Infancy And The Developing Brain (page 4)
Until just a few short years ago, scientists had to make a lot of guesses about what was happening in the brains of young children growing up. Now, using MRIs, researchers are able to take images over a period of years and see year-by-year how the brain changes. Let's take a look at what we know about the brain at its earliest stage of development, even before birth (see Figure 4.5 later in chapter).
The first understanding about our early developing brains is that of vulnerability. Even in the womb, we are highly vulnerable to both good and bad experiences. From birth, the brain is bursting with new, receptive neurons. How receptive? By the age of one, neurons (your largest brain cells) in the prefrontal cortex average around one hundred thousand synapses (connections) apiece. By comparison, neurons in the visual cortex have only twelve thousand synapses apiece.10 The myelination process (wherein each axon gains a fatty coating of tissue called myelin) is slowest in the frontal lobes as compared with other areas of the brain. Myelination is a process that's both genetic and experience dependent. This process increases your brain's efficiency dramatically, allowing for faster processing, decision making, and acting on those decisions. But it's dependent on which experiences the child has and on maturity levels.
Maturity is a critical matter, because without mature fontal lobes, the child's brain can't understand, rationalize, dismiss, or even reflect on the simplest of life experiences. Young children have billions of neurons and even more synapses making connections out of a chaotic, violent, whimsical, and nonsensical world. Good, bad, or ugly, what comes at the brain at this age is simply taken in and downloaded. You can't have a brain that is fabulous at sponging up new experiences like learning a language and somehow isn't also vulnerable to bad things.
The second condition that makes the brain especially vulnerable at this age is the brain state characteristic of very young children. Youngsters are in more highly receptive brain states than are adults. A brain state can be measured several ways: chemically, behaviorally, or electrically. Researchers most commonly talk about brain states in terms of cycles per second (CPS) of brain wave activity (Figure 4.2). The slowest is delta, the 0–4 CPS seen during deep sleep and coma. Theta, half-awake and half-asleep, is 4–7 CPS. Next higher is alpha, the alert but calm state, at 7–12 CPS. Activity or excitement invokes the beta state, 12–25 CPS. There are many other states, but those are the most common.
Of those mentioned, theta is the most passively receptive of the brain states. The delta state is "dead to the world" and too subdued for learning. Both the alpha and beta states are good for learning, but the brain may be analytical, unable to focus or even be critical of the new learning. Interestingly, theta is the state in which we are most receptive. Now, guess in what state children from ages zero to five spend most of their waking hours? You guessed it—it's the most receptive ones, especially theta, the state most conducive for uncritical, undisputed downloading of new information.11
It's the same state that hypnotists use for getting the best results with audience members participating in their stage acts. The problem is that kids this age are watching television in this state, too. Children begin watching television early, often by six months of age. The typical A.C. Nielson viewing pattern shows a steady rise in the number of hours of television watched from early childhood through preadolescence. Does this create a concern for the brain that's downloading culture instead of getting enriched? It should concern you very much, and here's why. More than a third (36 percent) of all children have a TV in their bedrooms. More than one in four (27 percent) have a VCR or DVD player, and 43 percent of four to six-year-olds do.12 The typical American household has the television set on for more than seven hours each day, and children ages two to eleven spend an average of twenty-eight hours per week viewing. The periods of most violent programming were between 6 A.M. and 9 A.M., with over 165 violent scenes per hour.13
Does all this have any effect on the young brains? One study compared three large groups of kids (one in a different city). One received typical, violent TV; another group received average or neutral TV; and the third group received no television at all (it's not yet broadcast to that city). In comparing the rates of violence of these kids with those of kids in cities that already had television, what do you think was found? Guess which group turned out to be more violent (hurting siblings, misbehavior, bullying, misdemeanor offenses, and so on)? The biggest increase in violence was in the city that went from no television to violent television. 14 Why? The brain is highly receptive to constant streams of images, especially in a receptive, theta state. This was an interesting study because cities were being measured without the "contamination" of having already had television available for decades. In other studies, the starting "baseline" already has the "television effect"; the subjects already may have a higher starting point for violence, since everyone's already been watching it.
Keep this in mind when it comes to choices you make for children. Their brains are going to download the world all day—that's exactly what they're designed to do for survival—brains download the culture. They suck in the images, the sounds, the actions, conversations, neglect, trauma, emotions, and values for every waking hour. The young brain is downloading stress, problems, how to be a mom, how to be a dad, how to deal with life, what humans do all day—both from direct observation and from images in television and movies. This is an undisputed, unedited download that shapes the young child's world in powerful, lifelong ways.
If children download an enhanced environment, loaded with positives, the result may be enrichment response. If children download environments full of chaos, distress, or trauma, their brains will also change dramatically but in a negative way. This can reduce the child's ability to regulate emotions later on.15 The stress response system can become hypervigilant or hyporesponsive. These kids may become very aggressive or very passive and struggle with daily social or emotional decisions. We see such kids in the foster care, juvenile justice, or criminal justice systems.
Brain Maximizer: Avoid all television for children under the age of two. Be highly selective of DVDs for infants and children under five. For children ages two to five, only the television shows Sesame Street and Blue's Clues have a well-researched, positive track record for social, emotional, and cognitive enhancement. Children's cartoons average about twenty to twenty-five violent acts per hour, which is five times more than typical primetime shows. A typical child's exposure to violent cartoons can lead to increased aggression.16 This is the time for children to socialize, crawl, explore, talk, try out things, build things, learn games, and be protected from violence and rapid, nonsense brain programming.
The brain areas involved with listening, learning new sounds, and eventually speaking are in the temporal lobes. Although no biological mandate requires language processing in the left brain, certain "soft biases" in information processing are preferential to language skills in the left hemisphere.17
The auditory cortex (in the temporal lobes) undergoes dramatic growth and stabilization from the beginning of the last trimester of gestation through the first postnatal year. Infants can discriminate most sounds in their normal environment by six months.18 Several developmental thresholds occur between birth and six months and again between six months and twenty-four months. These milestones suggest how the infant's auditory system matures toward adult levels in range (decibels), discrimination (in the presence of a masking noise), and temporal resolution (quick word interval changes).
The number of synapses in the language areas reaches its maximum at about one year; about the time children become most interested in receptive and expressive language.19 This is the time when parents and caregivers should pay special attention. The more the parent's conversations (more words, longer words, complete sentences) between birth and three, the greater the infant's vocabulary. Figure 4.3 shows the relationship between a mother's speech and the vocabulary growth in the infant. When mom talks, infants listen.20 This suggests the importance of eye contact, a gentle touch when speaking, and complete sentences. Short, one-word sentences that simply give a command like "Stop!" will not build a child's vocabulary very much. It's time to lavish the language on the young brain.
Amazingly, the synapses (connecting areas between neurons in the brain) are far more densely packed in the brains of infants and young children than in those of adults. This exuberance of connections may contribute toward greater activity and increased excitability among youngsters that age.21 High metabolic activity is overdone when you have fever and even convulsions. But it's just right for most children between birth and five years of age, since it is activity and experience that develop the language capacities of the brain. The first big burst in vocabulary occurs between fourteen and twenty-two months. During this spurt, children may learn up to three new words a day, and vocabulary growth will even pick up from there. By first grade, a child may well be learning up to twelve words a day!
Brain Maximizer: This is the time for children to hear real people talk (not television voices). It's the time for full sentences, using real English, in context. Limit the short one- and two-word commands and orders to a minimum. Talk through what you do with children. Expose children to a wide range of conversations with eye contact and gestures or props.
The young brain is burning with desire—desire to learn. There is a continuing rise in overall resting brain metabolism (glucose uptake) after the first year of life, with a peak—about 150 percent of adult levels—at around four to five years of age for some cortical areas.22
Development of the sensory motor systems occurs through exploration (especially visual, motor, and auditory) during the first two years. The vestibular system in the inner ear is responsible for balance, among other things. It's the system that needs to be activated often to "acclimate and set" itself in the developing brain. The motor cortex is pruning away unused connections very fast at this age. Figure 4.4 shows the number of connections between cells (synapses) in the human motor cortex in two layers of the human brain, graphed as a function of age.
From birth to age two, the human brain has the greatest number of neurons that it will ever have, yet the brain is only one-fourth the size of an adult's. Most of the synapses exist and are available for usage, but not yet functional. We call those silent synapses. Many of these connections do actually form in the first two years of life. By age twelve to twenty-four months, the brain has twice as many synapses as it will have as an adult. Synaptic formation peaks between ages one and five, depending on the area of the brain measured.23 This is a highly sensitive period, for better and for worse. Why? Because early childhood is a time of intense brain activity, and nature has prepared the newborn with excess capacity. During the first five years, the human brain overproduces synapses; there are connections between brain cells, but they're random. One researcher estimated we have about one trillion of them.24
The development of the brain relies not so much on having enough synapses as on having the right ones for the right jobs. Most of today's researchers support a connectionist viewpoint about brain development. This model suggests that input to the brain is what alters the "weighting" at the synapses (between the neurons). The altered weights bias and then help form new, complex neural networks based on life experiences. Unused synapses disappear and new ones get stronger through usage. If the experiences are negative, the brain is getting the opposite of enrichment—it's being impoverished.
The developing brain is especially sensitive to stress. When parents argue, it's very stressful for little children. Domestic violence is associated with suppression of IQ in young children.25 That's the last thing you'd ever want if you care about enrichment. Earlier you read about the downloading of culture in a child's brain. Early exposure to stress, neglect, abuse, or violence often causes the brain to reorganize itself, increasing receptor sites for alertness and stress chemicals.26 When the young brain becomes out of kilter and the chemical responses are abnormal, it leads to atypical stress responses that can last for a lifetime. There is no need to "toughen up" a child of five or under. Trust me, they'll get plenty of exposure to real-word stressors later on.
The young, vulnerable brain is unable to self-regulate exposures to stress. The frontal lobes are immature, so the child cannot understand, compartmentalize, or rationalize exposure to violence. That's why it is so important to keep stress low in the first five years. The research on early stress is both dramatic and troubling. It suggests that early stressful experiences, before a child is able to handle them, can cause serious problems later. Distress from maternal separation may cause brain cells to commit suicide in the infant's brain. The research from laboratory animal studies showed that distress caused abnormally high numbers of brain cells to die.27
Although the growing brain normally prunes excess synapses and cells, the neurons in the maternally deprived (highly stressed) animals died at twice the normal rate! Neglect is bad for any child. This does not mean parents should never leave their children, but it means making sure children are safe and have adults nearby at all times. Scary, abusing, or neglectful circumstances may lead to errant synaptic pruning in the frontal lobes, which impairs emotional development later on. Troubled early relationships cause the child's brain to consume glucose in dealing with stress, rather than using that glucose for early cognitive functions.
Brain Maximizer: Find large, safe, supervised places for your child to play. These can be parks, playgrounds, fields, lawns, the beach, or other open, interesting places. Children will enjoy nature on their own, but with other children, they'll really love it. Sitting indoors watching TV is not enriching.
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