Preschool

Four-month-old Meaghan has a marvelous toy. Lying on her back, she bats a sun-shaped toggle and makes lights flash and a song start to play. Sometimes her mom, Sara, stops her chores and joins in the melody, sometimes smiling into Meaghan's face, sometimes dancing for her. Often Sara gets down on the floor to play games with her daughter. Today, Sara bought new strings for her guitar so that they can make music together. Still she wonders, "Am I doing enough to stimulate my child?"

It's a question many parents ask themselves. After all, child-development experts have been telling us for decades that a secure and nurturing environment, like the one Meaghan's mother is providing, is an important factor in raising healthy, productive adults.

Now scientists who study the human brain have discovered that a child's environment does not merely provide a favourable context for development, but is the very food that determines how her brain will be wired. Indeed, new technology that can measure the location and volume of activity in the brain provides convincing evidence that the words we coo, songs we sing and peekaboo games we play have a direct impact on which connections will form, which will be strengthened and which discarded in the intricate brain circuitry that children carry with them into adulthood.

We didn't always know this. A mere 15 years ago, researchers believed that the structure of a baby's brain was set by the genes she inherited from her mother and father and, like her other organs, was essentially complete at birth, a miniature of its adult version. The brain's fourfold growth between birth and maturity, scientists believed, was simply the brain getting bigger rather than more complex.

Genes do play an essential role in the brain's formation - more than half of a child's 80,000 genes are devoted to growing the 100 billion brain cells (called neurons) it will need to perform its many tasks. During the nine months in the womb, a baby's brain produces the neurons and connections that control such basic functions as heartbeat and breathing. But when a child is born, the majority of neurons are still waiting to be wired. That astonishing activity - the building of the circuitry that results in a baby's ability to smile, walk, talk, reason and respond - occurs during the first decade of life, and is influenced by her experiences. After generations of debate, scientists and child-development experts now agree that the brain is a complex coupling of nature - the genes a person is born with - and nurture - the experiences she has after she is born.

To understand what goes on in a baby's head, it helps to know a little basic brain science. "Most cells in the body are round," say Derek Van der kooy, a professor of anatomy and cell biology at the University of Toronto. "But neurons are incredibly shaped." A neuron looks like an octopus, but with many more than eight tentacles; each one has a tendril that sends out signals to its neighbours and to other parts of the body. "There are neurons that go down to the bottom of your spinal cord - one cell goes for two feet." That's one reason why kids don't walk from the moment they're born. "It takes so long to grow the neurons down to the spinal cord, and it's not until those neurons are completely grown that kids can make the brain control their muscles."

Brain cells also need to receive signals. To do this, their tendrils feather out to form connections - or synapses - with other cells. By a child's third birthday, each neuron will link up with as many as 15,000 others, forming a remarkable 1,000 trillion connections. That's a lot of brain power. What's more, scientists now know that these connections multiply at a feverish pace during the first ten years of life. That contradicts the long-held theory that a child's brain is less active than an adult's; indeed, your adult brain gets by with only half the number of synapses a child has, using a fraction of the energy. No wonder parents often have difficulty keeping up with their kids!

But brain development is not just about creating links. As it matures, the brain also eliminates, or prunes, connections. In a child's first three years, very little pruning occurs, but after age ten the elimination of unnecessary or little-used synapses takes off, with connections in some parts of the brain being pruned at a rate of 33 per second.

The question is, what regulates this process of creation and elimination? "There is a lot of genetic selection," says Philip Seeman, who holds the Chair in Neuroscience at the University of Toronto and who has studied the childhood brain. "That's why the pruning, no matter what you do, is going to take place." Sex hormones also play a role. A third influence, Seeman and other neuroscientists agree, is a child's environment.

Here's how it works. When a child is stimulated, say by the sight of his mother's face, a connection is formed between the eye and the brain. Each time the child sees his mother's face, that pathway is strengthened. If reinforced often enough, it becomes permanently forged in the child's brain. A baby's recognition of his mother, for example, is hard-wired by his third month.

Because brain activity is so brisk in a child's first three years, stimulation during this period is particularly important. Without it, connections will not be made, or if made and not reinforced, they'll be pruned away. Take the case of language development. If you measure the brain activity of three-month-old babies listening to different languages, explains Bryan Kolb, professor of neuropsychology at the University of Lethbridge, you can't tell the children apart. Try the same test on two-year-olds, and that is no longer true. "The most obvious example is the distinction between the sounds L and R by the Japanese," says Kolb. "Those sounds don't occur in Japanese, so the distinction is not required." The result, he says, is that "the brain doesn't bother to keep that ability." That's why native speakers of Japanese have such difficulty learning the distinction as adults, and why it's much easier to learn a second language in early elementary grades.

Kids need stimulation to forge emotional connections as well. Children who are neglected or traumatized may not learn to soothe themselves or regulate their emotions. Some studies of children whose primary caregiver is suffering from untreated depression, for example, have found lower levels of activity in the region of the brain responsible for emotions like joy and anger. Similarly, children who receive too much of the wrong kind of stimulation may hard-wire connections that trigger impulsive, anxious or even violent behaviour.

Yet the brain also has amazing plasticity, a quality that makes children adaptable. Wayward connections can be redirected with timely intervention, but timely is key: the earlier the intervention, the better. "Imagine that neurons are like trees," Kolb explains. If each leaf represents a connection with another neuron, then one way you can increase the number of leaves is to grow longer branches. "Then the leaves are further apart and you can stick new leaves in easily. Another way is to grow new leaves on the existing branches, but there's going to be some limit there. In the very young brain, the branches are long and the leaves fairly far apart, and it's easy to stick new ones in later. With the older brain, it's much harder to grow those long branches. So we try to stick the leaves between the existing ones, and there's only so much space there."

The development of those long branches in the young brain is akin to what researchers refer to as "prime times" or "windows of opportunity," when learning is optimal. If a child doesn't receive certain types of stimulation within these time frames, forging connections later becomes more difficult. So, for example, children who lose an eye before they are eight are better able to compensate and develop more acute depth perception than if it had happened later in life. Parents will recognize these prime times as the milestones that mark their little ones' development. Motor skills, for example, progress rapidly in a child's first 18 months; the window for language learning is in the first six years.

That's not to say that change cannot happen outside these windows. Continuing his tree analogy, Kolb explains, "If you go down the wrong branch too far, it doesn't mean that you can't push toward the missed branch, but it's going to be a lot more difficult. And you certainly can't go back and start over."

Paediatrician Wendy Roberts has seen the results of timely intervention in her practice as head of the Child Development Clinic at Toronto's Hospital for Sick Children. The autistic children she works with often withdraw and stop talking before the age of two. "If we can get in at that early age with very intensive interaction," she explains, "we see a dramatic turnaround in the speed that they start to connect again and start to develop language." Roberts acknowledges that intervention is not always successful, but she's enthusiastic about what she sees as the coming union of science and clinical practice.

And she's pleased that this union may be hastened by government funding initiatives, at both the federal and provincial level in Ontario, that support early intervention programs. "That's going to be an enormous boost to early development," says Roberts. "And it's a wonderful recognition that the link between brain development and environmental stimulation is absolutely critical."

It also pleases psychiatrist Paul Steinhauer, chair of the national non-profit advocacy group Voices for Children. "But a great deal more needs to be done," he cautions. The federal government's National Longitudinal Study shows that "75 percent of our children are doing just fine," he says. "But 25 percent are, at the age of 11, already having significant problems in the academic, behavioural, emotional or social areas and are in danger of going into adult life with their health and productivity significantly impaired." While acknowledging that older children will continue to need support, Steinhauer insists that the solution will be found when society puts a greater emphasis on getting kids off to a good start.

Indeed, some of the most compelling brain research tells us how that can be done. The way kids learn best, writes child psychiatrist Stanley Greenspan in his new book The Growth of the Mind, is by grounding their experiences in emotion. And key to that emotional attachment, says Wendy Roberts, is the give and take that comes through one-on-one interaction with our children - encouraging them to join in our songs, eliciting their responses to our cooing and enticing them into our games of peekaboo.

Meaghan's musical toy teaches her that controlling the movements of her arms gives her the power to produce a sprightly song and enchanting light show. But better than that, it prompts her mom to take part, not simply in a song, but in the awesome and indispensable work her daughter's developing brain is engaged in.

Resources

The Growth of the Mind: and the Endangered Origin of Intelligence , by Stanley Greenspan, Addison-Wesley, 1997. Greenspan argues that the best way to encourage children's learning and growth is not through flash cards and computer time, but through relaxed, emotional interaction, like getting down on the floor and playing with them.

February 1998