The rapid change of gene expression patterns in the brain during the prenatal and neonatal stages of its development is associated with major neurodevelopmental trajectories (Colantuoni, et al., 2011; Kang, et al., 2011). The functional annotation of sets of co-expressed genes (i.e., genes expressed simultaneously or in concert), which show temporal dynamics in their expression levels during the prenatal development of the brain, suggests that genes related to neuronal differentiation, cell proliferation and migration show the highest expression levels in the early fetal cortex (at 10-13 pcw), which decrease after the mid-fetal period (16-19 pcw) until early childhood. By contrast, genes associated with dendrite and synapse development (such as genes controlling ionic channels and neuroactive ligand–receptor interaction) dramatically increase their expression between the late mid-fetal period (19-24 pcw) and late infancy (Kang, et al., 2011).
