This study used the largest and youngest cohort of hearing impaired (HI) children to investigate the effect age at implantation had on the trajectories of expressive and receptive language, and externalizing behavior problems. In addition, the temporal relationship between language and externalizing behavior problems was examined in children implanted before and after the age of 2. Univariate latent difference score analyses were conducted to test the effect of age at implantation on each trajectory and bivariate difference score analyses were conducted to test the temporal effect between language and externalizing behavior problems. Results showed that age at implantation had an effect on the initial level and growth of expressive and receptive language trajectory and an effect on the initial level of externalizing behavior problems. Expressive language was found to have an influence on the changes in externalizing behavior problems for both groups, children implanted before and after the age of 2. However, the relationship between receptive language and externalizing behavior problems differed between the two age groups. The effect was bidirectional for the younger group but unidirectional for the older group, with externalizing behavior problems influenced the change in receptive language. Future research and potential interventions to improve behavior difficulties in deaf children are discussed.

The current study sought to examine predictors of language acquisition for deaf children who received cochlear implants in a large, multi-center trial. General maternal sensitivity as well as two specific types of maternal sensitivity, cognitive and linguistic stimulation, were all evaluated in relation to speech production. Characteristics of the family and child (e.g. maternal education, family income, age at implantation, etc.) were also evaluated. The hypotheses tested were: 1) child age at implantation and gender, maternal education, and family income were expected to predict speech production across 6 and 12 months post-implantation, 2) both Cognitive and Linguistic Stimulation were expected to predict the growth of speech production at 6 and 12 months post-implantation, and 3) Cognitive and Linguistic Stimulation were expected to predict speech production above and beyond that predicted by general Maternal Sensitivity. Results indicated that, of the demographic variables, only child age at implantation was a significant predictor of speech production. Cognitive and linguistic stimulation were significantly associated with the development of speech production in the first year following activation of the implant. Furthermore, these important maternal behaviors accounted for gains in speech production beyond that accounted for by general maternal sensitivity. These findings have several clinical implications, including the development of formalized training for parents of children who receive cochlear implants.

Similarities between the peripheral auditory and vestibular systems suggest that children with sensorineural hearing loss (SNHL) may demonstrate vestibular and balance impairments. This hypothesis was studied in 40 children with severe to profound SNHL and unilateral cochlear implants (CI). Vestibular function was assessed with caloric, rotational, and vestibular evoked myogenic potential (VEMP) testing; balance was assessed with standardized static and dynamic tests. Horizontal semicircular canal function was abnormal in 53% (17/32) with caloric, and 39% (14/36) with rotational stimulation. Saccular function was absent bilaterally in 5/26 (19%) and unilaterally in 5/26 (19%) with VEMP. Balance abilities were significantly poorer (μ=12.9±5(SD)) than normal hearing controls (μ=17±5(SD); p=0.0006) and correlated best with horizontal canal function from rotational stimulation (p=0.004;R2=0.24). SNHL from meningitis was associated with worse balance function than other etiologies. Vestibular and balance dysfunction occurred in >1/3 of children with SNHL and CI, and is highly dependent on etiology.

Cochlear implants (CIs) provide coarse representations of pitch, which are adequate for speech but not for music. Despite increasing interest in music processing by CI users, the available information is fragmentary. The present experiment attempted to fill this void by conducting a comprehensive assessment of music processing in adult CI users. CI users (n =6) and normally hearing (NH) controls (n = 12) were tested on several tasks involving melody and rhythm perception, recognition of familiar music, and emotion of recognition in speech and music. CI performance was substantially poorer than NH performance and at chance levels on pitch processing tasks. Performance was highly variable, however, with one individual achieving NH performance levels on some tasks, probably because of low-frequency residual hearing in his unimplanted ear. Future research with a larger sample of CI users can shed light on factors associated with good and poor music processing in this population.

Cochlear implants (CIs) provide coarse representations of pitch, which are adequate for speech but not for music. Despite increasing interest in music processing by CI users, the available information is fragmentary. The present experiment attempted to fill this void by conducting a comprehensive assessment of music processing in adult CI users. CI users (n =6) and normally hearing (NH) controls (n = 12) were tested on several tasks involving melody and rhythm perception, recognition of familiar music, and emotion of recognition in speech and music. CI performance was substantially poorer than NH performance and at chance levels on pitch processing tasks. Performance was highly variable, however, with one individual achieving NH performance levels on some tasks, probably because of low-frequency residual hearing in his unimplanted ear. Future research with a larger sample of CI users can shed light on factors associated with good and poor music processing in this population.

Similarities between the peripheral auditory and vestibular systems suggest that children with sensorineural hearing loss (SNHL) may demonstrate vestibular and balance impairments. This hypothesis was studied in 40 children with severe to profound SNHL and unilateral cochlear implants (CI). Vestibular function was assessed with caloric, rotational, and vestibular evoked myogenic potential (VEMP) testing; balance was assessed with standardized static and dynamic tests. Horizontal semicircular canal function was abnormal in 53% (17/32) with caloric, and 39% (14/36) with rotational stimulation. Saccular function was absent bilaterally in 5/26 (19%) and unilaterally in 5/26 (19%) with VEMP. Balance abilities were significantly poorer (μ=12.9±5(SD)) than normal hearing controls (μ=17±5(SD); p=0.0006) and correlated best with horizontal canal function from rotational stimulation (p=0.004;R2=0.24). SNHL from meningitis was associated with worse balance function than other etiologies. Vestibular and balance dysfunction occurred in >1/3 of children with SNHL and CI, and is highly dependent on etiology.

<p>It is well established that cochlear implants (CIs) are able to provide many users with excellent speech recognition ability in quiet conditions; however, the ability to correctly identify speech in noisy conditions or appreciate music is generally poor for implant users with respect to normal-hearing listeners. This discrepancy has been hypothesized to be in part a function of the relative decrease in spectral information available to implant users (Rubinstein and Turner, 2003; Wilson et al., 2004). One method that has been proposed for increasing the amount of spectral information available to CI users is to include time-varying stimulation rate in addition to changes in the place of stimulation. However, previous implementations of multi-rate strategies have failed to result in an improvement in speech recognition over the clinically available, fixed-rate strategies (Fearn, 2001; Nobbe, 2004). It has been hypothesized that this lack of success was due to a failure to consider the underlying perceptual responses to multi-rate stimulation. </p><p>In this work, psychophysical experiments were implemented with the goal of achieving a better understanding of the interaction of place and rate of stimulation and the effects of duration and context on CI listeners' ability to detect changes in stimulation rate. Results from those experiments were utilized in the implementation of a tuned multi-rate sound processing strategy for implant users in order to potentially ``tune" multi-rate strategies and improve speech recognition performance. </p><p>In an acute study with quiet conditions, speech recognition performance with a tuned multi-rate implementation was better than performance with a clinically available, fixed-rate strategy, although the difference was not statistically significant. These results suggest that utilizing time-varying pulse rates in a subject-specific implementation of a multi-rate algorithm may offer improvements in speech recognition over clinically available strategies. A longitudinal study was also performed to investigate the potential benefit from training to speech recognition. General improvements in speech recognition ability were observed as a function of time; however, final scores with the tuned multi-rate algorithm never surpassed performance with the fixed-rate algorithm for noisy conditions. </p><p>The ability to improve upon speech recognition scores for quiet conditions with respect to the fixed-rate algorithm suggests that using time-varying stimulation rates potentially provides additional, usable information to listeners. However, performance with the fixed-rate algorithm proved to be more robust to noise, even after three weeks of training. This lack of robustness to noise may be in part a result of the frequency estimation technique used in the multi-rate strategy, and thus more sophisticated techniques for real-time frequency estimation should be explored in the future.</p> / Dissertation

The purpose of this thesis is to provide a review and discussion of the current literature on auditory processing, speech discrimination, word recognition, and early lexical representations in children with normal hearing and those with hearing impairment in addition to identifying areas in which current research is lacking. This information is needed to consider potential interactions between various factors affecting the development of spoken word recognition. This will also provide a starting point for identifying further research needs. Since children with hearing loss do not receive the same amount of exposure to speech and language as typically developing children, it can be expected that the development of speech and word recognition in this population may progress differently. If we can identify differences in auditory processing and phonological development in children with hearing impairment, we can modify speech and language therapy to focus on more specific and effective targets. The subsequent chapters will provide a critical review of the current literature on the aforementioned topics. In Chapters 2 and 3, studies assessing differences in processing, attention to sound, intersensory perception, and sound discrimination abilities in children with normal hearing and hearing impairment will be discussed. Chapters 4 and 5 focus on word recognition skills, and early lexical representations. Chapter 6 will synthesize results of available studies and suggest areas in which more research is needed. Together, these chapters will help us gain a better understanding of the complex interactions between auditory processing, executive functioning, phonological development and later word recognition outcomes. By identifying which avenues have the greatest effect on outcomes in cochlear implant users, we can modify speech and language therapy in order to address the unique needs of this special population. / text

Background: To date, there is a lack of research that has focused on the needs of late cochlear implanted adults with prelingual deafness. The specific study aims were: (1) to explore the met and unmet long-term needs of late cochlear implanted adults with prelingual deafness from their own perspectives and those of the employees at SCIP; and 2) to identify a consensus of the most important met and unmet long-term needs of late cochlear implanted adults with prelingual deafness. Method: This study used a modified Delphi technique with two rounds. In the first round, nine adults who were considered experts on this topic participated in semi-structured in-depth interviews. The participants were five late cochlear implanted recipients with prelingual deafness who were involved in the Southern Cochlear Implant Programme in New Zealand, and four clinicians from the programme. The interview transcripts were analysed using qualitative content analysis. The results from the first round were used to inform the development of the survey for the second round. The second round of the study involved surveying the same participants who participated in the first round. These surveys were quantitatively analysed so as to discover which needs were considered important and met, and important and unmet for the cochlear implant recipients, from the perspectives of the two categories of participants. Results: The first round of the study revealed 42 met needs and 39 unmet needs that fell into 15 categories. Of these needs, 26 met needs and 18 unmet needs were identified as being important by a majority of the participants in the second round. Conclusion: The results from the study may impact potential CI recipients’ and their families’ expectations of what the device can provide, as well as the development of future services and governmental policies in the area.

published_or_final_version / abstract / toc / Surgery / Master / Master of Philosophy