According to the Australian-based "Raising children network" and "Centre for Adolescent Health" (and a number of other sources): the main change occurring in the developing brain during adolescence is the (so-called) "pruning" of unused connections in thinking and processing. While this is occurring within the brain, retained connections are strengthened. Synaptic pruning occurs because the nervous system in humans develops by firstly, the over-producing of parts of the nervous system, axons, neurons, and synapses, to then later in the development of the nervous system, make the superfluous parts redundant, i.e. "pruning" (or apoptosis, otherwise known as "cell death"). These changes occur in certain parts of the brain firstly; the pre-frontal cortex, the brain location where decision-making occurs, is the concluding area for development. While the pre-frontal cortex is developing, children and teenagers might possibly rely more on the brain part known as the amygdala; involving thinking that is more emotionally active, including aggression and impulsiveness. As a consequence each individual is more likely to want to make riskier choices, and to do so more frequently.