A new study has found that deaf children who receive a cochlear implant had as much as five times the risk of experiencing delays in working memory, controlled attention, planning and conceptual learning as children with normal hearing.
For the new research, scientists at Indiana University evaluated 73 children who had the implants before age seven, and 78 children with normal hearing. All the children had average to above-average IQ scores, researchers noted.
A cochlear implant consists of an external component that processes sound into electrical signals that are sent to an internal receiver and electrodes that stimulate the auditory nerve. Although the implant restores the ability to perceive many sounds to children who are born deaf, some details and nuances of hearing are lost in the process, researchers explain.
“Delays in executive functioning have been commonly reported by parents and others who work with children with cochlear implants,” said William Kronenberger, Ph.D., a professor of clinical psychology in psychiatry at the Indiana University (IU) School of Medicine, a specialist in neurocognitive and executive function testing, and the study’s first author.
Based on these reports, the researchers set out to evaluate whether elevated risks of delays in executive functioning in children with cochlear implants exist, and what components of executive functioning were affected.
“Executive functioning, a set of mental processes involved in regulating and directing thinking and behavior, is important for focusing and attaining goals in daily life,” he noted.
“In this study, about one third to one half of children with cochlear implants were found to be at risk for delays in areas of parent-rated executive functioning, such as concept formation, memory, controlled attention, and planning,” he said. “This rate was two to five times greater than that seen in normal-hearing children.”
“This is really innovative work,” added co-author David B. Pisoni, Ph.D., director of the Speech Research Laboratory in the IU Department of Psychological and Brain Sciences.
“Almost no one has looked at these issues in these children. Most audiologists, neuro-otologists, surgeons, and speech-language pathologists — the people who work in this field — focus on the hearing deficit as a medical condition and have been less focused on the important discoveries in developmental science and cognitive neuroscience.”
“The study’s findings augment other research on interventions to help children with cochlear implants perform at a level similar to children without hearing deficits,” said Richard Miyamoto, M.D., chair of the IU School of Medicine Department of Otolaryngology-Head and Neck Surgery.
“The ultimate goal of our department’s research with cochlear implants has always been to influence higher-level neurocognitive functioning,” he said. “Much of the success we have seen to date clearly relates to the brain’s ability to process an incomplete signal. The current research will further assist in identifying gaps in our knowledge.”
“One possible answer may lie in earlier implantation,” he noted. “The age at which children are implanted has been steadily decreasing, which has produced significant improvement in spoken language,” he said.
As early implantation is related to better outcomes in speech and understanding, it is reasonable to believe that there may be less of a deficit in executive functioning with earlier implantation, he explained.
Children in the IU study were implanted at an average age of 18 months, and they had fewer executive function delays than school-age children who were implanted 10 months later, at an average age of 28 months, he reported.
Children in the study were divided into two age groups: preschool (three to five years) and school-age (seven to 17 years). Using an established scale, parents rated executive function in everyday life for children with cochlear implants and for the control group with normal hearing.
“We compared parent ratings and looked at the percentage of children in each group who scored above a cut-off value that indicates at least a mild delay in executive functioning,” Kronenberger said.
“In the critical areas of controlled attention, working memory, planning, and solving new problems, about 30 percent to 45 percent of the children with cochlear implants scored above the cut-off value, compared to about 15 percent or less of the children in the normal-hearing sample.”
“The research also shows that many children develop average or better executive functioning skills after cochlear implantation,” he noted.
“These results show that half or more of our group with cochlear implants did not have significant delays in executive functioning,” Kronenberger said. “Cochlear implants produce remarkable gains in spoken language and other neurocognitive skills, but there is a certain amount of learning and catch-up that needs to take place with children who have experienced a hearing loss prior to cochlear implantation. So far, most of the interventions to help with this learning have focused on speech and language.
“Our findings show a need to identify and help some children in certain domains of executive functioning as well.”
The study, funded by a grant from the National Institute on Deafness and Other Communication Disorders, was published in the Journal of the American Medical Association Otolaryngology — Head and Neck Surgery.
Source: Indiana University