Everyday Psychology

Visual representation of the pruning. [source]

Very early on in human life, around weeks 3 and 4 of prenatal life, Neurogenesis occurs. During this period there is a very high rate of new neurons forming in what is to become the infant's brain. During this rapid creation of neurons there is another process at work known as Synaptogenesis.  Connections between neurons that allow them to communicate to one another are known as synapses. In early life there is an excess of these synapses present in the brain.

The fate of these excess neurons and synapses will be determined by Synaptic Pruning. The goal of this pruning is to eliminate connections which are unnecessary, not used often, or are not useful. One way of looking at this process is to think of the quote "Use it or lose it". This process is also known as Neural Darwinism because like evolution, only the 'strong' neurons and synapses survive into adulthood.  This process begins before a baby is born and continues up until early adulthood. This pruning represents brain maturation and is also believed to represent learning. In total, around 50% of neurons and synapses are eliminated via this process.