Cochlear implants can allow profoundly deaf infants to hear speech - giving them the chance to eventually learn spoken language. However, a new study shows that the children receiving the implants don't automatically know how to listen when people speak to them.
Research presented this week at the Acoustical Society of America research meeting, showed that deaf babies with cochlear implants spent the same amount of time "listening" as normal-hearing infants of the same age. However, these children with implants spent less time than younger normal-hearing infants who had the same amount of hearing experience.
Cognitive psychologist Derek M. Houston, Ph.D., associate professor of otolaryngology and Philip F. Holton Scholar at Indiana University School of Medicine, said the insight would have implications for therapy for children receiving cochlear implants.
"When infants are born deaf, their development is shaped by a silent world. They learn to tune into the sights, smells, and touches that are relevant to them in their environment - but not the sounds," said Dr. Houston. "When they receive a cochlear implant, their world changes and are filled with sounds. But for these infants who have already begun to adapt to their silent environment, sounds may not - at least at first - be perceived as relevant to them."
In other words, they may hear the sounds around them but not have any motivation to focus on them, which slows their ability to learn speech and can be traced for years through word recognition testing.
Children with cochlear implants and normal-hearing children were tested in a sound-proof lab at Riley Hospital for Children at IU Health.
"It has been well-established that infants will look longer at a simple display - the checkerboard pattern - when hearing something they are interested in," Dr. Houston explained. "I measured their 'looking time' at the pattern when it was paired with a repeating speech sound, and compared that to the looking time at the same pattern with no sound."
Children with cochlear implants spent less time looking at the checkerboard pattern than children who could hear from birth. Furthermore, two years after implantation, children who were less attentive to speech early-on performed more poorly on a word recognition task.
An abstract of his research is available at http://asa.aip.org/web2/asa/abstracts/search.may11/asa220.html
Source: Indiana University
Wednesday, August 17, 2011
Monday, August 1, 2011
I want to share with you this interesting article.
By JANE E. BRODY Published: October 3, 2006
Jenni Ewald and her husband, Russ, both lost their hearing as young children after bouts with meningitis — Jenni when she was 1, Russ more gradually starting at age 3. They met in college, communicating with sign language and lip reading, fell in love, married and had a baby. But neither could hear their baby cry, at least not until Jenni got a cochlear implant at Loyola University Health System in Maywood, Ill.
Russ was so impressed with Jenni’s result that he underwent the same procedure a few months later. Now living in Tempe, Ariz., both Ewalds can hear their two young daughters.
As victims of profound bilateral sensorineural hearing loss — a destruction of the hair cells in the cochlea of the inner ear that transmit sound signals to the auditory nerve — the Ewalds were not candidates for hearing aids, which simply amplify sounds reaching the ear and depend on normally functioning hair cells.
But they benefited from an implant that makes it possible for profoundly deaf people to hear and learn to interpret speech and other sounds. Perhaps as many as one million people in the United States could benefit from a cochlear implant. For children born deaf or who lose their hearing before they are verbal, the implants enable them to learn to talk.
An Intense Controversy
The surgery cannot create normal hearing; people who receive it can hear but might be described as having mild or moderate hearing loss. That fact has rendered cochlear implants the subject of intense controversy. Many in the deaf community say these less-than-perfect devices can turn a healthy deaf person — who learned to communicate using sign language, lip reading or both — into someone with a hearing handicap whose self-image may be undermined.
Still, those arguments have not stopped some 100,000 people worldwide, including about 25,000 in the United States, from undergoing implant surgery. Roughly half of implant recipients are children. Well-known users of cochlear implants include the conservative commentator Rush Limbaugh; Jack Ashley, the well-known member of the British Parliament; and the 1995 Miss America, Heather Whitestone.
Miss Whitestone was nearly deaf for 28 years until she received an implant in her right ear at Johns Hopkins Medical Center in Baltimore in 2002, allowing her to hear the voices of her two young sons. Early this year she lost what little hearing she had in her left ear and, in August, underwent a second implant, also at Johns Hopkins.
But not everyone with profound hearing loss — uncorrectable with traditional hearing aids — is a candidate for a cochlear implant. Ideal candidates include people with severe sensorineural hearing loss in both ears who still have a functioning auditory nerve; those who have lived only a short time with hearing loss; those with good speech and language skills or, in the case of young children, those in a family willing to work hard to acquire speech and language skills through therapy; those medically able to withstand general anesthesia and surgery, and those who want to live in a hearing world and have realistic expectations about what can be achieved with a cochlear implant.
Dr. John P. Leonetti, a neurotologist at Loyola who performed the implant surgery for the Ewalds, said he depends on the evaluation by the audiologist, who tells him who is — and who is not — a good candidate for a cochlear implant. He said the need for cochlear implants is rising rapidly as the population ages and more and more people lose their hearing and cannot be helped by a hearing aid. Currently, Medicare reimburses only a fraction of the cost of the procedure, keeping it out of reach of many people. Insurance rarely covers the price of even one device, about $40,000, which does not include physicians’ fees, hospital charges and the audiologist’s services.
The Device and Procedure
After decades of experimentation, primarily in the United States, Austria and Australia, the first cochlear implant was approved for use in patients by the Food and Drug Administration in December 1984, initially only for adults and now in children as young as a year old. Special approval is sometimes granted for infants as young as 6 months.
Miniaturization of electronics over the years has resulted in a small two-piece device used in cochlear implants. One, consisting of a receiver and stimulator, is implanted under the skin behind the ear. The other is made up of a microphone, a sound processor and a transmitter that is placed externally over the receiver, held in place magnetically. In the case of young children, the sound processor may be worn in a hip pack or harness. No wires connect the two parts, reducing the risk of infection and damage to the device.
To create sound, the microphone picks up and amplifies noises that the sound processor then filters, giving priority to audible speech. The processor sends electrical signals to the transmitter, which in turn sends the processed sound signals to the internal receiver electromagnetically.
The receiver and stimulator convert the signals into electric impulses, which are sent to an array of up to 24 electrodes. They, in turn, send the impulses to the hair cells and into the brain via the auditory nerve. The two dozen electrodes must fill in for the 16,000 hair cells normally used for hearing.
Efforts are under way to improve the technology. Last week, the F.D.A. approved a system with 120 inputs that is said to enhance the ability to hear music and to improve hearing in noisy environments. It is called the Harmony Hi Resolution Bionic Ear System, developed by Boston Scientific Corporation.
A Two-Stage Installation
A cochlear implant is installed in two stages. The first involves surgically implanting the internal component into the cochlea, which permanently destroys any residual hearing the person may have in that ear. Though some doctors recommend implanting only one ear, bilateral implants typically result in better hearing. The main drawback of a double implant is the cost.
About four to six weeks later, after complete healing of the implant area, the second external part of the device is installed. This is accompanied by a lot of fine tuning to adjust the signals as well as many months and even years of audiological training and, for those who do not already speak intelligibly, speech therapy.
Without intensive therapy and periodic adjustments of the device, obtaining a cochlear implant is all but useless. An unequivocal commitment to a rehabilitation program — which, in the case of young children, necessarily involves a commitment of the parents — is essential to success.
But even with such a commitment, people who have been profoundly deaf for many years may have a harder time learning to interpret speech through cochlear implants because the part of the brain normally used for hearing can, over the years, become diverted to serve other functions.
Children born deaf who receive cochlear implants before age 2 generally do better
with spoken language than those who receive implants at a later age, though the window of opportunity for processing auditory signals in the brain does not close until adolescence. The sound transmitted through a cochlear implant has a robotic quality, but over time and with electrode adjustments, the sound of speech more closely resembles the human voice. and the doorbell, chirping of birds, and other noises sound pretty much as they do to people with normal hearing, Dr. Leonetti says.