Faculty Bibliography

The goal of this study was to test 2 hypotheses about language development in pediatric cochlear implant (CI) users. The 'language instinct' hypothesis states that children with CIs will develop language in the same sequence as children with normal hearing, but in a delayed fashion. In other words, noun plurals will develop first, and the use of the uncontractible copula and regular past tense will follow. An alternative hypothesis (the 'perceptual prominence' hypothesis) is that the pattern of language development in CI users will be strongly affected by the perceptual prominence of the relevant morphological markers. This hypothesis predicts that the uncontractible copula will develop first, followed by noun plurals, and then by regular past tense. A sentence completion task was used to measure the performance of 9 pediatric CI users and compare it to that of several groups of children with normal hearing. The results from the CI users were consistent with the perceptual prominence hypothesis. In particular, the scores for the copula probe were higher than those for the noun plural probe for 8 of the 9 CI users. This result represents a rather striking inversion with respect to the usual development pattern in children with normal hearing and even in children with specific language impairment. If the perceptual prominence hypothesis receives further support in future studies, clinicians who work in language rehabilitation of CI users may choose to target those aspects of grammar that are less acoustically prominent to these children. In addition, and from a theoretical standpoint, these results suggest that although there may well be an innate language acquisition mechanism, patterns of language development can be strongly affected by the acoustic input. $$:

A method is presented for analyzing cochlear implant stimulations and typical representations used in simulations. Filtered "white-noise" bands are modulated using sinusoids, representing differing stimulation channels. These representations, along with their corresponding envelopes, are used to generate neural activation patterns (NAPs), which represent "normal-hearing" responses in the auditory nerve to these stimuli. Additionally, NAPs are generated to represent the neural activity induced by cochlear implant stimulation strategies, assuming exponential rolloff from the electrodes. The mean squared error is measured between NAPs both directly, and after compensation for perceptual resolution. Results suggest that the noise-band approximation of the CIS implant signal actually has more in common with the original source than with the implant stimulation patterns.

Children with profound congenital or prelingual deafness encounter significant difficulties in the development of skills in an oral language such as English. Their language development, however, can be accelerated if they receive a cochlear implant-a sensory aid that facilitates language acquisition by providing important auditory information. The present study used the Reynell Developmental Language Scales (RDLS) to assess language skills pre- and postimplant in 44 pediatric cochlear implant users. All users were profoundly to totally deaf, either at birth or before the age of 3 years. They all received cochlear implants before the age of 6 and were programmed with state-of-the-art stimulation strategies (CIS or SPEAK) since the day of initial stimulation. The main finding was that postimplantation language development proceeded at a pace that was not significantly different from normal. Thus, the language gap present at implantation did not increase after children started using the device, as it would if they had not received cochlear implants. Nevertheless, it is important to conduct further studies to determine whether these conclusions apply when other language skills, such as the use of grammar, are measured

Cochlear implant (CI) users differ in their ability to perceive and recognize speech sounds. Two possible reasons for such individual differences may lie in their ability to discriminate formant frequencies or to adapt to the spectrally shifted information presented by cochlear implants, a basalward shift related to the implant's depth of insertion in the cochlea. In the present study, we examined these two alternatives using a method-of-adjustment (MOA) procedure with 330 synthetic vowel stimuli varying in F1 and F2 that were arranged in a two-dimensional grid. Subjects were asked to label the synthetic stimuli that matched ten monophthongal vowels in visually presented words. Subjects then provided goodness ratings for the stimuli they had chosen. The subjects' responses to all ten vowels were used to construct individual perceptual 'vowel spaces.' If CI users fail to adapt completely to the basalward spectral shift, then the formant frequencies of their vowel categories should be shifted lower in both F1 and F2. However, with one exception, no systematic shifts were observed in the vowel spaces of CI users. Instead, the vowel spaces differed from one another in the relative size of their vowel categories. The results suggest that differences in formant frequency discrimination may account for the individual differences in vowel perception observed in cochlear implant users

This study examined two possible reasons underlying longitudinal increases in vowel identification by cochlear implant users: improved labeling of vowel sounds and improved electrode discrimination. The Multidimensional Phoneme Identification (MPI) model was used to obtain ceiling estimates of vowel identification for each subject, given his/her electrode discrimination skills. Vowel identification scores were initially lower than the ceiling estimates, but they gradually approached them over the first few months post-implant. Taken together, the present results suggest that improved labeling is the main mechanism explaining post-implant increases in vowel identification