The Teenage Brain: A neuroscientist’s survival guide to raising adolescents and young adults. Frances Jensen E.

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СКАЧАТЬ grocery store, are exhausted or exasperated or both, and all of them could fill in the blank in that question with a whole host of perplexing actions, from “Why would my teenage daughter sneak out of the house in the middle of the night to be with her boyfriend after they just spent the whole weekend together?” to “How could my son raid the liquor cabinet of his friend’s parents—and then leave the empty bottles behind to boot?!”

      A neighbor of mine with a sixteen-year-old was flummoxed when she caught her son smoking pot in his room when he was supposed to be studying. That was bad enough, she told me, but what astonished her even more was the fact that he had the window wide open (it was the middle of winter, mind you) in order to air out his room—and the wind was blowing the smoke back into the room, under the door and down the stairs, where it wafted toward my horrified friend in the kitchen!

      “How could he be that stupid?” she asked me.

      Parents quickly blame themselves for a teen’s poor behavior, even though they’re not exactly sure how or why they’re to blame. With biological parents, the guilt may come from passing on flawed DNA; and with biological and nonbiological parents or guardians, the guilt comes from questioning how they raised the child. In either case, you, the parent, are to blame, right? Yes, the two scenarios are different, but no, it’s not because of the genes or anything you did or didn’t do or because the teenager was somehow struck on the head and woke up as an alien species from the planet Adolescent.

      Teenagers are different because of their brains and specifically because of two unusual aspects of their brains at this stage of their development. Their brains are both more powerful and more vulnerable than at virtually any other time in their lives. Even as they are learning things faster, their brains are eliminating gray matter and shedding neurons. How both of these facts can be true is because of something called neural plasticity.

      Even as a teenager I used to wonder about the brain. Did it make a difference where a person grew up? How he or she grew up? Was the brain at all like the rest of the body—capable of changing depending on what went into it or what it was exposed to? I enjoyed turning these questions over in my head, and when I got to college they turned up again, only this time I began to have inklings of some of the answers.

      During one summer while I was still in high school I volunteered at the Greenwich chapter of the Association for Retarded Citizens (ARC), now known simply as the Arc, which aids people with intellectual and developmental disabilities. Some of those who regularly attended the Greenwich ARC were born with Down syndrome, and though they had varying abilities, most were self-sufficient. They were able to swim and to participate in the theater program; some even learned to read and write. Because of Greenwich’s affluence, not only was the local ARC always well funded, but many of the kids came from very privileged backgrounds as well. To this day I remember being astonished when a limousine dropped off a tot for his day of activities with us. These children were really in an unusually enriched situation, and the effects of this gifted environment showed. Despite their handicaps and rather serious diagnoses, they were active and curious and engaged, and many were approaching milestones for reading and arithmetic close to those expected for normal kids their age. I knew that not only were they getting a great day at the ARC, but when they went home, they were often given physical therapy and tutoring there, too.

      While at Smith, I had an opportunity to see what life was like for the mentally and developmentally disabled who did not have the same advantages as the children at the Greenwich ARC. I volunteered several hours a week at the Belchertown State School, a seventy-year-old state institution for the cognitively handicapped, located just a few miles from Smith. Belchertown’s residents ranged from children to the very elderly, many of whom had spent most of their lives at the institution. Before it closed in 1992, Belchertown housed as many as 1,500 people, ages one to eighty-eight, living in thirteen dormitories. The hospital was understaffed, even after a local newspaper exposed overcrowding and maltreatment in the 1960s. When I volunteered in 1975, I primarily spent time in the children’s dormitory. It was not a pleasant place. The rooms smelled of disinfectant, toys were few and far between, and many of the kids hadn’t been bathed in quite some time. Like the children at Greenwich’s ARC, some were more disabled than others, but even those who were more functioning seemed to lag far behind their peers at ARC. They sat in corners and rocked and had difficulty speaking, and their eyes appeared vacant.

      This was a time at the height of the nature-versus-nurture debate, and my psychology and biology professors at Smith were keen on discussing how much a person’s makeup, from personality to intelligence to likes and dislikes, is dependent on genes (nature) and how much on the influence of environment (nurture). There was clearly little nurturing going on at Belchertown, while at ARC there were always activities, directed therapies, teaching, and, most of all, stimulation.

      At some point I realized the children at Belchertown who had the same disabilities and the same hurdles to overcome were far worse off than the kids at ARC in Greenwich, and at least from my limited viewpoint, environment seemed to be the overwhelming determining factor. It was pure and simple: the brains of the ARC children were being stimulated and encouraged, and the brains of the Belchertown children were not.

      Like fingerprints, no two brains are identical. Everything we do, think, say, and feel influences the development of our most precious organ, and those developments trigger ever more changes until the thread of action and reaction is too complex to unwind or undo. Our brains, in essence, are self-built. They not only serve the particular needs and functions of the particular individual, but also are shaped—landscaped if you will—by the individual’s particular experiences. In neuroscience, we refer to the human brain’s unique ability to mold itself as plasticity. Thinking, planning, learning, acting—all influence the brain’s physical structure and functional organization, according to the theory of neuroplasticity.

      As far back as Socrates, some believed the brain could be “trained,” or changed, much as a gymnast trains his or her body to balance on a high beam. In 1942 the British physiologist and Nobel Prize winner Charles Sherrington wrote that the human brain was like “an enchanted loom, where millions of flashing shuttles weave a dissolving pattern, always a meaningful pattern, though never an abiding one.” In essence, the human brain, said Sherrington, was always in a state of flux.

      Five years after Sherrington, Donald Hebb, an American neuropsychologist, was struck by a kind of accidental inspiration that led to the first quasi-experimental test of the theory of brain plasticity. When the forty-three-year-old researcher took rat pups home from his lab at Canada’s McGill University and gave them to his children as pets, he allowed the rodents to roam freely around the house. Hebb’s inspiration was to compare the brains of these free-roaming pet rats with those of rats kept in cages in his lab. After several weeks he put both groups of rats through a kind of intelligence test involving a maze. The pet rats, which had free access to explore the environment of Hebb’s home and unfettered interaction with one another as well as with Hebb and his family, performed significantly better on the maze test than the lab rats confined to small cages.

      By the late 1990s researchers had confirmed a range of changes associated with experience and stimulation, including brain size, gray matter volume, neuron size, dendritic branching, and the number of synapses per neuron. The more stimulation and experience, they concluded, the larger the neurons, the bushier the dendrites, the higher the number of synapses, and the thicker the gray matter.

      During my senior year at Smith College in 1977–78, I wrote my first professional journal article under the tutelage of Nico Spinelli, a professor in both the psychology department and the computer and information science department at the University of Massachusetts Amherst. He was doing pioneering experiments in the plasticity of the visual cortex. Previous research had looked at the brains of mammals raised in a deprived environment. Spinelli СКАЧАТЬ