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The studies on a rat optic nerve revealed that 15 days post-natal is when an increase in myelination is observed. Before this time period, most of the axons, roughly about 70%, are not myelinated. At this time, [35S] Sulfate was incorporated into sulfatide and the activity of cerebroside, sulfotransferase reached a peak in enzyme activity. This ...
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience.These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
Due to the methods involved with generating the organoids, there can be a large degree of experimental variability. [18] Additionally, due to the long duration over which myelination occurs, optimizing the dosage of molecules and treatments involved in myelin development can be difficult. [1]
The subplate is located beneath the cortical plate. It is named for both its location relative to the cortical plate and for the time frame in which it is created. While the cortical plate matures, the cells located in the subplate establish connections with neurons that have not yet moved to their destination layer within the cortical plate.
Pruning starts near the time of birth and continues into the late-20s. [2] During the pruning of a synapse, both the axon and the dendrite decay and die off. Synaptic pruning was traditionally considered to be complete by the time of sexual maturation , but MRI studies have discounted this idea.
However, the myelin layer does not ensure a perfect regeneration of the nerve fiber. Some regenerated nerve fibers do not find the correct muscle fibers, and some damaged motor neurons of the peripheral nervous system die without regrowth. Damage to the myelin sheath and nerve fiber is often associated with increased functional insufficiency.
The maturation of myelination in intracortical layers coincides with critical period closure in mice, which has led to further research on the role of myelination on critical period duration. [37] Myelin is known to bind many different axonal growth inhibitors that prevent plasticity seen in critical periods. [38]
The amount of time required to generate all the neurons of the CNS varies widely across mammals, and brain neurogenesis is not always complete by the time of birth. [3] For example, mice undergo cortical neurogenesis from about embryonic day (post-conceptional day) (E)11 to E17, and are born at about E19.5. [9]