Ten experiments examined the interactions between vision and audition in stimulusdriven spatial attention orienting and inhibition of return (IOR). IOR is the demonstration that subjects are slower to respond to stimuli that are presented at a previously stimulated location. In each experiment, subjects made go/no-go responses to peripheral targets but not to central targets. On every trial, a target was preceded by a sensory event, called a "cue," either in the same modality (intramodal conditions) or in a different modality (crossmodal conditions). The cue did not predict the location of the target stimulus in any experiment. In some experiments, the cue and target modalities were fixed and different. Under these conditions, response times to a visual target were shorter when it appeared at the same location as an auditory cue than when it appeared on the opposite side of fixation, particularly at short (100 ms) cue-target stimulus onset asynchronies (Experiments 1A and IB). Similarly, response times to an auditory target were shorter when it appeared at the same location as a visual cue than when it appeared at a location on the opposite side of fixation (Experiments 2A and 2B). These crossmodal effects indicate that stimulus-driven spatial attention orienting might arise from a single supramodal brain mechanism. IOR was not observed in either crossmodal experiment indicating that it might arise from modality specific mechanisms. However, for many subjects, IOR did occur between auditory cues and visual targets (Experiments 3A and 3B) and between visual cues and auditory targets (Experiment 4A and 4B) when the target could appear in the same modality as the cue on half of the trials. Finally, the crossmodal effects of stimulus-driven spatial attention orienting on auditory and visual event-related brain potentials (ERPs) were examined in the final two experiments. Auditory cues modulated the ERPs to visual targets and visual cues modulated the ERPs to auditory targets, demonstrating that the mechanisms for spatial attention orienting cannot be completely modality specific. However, these crossmodal ERP effects were very different from each other indicating that the mechanisms for spatial attention orienting cannot be completely shared.

Thesis (M. Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 37-41).

Ten experiments examined the interactions between vision and audition in stimulusdriven spatial attention orienting and inhibition of return (IOR). IOR is the demonstration that subjects are slower to respond to stimuli that are presented at a previously stimulated location. In each experiment, subjects made go/no-go responses to peripheral targets but not to central targets. On every trial, a target was preceded by a sensory event, called a "cue," either in the same modality (intramodal conditions) or in a different modality (crossmodal conditions). The cue did not predict the location of the target stimulus in any experiment. In some experiments, the cue and target modalities were fixed and different. Under these conditions, response times to a visual target were shorter when it appeared at the same location as an auditory cue than when it appeared on the opposite side of fixation, particularly at short (100 ms) cue-target stimulus onset asynchronies (Experiments 1A and IB). Similarly, response times to an auditory target were shorter when it appeared at the same location as a visual cue than when it appeared at a location on the opposite side of fixation (Experiments 2A and 2B). These crossmodal effects indicate that stimulus-driven spatial attention orienting might arise from a single supramodal brain mechanism. IOR was not observed in either crossmodal experiment indicating that it might arise from modality specific mechanisms. However, for many subjects, IOR did occur between auditory cues and visual targets (Experiments 3A and 3B) and between visual cues and auditory targets (Experiment 4A and 4B) when the target could appear in the same modality as the cue on half of the trials. Finally, the crossmodal effects of stimulus-driven spatial attention orienting on auditory and visual event-related brain potentials (ERPs) were examined in the final two experiments. Auditory cues modulated the ERPs to visual targets and visual cues modulated the ERPs to auditory targets, demonstrating that the mechanisms for spatial attention orienting cannot be completely modality specific. However, these crossmodal ERP effects were very different from each other indicating that the mechanisms for spatial attention orienting cannot be completely shared. / Arts, Faculty of / Psychology, Department of / Graduate

Photocopy of typescript. / Digitized by Kansas Correctional Industries

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / abstract / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

Com a obrigatoriedade da triagem auditiva neonatal universal a partir do ano de 2010 em todo território brasileiro, maior número de crianças estão sendo submetidas ao diagnóstico audiológico logo nos primeiros meses de idade. O Potencial Evocado Auditivo de Tronco Encefálico e o Potencial Evocado Auditivo de Estado Estável são amplamente utilizados para fechamento do diagnóstico audiológico nesta idade, já que auxiliam na caracterização da perda auditiva quanto ao grau, tipo e configuração. Os estímulos utilizados nestes procedimentos apresentam limitações inerentes às características acústicas de cada um e devem ser consideradas pelo profissional no momento de analisar os resultados obtidos. Diante disso, o objetivo deste trabalho foi analisar comparativamente a aplicabilidade do estímulo Narrow Band CE-Chirp® para predizer os limiares psicoacústicos nas perdas auditivas sensorioneurais de graus severo e profundo. Trata-se de um estudo prospectivo transversal, na qual foram avaliadas 28 crianças com perda auditiva neurossensorial com limiares superiores a 61 dBNA, idade entre 6 e 37 meses, sendo 15 do sexo feminino e 13 do sexo masculino. Os procedimentos utilizados foram: Potencial Evocado Auditivo de Tronco Encefálico com os estímulos tone burst e Narrow Band CE-Chirp®, Potencial Evocado Auditivo de Estado Estável e Audiometria com Reforço Visual ou Audiometria Lúdica Condicionada. Os resultados mostraram que os limiares eletrofisológicos no Potencial Evocado Auditivo de Tronco Encefálico foram mais próximos dos limiares psicoacústicos obtidos na Audiometria com Reforço Visual ou Audiometria Lúdica Condicionada quando utilizado o estímulo Narrow Band CE-Chirp® ao invés do tone burst. Na ausência de resposta no Potencial Evocado Auditivo de Tronco Encefálico com ambos os estímulos, observou-se que o Potencial Evocado Auditivo de Estado Estável realizado em intensidades fortes apresentou boa correlação com os limiares psicoacústicos, contudo, a utilização de forte intensidade deve ser cuidadosa nas frequências de 2000 e 4000 Hz para não se obter limiares eletrofisiológicos que não são reais. Conclui-se então, que, clinicamente, a utilização do PEATE com o estímulo Narrow Band CE-Chirp® mostrou limiares eletrofisiológicos mais próximos dos limiares psicoacústicos da Audiometria com Reforço Visual/ Audiometria Lúdica Condicionada do que quando o estímulo utilizado foi o tone burst. Ainda assim, mais estudos devem ser realizados para verificar os benefícios deste estímulo na população infantil e com alguma alteração auditiva. O Potencial Evocado Auditivo de Estado Estável, por utilizar estímulos em intensidades mais fortes, caracterizou a audição residual com precisão nas frequências de 500 e 1000 Hz. / With the requirement of universal newborn hearing screening from the year 2010, throughout the Brazilian territory, more children are undergoing audiologic diagnosis in their first months. The Brainstem Auditory Evoked Potential and the Steady State Evoked Potential are widely used for closing the audiologic diagnosis at this age, since they assist in the characterization of hearing loss as to the degree, type and configuration. The stimuli used in these procedures pose limitations inherent to the acoustic characteristics of each subject and should be taken into account by the professional analyzing the results. Therefore, this study aimed to compare the applicability of the Narrow Band CE-Chirp® stimulus to predict the psychoacoustic thresholds in severe and profound sensorineural hearing loss. This was a cross-sectional prospective study in which 28 children, being 15 females and 13 males, aged 6 to 37 months, presented with sensorineural hearing loss and with thresholds above 61 dBNA, were assessed. The used procedures were Brainstem Auditory Evoked Potential with tone burst stimuli and Narrow Band CE-Chirp®, Steady-state auditory evoked potential and audiometry with visual reinforcement or conditioned ludic audiometry. The results showed that the electrophysiological thresholds in the Brainstem Auditory Evoked Potential were closer to the psychoacoustic thresholds obtained in the visually reinforced audiometry or conditioned ludic audiometry when using the Narrow Band CE-Chirp® stimulus in lieu of the tone burst. In the absence of response in the Brainstem Auditory Evoked Potential with both stimuli, it was observed that the Steady State Auditory Evoked Potential performed at high intensities presented good correlation with the psychoacoustic thresholds, nevertheless, high intensity should be used with caution in the frequencies 2000 and 4000 Hz, for unreal electrophysiological thresholds not to be obtained. It was concluded that, clinically, the use of Brainstem Auditory Evoked Potential with the Narrow Band CE-Chirp® stimulus showed electrophysiological thresholds closer to psychoacoustic ones of the audiometry with visual reinforcement/conditioned ludic audiometry than when using the tone burst. Nevertheless, further studies should be performed to verify the benefits of this stimulus in children and with some hearing impairment. For using stimuli in higher intensities, the Steady-state auditory evoked potential characterized the residual hearing, accurately, at frequencies of 500 and 1000 Hz.

The purpose of this study was to determine whether the compression circuit of a hearing aid could be activated by a high frequency biasing tone such that its output for a transient stimulus could be made to approximate that of a continuous tone alone. Sufficient compression activation by a transient stimulus would mean that this type of hearing aid could be used in obtaining aided ABR measurements, since transient stimuli are commonly used for this procedure. Four hearing aids were used, and transient or continuous stimuli were introduced either alone or in combination with an 8 or 10 kHz biasing tone. The biasing tone was either held at one constant level or varied in intensity along with the transient or continuous signal.

In this study, I looked at the effects of sound level, temperature and dehydration/hypernatremia on the brainstem auditory evoked potential (BAEP) of four species of anuran amphibians (Rana pipiens, Rana catesbeiana, Bufo americanus and Bufo terrestris). The BAEP was used because it allowed me to monitor both the peripheral and central aspects of auditory nervous function simultaneously and over a long period of time.