Especially important in developing improved cochlear implants is to develop a deeper understanding of the processing of sound in the central auditory nervous system, for both acoustic and electrical stimulation of the auditory system. This thesis contributes to this objective through cochlear implant psychoacoustic research and modelling of auditory system sound processing. The primary hypothesis of the thesis was that the same underlying mechanisms are responsible for sound perception in both electric and acoustic hearing. Thus, if appropriate models are created for normal acoustic hearing, they should be able to predict psychoacoustic data from electric hearing when the model input is changed from acoustic to electrical stimulation. A second hypothesis was that electrode interaction could be measured by gap detection and that predictions of current spread in the cochlea could be obtained from gap detection data. Measured gap detection thresholds in three cochlear implant users were a function of the physical separation of electrode pairs used for the two stimuli that bound the gap, resulting in a U-shaped "tuning curve" for this across-channel condition. Models of gap detection in acoustic and electric hearing were created to explain these U-shaped curves. A technique was developed to obtain estimates of cochlear current spread from gap detection data. Predictions of electrode discrimination were obtained from the current spread estimates, and these were compared to data measured in cochlear implant users. The model for acoustic hearing could predict the U -shaped curves found in acoustic hearing, and when the input spike train statistics were adapted appropriately, the same model could also predict gap detection data for electric hearing. Predictions of current spread exhibited current peaks close to the electrodes and had length constants between 0.5 mm and 3 mm, similar to measured data quoted in literature. Predictions of electrode discrimination correlated well with measured data in one subject, but not in two others. The primary conclusion from the modelling results is that if the mechanisms of central auditory nervous system signal processing of acoustic stimulation are understood, these same mechanisms may be applied to understand the signal processing in auditory electrical stimulation and to predict psychoacoustic data for electrical stimulation. A second conclusion is that spatial mechanisms, as opposed to temporal mechanisms, may determine gap detection thresholds in the across-channel condition. This is important in cochlear electrical stimulation, where spike trains are strongly phase-locked to the stimulus and temporal mechanisms cannot predict gap detection thresholds. A third conclusion is that gap detection can be used to measure channel interaction and to predict current distributions in the cochlea, although there is still uncertainty about the accuracy of these predictions. However, the gap detection data and predictions for current distributions indicate that electrodes are not discriminable when they are closer than 1.5 mm. The implication of these last two conclusions taken together is that research should focus on obtaining better spatial resolution in cochlear implants. / Thesis (PhD)--University of Pretoria, 2001. / Electrical, Electronic and Computer Engineering / Unrestricted

Hearing loss afflicts as many as 10\% of our population.Fortunately, technologies designed to alleviate the effects ofhearing loss are improving rapidly, including cochlear implantsand the increasing computing power of digital hearing aids. Thisthesis focuses on theoretically sound methods for improvinghearing aid technology. The main contributions are documented inthree research articles, which treat two separate topics:modelling of human speech recognition (Papers A and B) andoptimization of diagnostic methods for hearing loss (Paper C).Papers A and B present a hidden Markov model-based framework forsimulating speech recognition in noisy conditions using auditorymodels and signal detection theory. In Paper A, a model of normaland impaired hearing is employed, in which a subject's pure-tonehearing thresholds are used to adapt the model to the individual.In Paper B, the framework is modified to simulate hearing with acochlear implant (CI). Two models of hearing with CI arepresented: a simple, functional model and a biologically inspiredmodel. The models are adapted to the individual CI user bysimulating a spectral discrimination test. The framework canestimate speech recognition ability for a given hearing impairmentor cochlear implant user. This estimate could potentially be usedto optimize hearing aid settings.Paper C presents a novel method for sequentially choosing thesound level and frequency for pure-tone audiometry. A Gaussianmixture model (GMM) is used to represent the probabilitydistribution of hearing thresholds at 8 frequencies. The GMM isfitted to over 100,000 hearing thresholds from a clinicaldatabase. After each response, the GMM is updated using Bayesianinference. The sound level and frequency are chosen so as tomaximize a predefined objective function, such as the entropy ofthe probability distribution. It is found through simulation thatan average of 48 tone presentations are needed to achieve the sameaccuracy as the standard method, which requires an average of 135presentations.

Cochlear implant (CI) devices afford many profoundly deaf individuals worldwide partially restored hearing ability. Although CI users achieve remarkable speech perception with contemporary multichannel CI devices, their music perception ability is generally unsatisfactory. Improved CI-mediated music perception ability requires that the underlying constraints hindering processing of music-relevant information need to be identified and understood. This study puts forward a systematic approach, informed by the neurocognitive mechanisms underlying music perception in normal hearing (NH), for investigating implant-mediated music perception. Psychoacoustical experiments were used to explore the extent to which music-relevant information delivered to the central auditory system following peripheral electrical stimulation supports music perception. Task-specific stimuli and test procedures were developed to assess perception of pitch, rhythm and loudness information, both as separate and in combined form, in sound-field listening conditions. CI users’ unsuccessful judgement of the musical character of short, novel single-voice melodies suggests that insufficient information reaches the central auditory processing system to effect a unified musical percept. This is despite sound field frequency discrimination behaviour being better than had been expected and rhythm perception ability with regard to short tone sequences of varying pitch and rhythmic complexity being comparable to that of NH listeners. CI listeners also performed similarly to NH listeners during pitch-dependent loudness perception tasks. Within the framework of a hierarchical, modular processing system underlying music perception, it appears that early pitch processing deficits propagate throughout the music processing system to exert an overriding inhibitory perceptual effect. The outcomes of this study not only underline the importance of delivering sufficient pitch information to the electrically stimulated auditory system but also show that music perception in CI-mediated hearing should be investigated and understood as the outcome of an integrated perceptual system. / Thesis (PhD)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / Unrestricted

Due to gaps in literature exploring communication outcomes in Deaf and Hard of Hearing (DHH) children with access to more than one spoken language, limited agreement on optimal language use for DHH children, and an ongoing cultural and linguistic loss in this population, the aim of this pilot study was to further the literature and comprehensively explore the impact of oral bilingualism in DHH children. Participants were self-selected and recruited primarily through relevant social media. Speech and language development in children were observed and quantified at two time points (at the time of enrollment into the study and subsequently after 3-4 months of initial assessment), through administration of standardized questionnaires and twenty minutes of conversational play language samples between the parent and child. Specific language constructs such as the mean length utterance, number of total words, number of different words, and rate of spoken words per minute were analyzed. Speech production skills were assessed by identifying the sounds the child was able to produce during the conversational play sample to compare to monolingual norms. The data from the five case studies presented in this paper indicated that DHH children with access to more than one language were able to develop language skills on par with their typical hearing peers when factors such as early acoustic access, linguistically rich environment, and active parent advocacy were present.

No description available.

Thesis (MAud (Interdisciplinary Health Sciences. Speech-Language and Hearing Therapy)--Stellenbosch University, 2008. / Over the past decade an increasing number of learners with cochlear implants have been placed in mainstream settings in South Africa (Müller & Wagenfeld, 2003). The aim of the present study was to describe possible factors that influence the initial grade 1 school placement as well as subsequent changes in placement of learners with cochlear implants. Data collection consisted of a retrospective record review of the children implanted at the Tygerberg Hospital-University of Stellenbosch Cochlear Implant Unit and a questionnaire aimed at assessing parental perceptions regarding the basis of grade 1 school placement for their children. The record review incorporated children implanted in 1988, the year of inception of the unit and included the most recently implanted children who have already started grade 1. Results of the 47 participants indicated that multiple factors influenced the selection of grade 1 school placement. Recommendations by professionals and parental preference were the most important determinants in the selection process. The mainstreamed learners were implanted at a much younger age than the learners placed in special school settings and therefore had a longer duration of implant use at the start of grade 1. Subsequent to grade 1 placement, the number of learners in mainstream placement, increased from 55% to 70%. The aspects identified in the study could be utilised when counselling parents during the school placement decision making process. Long term monitoring of the academic achievement of these learners needs to be an aim of future research.

Thesis (M Speech Path)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Various approaches to the communication-development of the young child with a hearing impairment exist, of which the auditory-verbal approach is one. This approach is based on the principle that the child with a hearingimpairment develops speech- and language skills by using his/her residual hearing that is appropriately strengthened with the use of a hearing aid and/or cochlear implant. One of the most important requirements for the successful application of this approach is the appropriate transfer of the techniques and strategies that is used in institution-based intervention to the child’s home environment. Parents, teachers, speech-language therapists and audiologists are responsible for facilitating the transfer of intervention methods and acquired skills to the home environment and it is important that all team members are aware of his/her own, as well as each other’s roles, in the application of this approach. The principal aim of the proposed research project was to describe and explain the perceptions of parents/caregivers, teachers, speech-language therapists and audiologists, that are involved in the intervention of the hearing impaired child, regarding the auditory-verbal approach to education. Semi-structured interviews were conducted with nine parents of hearing impaired children younger than the age of four, and with four teachers that are involved in the education of the said children. Lastly, semi-structured interviews were held with four speech-language therapists and two audiologists that are involved in the provision of the intervention to hearing impaired children younger than four years. All the participants were affiliated with a specific centre for children with hearing impairment in the Western Cape province of South Africa. All the participants noted that parents must take part in the decision-making process with regards to the selection of the most suitable communication approach for their child with a hearing loss. Participants also agreed that most parents choose the auditory-verbal approach to communication development of their child because speech as a communication medium, is familiar to them and it is also associated with normality. Parents also indicated that the auditory-verbal approach is the most suitable approach for all children with a hearing loss. Teachers, speech-language therapists and audiologists did not completely agree with the parents as they mentioned some aspects, e.g. the presence of additional disabilities must be taken into account before a decision can be made regarding whether the child with hearing loss could follow the auditory-verbal approach to communication development. All participants displayed a positive attitude towards the auditory-verbal approach and it appears that parents, teachers, speech-language therapists and audiologists have good insight into the principles and outcomes of this approach. / AFRIKAANSE OPSOMMING: Daar bestaan verskeie benaderings tot kommunikasie-ontwikkeling by die jong kind met gehoorverlies waarvan die ouditief-verbale benadering een opsie is. Hierdie benadering is gebaseer op die beginsel dat die kind met gehoorverlies spraak- en taalvaardighede ontwikkel deur gebruik te maak van hulle residuele gehoor wat deur middel van die gebruik van ‘n gehoorapparaat en/of kogleêre inplanting toepaslik versterk word. Een van die belangrikste vereistes vir die suksesvolle toepassing van die benadering is toepaslike oordrag van die tegnieke en strategieë wat in terapie gebruik word, na die kind se tuisomgewing. Ouers, onderwysers, spraak-taalterapeute en oudioloë speel ‘n baie belangrike rol om hierdie oordrag na alledaagse kontekste te fassiliteer en dit is belangrik dat elke spanlid bewus is van sy/haar rol asook die ander lede se rolle in die toepassing van die benadering. Die hoofdoelwit van die voorgestelde navorsingsprojek was om ouers/versorgers, onderwyseresse, spraaktaalterapeute en oudioloë, betrokke by die intervensie en opvoeding van die kind met gehoorverlies, se persepsies rakende die ouditief-verbale benadering tot opvoeding te beskryf en te verduidelik. Tydens die studie is daar semi-gestruktureerde onderhoude gevoer met onderskeidelik nege ouers van kinders, jonger as vier-jaar oud, met gehoorgestremdheid en met vier onderwyseresse wat betrokke is by die die opvoeding van genoemde ouers se kinders met gehoorverlies. Laastens is daar ook semi-gestruktureerde onderhoude gevoer met vier spraak-taalterapeute en twee oudioloë wat betrokke is by die verskaffing van intervensie aan kinders met gehoorverlies, jonger as vier-jaar oud. Al die deelnemers was verbonde aan ’n spesifieke sentrum vir kinders met gehoorverlies in die Wes-Kaap provinsie van Suid Afrika. Al die deelnemers het aangedui dat ouers betrek word by die besluitnemingsproses rakende die keuse van die mees geskikte kommunikasie-benadering vir die kind met gehoorverlies. Deelnemers het almal saamgestem dat ouers meestal die ouditief-verbale benadering tot kommunikasie-ontwikkeling vir hulle kind kies omdat spraak as kommunikasiemedium bekend is aan die ouers en verband hou met normaliteit. Ouers het aangedui dat die ouditief-verbale benadering die mees toepaslike benadering is vir enige kind met gehoorverlies. Onderwyseresse, spraak-taalterapeute en oudioloë het nie volkome saam met die ouers gestem nie en hulle het genoem dat daar sekere aspekte, byvoorbeeld die teenwoordigheid van bykomende gestremdhede, is wat oorweeg moet word voor daar besluit word of die kind die ouditief-verbale benadering tot kommunikasieontwikkeling moet volg. Deelnemers het oor die algemeen ‘n positiewe houding getoon teenoor die ouditief-verbale benadering en dit wil voorkom asof ouers, onderwyseresse, spraak-taalterapeute en oudioloë goeie begrip toon van die beginsels en uitkomstes van die benadering.

The present thesis investigated cognitive ability in children with severe to profound hearing impairment who have received cochlear implants (CIs). The auditory stimulation from a cochlear implant early in life influences most cognitive functions as a consequence of the plasticity of the brain in the young child. It is important to understand the cognitive consequences of auditory stimulation from CIs in order to provide adequate support to these children. This thesis examined three specific aspects of cognitive ability (working memory, phonological skill and lexical access), and reading ability in children with CIs, as compared to children with normal hearing in the same age. The relations between cognitive abilities and reading skills were also investigated, as well as the associations between demographic variables (e.g., age at implantation and communication mode), cognitive abilities and reading skills. The children with CI generally had lower performance levels than the normal hearing children in tasks of phonological and general working memory, phonological skills and lexical access. They had specific problems in tasks with high demands on phonological working memory, whereas their performance levels in tasks of visuospatial working memory were on par with the hearing children. A majority of the children with CI demonstrated reading skills within the normal range for hearing children, both for decoding and reading comprehension. The relations between demographic factors and cognitive skills varied somewhat between the studies. The patterns of result are discussed with reference to contemporary theories of working memory, phonological skills, and lexical access. / Avhandlingens övergripande syfte var att studera kognitiva förmågor hos barn med grav hörselskada eller dövhet som fått cochleaimplantat (CI). Auditiv stimulering från CI i tidig ålder påverkar de flesta kognitiva funktioner som en följd av hjärnans plasticitet hos små barn. Det är viktigt att förstå de kognitiva konsekvenserna av auditiv stimulering från CI för att kunna ge dessa barn bästa möjliga stöd. Avhandlingen undersökte tre specifika aspekter av kognitiv förmåga (arbetsminne, fonologiska förmågor och lexikal aktivering), samt läsförmåga hos barn med CI, i jämförelse med barn med normal hörsel i samma åldrar. Relationerna mellan kognitiva förmågor och läsförmåga studerades också, liksom sambanden mellan demografiska faktorer (t ex implantationsålder och kommunikationssätt) och kognitiva förmågor samt läsfärdigheter. Barnen med CI hade generellt lägre prestationsnivå än barnen med normal hörsel i uppgifter som mäter fonologiskt och generellt arbetsminne, fonologiska förmågor och lexikal aktivering. De hade specifika problem i uppgifter som i hög grad belastar fonologiskt arbetsminne, medan deras visuospatiala arbetsminneskapacitet var jämförbar med den hos barnen med normal hörsel. Majoriteten av barnen med CI hade läsfärdigheter i nivå med normalhörande barn, för både avkodning och läsförståelse. Sambanden mellan demografiska faktorer och kognitiva förmågor och läsförmåga varierade mellan studierna. Resultatmönstren diskuteras utifrån teorier om arbetsminne, fonologiska färdigheter och lexikal aktivering.

Thesis deals with issues of cochlear implants. It is focused on pre-school children one year before attending basic school. Thesis discusses all requisites that precede, accompany and follow cochlear implantation. We primarily determined the possibilities of children with cochlear implants, whether they can reach approximate levels of communication as intact children of the same age specifically in development of passive vocabulary and in the ability of understanding of speech. We choose the test Diagnosis of Language Development (Diagnostika jazykového vývoje) by Gabriela Seidlová Málková and Filip Smolík. The results of tests of children with cochlear implants were compared with tests of intact children of the same age. Next we used analysis of expert literature and interviews with teachers to determine which particular factors have underlying influence in the process of therapy of children after cochlear implantation and which influence them enough so children with cochlear implants approach communication levels of intact children. These factors were tracked in case studies of two girls with cochlear implants. KEYWORDS: cochlear implants, passive vocabulary, understanding of speech, preschool age, speech therapy

Introdução: O potencial evocado auditivo de estado estável (PEAEE) é um exame eletrofisiológico que permite a testagem simultânea e binaural do limiar auditivo por frequência específica. Por seu caráter objetivo vem sendo recomendada sua inclusão na bateria de testes para diagnóstico de crianças com deficiência auditiva. A possibilidade de diagnóstico precoce da perda de audição em crianças é fundamental para a redução dos agravos decorrentes da privação sensorial e a tomada de decisão quanto à intervenção adequada, como o uso do implante coclear (IC). A determinação do sucesso do uso do IC é dependente de múltiplos cofatores, entre eles, sugere-se que a presença de audição residual prévia ao implante poderia possibilitar a preservação das vias auditivas e áreas auditivas corticais, proporcionando melhor desenvolvimento das habilidades auditivas e de produção oral da linguagem com o reestabelecimento da entrada sensorial. Objetivo: Verificar a relação entre o PEAEE pré-operatório e a resposta auditiva pós-implante de crianças submetidas ao IC. Casuística e Método: Trata-se de um estudo observacional retrospectivo, desenvolvido a partir da análise de prontuários de pacientes do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, submetidos à cirurgia de IC. Foram incluídas 47 crianças menores de 6 anos à data de realização da cirurgia, diagnosticadas com perda auditiva neurossensorial pré-lingual de grau profundo. Foram coletadas informações audiológicas pré-implantação - PEAEE, PEATE, audiometria comportamental e demais aspectos de caracterização da perda auditiva; a categoria de percepção auditiva e de expressão oral da linguagem antes e após a implantação; além de informações socioeconômicas e da intervenção terapêutica. Resultados: O registro do PEAEE esteve presente em 34 (72,3%) crianças com limiar médio de 89,7 ± 10,2 dB NA na orelha implantada, consideradas as frequências de 0,5; 1; 2 e 4 kHz. A reavaliação foi conduzida em média 7,2 ± 2,1 meses após a cirurgia de IC, quando 23 (49%) sujeitos apresentaram avanço de uma categoria no desenvolvimento da percepção de fala e 4 (8,5%) alcançaram um desempenho dois níveis superior ao da avaliação anterior. O limiar obtido na audiometria em campo com o uso de IC teve média de 44,4 ± 12,4 dB NA, consideradas as frequências de 0,5; 1; 2 e 4 kHz. Quanto à expressão oral da linguagem, 13 (27,6%) crianças tiveram melhora em seu desempenho. Não houve correlação entre os resultados do PEAEE pré-implante e o limiar auditivo (p-valor=0,338) ou a categoria de linguagem (p-valor=0,358) com uso de IC quando controlado pela idade; nem em relação à melhora no desempenho de linguagem oral (p-valor= 0,095). Conclusão: Não houve correlação direta entre o limiar eletrofisiológico mensurado por meio do PEAEE e a resposta auditiva com uso de IC, quando analisados o limiar auditivo comportamental com IC ou a categoria de percepção de fala. / Background: The Auditory Steady State Response (ASSR) is an electrophysiological exam that allows simultaneous and binaural frequency specific testing of hearing thresholds. Considering its objectivity, the test has been recommended for hearing loss diagnosis in young children. This possibility of early identification of hearing impairment is fundamental for minimizing handicaps caused by sensory deprivation and for planning proper intervention, for example, suggesting the use of cochlear implants (CI). The determination of the success of CI prognosis depends on several cofactors. Researchers suggest that residual hearing and hearing thresholds before CI surgery could allow auditory pathways preservation and enable the development of hearing abilities, as well as speech production skills, after the reestablishment of sensory input. Objective: To verify the relation between pre-operatory ASSR and post-CI auditory response in young children. Casuistic and Method: An observational retrospective study was conducted. Medical records were assessed in 47 children, younger than six years old at the CI surgery, diagnosed with sensorineural pre-linguistic hearing loss of profound degree. Information was collected about (a) audiological data - ASSR, ABR, behavioral audiometry, and other hearing loss aspects; (b) category of speech perception and oral language production before and after CI; (c) socioeconomics data and therapy attendance. Results: ASSR record was present in 34 (72.4%) children with mean threshold of 89.7 (10.2 SD) dB HL in the implanted ear, considering the frequencies of 0.5; 1; 2 and 4 kHz. Post-implant evaluation was conducted after a mean of 7.2 (2.1 SD) months of surgery. Then, 23 (49%) subjects enhanced one category of speech perception and four (8.5%) improved two categories, compared to previous evaluation. Field auditory threshold with CI was measure at 44.4 (12.4 SD) dB HL in mean, considering the frequencies of 0.5; 1; 2 and 4 kHz. Analyzing language expression development, 13 (27.6%) children improved their performance. To the age at CI surgery there was no correlation between ASSR thresholds and CI thresholds (p-value=0.338) or speech perception category (p-value=0.358) after CI. No correlation has been found between ASSR and expressive language development (p-value=0.095). Conclusion: There was no direct correlation between electrophysiological thresholds measured by ASSR and hearing response after CI, when analyzed behavioral CI threshold or speech perception.