Brain development in Homo sapiens from fetus to adult

Neurons generate from neural stem cells, at 250,000/min and synapses at 40,000/sec beginning at 42 days post conception, establishing brain's neural networks, brain increases 4x in preschool, reaching 90% of adult size by age 6, has 2x synapses as in adulthood, surplus connections eliminated posteriorly by apoptosis. Epigenetics differentiate neuron stem cells into neurons and glia, thru molecular processes for Gene-Environment interactions. Hypothalamic-Pituitary-Adrenal axis, is activated at danger, produces cortisol, enhancing cardiovascular tone and attention. The human brain has 100 billion neurons, forming networks for thoughts, feelings and actions, each one connecting with 1,000 other neurons, creating 60 trillion neuronal connections thru synapses, ending at 6-layered structure in brain cortex. Proliferation of oligodendrocyte progenitor cells, begins prenatally, persist in the adult, in the forebrain subventricular zone and migrate into white matter, cortex, striatum and hippocampus, forming astrocytes and oligodendrocytes for myelin sheaths. Iron, Zinc, and Iodine should be given at prenatal period and early infancy to increase the world IQ by 10 points.