 |
|
| Advanced Search | Search Tips | Search A-Z | Glossary | |
| A Service of the Children's Bureau |
|
|
|
|||||||||
 |
 |
 |
 |
 |
 |
 |
 |
 |
View My Cart: 0 Items |
|
Home > Understanding the Effects of Maltreatment on Early Brain Development > Understanding the Effects of Maltreatment on Early Brain Development - How the Brain Develops
Understanding the Effects of Maltreatment on Early Brain Development
How the Brain Develops What we have learned about the process of brain development has helped us understand more about the influence of genetics and environment on our total development--the "nature versus nurture" debate. It appears that genetics predispose us to develop in certain ways. But our interactions with our environment have a significant impact on how our predispositions will be expressed; these interactions organize our brain's development and, therefore, shape the person we become (Shore, 1997). Forming the Structure During fetal development, the neurons that are created migrate to form the various parts of the brain. While the basic structure is intact at birth, much of the brain's growth occurs during the first few years after birth. This process of growth, or development, occurs sequentially from the "bottom up" (Perry, Pollard, Blakely, Baker & Vigilante, 1995; Perry 2000a). The first areas of the brain to fully develop are the brainstem and midbrain; they govern the bodily functions necessary for life, called the autonomic functions. The last regions of the brain to fully develop are the limbic system, involved in regulating emotions, and the cortex, involved in abstract thought. (See Exhibit 1.) Each region manages its assigned functions through complex processes, often using chemical messengers (such as neurotransmitters and hormones) to help transmit information to other parts of the brain and body (Perry, Pollard, Blakely, Baker & Vigilante, 1995; Perry 2000a). As the brain develops, it grows larger and more dense. By the age of 3, a baby's brain has reached almost 90 percent of its adult size (Perry, 2000c). The growth in each region of the brain largely depends on receiving stimulation, which spurs activity in that region. This stimulation provides the foundation for learning.
Organizing the Structure The development of synapses occurs at an astounding rate during children's early years. By the time children are 3, their brains have approximately 1,000 trillion synapses, many more than they will ever need. Some of these synapses are strengthened and remain intact, but many are discarded. By the time children have reached adolescence, about half of their synapses have been discarded, leaving about 500 trillion, the number they will have for most of the rest of their lives (Shore, 1997). Plasticity--The Influence of Environment "Plasticity is a double-edged sword that leads to both adaptation and vulnerability." Researchers use the term plasticity to describe the way the brain creates, strengthens, and discards synapses and neuronal pathways in response to the environment (Ounce of Prevention Fund, 1996). The brain's "plasticity" is the reason that environment plays a vital role in brain development. The early over-production of synapses appears to be the result of evolution that has led our brains to expect certain experiences (Greenough, Black & Wallace, 1987). Our brains prepare us for these experiences by forming the pathways needed to respond to those experiences. For example, our brains are "wired" to respond to the sound of speech; this is how we learn to talk. But these early synapses are weak; we must be repeatedly exposed to the expected experiences within a certain time period to activate and strengthen them. If this does not happen, the pathways developed in anticipation of those experiences may be discarded, and the development of the related functions will not occur as expected. This is often referred to as the "use it or lose it" principle (Greenough, Black & Wallace, 1987). In addition to strengthening or discarding existing synapses, researchers theorize that some synapses may be newly developed in response to unique environmental conditions (Greenough, Black & Wallace, 1987). It is through these processes of creating, strengthening, and discarding synapses that our brains adapt each of us to our unique environment. The ability to adapt to our environment is a part of normal development. Children growing up in cold climates or rural farms or large sibling groups learn how to function in those environments. But regardless of the general environment, all children need stimulation and nurturance for healthy development. If these are lacking-if a child's caretakers are indifferent or hostile-the child's brain development may be impaired. Because the brain adapts to its environment, it will adapt to a negative environment just as readily as it will adapt to a positive environment. Sensitive Periods "It is now clear that what a child experiences in the first few years of life largely determines how his brain will develop and how he will interact with the world throughout his life." Researchers believe that during these years there may be "sensitive periods" for development of certain capabilities (Greenough, Black & Wallace, 1987). Because synapses are being formed at such an intense pace during this time, the opportunities for learning are almost limitless. But as the process of pruning synapses starts to increase, especially after age 3, these opportunities begin to decrease (Shore, 1997). If certain synapses and neuronal pathways are not repeatedly activated, they may be discarded, and the capabilities they promised may be diminished. For example, all infants have the capacity, indeed the genetic predisposition, to form strong attachments to their primary caregivers. But if a child's caregivers are unresponsive or threatening, and the attachment process is disrupted, the child's ability to form any healthy relationships during his or her life may be impaired (Perry, 2001a). Although the first few years may be the "prime time" for learning, children and adults can learn later in life, but it is more difficult. This is especially true if a young child was deprived of certain stimulation, which resulted in the pruning of synapses and the loss of neuronal pathways. Helgeson (1997) offers the analogy of a country that has a dense network of branching streets; a traveler can go anywhere he wants, even unfamiliar places, by following the roads. If there are few roads, the traveler can still go places, but he has to travel "cross-country" and break new ground. It is doable, but much harder. As children progress through each developmental stage, they will learn and master each step more easily if their brains have built an efficient network of pathways.
While research has shown that the brain is more malleable in the first few years than at any other time in life, researchers disagree on how flexible or rigid the sensitive periods are. But they do agree that the experiences of the first few years form the foundation for children's future functioning. "While experiences may alter and change the functioning of an adult, experience literally provides the organizing framework for an infant and child" (Perry, Pollard, Blakely, Baker & Vigilante, 1995). Memories There are different types of memories, such as motor, cognitive, and emotional memories. Memories help us to navigate our world without having to really think about it (Perry, 1999). Children learn to put one foot in front of the other to walk. They learn words to express themselves. And they learn that a smile usually brings a smile in return. At some point, they no longer have to think much about these processes-their brains manage these experiences with little effort because the memories that have been created allow for a smooth, efficient flow of information. The creation of memories is part of our adaptation to our environment. Our brains attempt to understand the world around us and fashion our interactions with that world in a way that promotes our survival and, hopefully, our growth. But if the early environment is abusive or neglectful, our brains will create memories of these experiences that may adversely color our view of the world throughout our life.
This material may be freely reproduced and distributed. However, when doing so, please credit Child Welfare Information Gateway. |
||||||||||||||||||||
|
|||||||||||||||||||||
