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ABSTRACT Background: Accessibility to reliable and cost-effective assessment of auditory processing skills is limited in South Africa. With the development of tele-audiology, tools such as the Feather Squadron (FS) application have been developed to make this form of assessment more cost-effective and accessible. Purpose: To determine whether the performance on the FS correlates with performance on certain traditional assessment tasks, viz. Frequency Pattern Test (FPT) and Dichotic Digits Test (DDT), to establish its relevance in a South African population. Design: A retrospective, within-subject, comparative design was used. Study Sample: 66 South African participants, aged between 8 and 9 years of age and educated in English. Method: The FS, FPT and DDT were administered following a peripheral hearing assessment. The data were considered in two ways: Firstly, by comparing whether in each instance the participant had scored either at or below -2SD or whether they had scored above-2SD on the subtests of the FS and compared these scores to the same traditional tests, and secondly, by comparing the Z-scores obtained on the FS versus the Z-scores obtained on the same traditional test by applying a double arcsine transformation. Results: Using the -2SD criteria yielded no significant association when comparing the Dichotic Digits FS vs Dichotic Digits traditional test, or when comparing Tonal-Pattern Temporal Processing FS vs FPT in the humming or labelling conditions. Using the Z-score comparison, a statistically significant correlation was obtained when comparing the Tonal-Pattern Temporal Processing FS vs FPT, labelling condition and Dichotic Double-Words FS (linguistic) vs DDT. Conclusions: There is sufficient early evidence to suggest a statistically significant correlation between certain subtests of the FS with traditional tests of auditory processing to merit its use in the South African population. Further, using the broad pass/fail criteria of -2SD lacks the precision to adequately identify patterns of response and may need to be re-evaluated. Key Words: Feather Squadron, dichotic digits, frequency pattern, auditory processing, South Africa. / Dissertation (MA (Audiology)) University of Pretoria, 2020. / 2022/12/31 / Speech-Language Pathology and Audiology / MA (Audiology) / Restricted

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For individuals with Autism Spectrum Disorder or ‘ASD’ the ability to accurately process and interpret auditory information is often difficult. Here we review behavioural, neurophysiological and neuroimaging literature pertaining to the field of auditory processing in ASD, with the aim of providing a comprehensive account of auditory processing in this population and thus an effective tool to aid further research. Literature was sourced from peer-reviewed journals published over the last two decades which best represent research conducted in these areas. Findings show substantial evidence for atypical processing of auditory information in ASD. Behavioural studies provide support for widespread abnormalities ranging from atypical perception of various low-level perceptual features (i.e. pitch) to processing of more complex auditory information such as prosody. Magnetic resonance imaging studies have identified functional abnormalities to a range of auditory stimuli in ASD while structural abnormalities have been observed in several brain regions implicated in auditory processing. Electrophysiological research has found evidence for atypical auditory processing within the cortex and brainstem of individuals with ASD in a variety of experimental paradigms. Trends across studies suggest auditory processing impairments in ASD are more likely to present during processing of complex auditory information and are more severe for speech than for non-speech stimuli. Moreover, atypical auditory processing in ASD may not always be viewed as an impairment and in some cases may reflect the use of a compensatory strategy to make sense of auditory information. To this end, there is an urgent need for further research aimed at understanding the behavioural and neural basis of auditory processing in ASD.

Objective: The primary purpose of this study was to determine the influence of high frequency peripheral hearing loss on test performance on the University of Canterbury Adaptive Speech Test – Filtered Words (UCAST-FW). We also aimed to investigate (1) if there is an ear advantage in performing the UCAST-FW; (2) whether there is any correlation between the UCAST-FW score and age; (3) the effectiveness of a binaural practice run in reducing the learning effect; and (4) the average time required for older adults to complete the UCAST-FW. Method: A total of 18 participants with normal hearing (≤ 25 dB Hearing Level (HL) at octave intervals of 250 through 4000 Hz in both ears) and 19 participants with varying degrees of high frequency sensorineural hearing loss (>25 dB HL at frequencies above 1000 Hz) were included in this study. All participants were native New Zealand English speakers, aged between 55-71 years, with normal low frequency hearing (≤25 dB at 250, 500 and 1000 Hz), had speech scores consistent with their audiogram, normal cognition and judged by the examiner to be capable of completing test protocols in terms of sufficient eyesight, alertness and motor control. Participants underwent a full diagnostic hearing test, the Montreal Cognitive Assessment, the Dichotic Digits Test, the Random Gap Detection Test and the UCAST-FW. Results: Findings indicated that the presence of a high frequency peripheral hearing loss had no significant influence on the UCAST-FW score. Findings also showed no significant ear advantage, or any trend between the participant’s UCAST-FW score and their age. A binaural practice run comprised of 5 initial and 15 working reversals was effective in reducing any learning effect. The UCAST-FW took an average of 15 minutes to complete, and the results showed no correlation between the test completion time and the participant’s age. Conclusion: Findings suggested that the listener’s high frequency peripheral hearing sensitivity had no significant influence on their UCAST-FW score and thus the UCAST-FW can potentially be an effective test for assessing Auditory Processing Disorder (APD) in older adults and the elderly regardless of their high frequency peripheral hearing sensitivity. The development of test material in New Zealand English, as well as the investigation of the validity of the UCAST-FW in assessing APD in older adults and the influence of cognitive functioning on test performance is necessary before the UCAST-FW can be implemented in New Zealand clinical Audiology settings.

INTRODUCTION: Adults with hearing loss who report difficulty understanding speech with and without hearing aids often also report increased mental or listening effort. Although speech recognition measures are well known and have been in use for decades, measures of listening effort are relatively new and include objective measures such as working memory tasks, pupillometry, heart rate, skin conductance, and brain imaging. OBJECTIVES: The purpose of this study is to evaluate an electroencephalogram (EEG)-based method to assess cognitive states during a speech in noise perception task. METHODS: High frequency alpha (11-13 Hz), low frequency alpha (8-10 Hz), and theta (4-7 Hz) frequencies were assessed with EEG during the Words-In-Noise test that utilizes seven different signal-to-noise ratios (SNR). Changes in high frequency alpha have been associated with cognitive demands and low frequency alpha has been associated with cognitive inhibition. Changes in theta have been associated with encoding information and increased listening effort. RESULTS: Results from the current study indicate a strong negative correlation between self-reported listening effort and speech in noise word recognition performance. Low frequency alpha power results suggest a power curve reflecting a point of maximum cognitive inhibition as a function of SNR. Results for high frequency alpha power show possible increased cognitive demand in lower SNR. Theta frequency shows no effect of SNR. DISCUSSION: Low frequency alpha results show a possible role of cognitive inhibition in words-in-noise speech recognition. High frequency alpha results show that lower signal-to-noise ratio conditions could increase cognitive demand. The EEG methodology used to measure theta may not be optimal to capture signal-to-noise changes. Understanding the neurological underpinnings of these frequencies could assist in the future development of an objective clinical tool to measure listening effort in patients with and without hearing loss.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder in which individuals demonstrate deficits in social communication and repetitive or restricted behaviors or interests. About one-third never attain fluent expressive language and remain minimally or low verbal (ASD-MLV). We hypothesized that central auditory processing is particularly disrupted in ASD-MLV given the shared neural substrates of sound processing and language. To address this hypothesis, we conducted four empirical studies designed to capture neural and behavioral correlates of central auditory processing in children and adolescents who were either typically developing (TD), verbally fluent with ASD (ASD-V), or ASD-MLV. Our first study established that adult-like neural indices of sound organization as measured by mismatch responses (MMRs) during a passive stream segregation task were not observable until adolescence in TD participants, ages 3 to 21 (N=65). Findings led us to focus subsequent studies on adolescents. In our second study, we conducted a meta-analysis of experiments that had compared MMRs between TD and ASD samples (N=721). We identified that while there was some evidence suggesting that perceptual sound organization (as evidenced by MMR) was more dysfunctional in those with ASD, more research was needed to validate this pattern in adolescents and low verbal samples. In our third study (N=83), we determined that atypical auditory behaviors occurred most often in those with ASD with combined expressive and receptive language impairments; furthermore, the percentage of time exhibiting such behaviors was associated with weaker MMRs. In our final study (N=74), we quantified neural orienting responses to one’s own name in a multispeaker setting – a task that requires higher-order stream segregation and social auditory attention – in adolescents. We found that responses were weaker in ASD-MLV compared to ASD-V and TD participants. In addition, strength of response in those with ASD was negatively correlated with parent-reported signs of auditory-specific attentional deficits, as measured by the Short Sensory Profile Auditory Filtering Subscale. With this dissertation, we found atypical neural indices of auditory processing in ASD-MLV adolescents and discuss theoretical implications for why central auditory processing might be particularly pronounced in the ASD-MLV phenotype. / 2022-01-30T00:00:00Z

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