Starting Smart: How Early Experiences Affect Brain Development
Michael Stevens is a healthy, beautiful newborn baby. As his parents admire him, they wonder, "What will Michael be like when he grows up? Will he do well in school? Will he get along
with other kids and be happy?" Scientists now believe that the answers to these questions depend in large part on how young Michael’s brain develops, and that this development in turn depends largely on the nutritional, medical, emotional, and intellectual support his parents, extended family, and community provide for him during his childhood.
Recent advances in brain research have provided great insight into how the brain, the most immature of all organs at birth, continues to grow and develop after birth. Whereas this growth had been thought to be determined primarily by genetics, scientists now believe that it is also highly dependent upon the child’s experiences. Research shows that, like protein, fat, and vitamins, interactions with other people and objects are vital nutrients for the growing and developing brain, and different experiences can cause the brain to develop in different ways. It is this "plasticity" of the brain, its ability to develop and change in response to the demands of the environment, that will enable Michael to learn how to use computers as successfully as his ancestors learned how to hunt animals in the wild.
As he grows, Michael’s ability to understand language, solve problems, and get along with other people will be influenced by what he experiences as an infant and young child. This is not to say that individual genetic differences have no influence on how a child develops; they do. But there is mounting evidence that experiences affect the way genes are expressed (i.e., turned on and off) in the developing brain. While good early experiences help the brain to develop well, experiences of neglect and abuse can literally cause some genetically normal children to become mentally retarded or to develop serious emotional difficulties.
Understanding How the Brain Develops
To understand how this happens, we need to understand a bit about how the brain works. The brain is comprised of many regions that perform specific functions, such as identifying what we see, processing spoken language, or assessing whether we are in danger. Within each of these brain areas are millions of neurons, or nerve cells, which send messages to each other across synapses. These trillions of nerves and synapses and the pathways they form make up the "wiring" of the brain; they allow all of the various areas to communicate and
function together in a coordinated way. The number and organization of connections in the brain influence everything from the ability to recognize letters of the alphabet to facility at managing complex social relationships.
In most regions of the brain, no new neurons are formed after birth. Instead, brain development consists of an ongoing process of wiring and re-wiring the connections among neurons. New synapses between cells are constantly being formed, while others are broken or pruned away. This happens throughout life. However, in early childhood the brain is genetically programmed to produce more synapses than it will ultimately use. Indeed, by 8 months of age a baby may have an astounding 1,000 trillion synapses in his brain! This blooming of synapses happens at different times in different areas of the brain. Development then proceeds by keeping the synapses that are used and pruning away those that aren’t. The pruning of synapses happens over the childhood years as the different areas of the brain develop(Huttenlocher & Dabholkar, 1997). Pruning allows the brain to keep the connections that have a purpose, while eliminating those that aren’t doing anything. In short, pruning increases the efficiency with which the brain can do what it needs to do. But, because the brain operates on the "use it or lose it" rule, an "over-pruning" of these connections can occur when a child is deprived of normally expected experiences in the early years. This leaves the child struggling to do what would have come more naturally otherwise.
Some areas of the brain, such as those which help us see clearly, become less "plastic" or changeable when the pruning is over. This has led to tremendous concern about providing what the brain needs to prune and organize itself correctly before the "windows of opportunity" close. For example, surgeons now remove congenital cataracts as early in infancy as possible, because they know that if they wait until the child is older, the neural connections between his eyes and his brain will fail to develop properly, and he will never be able to see. Brain
scientists are also working diligently to unlock the secrets of how the brain turns on and off its ability to change itself. There is real hope that if we can understand the ways this happens, we can create therapies, both those that use drugs and those that use carefully structured experiences and training exercises, that can open up windows and re-wire brains that were deprived of normally expected experiences early in life or those that get damaged later in life.