Brain imaging and findings

Question 1

What are the parts of Broca’s complex?

Answer 1

Pars triangular, Pars opicullaris (left and right), Pars orbitalis (under) and bentral premotor cortext (posterior to the Pars)

Question 2

MRI

Roy and Sherringdon 1890

Answer 2

magnetic resonance imaging

• magnetic nuclear moment spins creating magnetic field
• protons (hydrogen atoms) particles in water spin
• oscillitating magnetic field is used to align in right orientation
• radio signals encode gradient coils
• signal detects contrasts in rate that they return to equilibrium

Question 3

evaluation of MRI

Answer 3

:) non-invasive, diseases often manifest as water content so good to see, no biological hazards,
:( expensive, loud (bad for language), claustrophobic.

Question 4

fMRI

Answer 4

-detects changes in blood oxygenation and flow that occur in response to neural activity
– when a brain area is more active it consumes more oxygen (capilary bed extracts more O2) so blood flow increases to meet demand
- Haem changes local mag field (Hbo+= dimagnetic, Hbo+ paramagnetic)
- mass action potential measurement- deoxygenated haem/iron distorts magnetic field.

Question 5

evaluation of fMRI

Answer 5

:) sensitive to oxygen levels (ogawa), non invasive

:( can only see blood not individual neurons, expensive and loud

Question 6

TMS

Answer 6

Transcranial Magnetic Stimulation

• directly stimulate area of brain to see the effects on the action it is responsible for
• Action potentials can carry current and show cortical localisation

Question 7

Evaluation of TMS

Answer 7

:) used for therapeutic and diagnostic purposes

:( rare risks associated with frequency used, discomfort and pain, and transient problems associated with stimulation

Question 8

example study using TMS

Answer 8

Buckner 95/Fiez 97: used fMRI to show brocas areaengages semantics and phonology even when not required
– Gough 2005: used TMS to create transient aphasia and disproved this claim.

Question 9

Diffusion Tensor Imaging (DTI)

Answer 9

Diffusion weighted MRI; self diffusion of water from brownian motion
- Grey matter- isotropic (3d) diffusion
- White matter- anisotrpic (cyllindrical) diffusion
SEED: where tracked from
TARGET: aiming to track motion towards
- produces a tractography (3d model showing dispersion)

Question 10

evaluation of DTI

Answer 10

:) water is always in motion so can be tagged and monitored easily; which has a principle direction, shows global information,
:( simplified to 3d, seeding to region of interest, can’t see function

Question 11

Example finding of DTI

Answer 11

Petrides and Pandya 94: found connections between areas:

• superior longitudinal fasciculus links B and W
• uncinate fasciculus links underneath
• Articuate fasciculus links Pars within Brocas complex
• • anatomical double dissociaion in function neuro imaging-> but is this a functional dissociation?

Question 12

voxel based morphometry VBM

Answer 12

registers brain to template and statistically maps; separates brain into voxels; compare density estimations in each voxel

Question 13

example study of VBM

Answer 13

Semantic dementia (mummer 00)- found A temporal lobe damage to be significant area 
Bates03: used stroke patients and compared comprehensibility and voxels-- posterior TL in word meanings