Overproduction of structures including neurons, dendrites, and synapses occurs during development in many neural systems. In human beings cerebral cortex synaptogenesis takes place prenatally and during early infancy. Maximum synaptic density, absolute number of synapses, and number of synapses per neuron are reached by age 1 year. Subsequently, there is progressive synapse elimination that is most rapid during the preschool years. Overproduction of synapses may impart plasticity to the brain of young children. This property of developing brain may be exploited for retraining when function is impaired. An example is the reversal of amblyopia by forcing strabismic children to use their squinting eye.