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Samenvatting Neural networks - deel 2

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Vak Neurological aspects, deel 2 Neural Networks, gegeven door Prof. Gilat (KUL). Deel 1 (gegeven door Prof. Alaerts) is ook beschikbaar.

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  • 2 november 2024
  • 25
  • 2023/2024
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LB2001
NEUROLOGICAL ASPECTS:
NEURAL NETWORKS AND
REORGANIZATION
Academiejaar 2023-2024 – 2MARE




H1. CLINICAL RELEVANCE AND
INTERPRETATION ISSUES

H2. PARKINSONIAN DEFICITS AND
SPONTANEAOUS ADAPTATION

H3. NEURAL CORRELATES OF FREEZING OF
GAIT

H4. NEURAL ASPECTS OF ADAPTATION




PART PROF. MORAN GILAT

, PART MORAN GILAT




Neurological aspects: neural networks
and reorganization
CHAPTER 1: CLINICAL RELEVANCE AND INTERPRETATION ISSUES


Why do we need to know about neural correlates en brain mechanisms as neurotherapists?
1. Behaviour alone can mask recovery as patients put in effort – true neural recovery hidden?
2. Knowledge of neural mechanisms → thinking more deeply about therapy
3. Provide inspiration for a different approach to therapy

But knowledge to date is very incomplete and comes from different sources. Interpretation into single
coherent picture is difficult.
 Link therapy improvement to changes in the brain → how did we as therapists make that
change happen?

Direct measures of brain activity Indirect measures of brain activity
• EEG (increasingly more mobile) • Magnetic resonance imaging
• Transcranial Magnetic Stimulation • Functional
• Resting state
The brain is a connection-organ: network analyses are • Diffusion tensor and structural imaging
increasing and combined methods (multimodal) • White matter integrity
 Indicates methods prone to network analyses • Grey matter thickness
• Functional Near-Infrared Spectroscopy (mobile)

→ Multiple areas in the brain are talking together to achieve certain behaviours
➢ Past: studies only look at activity
➢ Now: brain is always connected to each other (more network analysis studies)

1.1 Neuroplasticity & neuroscientific methods
Molecular imaging: indirect measures of brain activity PET using radio-tracers
 It typically binds to water, oxygen or glucose (glucose most common → the more active brain
region is, the more sugar it needs, more glucose attracted to those regions)

Measures of neurotransmitter metabolism PET imaging using radio-tracers
 Dopamine transporters (DAT)
 DAT-scan = we see areas where dopamine is mostly released (putamen is lighted up
in the left picture)
o PD in early stage: putamen only anteriorly (posterior part is diminished, goes down
first in PD)
▪ Anterior = involved with goal-directed movement and cognition
▪ Posterior = involved in automatic movements
o Left side more transporters compared to right side → unilateral-onset of the disease
(this is a left side onset patient, because the right side is diminished first
 Physiotherapy/ PA can slow down this process

→ Careful first evidence to suggest that regular physical activity can slow down this process.



1

, PART MORAN GILAT




1.2 Interpretation of neural markers of compensation - recovery
➢ Neurogenesis – only possible in hippocampus/striatum in humans, sometimes generated from
neural stem cells and mediated by brain-derived neurotrophic factor (BDNF)
o Hippocampus: short-term memory storage location
o Striatum: motor learning
o BDNF = stimulates neuronal growth

➢ Grey matter (change of cortical thickness or shape of subcortical nuclei)
o Exact neuronal cellular processes that underlie these changes are unknown.
o Exercise-induced higher cortical thickness appears to occur rapidly in M1, through
arborization of dendrites and dendritic spine growth
o Grey matter = neuronal bodies

➢ White matter (WM integrity)
o Decreased: probably refers to poor neural efficiency, but multimodal studies are not
providing consistent results
o White matter fibre structure changes are difficult to measure
o Increased: desirable outcome (slow) of rehabilitation. It can also indicate adaptive or
maybe maladaptive compensation. Therefore, comparison between pathological
groups and healthy controls is therefore very important!
▪ Decrease in myelinisation (loss of connection)
▪ Not necessarily less activity: the efficiency might increase (less ways needed
to get the same effect)
▪ There is a lot of crossing-fibres between axons
▪ Any structural change goes slow and the change has to be quite big to measure
it with neuro-imaging
1.2.1 Example of between group WM-changes
☞ Comparing WM tracts in 19 freezers,16 non-freezers and 18 controls, correlated to worse freezing
and behaviour on a balance task
• Visualization (3D) of WM streamlines between right mesencephalic locomotor region (MLR)
and left cerebellum from a randomly chosen non-freezer. The color of the streamline specifies
the direction (red: mediolateral; blue: inferior-superior; green: anteroposterior).
• There is a connection between a region in the brain stem (mesencephalon) and the cerebellum




INTERPRETATION:
- Freezers showed a lower biological connectivity in the WM tract between the right MLR
(mesencephalic locomotor region) and the right caudate than controls, associated with worse
severe freezing. (Right MLR-Putamen is not correlated with behaviour)
- Stronger biological integrity between cerebellar vermis en left pallidum, compensatory in
freezers (like controls)?

→ Right MLR – right caudate:
➢ Green: highest WM-integrity
➢ Connection: the lower, the worse the freezing → decreased WM-integrity = worse FIG


2

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