Automatic and Attentive Processing of Sounds in Cochlear Implant Patients – Electrophysiological Evidence

Restorative Neurology and Neuroscience, an IOS Press publication, recently published an article that concluded that cochlear implant users are "impaired in the preattentive registration of novel auditory events while attentive processing of a designated auditory stream appears intact."

Cochlear Implant Outcomes and Quality of Life in Adults with Prelingual Deafness

A recent article in Laryngoscope explores quality of life in prelingually deaf adults with cochlear implants and concludes that "with state of the art implants, speech perception and quality of life do improve..."

Production of Consonants by Prelinguistically Deaf Children with Cochlear Implants

Tne November 2007 issue of Clinical Linguistics & Phonetics includes an article that explores "consonant production following the sensory restoration of audition":

Spontaneous speech productions in 22 prelinguistically deaf French children who received cochlear implants were recorded at 6, 12, and 18 months post-surgery and consonant inventories were derived from both glossable and non-glossable phones using two acquisition criteria. The results showed that children initiated appropriate production of consonants after six months of implant use. Stops and labials were the most frequently produced speech sounds, whereas glides and palatals were still infrequent after 18 months.

Effects of Cochlear Implants on Children's Reading and Academic Achievement

A recent issue of Journal of Deaf Studies and Deaf Education includes a "critical analysis of empirical studies assessing literacy and other domains of academic achievement among children with cochlear implants."

The article concludes that:

This review, however, reveals that although there are clear benefits of cochlear implantation to achievement in young deaf children, empirical results have been somewhat variable. Examination of the literature with regard to reading achievement suggests that the lack of consistent findings might be the result of frequent failures to control potentially confounding variables such as age of implantation, language skills prior to implantation, reading ability prior to implantation, and consistency of implant use. Studies of academic achievement beyond reading are relatively rare, and the extent to which performance in such domains is mediated by reading abilities or directly influenced by hearing, language, and speech remains unclear.

New Hearing Mechanism Discovered

MIT scientists have discovered an important new element in understanding human hearing:

MIT Professor Dennis M. Freeman, working with graduate student Roozbeh Ghaffari and research scientist Alexander J. Aranyosi, found that the tectorial membrane, a gelatinous structure inside the cochlea of the ear, is much more important to hearing than previously thought. It can selectively pick up and transmit energy to different parts of the cochlea via a kind of wave that is different from that commonly associated with hearing.

Ghaffari, the lead author of the paper, is in the Harvard-MIT Division of Health Sciences and Technology, as is Freeman. All three researchers are in MIT's Research Laboratory of Electronics. Freeman is also in MIT's Department of Electrical Engineering and Computer Science and the Massachusetts Eye and Ear Infirmary.

It has been known for over half a century that inside the cochlea sound waves are translated into up-and-down waves that travel along a structure called the basilar membrane. But the team has now found that a different kind of wave, a traveling wave that moves from side to side, can also carry sound energy. This wave moves along the tectorial membrane, which is situated directly above the sensory hair cells that transmit sounds to the brain. This second wave mechanism is poised to play a crucial role in delivering sound signals to these hair cells.

In short, the ear can mechanically translate sounds into two different kinds of wave motion at once. These waves can interact to excite the hair cells and enhance their sensitivity, "which may help explain how we hear sounds as quiet as whispers," says Aranyosi. The interactions between these two wave mechanisms may be a key part of how we are able to hear with such fidelity - for example, knowing when a single instrument in an orchestra is out of tune.

"We know the ear is enormously sensitive" in its ability to discriminate between different kinds of sound, Freeman says. "We don't know the mechanism that lets it do that." The new work has revealed "a whole new mechanism that nobody had thought of. It's really a very different way of looking at things."

Speech Intelligibility in Cochlear Implant Simulations

A recent article in the Acoustical Society of America Digitial Library describes an experiment to simulate cochlear implant processing in normal hearing listeners:

Channel vocoders using either tone or band-limited noise carriers have been used in experiments to simulate cochlear implant processing in normal-hearing listeners.

Imitative Production of Rising Speech Intonation in Pediatric Cochlear Implant Recipients

An article in the Journal of Speech, Language and Hearingexplains that:

Pediatric cochlear implant recipients did not consistently use appropriate intonation contours when imitating a yes–no question. Acoustic properties of speech intonation produced by these individuals were discernible among utterances of different intonation contour types according to normal hearing listeners' perceptual judgments.

The findings delineated the perceptual and acoustic characteristics of speech intonation imitated by prelingually deafened children and young adults with a CI. Future studies should address whether the degraded signals these individuals perceive via a CI contribute to their difficulties with speech intonation production.