Lecture 3 - Neuroscientific Methods

Question 1

Magnetencephalography (MEG)

Answer 1

direct external recordings of magnetic fields created by electrical currents in cortex

expensive equipment
stationary

Question 2

computer tomography (CT)

Answer 2

x-ray scanner rotated 1 degreee at a time over 180 degrees

contrast agent

Question 3

magnetic resonance imaging (MRI)

Answer 3

strong magnetic field causes hydrogen atoms to align in the same orientation

when radiowave passed through head, atoms emit electromagnetic energy as they relax

Question 4

hemodynamic techniques

Answer 4

oxygen and glucose supplied by blood as fuel for the brain

blood flow increases due to this in certain areas

Question 5

positron emission tomography (PET)

Answer 5

• Positron emitting radionuclide is injected (e.g. 2-deoxyglucose, 15O radioactive oxygen)
• Positrons interact with electrons which produce photons (gamma rays)
• PET scanner detects photons

Question 6

fMRI

Answer 6

data based on blood oxygen level dependent (BOLD) signal

Question 7

limitations of fMRI

Answer 7

physical - spatial and temporal resolution

physiological limitations - Noise due to head motion, artifacts (respiration, cardiac pulse. Localisation of BOLD response bound to vasculature

current conceptual limitations - How can we analyse highly complex data sets –> brain networks. How are neural changes manifested in fMRI activation?

ecological validity

Question 8

diffusion tensor imaging (DTI)

Answer 8

images fibre tracts in white matter

measures diffusion of water molecules along neural tracts

Question 9

anisotropic

Answer 9

diffusion varies with direction

Question 10

isotropic

Answer 10

same diffusion in all areas

Question 11

DTI tractography

Answer 11

3D visualisation of white matter tracts

Question 12

Near infrared spectroscopy (NIRS)

Answer 12

optical imaging technique using infrared light

emitted through scalp

• Absorbed differently by oxygenated and deoxygenated haemoglobin
• Inference on cortical blood flow similar to fMRI

Question 13

transcranial magnetic stimulation (TMS)

Answer 13

magnetic field induces current, that stimulates neurone

facilitates/inhibits cortical excitability depending on frequency of stimulation

virtual lesion allows for evaluating functional relevance of a brain area for a specific taskt

Question 14

transcranial electric stimulation (TES)

Answer 14

similar ideas to TMS but applies current to the scalp

facilitates/inhibits cortical excitability