MRI

Question 1

How does an MRI work?

Answer 1

MRI’s use strong magnetic fields

• forces protons in the body to align with field
• radiofrequency current is pulsed through the patient, stimulating protons to strain against the pull of the magnetic field.
• When current is turned off, MRIsensors detect the energy released as the protons realign with the magnetic field.
• Each molecule has different magnetic properties (time taken to realign, energy released), changing how these tissues appear

Question 2

Strengths

Answer 2

• good for soft tissues (brain + spinal cord)
• detailed 3D image
• does not use ionising radiation
• contrasting agent is less likely to produce an allergic reaction

Question 3

Limitations

Answer 3

• higher cost
• patient discomfort - noise, claustrophobia
• contrast material can be problematic,
• can’t be used if patient has metal implants or is pregnant

Question 4

HM - Milner

Answer 4

• experienced seizures after brain injury at 9 yrs, couldn’t function at 27 yrs
• lobotomy - removed hippocampus + hypothalamus
• studied by Milner using questionnaires, observations, memory experiments

Results:

• unable to form new episodic or semantic memory
• episodic: long-term memory that involves the recollection of specific events, situations, and experiences
• semantic: portion of long-term memory that processes ideas and concepts that are not drawn from personal experience
• still able to form procedural memory + motor skills

Conclusions:
Concluded the hippocampus is responsible for new episodic and semantic memory, however other structures are responsible for procedural memory and past events,

Question 5

Maguire et al

Answer 5

Aim: to investigate whether brains of London taxi drivers would be somehow different as a result of their exceptional knowledge of the city
- quasi experiment
- correlational data
- single blind
London taxi drivers have to know every street in London (mental map)

Participants were:

• 16 right-handed male taxi drivers
• 50 right handed males (non-taxi drivers) taken from database - pre-existing

Results:

• posterior hippocampi were significantly larger in taxi drivers
• however, anterior hippocampi were significantly smaller
• right posterior hippocampi correlated with amount of time spent as a taxi driver

Conclusions: Posterior hippocampi must be involved with spacial navigation