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When doing experiments with cochlear implant users it is highly desirable to specify stimuli at the electrical stimulation level, or at least to analyze the electrical output of the speech processor. This allows separate analysis of two qualitatively different objects of study: the cochlear implant subject and his speech processor. In the specific case of the gap detection experiments we performed on subjects wearing multichannel cochlear implants, analysis of speech processor output confirmed our hypothesis that previous results obtained with broadband noise were more a function of the processing scheme rather than a psychophysical limit per se. Our cochlear implant subjects showed worse performance at 200 Hz and a tendency toward better performance at 400 Hz, when running gap detection and second formant transition experiments at 80, 120, 200 and 400 Hz Our approach to designing speech processing strategies for cochlear implants consists on trying to maximize perceptual contrast between stimulation patterns caused by different phonemes. This approach was useful when we designed and tested a number of frequency-to-electrode maps. Subjects obtained better vowel discrimination when using maps that minimized the probability that different vowels would cause different stimulation patterns. Subject preference for a given map was not a good performance predictor. Using maps that, given a formant frequency, stimulated cochlear areas that are close to those maximally stimulated by the same formant frequency in a normal cochlea did not result in any performance improvement either We wrote software to test speech processing strategies that cannot be implemented by the Nucleus speech processor, and used this software to test an experimental voicing encoding strategy. Voicing was encoded by stimulating the most apical electrode during voiced speech segments, in addition to the two electrodes stimulated each fundamental period by the current Nucleus strategy. The presence or absence of this third pulse per period was easily discriminated by our subject, making this a promising way to encode voicing or other speech features. The software we wrote to test alternative speech processing strategies has some limitations, but it could be used to test a much wider set of strategies than can be implemented with current Nucleus processors / acase@tulane.edu

Auditory sequencing ability was studied in 18 five and 18 nine year old normal-hearing children, and in 18 hearing-impaired children aged 6 to 14 years. Subjects selected were able to repeat syllables differing in initial consonant or final vowel and identify pictures corresponding to 200-msec. environmental sounds. Sequences of 2, 3 and 4 such items were recorded at 1, 2 and 4 items per second. Significant interactions between type of stimuli, sequence length and rate were obtained. Normal-hearing children and, to a lesser extent, hearing-impaired children had greater facility in recalling verbal than nonverbal sequences. For aIl groups, the fastest rate was optimal for consonants, and the slowest rate for nonverbal sounds. Normal children were superior to hearing-impaired subjects on verbal sequences. On nonverbal sequences, hearing-impaired were more accurate than normal five year olds, but less accurate than nine year olds. Implications for auditory training are discussed. / L'habilite de suivre un ordre auditif fut étudiee chez des enfants d'audition normale de cinq et neuf ans et chez des sujets atteints de surdite, ages de 6 à 14 ans, 18 pour chaque groupe. Les sujets choisis pouvaient repeter des syllabes enregistrees, identifier des images correspondant à des sons d'entourage de 200 msec. de duree. Des ordres de 2, 3 et 4 de ces stimuli furent enregistrés au rythme de 1, 2 et 4 stimuli par seconde. Les enfants d'audition normale et, d'une façon moins eVidente, les enfants atteints de surdité avaient une plus grande facilite à se rappeler des ordres verbaux plutôt que non-verbaux. Pour tous les groupes, la vitesse la plus rapide fut optimale pour les consonnes, et la vitesse la plus lente, pour les sons non-verbaux. Les sujets d'audition normale furent superieurs à ceux atteints de surdité, pour les ordres verbaux mais ces derniers, furent supérieur aux sujets ages de cinq ans et non pas de neuf ans, pour les ordres non-verbaux. Des implications pour l'entraînement auditif sont discutes. fr

Background. Childhood hearing loss has a negative impact on healthy child development and is associated with poor outcomes in communication, social and academic development. Population-based infant hearing screening has received worldwide attention as an opportunity to improve developmental outcomes for children with hearing loss. Universal newborn hearing screening (UNHS) has become standard protocol in many countries and has recently been implemented in several Canadian provinces and territories. This study concerns population-based infant hearing screening and the potential benefits of this intervention for children and families. While there is evidence that screening can accurately identify babies with hearing loss before three months of age, less information is available on the effectiveness of early identification initiatives and how to maximize the potential opportunities provided by early detection of hearing loss. It is well recognized that UNHS must be part of an early hearing and communication development program. Objectives. The objectives of this thesis were to contribute to this developing field by: (1) exploring the effectiveness of infant hearing screening through traditional communication outcome measures, (2) identifying process and other outcomes that parents view as important benefits of early diagnosis of hearing loss, (3) examining parents' needs following identification of hearing loss, and (4) exploring parent preferences for service delivery following the diagnosis of hearing loss. Methods. Following a comprehensive review of the current state of knowledge, this study used combined quantitative and qualitative methodology approaches to examine these objectives through three interrelated inquiries: (1) an exploration of data from a prospective longitudinal study investigating the impact of early identification, (2) semi-structured interviews with parents whose children were diagnosed through screening and traditional referral routes and (3) a conjoint analysis survey to quantify parent preferences for service delivery. Conclusions and Implications for Practice and Policy. Applying a population health perspective, this research defined broader outcomes of early identification of childhood hearing loss from the perspective of families and highlighted contextual factors such as access to parent support and coordinated services, which may be important determinants of outcome to consider in program evaluation of screening initiatives. This study can inform the development and implementation of population hearing screening programs as they continue to grow across Canada and elsewhere. This project has the potential to impact health practice and policy by providing evidence-based direction for the delivery of services to young children with hearing loss and their families.

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