When a baby is first born the number of synapses it has is low. After two months there is a huge growth in their number - synaptogenesis. A steady pattern of growth continues until the age of ten year's old, when an "adult" number of synapses is reached.
The brain grows most quickly between 10 and 26 weeks after conception. After birth, the brain has most of the cells that it is ever likely to have – between 15 and 32 billion (this varies a lot between people). The brain is 90% of adult size by the age of 6. Constantly new connections are made, connections reinforced and some lost - pruned. Its not the number of neurons that is important but the richness of connections between them that is highly vital.
It is a fallacy to say that the brain loses ten thousand neurons a day – when we get older the large neurons decline but the amount of smaller neurons increases thus levelling things out. New neurons can appear throughout a person’s life. Connections that are used a lot are strengthened. This tends to be more pronounced in childhood. The more the neuron is used; the fatty sheath (myelin) surrounding the axon tends to get thicker – myelination. This allows the electrical signal to travel faster (up to 100x) through the neuron. Likewise those that are not used a lot are weakened or lost – pruned. This tends to be more pronounced in adulthood.
Research has shown that if you don’t use your brain cognitively, as you age the brain processes decline. Often older people when they do tasks don’t have to think about them ie they are fluent and experienced with tasks.
More and more evidence is pointing to the fact that using your brain and taking exercise enhances performance even in old age e.g. the old adage: "a healthy mind in a healthy body." Indeed life long learning can help combat against degenerative brain diseases such as Alzheimer’s and senility. Depression in older people is harder to treat, but studies have shown that in part it is due to decreasing cognitive capacity as well as more obvious factors such as loss of loved ones and lack of social role.
Neuroscience research has shown that the more you learn, the more you can learn. The more you continue your learning the more effective it is.
The frontal lobe is one part of the brain that takes one of the longest to develop. This deals with our rationality: planning and logic and therefore counteracts against the emotionally charged amygdala-hypothalamus. This in part explains why adolescents have problems controlling their emotions.
This means the person has a superb visual memory. More children tend to have an eidetic memory than adults. So it must be learning / age that lessens this memory.
Click here to explore Learning and Neurogenesis.