7 Survival and death
7.1 Neuron proliferation
There is a huge proliferation of neurons in early life. Even whilst that proliferation continues, some cells, e.g. neuroblasts, stop being able to divide. At some later stage the proliferation itself virtually ceases. It follows that cells switch from being able to divide, to being unable to divide, and that they switch at the appropriate time: the process of cell proliferation is controlled. The details of the control of proliferation are not yet understood and are not considered here. But one feature of the proliferation is worthy of note; it is very wasteful. Over half of the neuroblasts produced die without achieving any functional capacity. This section addresses the question of which neurons live and which neurons die.