetic resonance imaging

Question 2

Types of brain imaging techniques (functional imaging)

Answer 2

Allow us to see bain activity
* fMRI: functional magnetic resonance imaging
* PET: positron emission tomography
* SPECT: single positron emission computed tomography

Question 3

Computerised Tomography (CT) (function and use)

Answer 3

A combination of x-rays and computer technology produce axial (slice-like) images of the brain
* assess head injuries and symptoms of aneurysm, stroke and brain tumors

Question 4

Magnetic resonance imaging (MRI)

Answer 4

Applies very strong magnetic field which allows us to map the activity of hydrogen protons (found in water throughout our body) in brain tissue to different degrees
* image can be viewed as slice of brain or used to create three-dimensional image of brain

Question 5

Functional Magnetic Resonance Imaging (fMRI)

Answer 5

Uses same basic principles of atomic physics as MRI but image metabolic function
* create three dimensional pictures of anatomic structure and the metabolic activity within them

Question 6

Positron Emission Tomography (PET)

Answer 6

Shows metabolic processes using sugar glucose in brain to show where neurons are “firing”
* radiactive isotope (gamma ray) is injected into bloodstream
* where more glucose is used radioactive tracer is detected
* areas of high radioactivity are associated with brain activity

Question 7

Single Positron Emission Computed Tomography (SPECT)

Answer 7

Primarily used to view how blood flows through brain arteries and veins - can give info about blood flow allowing sign of injured locations
* small amount of radioactive drug injected into a vein
* scanner used to make detailed images of areas inside brain where radioactive material is taken in by cells

Question 8

Limitations of brain imaging techniques (3)

Answer 8

• Unnatural environment: susceptibility to claustrophobia (Poldrack (2008) - 20% subjects), exclusion of obesity - can lead to sampling bias
• Colours exaggerate effects of the brain: usually areas are not realistically as deined and can frequently be spontaneous and not stimulus driven
• Brain images are compilations: final image is assembled from series not a single one from a specific time

Question 9

Strengths of brain imaging techniques

Answer 9

• Have been major help in our understanding of how the brain works - help diagnose people (e.g. Alzheimer, schizophrenia)
• Research is more ethical than before - non-invase techniques
• Practical: communication allows for international research and allows researcher and data triangulation - lead to higher validity

Question 10

MRI Advantages (name 3)

Answer 10

• excellent resolution
• non-invasive
• practical (easy to use & accessible in most hospitals)
• safer
• individuals can be tested repeatedly
• fast (1-2 mins for most of the brain)
• provides controlled experimental conditions

Question 11

Disadvantages of MRI (name 3)

Answer 11

• expensive
• limited to activation studies
• gives correlation but not causation
• can be inaccurate: slight movement affects quality of image and allows misinterpretation
• cannot be used on everone: claustrophobia, obesity, pacemakers or metallic implants unallowed due to magnetic field

Question 12

Advantages of fMRI (3)

Answer 12

• good spatial resolution
• non-invasive
• good temporal resolution - ability to revisit and aquire data for the exact same location within short intervals of time

Question 13

Disadvantages of fMRI (3)

Answer 13

• exclusion of certain patients
• measuring blood oxygenation is an indirect measure of brain activity: can’t be sure areas wth deoxygenated blood are actually most active + activity doesn’t correlate with function
• incredibly complex to analyse: misinterpretation, lack of reliability