A newborn infant is diagnosed with phenylketonuria. The neonatologist prescribes a special diet for the baby and explains to the parents the importance of maintaining this diet in order to prevent mental retardation. In this patient abnormal development of which of the following structures will most likely lead to mental retardation?
A) Dendritic spines B) Nodes of Ranvier C) Ependymal cells D) Microglia E) Oligodendrocytes