Spoken word recognition in adolescent cochlear implant users during quiet and multispeaker babble conditions

Development of a feline model for preclinical research of a new translabyrinthine auditory nerve implant

Cochlear implants are among the most successful neural prosthetic devices to date but exhibit poor frequency selectivity and the inability to consistently activate apical (low frequency) spiral ganglion neurons. These issues can limit hearing performance in many cochlear implant patients, especially for understanding speech in noisy environments and in perceiving or appreciating more complex inputs such as music and multiple talkers. For cochlear implants, electrical current must pass through the bony wall of the cochlea, leading to widespread activation of auditory nerve fibers. Cochlear implants also cannot be implanted in some individuals with an obstruction or severe malformations of the cochlea. Alternatively, intraneural stimulation delivered via an auditory nerve implant could provide direct contact with neural fibers and thus reduce unwanted current spread. More confined current during stimulation can increase selectivity of frequency fiber activation. Furthermore, devices such as the Utah Slanted Electrode Array can provide access to the full cross section of the auditory nerve, including low frequency fibers that are difficult to reach using a cochlear implant. However, further scientific and preclinical research of these Utah Slanted Electrode Array devices is limited by the lack of a chronic large animal model for the auditory nerve implant, especially one that leverages an appropriate surgical approach relevant for human translation. This paper presents a newly developed transbullar translabyrinthine surgical approach for implanting the auditory nerve implant into the cat auditory nerve. In our first of a series of studies, we demonstrate a surgical approach in non-recovery experiments that enables implantation of the auditory nerve implant into the auditory nerve, without damaging the device and enabling effective activation of the auditory nerve fibers, as measured by electrode impedances and electrically evoked auditory brainstem responses. These positive results motivate performing future chronic cat studies to assess the long-term stability and function of these auditory nerve implant devices, as well as development of novel stimulation strategies that can be translated to human patients.

Perception of polyphony with cochlear implants for 2 and 3 simultaneous pitches

HYPOTHESIS

It was hypothesized that cochlear implant (CI) subjects would be able to correctly identify 1, 2, and 3 simultaneous pitches through direct electrical stimulation. We further hypothesized that the location on the implant array and the fundamental frequency of the pitches would have an impact on the performance.

BACKGROUND

"They gave me back speech but not music" is a sentence commonly heard by CI subjects. One of the reasons is that in music, multiple streams are frequently played at the same time, which is an essential feature of harmony. Current CI speech processors do not allow CI users to perceive such complex polyphonic sounds.

METHODS

In the present study, the authors assessed the ability of CI subjects to perceive simultaneous modulation frequencies based on direct electrical stimulation. Ten CI subjects were asked to identify 1, 2, and 3 simultaneous pitches applied on different electrodes using sinusoidal amplitude modulation. All stimuli were loudness balanced before the actual identification task.

RESULTS

Subjects were able to identify 1, 2, and 3 simultaneous pitches. The further the distance between the 2 electrodes, the better was the performance in the 2-pitch condition. The distance between the modulation frequencies had a significant effect on the performance in the 2-and 3-pitch condition.

CONCLUSION

Subjects are able to identify complex polyphonic stimuli based on the number of active electrodes. The additional polyphonic rate pitch cue improves performance in some conditions.

Inferences and metaphoric comprehension in unilaterally implanted children with adequate formal oral language performance

OBJECTIVES

To assess skills in inferences during conversations and in metaphors comprehension of unilaterally cochlear implanted children with adequate abilities at the formal language tests, comparing them with well-matched hearing peers; to verify the influence of age of implantation on overall skills.

METHODS

The study was designed as a matched case-control study. 31 deaf children, unilateral cochlear implant users, with normal linguistic competence at formal language tests were compared with 31 normal hearing matched peers. Inferences and metaphor comprehension skills were assessed through the Implicit Meaning Comprehension, Situations and Metaphors subtests of the Italian Standardized Battery of "Pragmatic Language Skills MEDEA". Differences between patient and control groups were tested by the Mann-Whitney U test. Correlations between age at implantation and time of implant use with each subtest were investigated by the Spearman rank correlation coefficient.

RESULTS

No significant differences between the two groups were found in inferencing skills (p=0.24 and p=0.011 respectively for Situations and Implicit Meaning Comprehension). Regarding figurative language, unilaterally cochlear implanted children performed significantly below their normal hearing peers in Verbal Metaphor comprehension (p=0.001). Performances were related to age at implantation, but not with time of implant use.

CONCLUSIONS

Unilaterally cochlear implanted children with normal language level showed responses similar to NH children in discourse inferences, but not in figurative language comprehension. Metaphors still remains a challenge for unilateral implant users and above all when they have not any reference, as demonstrated by the significant difference in verbal rather than figurative metaphors comprehension. Older age at implantation was related to worse performance for all items. These aspects, until now less investigated, had to receive more attention to deeply understand specific mechanisms involved and possible effects of different levels of figurative language complexity (presence or absence of contextual input, degree of transparency and syntactic frozenness). New insight is needed to orient programs in early intervention settings in considering and adequately responding to all these complex communicative need of children with hearing loss.

Cochlear implantation updates: the Dallas Cochlear Implant Program

This report provides an overview of many research projects conducted by the Dallas Cochlear Implant Program, a joint enterprise between the University of Texas at Dallas, the University of Texas Southwestern Medical Center, and Children's Medical Center. The studies extend our knowledge of factors influencing communication outcomes in users of cochlear implants. Multiple designs and statistical techniques are used in the studies described including both cross sectional and longitudinal analyses. Sample sizes vary across the studies, and many of the samples represent large populations of children from North America. Multiple statistical techniques are used by the team to analyze outcomes. The team has provided critical information regarding electrode placement, signal processing, and communication outcomes in users of cochlear implants.