Lecture 7: Methods to Study the White Matter Flashcards
1
Q
Name all the methods to study white matter
A
- Dissection
- Injection of tracers in a specific cortical area
- Diffusion Imaging Tractography (dMRI)
2
Q
Dissections
A
- Post-mortem
- Pros:
- Cons:
- Hard to see where the axons start and terminate
- Important notes:
- Dejerine identified arching white matter tract: arcuate
3
Q
Injection of tracer in a specific cortical area
A
- Participants: Living macaque monkey studies (not humans)
- Usage:
- Study anatomical connections
- See the exact termination and course of the axons
- Pros:
- Indicate direct connectivity
- Cons: na
- Important notes:
-
Types:
-
anterograde
- From soma to dendrites
-
retrograde
- From dendrites to soma
-
anterograde
-
Types:
4
Q
Diffusion Image Tractography
A
- Participants: Living humans
- Usage: reconstruct or virtually dissect white matter tracts in vivo
- Pros:
- in vivo
- Useful to have anatomical priors
- Cons:
- not exact method to find out where fibres go or which brain areas are anatomically connected
-
Limitations:
- crossing fibres
- parallel tracts within same white matter area
- Cannot detect if there is a synapse
-
Limitations:
- not exact method to find out where fibres go or which brain areas are anatomically connected
- Important notes:
-
dMRI:
- water diffusion along the axons
-
dMRI:
5
Q
Give a research example where they use diffusion tractography
A
- Language tracts
- Specifically the arcuate fasciculus which connects Broca’s area to Wernicke’s area
- Studied and reconstructed many times using dMRI
6
Q
dMRI is a very limited technique, which errors could come up?
A
- Mixing up tracts
- ex: AF and MLF or AF and SLF
7
Q
One error that might come up using dMRI is to mix up the tracts, how was AF and SLF differentiated?
A
- Based on what is know:
- injection of tracers in macaque monkeys showed that SLF has 2 branches
- landmarks
- This allowed to separate SLF 2 and 3
- Research allowed us to better understand and define the functional role of each of those tracts in human congnition
8
Q
how can we use anatomical landmarks to separate SLF II and III?
A
- Goal:
- restrict the tract from frontal to:
- supramarginal gyrus
- angular gyrus
- posterior temporal
- restrict the tract from frontal to:
9
Q
What is another way to separate SLF II and SLF III?
A
- We can combine resting-state:
10
Q
How can we identify the different landmarks?
A
- By identifying the sulci and gyri
- Another way is by using MNI coordinates
11
Q
DWI Tractography
A
- Can detect true or false connections