Synaptic Pruning

In neuroscience, synaptic pruning, neuronal pruning or axon pruning refer to neurological regulatory processes, which facilitate changes in neural structure by reducing the overall number of neurons and synapses, leaving more efficient synaptic configurations. Pruning is a process that is a general feature of mammalian neurological development. Pruning starts near the time of birth and is completed by the time of sexual maturation in humans. At birth, the human brain consists of over 100 billion neurons. The infant brain will increase in size by a factor of up to 5 by adulthood. Two factors contribute to this growth: the growth of synaptic connections between neurons, and the myelination of nerve fibers. Generally, the number of neurons in the cerebral cortex increases until adolescence reflecting a growth of synapses. A decrease in synapses is seen after adolescence reflecting synaptic pruning, and approximately 50% of neurons during development do not survive until adulthood. Pruning is influenced by environmental factors and is widely thought to represent learning.