White matter tracts

Question 1

What are the 3 catergories that the white matter tracts are subdivided into?

Answer 1

1. Projection pathways
2. Association pathways
3. Commissural pathways

Question 2

What are the projection pathways?

Answer 2

Everything that connects from cortex to outside the brain

Fibres connecting cortex with subcortical centres

Question 3

What is the definition of pyramidal tract within projection pathway?

Answer 3

Longitudinal fibres from cortex through the pyramid

Only 3-4% from pyramidal cells of Betz

Only 50% to spinal cord (CST)

Many axons terminate in, or send collateral to stratium, thalamus, brainstem nuclei

Question 4

What does the projection pathway consist of?

Answer 4

Both afferent and efferent nerve fibres that couples brain with spinal cord

Question 5

What is the origin of Corticospinal/-bulbar tract?

Answer 5

1. Frontal lobe - M1 (BA4) 60%
   Pre-motor and SMA (BA6)
2. Parietal lobe PCG 30%

Question 6

Where is premotor located?

Answer 6

Anterior to precentral gyrus

Question 7

Where is Suplementary motor area (SMA) located?

Answer 7

Midline surface of hemisphere anterior to primary motor cortex

Contributes to control of movement

Question 8

What is the cortico-motoneuronal (CM) system

Answer 8

Component of CST

Direct monosynaptic CM connections to motoneurons of many muscles

CM projections particularly strong to most distal musculature (face-hand-feet)

Only present in primates

Question 9

What is present only in primates?

Answer 9

Direct, cortico-motoneuronal projections

Question 10

What is not present in all primates?

Answer 10

CM connections

Best developed in most dexterous primates

Question 11

What are association pathways?

Answer 11

1. Connection within one hemisphere
2. Fibre pathways that lie within cerebrum that connect one part of cerebral cortex with another within same hemisphere
3. Long and short fibres interconnecting cortical areas of same hemisphere

Question 12

What is Neuronavigating system?

Answer 12

Makes a relationship between image and what it is observed in surgery

Question 13

What are the major tracts of association pathways?

Answer 13

1. Superior longitudinal fascicle (I-III)
2. Arcuate fascicle
3. Uncinate fascicle
4. Inferior longitudinal fascicle
5. Inferior fronto-occipital fascicle
6. Frontal Aslant tract

Question 14

What are involved in speech production and speech understanding/comprehension?

Answer 14

Multiple areas

Question 15

What is dual stream model?

Answer 15

Two functionally distinct/neural network that process speech/language information

Question 16

What does the dual stream model interface?

Answer 16

Sensory/phonological network with:

1. conceptual-semantic system
2. motor- articulatory system

Question 17

What does ventral of dual stream model deal with?

Answer 17

Comprehension = understanding

Mapping sound-to-meaning

Bilateral location in temporal lobe

Time invariant

Question 18

What does dorsal of dual stream model deal with?

Answer 18

Sensory-motor integration

Sound to motor mapping

Left dominance

Time variant

Question 19

What are the language concepts?

Answer 19

Broca-Wernicke- HG

Dorsal Stream - Arcuate fascicle

Ventral stream - Uncinate fascicle and Inferior longitudinal fascicle

Question 20

What is the Arcuate Fascicle?

Answer 20

Subdivision of the Superior longitudinal Fascicle

Question 21

What is the function of Arcuate Fascicle?

Answer 21

Connects Broca (or PrCG) to Wernicke

Question 22

Where is Arcuate Fascicle located?

Answer 22

Around Sylvian Fissure

Deep to Insula and Parietal Lobe

Question 23

What is the feature of AF?

Answer 23

1. Dorsal pathway Direct + Indirect

2. Phonolgy

Question 24

What are the 3 segments that Catani showed?

Answer 24

1. Long segment coming from Broca going down to Temporal Lobe
2. Short segment connecting region of Broca with an area in Parietal Lobe
3. Another connecting parietal lobe to temporal lobe

Question 25

What is anterior segment of SLF connected to?

Answer 25

1. Precentral Gyrus | 2. Supramarginal Gyrus

Question 26

What is the posterior segment of SLF connected to?

Answer 26

1. Middle Temporal Gyrus | 2. Angular Gyrus

Question 27

Arcuate Fascicle

Answer 27

Left lateralised in 95% R handed Connects PrCG (or Broca IFG) with Post temp Lesions Conductive aphasia

Question 28

What is left lateral good for?

Answer 28

Better verbal intelligence Phonological processing

Question 29

What are Broca's connections

Answer 29

1. U fibres - premotor/motor 2. Ascending fibres - dorsal premotor cortex 3. Caudo-posterior - supramarginal gyrus

Question 30

What is Frontal Aslant Tract?

Answer 30

Connect superior and Inferior frontal gyri Pars opercularis - IFG - Broca Goes up to Anterior Cingulate and medial SFG - pre SMA

Question 31

What is the deficit of Frontal Aslant Tract?

Answer 31

Verbal Fluency

Question 32

What faciliates speech initiation?

Answer 32

pre SMA

Question 33

What is Inferior Longitudinal Fascicle?

Answer 33

1. Occipital - Anterior Temporal Lobe 2. Part of ventral semantic stream/language comprehension 3. Deficits: Object recognition Face processing Visual semantic memory

Question 34

What is Uncinate Fascicle?

Answer 34

``` Ant TL – Po-IFG & Fronto-orbital TL – Sylvian fissure – Inf PL – FL Indirect semantic pathway (+ ILF) Auditory working memory Deficits Single word comprehension & Naming ```

Question 35

What are examples of Optic Radiation?

Answer 35

1. Inferior Longitudinal Fascicle 2. Splenium fibre 3. Optic Radiation 4. Optic Tract

Question 36

What are Comissural pathways?

Answer 36

Connects cortex between hemispheres

Question 37

What are the main types of commissural pathways?

Answer 37

1. Corpus Callosum 2. Anterior Commissure 3. Posterior Comissure 4. Hippocampal commissure

Question 38

What is Corpus Callosum?

Answer 38

1. most prominent mammalian fibre system 2. Compact 3. 300 million axons 4. Connects most of the cortical areas, homologous and heterotypical areas

Question 39

What are examples of Topography (post-mortem)?

Answer 39

1. Tracer 2. Histology 3. Wallerian Degeneration

Question 40

What are examples of Topography (In vivo)?

Answer 40

1. Lesion/resection 2. Electophysiology 3. Imaging - DTI/fMRI

Question 41

What are the classic segmentation of corpus callosum?

Answer 41

1. Rostrum 2. Genu 3. Body 4. Isthmus 5. Splenium However, no landmarks

Question 42

What are connected by larger, more myelinated fibres?

Answer 42

Areas requiring fast conduction, the auditory, motor and visual areas

Question 43

What are connected by smaller, less myelinated fibres?

Answer 43

Specialised cognitive regions

Question 44

What does segment I of Corpus callosum contain?

Answer 44

prefrontal, premotor and supplementary motor

Question 45

What does segment II of Corpus Callosum contain?

Answer 45

Anterior midbody contains the motor fibres

Question 46

What does segment III of Corpus callosum contain?

Answer 46

The posterior midbody contains fibres to sensory and posterior parietal region

Question 47

What does segment IV and V contain?

Answer 47

The isthmus and splenium contain fibres to the posterior parietal, temporal and occipital lobes

Question 48

What does the correspondence rate maps represent?

Answer 48

represent inter-individual variability of fiber connections Body and dorsal splenium high reliability of dominant CC connection maps (sup frontal & parietal cortex) Ventral splenium low reliability (temporal cortex)

Question 49

What are the Interhemispheric transfer deficit?

Answer 49

Middle genu Simple bimanual tasks Ant genu Complex bimanual tasks Ant body Deficient tactile localisation Subclinical deficits

Question 50

What is evolutionary concept of lateralisation?

Answer 50

Increased brain size decreased Inter & increased Intra-hemispheric connectivity Tract loss (vent prefront; vent temp cortex) Extend new function to opposite hemisphere whilst retaining old function in original one

Question 51

What are the indications for preoperative visualisation of WM tracts?

Answer 51

1. Plan surgery 2. Inform patients 3. Common tumours, epilepsy