Hi, you can research the brain development of a baby in your handbook, from there you can write a summary of what you learnt.
Page 23 and 24 of the EYE handbook explains how the brain grows and how it is thought that most of the brain cells are formed before birth (pre-natal) but that the connections among those cells are made during infancy and early childhood (post-natal)
Use the index in the textbook you say you have and see if
brain development is listed.
You'll need to reference where your information is from so reliable, good sources are needed.