Techniques used to study the brain in relation to behaviour - SAQ Flashcards
How was brain research done?
Limited to studying victims of strokes or accident and using invasive methods such as autopsy to study their brains.
This is how Broca’s area was discovered for example.
What does MRI stand for?
Magnetic resonance imaging
How are today’s techniques better?
They are less invasive
What is the MRI mostly based on?
The principle that some atomic nuclei - in particular those of hydrogen atoms - can emit energy when placed in an external magnetic field.
What happens when the pulses of energy are detected by the scanner?
The relative distribution of hydrogen atoms in the brain can be mapped.
Why do we focus on hydrogen atoms?
Hydrogen atoms exist naturally in the body, but their concentration in different types of tissue is different.
Water and fat have the highest concentration.
Analysing the pattern of emission of energy in response to magnetic fields, we can see inside the brain.
What study is used for MRI?
Maguire
When was the Maguire study?
2000
What is the aim of Maguire (2000)?
To see whether the brains of London taxi drivers would be somehow different as a result of their exceptional knowledge of the city and the many hours that they spend behind the wheel navigating the streets of London.
What was the sample?
16 right-handed male London taxi drivers.
How were the participants chosen?
Had to have completed the “Knowledge” test and have their license for at least 1.5 years
To who were the taxi drivers compared to?
50 right-handed males who did not drive taxis
How were they compared?
Compared using MRI scans
From where were the control participants taken from?
Were taken from an MRI database
What were the 2 different techniques used to analyse the MRI scans?
Voxel-based morphometry (VBM)
Pixel counting
Voxel-based morphology (VBM)
Used in this study to measure the density of grey matter in the brain
Pixel counting
Consists of counting the pixels in the images provided by the MRI scans in order to calculate the area of the hippocampus
Results from the pixel counting
The pixel counting showed that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and the anterior hippocampi were significantly smaller.
Results from the Voxel-based morphometry (VBM)
VBM showed that the volume of the right posterior hippocampi correlated with the amount of time spent as a taxi driver.
No differences were observed in other parts of the brain.
Maguire argues that this demonstrates that the hippocampus may change in response to environmental demands.
What to know for techniques used to study the brain in relation to behaviour
How was brain research done?
MRI - based on, used
Why are hydrogen atoms important
Maguire (2000)
Strength of MRI
There is no radiation exposure
MRI has a better spatial resolution that CAT
Limitations of MRI
Due to its high resolution, the scanner sometimes picks up slight abnormalities in the brain that are not related to he original complaint. this may create anxiety and cause people to pursue unnecessary treatment
Due to the strong magnetic fields, people with metal in their body cannot undergo the procedure.
No good for people with claustrophobia as it is a small space
Expensive
Difficult for small children
What happens after excitation?
After excitation by the magnetic field each tissue returns to its equilibrium state - and the time required to do so differs in different types of tissue.
What does MRI use?
MRI uses a high resolution three-dimensional image of brain structure.
