Call number: LD2668 .T4 1956 W43 / Master of Science

Although there is extensive evidence that auditory spatial processing can adapt to changes in auditory spatial cues both in infancy and adulthood, the mechanisms underlying adaptation appear to differ across species. Whereas barn owls compensate for unilateral hearing loss throughout development by learning abnormal mappings between cue values and spatial position, adult mammals seem to adapt by ignoring the acoustical input available to the affected ear and learning to rely more on unaltered spatial cues. To investigate these differences further, ferrets were raised with a unilateral earplug and their ability to localize sounds was assessed. Although these animals did not fully compensate for the effects of an earplug, they performed considerably better than animals that experienced an earplug for the first time, indicating that adaptation had taken place. We subsequently found that juvenile-plugged (JP) ferrets learned to adjust both cue mappings and weights in response to changes in acoustical input, with the nature of these changes reflecting the expected reliability of different cues. Thus, the auditory system may be able to rapidly update the way in which individual cues are processed, as well as the way in which different cues are integrated, thereby enabling spatial cues to be processed in a context- specific way. In attempting to understand the mechanisms that guide plasticity of spatial hearing, previous studies have raised the possibility that changes in auditory spatial processing may be driven by mechanisms intrinsic to the auditory system. To address this possibility directly, we measured the sensitivity of human subjects to ITDs and ILDs following transient misalignment of these cues. We found that this induces a short-term recalibration that acts to compensate for the effects of cue misalignment. These changes occurred in the absence of error feedback, suggesting that mutual recalibration can occur between auditory spatial cues. The nature of these changes, however, was consistent with models of cue integration, suggesting that plasticity and integration may be inextricably linked. Throughout the course of this work, it became clear that future investigations would benefit from the application of closed-field techniques to the ferret. For this reason, we developed and validated methods that enable stimuli to be presented to ferrets over earphones, and used these methods to assess ITD and ILD sensitivity in ferrets using a variety of different stimuli. We found that the Duplex theory is able to account for binaural spatial sensitivity in these animals, and that sensitivity is comparable with that found in humans, thereby confirming the ferret as an excellent model for understanding binaural spatial hearing.

Orientadora: Ana Cláudia Vieira Cardoso / Banca: Fátima Cristina Alves Branco-Berreiro / Banca: Cristiane Moço Canhetti de Oliveira / Resumo: O Processamento Auditivo Central (PAC) tem sido investigado há várias décadas, porém são escassas as pesquisas conduzidas com adolescentes, além disso, não há estudos que avaliem a autopercepção por meio da aplicação de questionários padronizados, que é de suma importância para identificação de riscos referentes aos comportamentos auditivos que podem estar relacionados com o Transtorno do Processamento Auditivo Central (TPAC). Dessa forma, os objetivos deste estudo foram avaliar a autopercepção dos adolescentes e a percepção dos pais em relação ao comportamento auditivo; avaliar o processamento auditivo central dos adolescentes e compará-la com a autopercepção dos adolescentes e a percepção dos pais. Este foi um estudo transversal, prospectivo e descritivo, no qual participaram 80 indivíduos de ambos os sexos, sendo 40 adolescentes, com idade entre 12 e 18 anos e 40 pais e/ou responsáveis. Todos os participantes responderam ao questionário Scale of Auditory Behaviors e, se realizou a avaliação comportamental do processamento auditivo central com os adolescentes. Os achados foram analisados de forma descritiva e inferencial. Na análise inferencial aplicaram-se os seguintes testes: Kolmogorov-Smirnov (KS), Igualdade de Duas Proporções, Qui-Quadrado, Mann- Whitney e o índice de Concordância de Kappa. Adotou-se o nível de significância de 5%, (p ≤ 0,05). A análise dos resultados da autopercepção dos adolescentes e da percepção dos pais em relação ao comportamento auditivo demonst... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Central Auditory Processing (CAP) has been investigated for several decades, but there are few studies conducted with adolescents; in addition, there are no studies that screen self-perception through the application of standardized questionnaires, which is extremely important for the identification of risks regarding auditory behaviors that may be related to Central Auditory Processing Disorder (CAPD). Therefore, the purposes of this study were to evaluate the adolescent' self-perception and the parents' perception regarding the auditory behavior; to evaluate the central auditory processing of adolescents and to compare it with the adolescents' self-perception and the parents' perception. This was a cross-sectional, prospective and descriptive study in which 80 individuals of both genders participated, 40 adolescents, aged between 12 and 18 years and 40 parents and/or guardians. All participants answered the Scale of Auditory Behaviors questionnaire and were tested with the behavioral evaluation of central auditory processing. The findings were analyzed in a descriptive and inferential manner. In the inferential analysis the following tests were applied: Kolmogorov-Smirnov (KS), Equality of Two Proportions, Chi-Square, Mann-Whitney and the Kappa Concordance index. The level of significance was set at 5%, (p ≤ 0.05). The analysis of the results of the adolescents' selfperception and the parents' perception in relation to the auditory behavior demonstrated homogeneity in the s... (Complete abstract click electronic access below) / Mestre

Digitized by Kansas Correctional Industries

The first stage of mammalian auditory processing occurs within the dorsal and ventral divisions of the cochlear nucleus. The dorsal cochlear nucleus (DCN) is remarkable in that it shares striking similarities with the cerebellum in terms of its development, gene expression patterns, and anatomical organization. Notably, principal cells of the DCN integrate auditory nerve input with a diverse array of signals conveyed by a mossy fiber- granule cell system. Yet how the elaborate cerebellum-like circuitry of DCN contributes to early auditory processing has been a longstanding puzzle. The work in this thesis shows that, in mice, that the DCN functions to cancel responses to self-generated sounds. While the DCN and ventral cochlear nucleus (VCN) neurons respond similarly to externally-generated acoustic stimuli, sounds generated by licking behavior evoke much weaker responses in DCN than in VCN. Recordings in deafened mice revealed non- auditory signals related to licking in Purkinje-like neurons of DCN. Moreover, silencing somatosensory mossy fiber inputs revealed prominent DCN responses to sounds generated by licking, suggesting that these inputs normally function to cancel responses to self-generated sounds. Finally, I show that this cancellation is not fixed, but involves an adaptive process whereby neural responses correlated with the animal’s own behavior are gradually reduced. Together, these findings suggest that the fundamental process of distinguishing self-generated from external stimuli begins at the very first stage of mammalian auditory processing. Related adaptive filtering functions have been described for cerebellum-like sensory structures in fish and hypothesized for the mammalian cerebellum. Hence our findings also suggest that, despite their wide phylogenetic separation, different cerebellum-like structures and the cerebellum itself may all perform a similar computation.

No description available.

Research over the last decade has shown that auditorily cuing the location of visual targets reduces the time taken to locate and identify targets for both free-field and virtually presented sounds. The first study conducted for this thesis confirmed these findings over an extensive region of free-field space. However, the number of sound locations that are measured and stored in the data library of most 3-D audio spatial systems is limited, so that there is often a discrepancy in position between the cued and physical location of the target. Sampling limitations in the systems also produce temporal delays in which the stored data can be conveyed to operators. To investigate the effects of spatial and temporal disparities in audio cuing of visual search, and to provide evidence to alleviate concerns that psychological research lags behind the capabilities to design and implement synthetic interfaces, experiments were conducted to examine (a) the magnitude of spatial separation, and (b) the duration of temporal delay that intervened between auditory spatial cues and visual targets to alter response times to locate targets and discriminate their shape, relative to when the stimuli were spatially aligned, and temporally synchronised, respectively. Participants listened to free-field sound localisation cues that were presented with a single, highly visible target that could appear anywhere across 360° of azimuthal space on the vertical mid-line (spatial separation), or extended to 45° above and below the vertical mid-line (temporal delay). A vertical or horizontal spatial separation of 40° between the stimuli significantly increased response times, while separations of 30° or less did not reach significance. Response times were slowed at most target locations when auditory cues occurred 770 msecs prior to the appearance of targets, but not with similar durations of temporal delay (i.e., 440 msecs or less). When sounds followed the appearance of targets, the stimulus onset asynchrony that affected response times was dependent on target location, and ranged from 440 msecs at higher elevations and rearward of participants, to 1,100 msecs on the vertical mid-line. If targets appeared in the frontal field of view, no delay of acoustical stimulation affected performance. Finally, when conditions of spatial separation and temporal delay were combined, visual search times were degraded with a shorter stimulus onset asynchrony than when only the temporal relationship between the stimuli was varied, but responses to spatial separation were unaffected. The implications of the results for the development of synthetic audio spatial systems to aid visual search tasks was discussed.

Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed Jan. 21, 2010). Advisor: Peter Mueller. Keywords: acoustic measures, voice, older singers, non-singers. Includes bibliographical references (p. 78-91).

Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 127-139). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p3045096.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.