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Frederick Travis
More books by Frederick Travis…
“Figure 2.2 Number of connections over 25 years across brain areas. This process — neural exuberance followed by pruning of connections — makes the human brain highly adaptable to any environment. Is the infant born in an urban or an agricultural society? Is it the year 2012 or 1012? It doesn’t really matter. The brain of a child born in New York City or in Nome, Alaska, is similar at birth. During the next two decades of life, the process of neural exuberance followed by pruning sculpts a brain that can meet the demands, and thrive in its environment. Brain differences at the “tails” of the distribution As with any natural process there is a range of functioning, with most individuals in the middle and a small percentage of individuals being far above and far below the mean. While the general pattern of increasing and decreasing brain connections is seen in all children, important differences are reported in children whose abilities are above or below those of the average population. To investigate children above the normal range, Shaw used Magnetic Resonance Imaging (MRI) to follow brain structure in 307 children over 17 years. Children with average IQs reached a peak of cortical thickness (and therefore number of neural connections) around age 10, and then pruning began and continued to age 18. Children with above-average IQs had a different pattern: a brief pruning period around age 7 followed by increasing connections again to age 13. Then pruning ensued more vigorously and finished around age 18. There were also differences in brain structure. At age 18, those with above-average IQs had higher levels of neural connections in the frontal areas, which are responsible for short-term memory, attention, sense of self, planning, and decision-making — the higher brain functions. At the other end of the spectrum, individuals diagnosed with schizophrenia, compared to normal children, lose 3% more connections each year from age 10 to 18. Symptoms of schizophrenia emerge in the late teens, when the cortical layer becomes too thin to support coherent functioning. A thinner cortical layer as a young adult — about 20% less than the average — could account for the fragmented mental world of people diagnosed with schizophrenia. Who is in control? Neural exuberance — increasing and decreasing connections — is genetically controlled, but the child’s experiences affect which connections are pruned and which remain. Circuits that a child uses are strengthened. So a youngster who learns to play the piano or to speak Italian is setting up brain circuits that support those activities — she will find it easier to learn another instrument or language. Warning to parents: This doesn’t mean you should inundate your toddler with Italian, violin, martial arts, and tennis lessons. Young children learn best when following their natural tendencies and curiosity. Children learn through play. Undue stress and pressure inhibits the brain’s natural ability to learn.”
― Your Brain Is a River, Not a Rock
― Your Brain Is a River, Not a Rock
“The corpus callosum, which connects the left and right hemispheres of the cortex, myelinates from 7 to 10 years of age. At age 10, a child’s thinking speeds up noticeably. Ask seven-year-olds a question and it will take a long time for them to respond. Sometimes you can almost see the question move up to the brain and the answer go slowly back down to the mouth. This really became clear to me at our dining table. Our family knows seven different graces to say before meals, and each of our three daughters wanted to choose grace. So we suggested that each daughter could choose grace before breakfast, before lunch, or before dinner. Our youngest daughter, then age six, chose grace before lunch. Lunch is the shortest meal time — we have to walk home, eat, clean up, and walk back to school. Every lunch when we asked her what grace we should say, she would be absolutely quiet for a very long time. She would look around the room, furl her brows, obviously thinking hard, and then announce which grace to say — and it was always the same one. I got a little angry. Was this a power trip? Was she trying to control us? After all, we couldn’t eat until she chose a grace. I finally realized that, because her corpus callosum connecting her left and the right hemispheres was not fully myelinated, the signal was going very slowly back and forth in considering which of the seven graces to say. She was thinking as fast as her brain would allow. The teenage brain The last connections to mature are those between the front and the back of the brain; these connections begin to myelinate at age 12 and continue through age 25. The back of the brain is the concrete present. Environmental stimuli from the senses activate the back of the brain, where a picture of the world is created, like a movie on a screen. This picture is then sent to the front of the brain, the executive centers — the “CEO” or boss of the brain. The frontal lobes place the concrete present — what is happening right now — in the larger context of past and future, plans, goals, and values. Even though teenagers may look like adults, their brains are still maturing. The teen’s brain, whose frontal connections are not fully myelinated, is like a company whose CEO is on vacation. Each department is moving full speed ahead without the benefit of knowing the big picture. Teens are very passionate; they are engulfed by their ideas. They can generate a plan that takes into account their immediate circumstances, but they don’t see the bigger picture.”
― Your Brain Is a River, Not a Rock
― Your Brain Is a River, Not a Rock
“Here’s a research study that shows just how differently teens’ brains function: In a Magnetic Resonance Imaging (MRI) study, teenagers and adults were presented pictures of people who looked scared or anxious. The adults recognized the fear in the faces but placed the experiences in a larger context, so it didn’t affect them personally. The opposite was true of the teens: they did not report that the faces were fearful, but they became emotionally involved and reported more fear and anxiety themselves. In teens, the parts of the brain that process gut reactions and primitive emotions — the amygdala and insula — were active. But in adults, the frontal lobes were activated as well. In other words, the teenagers’ brains responded emotionally. They felt upset but their brains did not identify the source of those feelings. The adults’ brains added reason to that response. Remember this when your teen gets upset “for no reason.” He may not be able to say why he’s feeling that way, but his feelings are still valid. He doesn’t have the connections between his rational brain and his emotional brain that would allow him to explain it. Logic doesn’t help because the teen’s brain cannot follow abstract logic. They are doing the best they can with the brain connections they have. This is especially true if your teen is a boy. As we see later, girls have more connections between their emotional and executive centers. Astrocytes: Functional and structural support Astrocytes are another class of glial cells. They are star-shaped, hence their name, and provide structural and functional support for the neuron. Astrocytes form the matrix that keeps neurons in place. But they are more than inert bricks in a passive wall. Rather, they function more like the mother who ensures her children have brushed their teeth, are wearing their coats in winter, and are eating good meals. An astrocyte is pictured in Figure 3.3. Astrocytes sit between blood vessels and neurons and breakdown glucose from the capillaries into lactic acid, which the mitochondria of the neurons use for energy. As a wise mother, they do not break down all of the glycogen they receive from the blood, but create a reserve for times when the metabolic need of neurons are especially high.”
― Your Brain Is a River, Not a Rock
― Your Brain Is a River, Not a Rock
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