Helen Glyde

The effects of hearing impairment and aging on spatial processing.

Objectives: Difficulty in understanding speech in background noise is frequently reported by hearing-impaired people despite well-fitted amplification. Understanding speech in the presence of background noise involves segregating the various auditory stimuli into distinct streams using cues such as pitch characteristics, spatial location of speakers, and contextual information. One possible cause of listening difficulties in noise is reduced spatial-processing ability. Previous attempts to investigate spatial processing in hearing-impaired people have often been confounded by inadequate stimulus audibility. The present research aimed to investigate the effects of hearing impairment and aging on spatial-processing ability. The effect of cognitive ability on spatial processing was also explored. In addition, the relationship between spatial-processing ability and self-report measures of listening difficulty was examined to investigate how much effect spatial-processing ability has in real-world situations. Design: Eighty participants aged between 7 and 89 years took part in the study. Participants’ hearing thresholds ranged from within normal limits to a moderately severe sensorineural hearing loss. All participants had English as their first language and no reported learning disabilities. The study sample included both hearing aid users and non–hearing aid users. Spatial-processing ability was assessed with a modified version of the Listening in Spatialized Noise-Sentences test (LiSN-S). The LiSN-S was modified to incorporate a prescribed gain amplifier that amplified the target and distracting stimulus according to the National Acoustic Laboratories-Revised Profound (NAL-RP) prescription. In addition, participants aged 18 years and above completed the Neurobehavioral Cognitive Status examination and the Speech, Spatial and Qualities questionnaire. Participants aged under 18 years completed the Listening Inventory for Education questionnaire. Results: Spatial-processing ability, as measured by the spatial advantage measure of the LiSN-S, was negatively affected by hearing impairment. Aging was not significantly correlated with spatial-processing ability. No significant relationship was found between cognitive ability and spatial processing. Self-reported listening difficulty in children, as measured with the Listening Inventory for Education, and spatial-processing ability were not correlated. Self-reported listening difficulty in adults, as measured by the Speech, Spatial and Qualities questionnaire, was significantly correlated with spatial-processing ability. Conclusions: All hearing-impaired people will have a spatial processing deficit of some degree. This should be given due consideration when counseling patients in regard to realistic expectations of how they will perform in background noise. Further research is required into potential remediation for spatial-processing deficits and the cause of these deficits.

An opinion on the assessment of people who may have an auditory processing disorder.

We need to rethink how we assess auditory processing disorder (APD). The current use of test batteries, while necessary and well accepted, is at risk of failing as the size of these batteries increases. To counter the statistical, fatigue, and clinical efficiency problems of large test batteries, we propose a hierarchical approach to APD assessment. This begins with an overall test of listening difficulty in which performance is measurably affected for anyone with an impaired ability to understand speech in difficult listening conditions. It proceeds with a master test battery containing a small number of single tests, each of which assesses a different group of skills necessary for understanding speech in difficult listening conditions. It ends with a detailed test battery, where the individual tests administered from this battery are only those that differentiate the skills assessed by the failed test(s) from the master test battery, so that the specific form of APD can be diagnosed. An example of how hierarchical interpretation of test results could be performed is illustrated using the Listening in Spatialized Noise-Sentences test (LiSN-S). Although consideration of what abilities fall within the realm of auditory processing should remain an important issue for research, we argue that patients will be best served by focusing on whether they have difficulty understanding speech, identifying the specific characteristics of this difficulty, and specifically remediating and/or managing those characteristics.

Problems hearing in noise in older adults: a review of spatial processing disorder.

Difficulty understanding speech in background noise, even with amplification to restore audibility, is a common problem for hearing-impaired individuals and is especially frequent in older adults. Despite the debilitating nature of the problem the cause is not yet completely clear. This review considers the role of spatial processing ability in understanding speech in noise, highlights the potential impact of disordered spatial processing, and attempts to establish if aging leads to reduced spatial processing ability. Evidence supporting and opposing the hypothesis that spatial processing is disordered among the aging population is presented. With a few notable exceptions, spatial processing ability was shown to be reduced in an older population in comparison to young adults, leading to poorer speech understanding in noise. However, it is argued that to conclude aging negatively effects spatial processing ability may be oversimplified or even premature given potentially confounding factors such as cognitive ability and hearing impairment. Further research is required to determine the effect of aging and hearing impairment on spatial processing and to investigate possible remediation options for spatial processing disorder.

Listening in Spatialized Noise- Sentences Test (LiSN-S): Normative and retest reliability data for adolescents and adults up to 60 years of age

BACKGROUND The Australian version of the Listening in Spatialized Noise-Sentences Test (LiSN-S) was originally developed to assess auditory stream segregation skills in children aged 6 to 11 yr with suspected central auditory processing disorder. The LiSN-S creates a three-dimensional auditory environment under headphones. A simple repetition-response protocol is used to assess a listeners speech reception threshold (SRT) for target sentences presented in competing speech maskers. Performance is measured as the improvement in SRT in decibels gained when either pitch, spatial, or both pitch and spatial cues are incorporated in the maskers. PURPOSE To collect additional normative data on the Australian LiSN-S for adolescents and adults up to 60 yr of age, to analyze the effects of age on LiSN-S performance, to examine retest reliability in the older population, and to extrapolate findings from the Australian data so that the North American version of the test can also be used clinically with older adults. RESEARCH DESIGN In a descriptive design, normative and test-retest reliability data were collected from adolescents and adults and combined with previously published data from Australian children aged 6 to 11 yr. STUDY SAMPLE One hundred thirty-two participants with normal hearing aged 12 yr, 0 mo, to 60 yr, 7 mo, took part in the normative data study. Fifty-five participants returned between 2 and 4 mo after the initial assessment for retesting. RESULTS Analysis of variance revealed a significant effect of age on LiSN-S performance (p < .01 for all LiSN-S measures, ηp2 ranging from 0.16 to 0.54). On the low and high cue SRT measures, planned contrasts revealed significant differences between adults and children aged 13 yr and younger, as well as between 50- to 60-yr-olds and younger adults aged 18-29 yr. Whereas there were significant differences between adults and children on the talker, spatial, and total advantage measures, there were no significant differences in performance in adults aged 18-60 yr. There was a small but significant improvement on retest ranging from 0.5 to 1.2 dB across the four LiSN-S test conditions (p ranging from .01 to <.001). However, there was no significant difference between test and retest on the advantage measures (p ranging from .143 to .768). Test-retest differences across all LiSN-S measures were significantly correlated (r ranging from 0.2 to 0.7, p ranging from .023 to <.00000001) and did not differ as a function of age (p ranging from .178 to .980). CONCLUSIONS As there was no significant difference among adults aged 18-60 yr on the LiSN-S talker, spatial, and total advantage measures, it appears that the decline in ability to understand speech in noise experienced by 50- to 60-yr-olds is not related to their ability to use either spatial or pitch cues. This result suggests that some other factor/s contributes to the decline in speech perception in noise experienced by older adults that is reported in the literature and was demonstrated in this study on the LiSN-S low and high cue SRT measures.

The effect of better-ear glimpsing on spatial release from masking

The current experiment investigated whether better-ear glimpsing can explain the spatial release achieved by normal-hearing adults when situations are high in informational masking. Both modeling and behavioral methods were used. The speech reception thresholds of 38 young adults were measured for co-located, spatially separated and two better-ear glimpsed conditions. In the better-ear glimpsed conditions the binaural signals were processed so that in each time-frequency segment, the signal with the better SNR (left or right ear) was presented diotically. To investigate the effect of widening auditory filters on better-ear glimpsing, adjacent frequency bands were combined in one of the better-ear glimpsing conditions. Twenty-two participants were tested with maskers high in informational masking, while 16 participants were tested with maskers lower in informational masking. The mean speech reception thresholds achieved in the glimpsed conditions were significantly worse than in the spatially separated condition. This suggests that better-ear glimpsing can explain some but not all of the observed spatial release from masking. The difference between performance in the spatially separated and glimpsed conditions was largest when informational masking was high, suggesting better-ear glimpsing may release energetic rather than informational masking. Reducing the number of frequency bands sampled had a small effect on performance.

The importance of interaural time differences and level differences in spatial release from masking

Numerous studies have described improvements in speech understanding when interaural time differences (ITDs) and interaural level differences (ILDs) are present. The present study aimed to investigate whether either cue in isolation can elicit spatial release from masking (SRM) in a speech-on-speech masking paradigm with maskers positioned symmetrically around the listener. Twelve adults were tested using three presentations of the Listening in Spatialized Noise-Sentences Test, with each presentation modified to contain different interaural cues in the stimuli. Results suggest that ILDs provide a similar amount of SRM as ITDs and ILDs combined. ITDs alone provide significantly less benefit.

Efficacy of the LiSN & Learn auditory training software: randomized blinded controlled study

Children with a spatial processing disorder (SPD) require a more favorable signal-to-noise ratio in the classroom because they have difficulty perceiving sound source location cues. Previous research has shown that a novel training program - LiSN & Learn - employing spatialized sound, overcomes this deficit. Here we investigate whether improvements in spatial processing ability are specific to the LiSN & Learn training program. Participants were ten children (aged between 6;0 [years;months] and 9;9) with normal peripheral hearing who were diagnosed as having SPD using the Listening in Spatialized Noise - Sentences test (LiSN-S). In a blinded controlled study, the participants were randomly allocated to train with either the LiSN & Learn or another auditory training program - Earobics - for approximately 15 min per day for twelve weeks. There was a significant improvement post-training on the conditions of the LiSN-S that evaluate spatial processing ability for the LiSN & Learn group (P=0.03 to 0.0008, η2=0.75 to 0.95, n=5), but not for the Earobics group (P=0.5 to 0.7, η2=0.1 to 0.04, n=5). Results from questionnaires completed by the participants and their parents and teachers revealed improvements in real-world listening performance post-training were greater in the LiSN & Learn group than the Earobics group. LiSN & Learn training improved binaural processing ability in children with SPD, enhancing their ability to understand speech in noise. Exposure to non-spatialized auditory training does not produce similar outcomes, emphasizing the importance of deficit-specific remediation.

Prevalence and remediation of spatial processing disorder (SPD) in Indigenous children in regional Australia

Abstract Objective: This study aimed to determine the prevalence of spatial processing disorder (SPD) in the Indigenous Australian population and the benefit of and logistical issues arising from remediation of the disorder. Design: Participants were assessed for SPD with the Listening in Spatialized Noise – Sentences test (LiSN-S). Participants diagnosed with SPD were instructed to use the LiSN & Learn auditory training software until 100 games had been completed. Study sample: Participants were 144 Indigenous Australian children (aged between 6;0 [years;months] and 12;2). Results: Ten participants (6.9%) presented with SPD. Nine took part in the auditory training study. Post-training LiSN-S performance improved on average by 0.9 population standard deviations (1.4 dB). There was a significant correlation (r = 0.71, p = 0.031, η2 = 0.51) between total number of LiSN & Learn games played (mean = 65, SD = 27) and improvement in LiSN-S performance. Teachers rated all participants as improving in their listening abilities post-intervention. Conclusions: There is a high prevalence of SPD in the Indigenous Australian population. LiSN & Learn training is effective in remediating SPD in this population and is considered a beneficial intervention by teachers, however improvement in spatial processing is dependent on training program uptake.

Results from a National Central Auditory Processing Disorder Service: A Real-World Assessment of Diagnostic Practices and Remediation for Central Auditory Processing Disorder

This article describes the development and evaluation of a national service to diagnose and remediate central auditory processing disorder (CAPD). Data were gathered from 38 participating Australian Hearing centers over an 18-month period from 666 individuals age 6, 0 (years, months) to 24, 8 (median 9, 0). A total of 408 clients were diagnosed with either a spatial processing disorder (n = 130), a verbal memory deficit (n = 174), or a binaural integration deficit (n = 104). A hierarchical test protocol was used so not all children were assessed on all tests in the battery. One hundred fifty clients decided to proceed with deficit-specific training (LiSN & Learn or Memory Booster) and/or be fitted with a frequency modulation system. Families were provided with communication strategies targeted to a childs specific listening difficulties and goals. Outcomes were measured using repeat assessment of the relevant diagnostic test, as well as the Client Oriented Scale of Improvement measure and Listening Inventories for Education teacher questionnaire. Group analyses revealed significant improvements postremediation for all training/management options. Individual posttraining performance and results of outcome measures also are discussed.

Comparison of two working memory test paradigms: Correlation with academic performance in school-aged children

The purpose of this study was to examine the relationship between two different working memory task paradigms and academic achievement. Participants were 202 Australian primary-school children who were assessed on the Complex Auditory Span Evaluation (CASE) - a dual-task paradigm - and a reverse digit span paradigm, the number memory reversed test (NMR). Performance was correlated against the participants’ National Assessment Program - Literacy and Numeracy (NAPLAN) results. Both the CASE and NMR were significant predictors of academic ability in literacy and numeracy. Whereas there was a significant correlation between the CASE and NMR, the relationship was weak (r=0.18, p=0.012). It was concluded that, although both types of test are related to academic achievement, NMR and dual-task paradigm tasks may be differentially sensitive to the working memory abilities required in different real-world situations. This result has implications for use of such tasks to predict academic performance.