ASU scientists link implants to brain development in deaf children

From: Arizona Republic, AZ - 25 Feb 2003

By Barbara Yost
The Arizona Republic
Feb. 25, 2003

Scott and Shannon Jones had no clue their daughter, Mykella, was deaf until she popped a balloon on her first birthday. Everyone jumped. Mykella didn't.

Tests revealed she was deaf, apparently lacking the cilia, or hair cells, that stimulate the auditory nerve. Nine years ago, when Mykella was born, infant-hearing tests were not routine as they are today. Scott Jones says his daughter had neatly compensated by using her other senses.

"She could see shadows (of people approaching), and felt vibrations of the floor and chairs," Jones says.

Concerned about her educational development, the Joneses, both teachers in the East Valley, began to research cochlear implants. Simple versions of the device were first used in the early 1960s and have become more sophisticated, convenient and effective.

Mykella was fitted with an implant when she was 3. A tiny wire studded with hairlike fibers was inserted into her cochlea, an organ of the inner ear that converts external sound into a set of neural impulses. She wears a small microphone and headpiece behind her right ear.

Within months, Mykella was talking. She listens to music, plays the recorder and is taking piano lessons. She's also involved in sports and is gifted academically.

"We were amazed at what this child was able to do," Jones says.

Two scientists at Arizona State University say Mykella is a poster child for research they recently published on the best time to insert cochlear implants in children. Their findings were printed in the December issue of the journal Ear and Hearing.

Using brain waves as a guide, Michael Dorman, a developmental psychologist and professor in ASU's department of speech and hearing science, and speech and hearing doctoral student Anthony Spahr determined that children fitted with implants after the age of 3 1/2 experience reduced benefits from the device as the auditory pathway in the brain loses its capacity for stimulation.

After the age of 7, results are extremely diminished, though an older child might receive some benefits with implantation. The loss comes not in the ability to hear sounds but to interpret them and to comprehend speech, Dorman says.

Stimulating the auditory pathway within that window actually renders physical changes in the brain, Dorman says. He and Spahr studied about 100 children fitted with cochlear implants and attending Desert Voices, an oral school for deaf children in Phoenix. They compared brain waves in those children with hearing children whose data had been collected by Anu Sharma, formerly an ASU colleague of Dorman and Spahr's and now an associate professor of human development at the University of Texas-Dallas.

The brain waves of a hearing newborn record minimal response to sound. Response increases rapidly with age.

Deaf children exhibit responses similar to newborns. But, fitted with a cochlear implant at an early age, they, too, develop rapidly.

With an implant, Dorman says, "90 percent of kids at the right age would have normal pathway development."

The Food and Drug Administration has approved cochlear implants for children as young as 12 months.

Carla Zimmerman, who directs the birth to 3 program at Desert Voices, applauds the research.

"When a baby is born, the brain has the potential to establish a lot of neural connections. It's very plastic when they are young," she says. "You want to take advantage of that ability to organize sounds."

She says the Dorman-Spahr study is significant "because it's the first study that shows an actual change in the brain."

Mykella Jones was one of the children participating in the study.

Findings from this study could lead to similar experiments, Spahr says.

"Now that we have a nice measure to look at development of the pathway, we can turn to other areas," he says. "One of those areas is children with hearing aids. . . . This can tell you if the hearing aid is doing enough."

Some children, Spahr says, use hearing aids and a cochlear implant in tandem.

Michael Novak, director of a cochlear-implant team at the Carle Clinic and Hospital in Champaign-Urbana, Ill., says the Dorman study confirms what other scientists have suspected. They now will have hard data to follow.

"Dr. Dorman's work has been very good not only looking at it from a functional standpoint but from a brain physiology standpoint," Novak says from his office. "If you miss these critical time periods, you can't go back."

He cautions that parents should not take the study as a reason to delay implantation until age 3, however. The earlier the child is implanted, he says, the better, and children at his clinic have been fitted as young as 9 months.

Though the FDA has issued guidelines for implantation at a year, doctors can use their discretion, he says.

Dorman agrees waiting until 3 might lose valuable learning years, but he counters that "you shouldn't give up hope if your child is 2 or 3."

Dorman believes their research offers a tool for audiologists to track the development of the auditory pathway and gives scientists further insight into the plasticity of the brain.

For families, he says, "we've done something really, really useful. . . . We can give parents advice."

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