Lecture 7: Methods to Study the White Matter Flashcards

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1
Q

Name all the methods to study white matter

A
  • Dissection
  • Injection of tracers in a specific cortical area
  • Diffusion Imaging Tractography (dMRI)
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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
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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
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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
  • Important notes:
    • dMRI:
      • water diffusion along the axons
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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
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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
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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
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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
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9
Q

What is another way to separate SLF II and SLF III?

A
  • We can combine resting-state:
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10
Q

How can we identify the different landmarks?

A
  • By identifying the sulci and gyri
  • Another way is by using MNI coordinates
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11
Q

DWI Tractography

A
  • Can detect true or false connections
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