Professor’s research targets speech development in toddlers with cochlear implants

8/26/2016 |

The American Academy of Pediatrics estimates three per 1,000 babies are born with moderate to profound hearing loss. But thanks to newborn hearing screenings, deaf and hard of hearing infants can be identified within the first months of life. These children will then have earlier access to hearing aids, cochlear implants and communication intervention and, ultimately, increased potential for developing age-appropriate language skills.

“Before newborn screenings began in the late ’90s, profound hearing loss was not routinely detected until a child was around 18 months old,” says David Ertmer, professor of speech, language, and hearing sciences (SLHS). “Because of earlier detection and advances in hearing technology, children now have a much brighter future.” These technological advancements include cochlear implants, a focus of Ertmer’s research.

Ertmer began his career as a school speech pathologist and became acquainted with the communication needs of deaf children while employed at a Milwaukee school for deaf children in the late 1970s. Of this experience, he notes, “No matter how hard the students worked there were significant limitations to how far their spoken language would develop.”

Ertmer went on to earn his PhD from Purdue in 1994, working with former SLHS Department Head Rachel Stark, who had done pioneering research into typically developing children’s prelinguistic speech. “Not much was known about children’s speech before they attempted to produce words,” he says. “She and others discovered that children’s vocalizations show predictable advancements before words are produced on a regular basis.”

Ertmer’s own research in early speech and language development focuses on deaf children who receive cochlear implants during the first three years of life. Cochlear implants are surgically implanted electronic devices that bypass damaged hearing hair cells to stimulate the auditory nerve directly and provide a sense of hearing. Cochlear implants consist of externally worn microphones and speech processors. Internal components include a receiver-stimulator and an array of electrodes that are inserted into the cochlea. “Cochlear implants don’t restore normal hearing sensitivity levels, but they do give much-improved auditory access to conversational-intensity speech in most cases,” he notes.

NOT JUST BABY TALK
Partnering with several special schools in the Midwest, Ertmer video-records sessions of mothers and their children playing together. Research assistants in Ertmer’s laboratory listen to the recordings and classify the sounds that children produce into three developmental levels. Precanonical vocalizations include squeals, crying and laughter. These sounds emerge between birth and six months of age. Basic Canonical Syllables are represented at the next level. These include syllables in which consonants and vowels are combined with adult-like timing. These sounds typically emerge between 6 and 10 months of age. Finally, the Advanced Forms level includes complex syllables, jargon and diphthongs. These become more plentiful between 10 and 18 months. Vocalizations from all three levels continue to be produced as children begin to say meaningful words.

Ertmer’s studies show that children who receive a cochlear implant at a young age make more-rapid-than-typical advancements in prelinguistic speech development. “We believe this occurs because of the relatively greater maturity of the implant recipients when they first begin to hear,” he says. “However, the children also receive family-centered intervention that likely contributes to their progress.

“One of our most revealing findings is that deaf children don’t establish the Advanced Forms before they receive cochlear implants,” he continues. “This suggests that the cochlear implants provide information about some aspects of adult speech that isn’t available through hearing aids.”

What does the future hold for hearing loss research? Recent studies are showing that having two, rather than one, cochlear implants can lead to improved hearing in noise and better sound localization. Ertmer also suggests that gene therapy to repair damaged hair cells in the pea-sized cochlea might become practical in the not too distant future.

From HHS Researchers Spotlight, http://bit.ly/2c1DyXj