Summary Table of the Stages of Brain Development

Developmental Stage

Main Feature of Developmental Stage

Induction

Production of cells that will become nervous tissue

Proliferation

Cell reproduction (mitosis)

Migration

Location of cells in appropriate brain areas

Differentiation

Development of neurons into particular type

Synaptogenesis

Formation of appropriate synaptic connections

Selective cell death

Elimination of mislocated cells and cells that failed to form the proper synaptic connections

Functional validation

Strengthening of synapses in use, weakening of unused synapses

By the sixth month of pregnancy the foetus will have reached a length of about 255 millimetres (10 inches). Sebaceous glands are evident and lymph glands which will help to protect the foetus from noxious substances from this moment to the end of its days. Up until now the foetus has relied exclusively on mother's anti-bodies for protection from toxins including environmental ones. It is here that the rooting reflex emerges, this reflex will be required for early feeding after birth.

The cerebral hemispheres now cover the whole top and sides of the brain including the cerebellum. Cerebellar development begins from this moment, but will not be complete until two years after birth. Six distinct layers are now differentiated within the cerebral cortex, and almost all of the neurons within the central nervous system are present by the end of this sixth month of life and neural 'circuitry' continues to develop 

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