What happens to these extra neurons and connections then? The answer is synaptic pruning (or neuron pruning). Synaptic pruning is a regulatory process that reduces the overall number of overproduced neurons by the weaker synapses. Brain Plus IQ  A weak synapse is a synapse that is not used much, which shows that experience is an essential part of brain development. A: No. Brain development is a continuum from birth to age 20 or so. A ??critical period?? in development is a time, in the early stages of an organism’s life, during which the organism shows a very high sensitivity to some stimuli in the environment. If the stimuli in the environment are present, the organism will develop in a specific way. http://www.healthcaresups.com/brain-plus-iq-scam/