CAT, PET, fMRI Flashcards
What does a CAT scan show?
Shows structure not function
Why is a CAT scan useful?
Useful for detecting areas of brain damage following an accident or positioning of trumours
How does a CAT scan work?
X ray beams passed through the head from different angles to create cross sectional images of the brain showing structure
Is a CAT scan invasive?
No
What does a PET scan show?
Activity, most and least active areas. Warm colours = more activity. Cool colours = less activity
What is injected into the bloodstream for a PET scan to work?
A radioactive tracer that is used up during brain activity, reaches the brain after 1 minute
What is radioactivity in the form of in PET scans?
Gammar rays
How does a PET scan work?
Brain cells take up oxygen in the water/glucose, tracer decays, releases radioactivity - positrons, active areas have more radioactivity
Why is a PET scan reliable?
Same areas would be highlighted if replicated
Why is a PET scan ethical?
Images taken outside of the body, non invasive
Why is a PET scan high in validity?
Measures activity which is what it claims to measure
Why is a PET scan unethical?
Injections are invasive
Why can PET scans lack validity?
Hard to pinpoint exact areas of the brain so even if PET scans are clear, they are only valid up to a point as it is hard to claim from a scan exactly which part of the brain is performing which function
What is an fMRI scan based on the idea of?
That brain activity is associated with blood flow in the brain and this activity is used to gather the info by the scanner to produce a picture
What does an fMRI scan involve a person doing?
Putting your head in a large, very powerful electromagnet
What happens inside the magnetic field of an fMRI?
The nuclei within the hydrogen molecules in water align themselves with the direction of the magnetic field
What happens as neural activity increases in the brain of fMRI?
Blood flow increases in the active areas to keep up with the demand for oxygen which is carried to the neurons in haemoglobin within red blood cells
What happens when haemoglobin carries oxygen in fMRI?
It repels a magnetic field and when deoxygenated it will follow the same direction of the magnetic field
What does deoxygentated blood do in fMRI and why is this significant?
Causes disturbances to the magnetic field, whereas oxygenated blood doesn’t, these changes will create an image
What are more active parts of the brain like in fMRI?
More active part of the brain = more oxygen = less magnetic field disturbances = signal measured for longer
How long does an fMRI take?
2 hours
Strengths of fMRI?
- Identifies function
- More ethical than surgery
- Scientific, replicable and reliable
Weaknesses of fMRI?
- Brain never at rest, can’t isolate regions
- Lacks ecological validity
- Risk for people with pacemakers due to magnetic field
