CHILDHOOD: A WINDOW OF OPPORTUNITY



The human brain is by no means fully formed at birth. It continues to shape itself through life, with the most intense growth occurring during childhood. Children are born with many more neurons than their mature brain will retain; through a process known as "pruning" the brain actually loses the neuronal connections that are less used, and forms strong connections in those synaptic circuits that have been utilized the most. Pruning, by doing away with extraneous synapses, improves the signal-to-noise ratio in the brain by removing the cause of the "noise." This process is constant and quick; synaptic connections can form in a matter of hours or days. Experience, particularly in childhood, sculpts the brain.

The classic demonstration of the impact of experience on brain growth was by Nobel Prize-winners Thorsten Wiesel and David Hubel, both neuroscientists.10 They showed that in cats and monkeys, there was a critical period during the first few months of life for the development of the synapses that carry signals from the eye to the visual cortex, where those signals are interpreted. If one eye was kept closed during that period, the number of synapses from that eye to the visual cortex dwindled away, while those from the open eye multiplied. If after the critical period ended the closed eye was reopened, the animal was functionally blind in that eye. Although nothing was wrong with the eye itself, there were too few circuits to the visual cortex for signals from that eye to be interpreted.

In humans the corresponding critical period for vision lasts for the first six years of life. During this time normal seeing stimulates the formation of increasingly complex neural circuitry for vision that begins in the eye and ends in the visual cortex. If a child's eye is taped closed for even a few weeks, it can produce a measurable deficit in the visual capacity of that eye. If a child has had one eye closed for several months during this period, and later has it restored, that eye's vision for detail will be impaired.

A vivid demonstration of the impact of experience on the developing brain is in studies of "rich" and "poor" rats.11 The "rich" rats lived in small groups in cages with plenty of rat diversions such as ladders and treadmills. The "poor" rats lived in cages that were similar but barren and lacking diversions. Over a period of months the neocortices of the rich rats developed far more complex networks of synaptic circuits interconnecting the neurons; the poor rats' neuronal circuitry was sparse by comparison. The difference was so great that the rich rats' brains were heavier, and, perhaps not surprisingly, they were far smarter at solving mazes than the poor rats. Similar experiments with monkeys show these differences between those "rich" and "poor" in experience, and the same effect is sure to occur in humans.

Psychotherapy—that is, systematic emotional relearning—stands as a case in point for the way experience can both change emotional patterns and shape the brain. The most dramatic demonstration comes from a study of people being treated for obsessive-compulsive disorder.12 One of the more common compulsions is hand washing, which can be done so often, even hundreds of times in a day, that the person's skin cracks. PET scan studies show that obsessive-compulsives have greater than normal activity in the prefrontal lobes.13

Half of the patients in the study received the standard drug treatment, fluoxetine (better known by the brand name Prozac), and half got behavior therapy. During the therapy they were systematically exposed to the object of their obsession or compulsion without performing it; patients with hand-washing compulsions were put at a sink, but not allowed to wash. At the same time they learned to question the fears and dreads that spurred them on—for example, that failure to wash would mean they would get a disease and die. Gradually, through months of such sessions, the compulsions faded, just as they did with the medication.

The remarkable finding, though, was a PET scan test showing that the behavior therapy patients had as significant a decrease in the activity of a key part of the emotional brain, the caudate nucleus, as did the patients successfully treated with the drug fluoxetine. Their experience had changed brain function—and relieved symptoms—as effectively as the medication!

CRUCIAL WINDOWS

Of all species we humans take the longest for our brains to fully mature. While each area of the brain develops at a different rate during childhood, the onset of puberty marks one of the most sweeping periods of pruning throughout the brain. Several brain areas critical for emotional life are among the slowest to mature. While the sensory areas mature during early childhood, and the limbic system by puberty, the frontal lobes—seat of emotional self-control, understanding, and artful response—continue to develop into late adolescence, until somewhere between sixteen and eighteen years of age.14

The habits of emotional management that are repeated over and over again during childhood and the teenage years will themselves help mold this circuitry. This makes childhood a crucial window of opportunity for shaping lifelong emotional propensities; habits acquired in childhood become set in the basic synaptic wiring of neural architecture, and are harder to change later in life. Given the importance of the prefrontal lobes for managing emotion, the very long window for synaptic sculpting in this brain region may well mean that, in the grand design of the brain, a child's experiences over the years can mold lasting connections in the regulatory circuitry of the emotional brain. As we have seen, critical experiences include how dependable and responsive to the child's needs parents are, the opportunities and guidance a child has in learning to handle her own distress and control impulse, and practice in empathy. By the same token, neglect or abuse, the misattunement of a self-absorbed or indifferent parent, or brutal discipline can leave their imprint on the emotional circuitry.15

One of the most essential emotional lessons, first learned in infancy and refined throughout childhood, is how to soothe oneself when upset. For very young infants, soothing comes from caretakers: a mother hears her infant crying, picks him up, holds and rocks him until he calms down. This biological attunement, some theorists propose, helps the child begin to learn how to do the same for himself.16 During a critical period between ten and eighteen months, the orbitofrontal area of the prefrontal cortex is rapidly forming the connections with the limbic brain that will make it a key on/off switch for distress. The infant who through countless episodes of being soothed is helped along in learning how to calm down, the speculation goes, will have stronger connections in this circuit for controlling distress, and so throughout life will be better at soothing himself when upset.

To be sure, the art of soothing oneself is mastered over many years, and with new means, as brain maturation offers a child progressively more sophisticated emotional tools. Remember, the frontal lobes, so important for regulating limbic impulse, mature into adolescence.17 Another key circuit that continues to shape itself through childhood centers on the vagus nerve, which at one end regulates the heart and other parts of the body, and at the other sends signals to the amygdala from the adrenals, prompting it to secrete the catecholamines, which prime the fight-or-flight response. A University of Washington team that assessed the impact of childrearing discovered that emotionally adept parenting led to a change for the better in vagus-nerve function.

As John Gottman, the psychologist who led the research, explained, "Parents modify their children's vagal tone"—a measure of how easily triggered the vagus nerve is—"by coaching them emotionally: talking to children about their feelings and how to understand them, not being critical and judgmental, problem-solving about emotional predicaments, coaching them on what to do, like alternatives to hitting, or to withdrawing when you're sad." When parents did this well, children were better able to suppress the vagal activity that keeps the amygdala priming the body with fight-or-flight hormones—and so were better behaved.

It stands to reason that the key skills of emotional intelligence each have critical periods extending over several years in childhood. Each period represents a window for helping that child instill beneficial emotional habits or, if missed, to make it that much harder to offer corrective lessons later in life. The massive sculpting and pruning of neural circuits in childhood may be an underlying reason why early emotional hardships and trauma have such enduring and pervasive effects in adulthood. It may explain, too, why psychotherapy can often take so long to affect some of these patterns—and why, as we've seen, even after therapy those patterns tend to remain as underlying propensities, though with an overlay of new insights and relearned responses.

To be sure, the brain remains plastic throughout life, though not to the spectacular extent seen in childhood. All learning implies a change in the brain, a strengthening of synaptic connection. The brain changes in the patients with obsessive-compulsive disorder show that emotional habits are malleable throughout life, with some sustained effort, even at the neural level. What happens with the brain in PTSD (or in therapy, for that matter) is an analog of the effects all repeated or intense emotional experiences bring, for better or for worse.

Some of the most telling of such lessons come from parent to child. There are very different emotional habits instilled by parents whose attunement means an infant's emotional needs are acknowledged and met or whose discipline includes empathy, on the one hand, or self-absorbed parents who ignore a child's distress or who discipline capriciously by yelling and hitting. Much psychotherapy is, in a sense, a remedial tutorial for what was skewed or missed completely earlier in life. But why not do what we can to prevent that need, by giving children the nurturing and guidance that cultivates the essential emotional skills in the first place?

 

 

PART FIVE

EMOTIONAL LITERACY

 

 

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