There are two regions of development which are separated by the sulcus limitans. The alar plate which will form the dorsal horn of the mature spinal cord and the basal plate which will form the ventral horn . The migration of neurons is localized so that no migration occurs across spinal cord segments. Differentiation of Neurons - Local environment can affect neuronal differentiation. Timing of development affects differentiation.
Cells can become adrenal gland or sympathetic ganglion depending on their location.
The connectivity is affected by experience. Major projections are less affected by experience. For example, the retinal ganglion cells projecting to the thalamus are not as affected as the connection between the cells in the thalamus and cortex. About half the neurons die. Twice as many a motor neurons are produced than will be present in the adult.