Techniques Flashcards
MRI full name
Magnetic resonance imaging
What are the main components of MRI and how does it work?
Main components: Magnet, radio wave, gradient & computer
- detect radio waves emitted by atoms when they’re subjected to a different magnetic field strength.
- Different atom arrangements and tissues emit different radio waves allow researchers to differentiate between them with high resolution.
- The use of magnetic fields and radio waves/frequency produces images. Images shows cross sections or “slices “of the brain. Allowing researchers to see structure of the brain. (Ex. identify tumours, injuries or missing parts).
- does not contain harmful radiation used in cat or pet scanning.
- Instead it uses extreme magnets that are dangerous for people with metals inside their body which can cause extreme pain
Two possible names to analyse MRIs
* VBM - measure the density fo grey matter
* Pixel counting - calculate the area of certain brain structure
fMRI full name
Functional magnetic resonance imaging
What is fMRI?
- shows actual brain activity
- indicates which areas of the brain are active when engaged in a behaviour or cognitive process.
- It tracks changes in blood flow and oxygen level as a measurement of neural activity.
- When a specific brain area is active, it uses more oxygen, and therefore the blood flow increases.
- fMRIs are non-invasive.
- Better quality image and rather than a static image, a film is produced that demonstrates a change in the brain over the period of the scan.
- powerful magnet, can be painful for participant with metals inside their body (e.g. implants)
The aim of Maguire study
To examine whether structural changes could be detected in the brain of people with extensive experience of spatial navigation.
Method of Maguire (Participants + procedure)
Taxi drivers undergo extensive training, known as ‘The Knowledge’ and therefore make an ideal group for the study of spatial navigation.
Structural MRI scans were obtained. 16 right-handed male London taxi drivers participated, all had been driving for more than 1.5 years. Scans of 50 healthy right-handed males who did not drive taxis were included for comparison. The mean age did not differ between the two groups.
Findings of Maguire
1) Increased grey matter was found in the brains of taxi drivers compared with controls in two brain regions, the right and left hippocampi. The increased volume was found in the posterior hippocampus.
2) A correlation was found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus.
Conclusion of Maguire
- Provide evidence for structural differences between the hippocampi of London taxi drivers and control participants,
- suggesting that extensive practice with spatial navigation affects the hippocampus.
Aim of Antonova
To see if scopolamine affected the hippocampal activity in the creation of spatial memory
Method of Antonova
- PPTS randomly allocated to one of the two conditions
- Either injected with scopolamine (An exogenous antagonist for acetylcholine) or a placebo 70-90 min before the experimental task
- PPTS put into an fMRI where they were scanned while playing the “arena task” (video game)
- Researchers observed how well ppts were able to create spatial memories
- The goal for the ppts was to navigate around the arena and reach a pole and later they reached it the screen would go black for 30 seconds
- During the black screen the ppts were asked to rehearse how to get to the pole in the arena
- When the new arena appeared they had to use their spatial memory to determine how to get back to the pole
- 6 trials were done per participant
After 3-4 weeks, ppts would return and redo the test receiving the opposite condition
Findings of Antonova
- Ppts injected with scopolamine demonstrated a significant reduction in the activity of the hippocampus compared to when they received the placebo
- It appears acetylcholine could play a part in the encoding of spatial memories in humans as well as rats
Conclusion of Antonova
- scopolamine results in the reduction of activation of the hippocampus and acetylcholine helps with the encoding of spatial memory
Evaluate fMRI vs MRI
MRI
* structure
* less expensive
* No functional info
fMRI
* function
* more expensive relative to MRI
* can record metabolic activity over time
* Indirect
* Good spatial resolution, but relatively poor temporal resolution - scanner do not quickly detect changes in brain activity (1-4seconds)
* Difficult to interpret
* Can give false positive
Both
* strong magnets - pain to ppl with magnet in body
* Claustrophobic
* highly detailed
* non invasive methods
* Both 3D images
* Not portable
* Need extensive training
* No demand characteristics
* Lack of ecological validity, in artificial setting and task
