PLASTICITY DURING DEVELOPMENT (OTHER FACTORS INCREASING FUNCTIONAL…
PLASTICITY DURING DEVELOPMENT
AGE AT INJURY
3 Time Windows
< 1 year
: Great impairment compared to later injury
1 to 5 years
: Some reorganization, including the rescue of language
> 5 years
: Little of no sparing of function
(sever effects of injury; disturbance of
stem cell activit
How does this relate to the above mentioned time windows???
REORGANIZATION OF LANGUAGE
Language survives early left-hemisphere injury. Much of this survival seems attributable to a-proportion of a potential language zone in the right hemisphere.
Shift of language has a price: some kinds of visuospatial orientation are impaired.
Early lesions of the right-hemisphere produce deficits similar to those produce by such lesions in adulthood. Right-hemisphere functions do not shift sufficiently to interfere with language.
Speech has a strong affinity for the left-hemisphere and will not abandon it unless the entire center is destroyed. Even then it might only shift partly. This is due to the assumed innate anatomical organization of the left-hemisphere. After the age of 6, recovery is only due to intra-hemispheric reorganization.
PLASTIC CHANGES SUPPORTING RECOVERY
1. Changes in the organization of the remaining intact circuits in the brain
Might be possible, but the overwhelming evidence suggests that this is rare and just as likely to be associated with abnormal functioning as with recovery.
3. Generation of neurons and glia to replace at least some lost neurons
Stem cells remain active in the sub ventricular zone throughout life, so perhaps neurogenesis could be stimulated after injury, especially in development.
2. Generation of new circuitry
The induced neuronal changes would most likely take place in the intrinsic organization of the cortex rather than throughout the brain as a whole.
OTHER FACTORS INCREASING FUNCTIONAL RECOVERY
General sensory experience
Diet and nutrition
Benefit of exposure to complex environments
(increase of brain size, synapses, density of cells and neurons)
Experience and neural connectivity
: use it or lose it