Our objective was to review the spatial and temporal factors which determine structural
plasticity of the developing fiber pathways in the human fetal and preterm brain.
The fiber pathways show structural plasticity (detouring, rerouting, sprouting) during
initial outgrowth, pathway selection phase, „waiting“, target- and address selection
phase (temporal parameters) occuring in sequential developmental „windows“. The „plastic“
changes take place in the following compartments: internal capsule, periventricular
cross-roads, intermediate zone, subplate and cortical plate (spatial parameters).
The most prominent compartment in the human cerebrum is subplate which contains afferent
fibers during „waiting“ period.
Using histological techniques on postmortem brains of preterms and children who died
after various post-lesion survival and histological-magnetic resonance correlation
on „normal“ brains we have obtained results which shed new light on pathways plasticity.
Thalamocortical fibers may be rerouted if periventricular lesion occurs before 24–26
weeks post conception (wpc), during a „waiting“ period in the subplate. Long cortico-cortical
pathways cause formation of new convolutions around porencephalic cavity, after damage
of their prospective cortical target area. The developmental peak of this plasticity
is around 34 wpc, during the existence of subplate zone. Corpus callosum is the most
affected fibre system due to the fact that it grows through numerous periventricular
cross-roads, rich in axonal guidance molecules. In analysis of efferent pathways we
have found enhanced compartmentalization of the putamen after bilateral caudate lesion.
This phenomenon may be explained by rerouting of ipsilateral and contralateral corticocaudate
projection to putamen.
The presented spatial and temporal parameters of structural plasticity of growing
pathways can be studied using neuroimaging methods and applied for planing the treatment
in children with prenatal brain injury.
