techniques used

Question 1

CAT

Answer 1

• computerized axial tomography.
• works on the principle of differential absorption of X-rays
• bone and hard tissue absorb X-rays better than soft tissue.
• investigates brain structure
• a quick non-invasive method
• records images of hard and soft tissue as well as blood vessels simultaneously.
• can be made for people who have implanted medical devices
• radiation exposure

Question 2

MRI

Answer 2

• Magnetic resonance imaging
• does not involve x-rays
• invastigate brain structure
• purpose- to produce a high-resolution three dimensional image of brain structure.
• based on the principle that some atomic nuclei-hydrogen atoms- can emit energy when placed in an external magnetic field.
• when these pulses of energy are detected by the scanner, the relative distribution of hydrogen atoms in the brain can be mapped.
• after excitation by the magnetic field, each tissue returns to its equilibrium state.
• necessary to rapidly change the parameters of the magnetic field and switch it on and off repeatedly–> results is the loud noise

Question 3

limitations and strengths of MRI

Answer 3

limitation:

• ppl w metal in their body (i.g. cardiac pacemakers or shrapnel) cannot undergo the procedure
• can be an issue for claustrophobic ppl
• lying still for a long time
• noisy
• more expensive
• unnecessary treatment
• up to 40 minutes spent without move. meant in a narrow noisy tube.
  strengths:
• less risk of radiation-induced cancer
• better resolution

Question 4

fMRI

Answer 4

-Functional magnetic resonance imaging
-investigates processes
-scan is dynamic
-shows the ongoing brain processes
-the response of blood to rapidly changing magnetic fields differs depending on the flow and the level of oxygenation
-BOLD (blood-oxygen-level dependent) signal.
-voxels
-small voxels have less blood flow
we can only see a relatively crude picture of brain functioning.

Question 5

advantages and disadvantages of fMRI

Answer 5

advantages:
-excellent spatial resolution (up to 1-2mm)
-allows us to see brain processes
disadvantages:
-poor temporal resolution (abt 1 second)
-claustrophobia, cost, lengthy procedure and inability to use it with medical implants.

Question 6

spatial resolution

Answer 6

is the ability to discriminate between nearby locations (with voxels)

Question 7

temporal resolution

Answer 7

is the smallest time period in which changes in brain activity can be registered.

Question 8

PET

Answer 8

• positron emission tomography
• uses blood flow as the indicator of brain activity
• radioactive tracers such as glucose
• brain areas that are more active requires more blood supply.
• useful for detecting tumours and metastases

Question 9

strengths and limitations of PET

Answer 9

strengths:
-good spatial resolution (abt 4mm)
-scanners can be small
limitations:
-poor temporal resolution (30-40seconds)

Question 10

EEG

Answer 10

• electroencephalography
• measures electric potentials generated by neural circuits
• when large groups of neurons fire synchronously, electric potentials generated by these impulses become detectable at the head surface
• good for measuring brain activity “on the whole”
• diagnoses such conditions as epilepsy and sleep disorders

Question 11

strengths and limitations of EEG

Answer 11

strengths:
-has a perfect temporal resolution (<1 milliseconds)
-low-cost
-measures neuronal activity directly
-can be manually transported
-is silent
-non-invasive
limitations:
-extremely low spatial resolution
-the farther away from the surface of the scalp, the weaker the signal
-signal-noise ratio is quite low

Question 12

studies

Answer 12

1) Draganski et al (2004 and 2006) used MRI
2) Maguire et al (2000) used MRI
3) Meyer et al (2006) used PET
4) Fisher et al (2005) used fMRI