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Nov.16, 2011

Vol. 112, No. 4

Web Exclusives

Ask the expert: Sam Wang

The professor and author responds to reader questions about the brain

Published in the November16, 2011, issue




Sam Wang, who was profiled in the Oct. 26, 2011, issue of PAW, is an associate professor of molecular biology and neuroscience at Princeton and the co-author, with Sandra Aamodt, of two books: Welcome to Your Child’s Brain: How the Mind Grows from Conception to College, released in September; and Welcome to Your Brain: Why You Lose Your Car Keys but Never Forget How to Drive and Other Puzzles of Everyday Life, published in 2008.

Wang fielded a series of brain-related questions from alumni readers earlier this month.

At what age would you recommend children begin using interactive educational toys like those made by Leapfrog?

– Jason Lovelace *00

I’d suggest waiting until preschool – and longer is OK, especially if the alternative is live, in-person interaction. “Interactive” products like Leapfrog make the promise of improving a child’s development. However, at early ages the attention-control mechanisms of a small child’s brain aren’t mature. They easily fall into the thrall of the bright moving images. Pediatricians recommend no television at all before age 2 – yet on average, U.S. babies get their first TV at 5 months of age. It has been demonstrated that TV before age 2, including “baby DVDs,” can slow language acquisition. Interactive products might be a little better since the experience is less passive, but again, wait until preschool or later.

There is good evidence that programs like Sesame Street can help with learning after age 3, though to my eye the older seasons of the program have more substance. I’m not a fan of the Elmo era.

My daughter Georgia, currently 15, spent the first seven months of her life in a Chinese orphanage.She has grown up as a bright, engaged, and talented young woman in many dimensions of her life. At the same time, she has struggled mightily with certain areas of learning throughout her life. I’ve always wondered – and here’s the question for you – what the connection might be between the intellectual challenges she’s faced and the fact that she spent her first seven months in what I assume was a less-than-ideal environment for language and other intellectual development, after which she was scooped out and thrust into another language altogether.

– Jane Fremon ’75

A baby’s prenatal and early life are times of great sensitivity to adverse events. As we wrote in Welcome To Your Child’s Brain, stress profoundly affects the developing brain. Experiences ranging from induced early birth to the death of a mother’s close relative increased the risk of developmental disorders and slowed intellectual development. Social deprivation in a baby’s early life can also be harmful. Some of the learning disabilities might be traceable to such events.

However, you should not be concerned in any way about the change of language. Babies are incredibly malleable in their ability to soak up language. Since she is socially engaged, it is unlikely that changing from Chinese to English affected her adversely in any way.

As a lifelong student of languages, I very painfully experienced the decay of the ability to learn another language in old age, beginning at 50, when I commenced to add a Slavonic language, tcheque, to my repertoire. There was a wave of emigration after the Nazi takeover in the 1930s, and it was reported that emigrants above this age no longer mastered the language of their country of refuge. What can be said about this phenomenon?

– Otto L. Ortner ’58
The developing brain goes through periods in which particular capacities, ranging from vision to social capacity to language, are quite malleable. These times are called sensitive periods. They come at times when “arborizations” of axons and dendrites, which link neurons to one another within some brain area, are more changeable in their structure. In the case of language, for most children the first transition comes around age 6, before which languages become native: no accent and idiomatic speech. Until puberty, language can still be learned, but with an accent. As you have found, in adulthood these processes are more difficult, suggesting that language areas of the brain are biologically far harder to rewire.

What are the things or areas that are not known [about the brain]? What is being done about this?

– Walter Mickleburgh *54

There is so much to learn about brain development at all levels, from fundamental levels such as proteins and synapses to complex behavioral processes. One of my favorite examples is early development. Genes set up a developmental program for building a brain that proceeds largely automatically, needing only normal experience and a nondeprived environment. Even though we know what proteins most of these genes encode, we don’t understand how they interact as a whole with one another. A similar story is true for single synapses, which my lab and many others have studied for their ability to change with experience. When the program goes off track, such as in autism, it is often because of combinations of genes that in other combinations would be fine. But it is not known how these combinations contribute to overall function – or dysfunction.

These issues and many more are being studied by thousands of neuroscientists in the United States and around the world who are developing technologies and concepts to build a framework to understand how brains develop and work. At Princeton, we have strengths in visualizing brain circuits from levels of a few neurons to the entire brain. We also have conceptual strength in understanding brain-wide, integrated functions. In the next few decades I think the field will develop much sharper ideas about how cells and circuits drive learning, and how brain areas work together to drive thought, personality, mood, decision-making, and coordinated movement. All of this work is supported by taxes as well as private donations. So in fact you are also a part of what is being done.

I complain to my audiologist that I only understand dialogue in films when characters speak slowly and emphatically.When they speak more naturally, streams of words may reach me with the same volume but transformed into a kind of thick and unintelligible soup. This also occurs in daily life.

She suggests politely that words received in my ears proceed more slowly with age from eardrum to cerebellum, or whatever part of the brain may be most receptive.I am 94.In the milliseconds required for their meaning to become clear to me and stimulate whatever reaction may be appropriate, these impulses are succeeded by new impulses that overwhelm and confuse their predecessors. In other words, my internal communications are colliding because of age.

Questions: Does this seem a good explanation? If so, is anything being done about it? Do you know of any work being done to strengthen these internal communications, through new types of hearing aids or otherwise?

– Carl Hartman ’36

That explanation sounds vague. It is known that the cochlea, which is in your ear and detects sound, as well as other parts of the auditory system, loses function in age. So your brain has a harder task to decipher sounds at the very first stage of processing. You might find it harder to understand a voice in a noisy room. After the information enters the brain from those pathways, more fundamental processing of sound happens in the midbrain, but I do not think that is the biggest problem.

Your reaction times also slow down with age. Physical exercise sharpens brain function, probably for similar reasons that it helps heart function. Try that, as much as you can. Electronic “brain training” exercises are mostly not very effective, except for one area – reaction times. So that is another possibility.

I do not know about developments in hearing aids. However, you can help the situation a little by looking at people’s mouths carefully when they talk. You integrate visual information as part of the hearing process, so this is a valuable source of information.

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