Thesis (doctoral)--Ludwig Maximilians-Universität zu München, 1979.

Dissertation (MCommunication Pathology)--University of Pretoria, 2013. / Speech-Language Pathology and Audiology / Unrestricted

This study investigates the performance of two hemispherec-tomized subjects and ten normal subjects on a dichotic binaural frequency fusion (DBFF) test and on a competing dichotic message test. The DBFF test was designed to examine whether binaural integration of two complementary frequency segments of the same word, dichotically presented, necessitates the presence of two intact hemispheres. The competing dichotic message test was presented to provide a measure of the extent of strengthening of ipsilateral pathways in the hemispherectomized subjects. The DBFF test consisted of three fifty-word CNC lists which were processed through two band-pass filters and recorded on a two--channel magnetic tape. The test consisted of two binaural conditions. In the Dichotic A condition, the high band was delivered to the left ear and the low band to the right. The Dichotic B condition was the reverse of the first. For each condition 50 phonetically balanced (PB) words were presented and the subject was required to repeat the word in a 4 second interval between words. The competing dichotic message test consisted of 15 sets of three pairs of words, one of each pair being presented simultaneously to either ear, using stereophonic head-phones. The subject was required to repeat as many words from each set as possible. The Z scores, measuring the deviation in standard deviation units of the raw scores of the operated subjects from the mean scores of the normals indicated that the removal of a hemisphere did not significantly decrease the scores of two hemispherectomized subjects on a DBFF test. Removal of a hemisphere, however, decreased the scores of the hemispherectomees on the competing dichotic message test in one of the ears -- specifically the ear contralateral to the removed hemisphere. A comparative analysis of how the central auditory nervous system (CANS) of a hemispherectomized subject might process a complementary dichotic message (exemplified by the DBFF test), as opposed to a competing dichotic message, provides an interesting basis for a discussion on the nature of the "biological detector" of speech elements in the CANS. / Medicine, Faculty of / Audiology and Speech Sciences, School of / Graduate

The purpose of this investigation was (1) to perform hearing screening tests on 100 youths who are classified as delinquent; (2) to evaluate more completely the hearing of those who fail the hearing screening tests in order to determine the nature and severity of the losses; and (3) to determine whether or not any significant number of the youths tested demonstrate nonorganic components in their reported audiometric thresholds.

This paper purports to give (1) a systematic review of the background and theoretical development leading to the evolvement of the modern approach of language instruction for the hearing impaired child, and (2) a comparison of the grammatical and the developmental schools from the instructional point of view.

Uncomfortable listening level (UCL) is a behavioral measure which is currently used to set the maximum outputs of hearing aids. This study explored the feasibility of prescribing the maximum outputs of hearing aids by using results obtained from auditory brainstern response (ABR) testing. More specifically, this study compared ABR wave latencies with behaviorally-measured UCLs for a single cycle 3 kHz stimulus in normal-hearing adults.

Regulators of G-protein signaling (RGS) are a multifunctional and highly diverse group of proteins that negatively regulate G-protein coupled receptor (GPCR) signaling pathways. The common mechanism of RGS is to act as GTPase accelerating proteins (GAP) to accelerate the hydrolysis of active GTP bound G proteins and terminate the actions of the associated GPCR. In addition to the traditional function of inhibiting G-protein signaling, recent studies have highlighted the role of RGS proteins in modulating GPCRs in GAP-independent way. There are more than 30 RGS proteins, and depending upon cell/tissue type, they interact and associate with different G proteins and GPCRs to modulate various physiological functions. RGS17, a member of the RGS-RZ subfamily, commonly targets GTP bound Gαz, Gαi, and Gαo for hydrolysis and signal termination. RGS17 is abundantly expressed in the central nervous system and is highly associated with opioid, dopamine and cannabinoid receptors in the brain. RGS17 is also upregulated in many malignant tumors such as lung, prostate and breast cancers. Analysis of whole cochlea transcriptome data from our lab revealed higher levels of RGS17 in the cochlea after cisplatin treatment. This highlights a possible role of RGS17 (and probably other RGS proteins) in cisplatin ototoxicity. Activation of endogenous, otoprotective GPCRs such as adenosine (A1AR) and cannabinoid (CB2) receptor is beneficial for promoting protection against cisplatin-induced hearing loss. Taking all this together, the underlying hypothesis for this study is that cisplatin could possibly mediate ototoxicity by increasing the expression of RGS17, which reduces the otoprotective effect of endogenous receptors such as cannabinoid receptor 2. The main objective of the study is to examine the expression and function of RGS17 in the cochlea and determine if inhibition of RGS17 could protect against cisplatin ototoxicity.The expression of RGS17 was observed in the both in vitro and in vivo models of cochlear cell types. Immunofluorescence study, western blot analysis, and RT-qPCR results showed the presence of RGS17 in UB\OC-1, as well as Wistar rat cochlea; expression levels increased after cisplatin treatment. To determine the role of RGS17 in hearing, first, it was overexpressed in the cochlea using adenoviral vector that was found to significantly increase ABR threshold shifts and decrease ABR Wave I amplitude. Conversely, knockdown of RGS17 (by siRGS17) decreased cisplatin-induced elevations in ABR thresholds along with increased wave I amplitude and latency. Furthermore, siRGS17 pretreatment prevented cisplatin-mediated synapse loss at inner hair cells. This indicates inhibition of RGS17 can preserve the functional and physiological integrity of the cochlea, which is essential for hearing. Cochleae that were treated with siRGS17, followed by cisplatin, showed fewer TUNEL-positive cells and reduced loss of Outer hair cells (OHC) as compared to cisplatin-treated rats. Moreover, overexpression of RGS17 increased the ratio of the transcription factors, pSTAT1/pSTAT3, which may indicate initiation of the apoptotic pathway. Moreover, UB\OC-1 cells treated with Celastrol, a RGS17 inhibitor, showed an increase in cell viability against cisplatin toxicity. In addition to apoptosis, overexpression of RGS17 also elevated ROS production and oxidative stress. But, the inhibition of RGS17 attenuated the cisplatin-induced increase in transcripts for oxidative and inflammatory stress markers, such as NOX3, iNOS, KIM1, TNF-α, and COX2, whereas the mRNA level of antioxidant genes such as Nrf2 and SOD2 were increased. Activation of CB2 via JWH-015 (a CB2 agonist) prior to cisplatin administration significantly reduced the cisplatin-induced elevated levels of RGS17, while knockdown of CB2 increased RGS17 expression in the cochlea. siRGS17 treatment boosted endogenous CB2R-Gα expression. Additionally, cisplatin decreased the expression of Gαi/o and Gαz in vitro, but the activation of CB2 increased the expression of these G proteins. Furthermore, JWH-015 treatment alleviated RGS17-dependent cell death. This study suggests that RGS17 could serve as a mediator of cisplatin ototoxicity by reducing the duration of active CB2R-G protein signaling, which normally suppresses cochlear oxidative stress, inflammation and hair cell apoptosis, and thereby preserves normal hearing. These data also indicate the existence of tonic reciprocal inhibition between RGS17 and CB2 mediated via the G proteins. Thus, we propose that RGS17 inhibitors could serve as an effective treatment against cisplatin ototoxicity when used alone and can potentiate the actions of CB2 agonists when used in combination therapy against cisplatin-induced hearing loss.

According to the CDC, one in three children per thousand are diagnosed with hearing loss. Educational professionals should be familiar with the care, use, and maintenance of the various hearing devices available for students with hearing loss. Due to a shortage of audiological personnel in the educational setting, teachers are increasingly filling the role of hearing specialists. Minimal educational resources are available for educators online, or they are not easily accessible. Therefore, we investigated if a one-time ZOOM workshop for educators would improve their self-efficacy as it relates to the care, use, and maintenance of these devices. To determine whether the professionals' self-efficacy improved, participants were emailed identical survey questionnaires both before and after attending an in-depth ZOOM workshop. The workshop covered the following topics related to hearing devices: an overview of the auditory system, device battery care and use, parts, and functions, as well as how to power devices on and off. Results of the post-test ( M= 36.53, SD = 8.36) were significantly higher than the pre-test (M= 25.77, SD = 7.23), p = < 0.0001 indicating a significant increase in self-efficacy skills for the educational professionals. Further analysis to determine differences across survey questions and educational professional demographics is underway. Access to educational materials and understanding care and use of hearing devices is critical to improving the confidence of educational professionals seeking to provide care to their students with hearing loss.

Federal law requires hearing protection device (HPD) manufacturers to provide attenuation ratings for use in estimating workers’ protection levels. These ratings, which are laboratory obtained, typically overestimate the actual protection levels achieved in the workplace. This research investigated laboratory protocols for yielding improved estimates of HPD in-field performance. Two experiments were conducted. The first was a pilot study developed by an American National Standards Institute (ANSI) working group. In this experiment, two types of earplugs were tested, a user-molded, malleable foam plug and a pre-molded, multi-sized rubber plug. Attenuation data (obtained using a psychoacoustical real-ear-attenuation-at-threshold measurement procedure) were collected across 10 subjects who entered the study as novice HPD users but were considered experienced HPD users in the latter half of the study. Four testing protocols involving two levels of HPDs, two levels of instruction-insertion techniques, and two levels of user experience were investigated. The same 10 subjects participated in all treatment conditions of the experiment. The second experiment involved similar protocols as the first; however, only one plug type was tested (the pre-molded, multi-sized rubber plug). Four testing protocols involving two levels of instruction-insertion techniques, two levels of user experience, and two levels of auditory feedback [fitting noise] were investigated. Forty subjects participated; each subject was tested in two treatment conditions. The attenuation results of each experiment were analyzed by statistical techniques. Statistical comparisons of results were made between the two experiments as well as between the experiments and selected field data. The major finding of the research was that fitting noise did not help subjects achieve higher attenuation [better protection] when consciously used for that purpose. Other findings indicated that novice subjects using only HPD manufacturer's instructions achieved attenuation that more closely represented the field attenuation than subjects tested under other conditions. However, the results were plug specific, in that no laboratory protocols yielded attenuation similar to the field data for the foam plug. / Master of Science

Certain U. S. and international consensus standards governing hearing protection device (HPD) attenuation testing specify the use of a diffuse sound field to ensure the sound field remains uniform and random-incidence in an envelope about the subject’s head (ANSI, 1974; ANSI, 1984; British BSI 5108:1983; Canadian CSA Z94.2-M1984; ISO 4869- 1:1990; Swedish SS 882151). However, there are very few experimental data to support these restrictive requirements. The research presented herein investigated this issue by applying three different environments in tests of the attenuation of four different hearing protectors (three earmuffs and one earplug) at each of nine 1/3 octave band frequencies centered at 125, 250, 500, 1000, 2000, 3150, 4000, 6300, and 8000 Hz. One testing environment comprised a reverberant room with three loudspeakers, one firing in each room plane, that met all the specifications for testing under ANSI S3.19-1974 (ANSI, 1974). The other two environments progressively degraded the diffusivity of the sound field through the use of a single loudspeaker and room surface treatment with absorptive panels. A psychophysical real-ear-attenuation-at-threshold procedure was used to obtain attenuation data. The results showed small, but statistically significant, differences in attenuation among the three environments for specific test frequencies. Due to their statistical significance, these differences preclude direct comparison of attenuation data obtained in these different environments, especially when the data are used for purposes such as technical design research, product comparison and/or labeling, and testing standards development. However, being of small magnitude, these differences are not great enough to prevent obtaining an estimation of the attenuation that an individual is achieving with a particular device under these alternative environments. With this in mind, the use of an industrial audiometric test booth may be beneficial for determining an individual worker’s protection levels actually achieved on the job. In sum, the interpretation of the results differs depending upon the intended purpose of the testing. / Master of Science