- Slow-growth of low grade tumours allow the long-lasting neural adaptation could be mediated by a multistep process involving not only fast-adjusting neuronal systems (i.e. synaptic changes), but also a combination of slow-evolving mechanisms such as myelination, axonal remodeling or angiogenesis
- Particularly low occurrence of neuropsychological impairments typically observed at the time of diagnosis, despite sometimes very large tumours;
- This strongly contrasts with clinical observations made in patients with sudden lesions (as stroke injury) for whom functional diagnostic is much worse
- Training-induced morphological changes, at both the cortical and WM levels, can be induced, in the context of the acquisition of either basic or complex learning/cognitive expertise.
- How to find out if a part of a brain has high or low plasticity
- Weakly plastic (no functional compensation):
- A region that remains systematically functional despite infiltration
- Strongly plastic (high functional compensation):
- Infiltrated region that never respond to stimulation
- Factors that affect plasticity
- Cortical plasticity
- Generally strong,
- Can be weak in cortical areas of unimodal and a handful of neural hubs,
- Primary motor areas
- Somatosensory areas
- Neurobiological basis of gray matter changes are not clear. It could be the reflect of many suspected factors, including neurogenesis, gliogenesis, glial hypertrophy, possibly mediated by the interactions between astrocytes and neurons (since the molecular and functional profiles of astrocytes seem to be regulated by the neurons via the sonic hedgehog pathway)
- Subcortical (Axonal) plasticity
- Mostly refractory to functional compensation
- Because subcortical areas are part of input or output subcircuits
- Projection fibers
- Cortico-spinal and thalamocortical tracts and the optic radiations,
- These zones are mainly unimodal and organized serially, with an absence of parallel alternative pathway explaining the impossibility to restore their function after any insult
- Associative WM tracts
- IFOF or the SLF/AF
- Because their injury would induce so major breakdowns in both network and between-network communication that the plastic potential would be overwhelmed
- Should be preserved to allow postlesional functional compensation in the context of neurosurgery
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