Up to 50% of neurons that develop die during the course of normal development. The fact that neurons that make incorrect connections are more likely to die suggests that cell death increases the overall accuracy of synaptic connections.
There are three evidences that suggest that neural cells die since they fail to compete with others and fail at life preserving:
- Implantation of an extra target site decreases neuron death
- Destroying some neurons before the period of neuron death increases the survival rate of the remainder
- Increasing the number of axons that initially synapse on a target decreases survival rate of the remainder