Astrid Van Wieringen

LIST and LINT: Sentences and numbers for quantifying speech understanding in severely impaired listeners for Flanders and the Netherlands

A Dutch sentence test (LIST) and a Dutch number test (LINT) have been developed and validated for the accurate measurement of speech reception thresholds (SRT) in quiet and in noise with severely hearing-impaired individuals and cochlear implant recipients in Flanders and the Netherlands. The LIST consists of 35 lists of 10 sentences of equal known difficulty uttered by a female speaker; while the LINT consists of 400 numbers (1–100) by two male and two female speakers. Normative values were determined at fixed S/N ratios and using the adaptive method (Plomp & Mimpen, ), yielding identical results for SRT and slope. For the LIST, average fitted SRTs were 27.1 (0.9) dB SPL in quiet and −7.8 dB (0.2) SNR in noise. In addition, the LIST in noise displayed a steep discrimination function (17%/dB) and good reliability (within-subject standard deviation=1.2 dB). For the LINT average fitted SRTs in quiet were 20.7 (0.9) dB SPL and about −9.0 dB SNR in noise. Again, the slopes of the performance intensity functions were relatively steep, i.e. 8.5%/dB in quiet and 15.2%/dB in noise, suggesting that the LINT is accurate and efficient and thus capable of reflecting subtle changes in performance. First data with cochlear implanted subjects show that both LIST and LINT are feasible and are capable of mapping a large range of hearing disabilities.

Modelling relations between sensory processing, speech perception, orthographic and phonological ability, and literacy achievement

The general magnocellular theory postulates that dyslexia is the consequence of a multimodal deficit in the processing of transient and dynamic stimuli. In the auditory modality, this deficit has been hypothesized to interfere with accurate speech perception, and subsequently disrupt the development of phonological and later reading and spelling skills. In the visual modality, an analogous problem might interfere with literacy development by affecting orthographic skills. In this prospective longitudinal study, we tested dynamic auditory and visual processing, speech-in-noise perception, phonological ability and orthographic ability in 62 five-year-old preschool children. Predictive relations towards first grade reading and spelling measures were explored and the validity of the global magnocellular model was evaluated using causal path analysis. In particular, we demonstrated that dynamic auditory processing was related to speech perception, which itself was related to phonological awareness. Similarly, dynamic visual processing was related to orthographic ability. Subsequently, phonological awareness, orthographic ability and verbal short-term memory were unique predictors of reading and spelling development.

Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System.

Objective: This paper evaluates the benefit of the two-microphone adaptive beamformer BEAM™ in the Nucleus Freedom™ cochlear implant (CI) system for speech understanding in background noise by CI users. Design: A double-blind evaluation of the two-microphone adaptive beamformer BEAM and a hardware directional microphone was carried out with five adult Nucleus CI users. The test procedure consisted of a pre- and post-test in the lab and a 2-wk trial period at home. In the pre- and post-test, the speech reception threshold (SRT) with sentences and the percentage correct phoneme scores for CVC words were measured in quiet and background noise at different signal-to-noise ratios. Performance was assessed for two different noise configurations (with a single noise source and with three noise sources) and two different noise materials (stationary speech-weighted noise and multitalker babble). During the 2-wk trial period at home, the CI users evaluated the noise reduction performance in different listening conditions by means of the SSQ questionnaire. In addition to the perceptual evaluation, the noise reduction performance of the beamformer was measured physically as a function of the direction of the noise source. Results: Significant improvements of both the SRT in noise (average improvement of 5–16 dB) and the percentage correct phoneme scores (average improvement of 10–41%) were observed with BEAM compared to the standard hardware directional microphone. In addition, the SSQ questionnaire and subjective evaluation in controlled and real-life scenarios suggested a possible preference for the beamformer in noisy environments. Conclusions: The evaluation demonstrates that the adaptive noise reduction algorithm BEAM in the Nucleus Freedom CI-system may significantly increase the speech perception by cochlear implantees in noisy listening conditions. This is the first monolateral (adaptive) noise reduction strategy actually implemented in a mainstream commercial CI.

Psychophysical evidence for a general temporal processing deficit in children with dyslexia

The hypothesis of a general (i.e. cross-modal) temporal processing deficit in dyslexia was tested by examining rapid processing in both the auditory and the visual system in the same children with dyslexia. Participants were 10- to 12-year-old dyslexic readers and age-matched normal reading controls. Psychophysical thresholds were estimated for auditory gap and visual double flash detection, using a two-interval, two-alternative forced-choice paradigm. Significant group differ- ences were found for the auditory and the visual test. Furthermore, temporal processing measures were significantly related to word and pseudo-word reading skills. As 70% of the dyslexic readers had significantly higher thresholds than controls for both auditory and visual temporal processing, the evidence tends to support the hypothesis of a general temporal processing deficit in children with dyslexia.

Auditory temporal information processing in preschool children at family risk for dyslexia : relations with phonological abilities and developing literacy skills

In this project, the hypothesis of an auditory temporal processing deficit in dyslexia was tested by examining auditory processing in relation to phonological skills in two contrasting groups of five-year-old preschool children, a familial high risk and a familial low risk group. Participants were individually matched for gender, age, non-verbal IQ, school environment, and parental educational level. Psychophysical thresholds were estimated for gap-detection, frequency modulation detection, and tone-in-noise detection using a three-interval forced-choice adaptive staircase paradigm embedded within a computer game. Phonological skills were measured by tasks assessing phonological awareness, rapid serial naming, and verbal short-term memory. Significant group differences were found for phonological awareness and letter knowledge. In contrast, none of the auditory tasks differentiated significantly between both groups. However, both frequency modulation and tone-in-noise detection were significantly related to phonological awareness. This relation with phonological skills was not present for gap-detection.

Earlier intervention leads to better sound localization in children with bilateral cochlear implants.

We present sound localization results from 30 children with bilateral cochlear implants. All children received their implants sequentially, at ages from 6 months to 9 years for the first implant and 1.5–12 years for the second implant, with delays of 10 months to 9 years. Localization was measured in the sound field, with a broadband bell-ring presented from 1 of 9 loudspeakers positioned in the frontal horizontal plane. The majority of the children (63%) were able to localize this signal significantly better than chance level. Mean absolute error scores varied from 9 to 51° (root mean square error scores from 13 to 63°). The best scores were obtained by children who received their first implant before the age of 2 years and by children who used hearing aids prior to implantation for a period of 18 months or longer. Age at second implantation was important in the group of children who did not use a contralateral hearing aid during the unilateral implant period. Additionally, children who attended a mainstream school had significantly better localization scores than children who attended a school for the deaf. No other child or implantation variables were related to localization performance. Data of parent questionnaires derived from the Speech, Spatial and Qualities of Hearing Scale were significantly correlated with localization performance. This study shows that the sound localization ability of children with bilateral cochlear implants varies across subjects, from near-normal to chance performance, and that stimulation early in life, acoustically or electrically, is important for the development of this capacity.

APEX 3: a multi-purpose test platform for auditory psychophysical experiments

APEX 3 is a software test platform for auditory behavioral experiments. It provides a generic means of setting up experiments without any programming. The supported output devices include sound cards and cochlear implants from Cochlear Corporation and Advanced Bionics Corporation. Many psychophysical procedures are provided and there is an interface to add custom procedures. Plug-in interfaces are provided for data filters and external controllers. APEX 3 is supported under Linux and Windows and is available free of charge.

Predictors of Spoken Language Development Following Pediatric Cochlear Implantation

Objectives: Although deaf children with cochlear implants (CIs) are able to develop good language skills, the large variability in outcomes remains a significant concern. The first aim of this study was to evaluate language skills in children with CIs to establish benchmarks. The second aim was to make an estimation of the optimal age at implantation to provide maximal opportunities for the child to achieve good language skills afterward. The third aim was to gain more insight into the causes of variability to set recommendations for optimizing the rehabilitation process of prelingually deaf children with CIs. Design: Receptive and expressive language development of 288 children who received CIs by age five was analyzed in a retrospective multicenter study. Outcome measures were language quotients (LQs) on the Reynell Developmental Language Scales and Schlichting Expressive Language Test at 1, 2, and 3 years after implantation. Independent predictive variables were nine child-related, environmental, and auditory factors. A series of multiple regression analyses determined the amount of variance in expressive and receptive language outcomes attributable to each predictor when controlling for the other variables. Results: Simple linear regressions with age at first fitting and independent samples t tests demonstrated that children implanted before the age of two performed significantly better on all tests than children who were implanted at an older age. The mean LQ was 0.78 with an SD of 0.18. A child with an LQ lower than 0.60 (= 0.78−0.18) within 3 years after implantation was labeled as a weak performer compared with other deaf children implanted before the age of two. Contralateral stimulation with a second CI or a hearing aid and the absence of additional disabilities were related to better language outcomes. The effect of environmental factors, comprising multilingualism, parental involvement, and communication mode increased over time. Three years after implantation, the total multiple regression model accounted for 52% of the variance in receptive language scores and 58% of the variance in expressive language scores. Conclusions: On the basis of language test scores of this large group of children, an LQ of 0.60 or lower was considered a risk criterion for problematic language development compared with other deaf children using CIs. Children attaining LQs below 0.60 should be monitored more closely and perhaps their rehabilitation programs should be reconsidered. Improved language outcomes were related to implantation under the age of two, contralateral stimulation, monolingualism, sufficient involvement of the parents, and oral communication by the parents. The presence of an additional learning disability had a negative influence on language development. Understanding these causes of variation can help clinicians and parents to create the best possible circumstances for children with CIs to acquire language.

Speech perception in preschoolers at family risk for dyslexia: Relations with low-level auditory processing and phonological ability

We tested categorical perception and speech-in-noise perception in a group of five-year-old preschool children genetically at risk for dyslexia, compared to a group of well-matched control children and a group of adults. Both groups of children differed significantly from the adults on all speech measures. Comparing both child groups, the risk group presented a slight but significant deficit in speech-in-noise perception, particularly in the most difficult listening condition. For categorical perception a marginally significant deficit was observed on the discrimination task but not on the identification task. Speech parameters were significantly related to phonological awareness and low-level auditory measures. Results are discussed within the framework of a causal model where low-level auditory problems are hypothesized to result in subtle speech perception problems that might interfere with the development of phonology and reading and spelling ability.

Spatial speech perception benefits in young children with normal hearing and cochlear implants.

Objectives: Several studies have demonstrated better speech perception performance in children using two rather than one cochlear implant (CI). The extent to which bilaterally implanted children benefit from binaural cues to segregate speech and noise in a spatial configuration is less clear. Although better-ear effects are expected to be similar to adults, it is unknown whether electrical stimulation allows true binaural processing of speech signals in noise. Moreover, little data are available on the binaural hearing abilities of normal-hearing children. This study aimed at (1) developing and evaluating a speech test based on numbers to determine speech reception thresholds (SRTs) fast and accurately in young children, (2) evaluating a setup for measuring benefits of speech perception in a spatial configuration in young children and determining normative values of normal-hearing children, and (3) measuring spatial speech benefits in cochlear-implanted children with good sound localization abilities. Design: The speech test was conducted using the Leuven Intelligibility Number Test (LINT) data base. The test was limited to the numbers 1 to 10 spoken by one female speaker (“LittleLINT”). The LINT speech-weighted noise was used as a masker. Perception of this speech material was evaluated at fixed signal-to-noise ratios (SNRs) through monaural presentation via headphones in 34 normal-hearing children of 4 and 5 yrs of age and 20 normal-hearing adults. Subsequently, spatial speech perception benefits were measured in 50 normal-hearing children between 4 and 8 yrs of age, 15 normal-hearing adults, and eight children with bilateral CIs. An adaptive procedure was used for estimating unilateral and bilateral SRTs for different spatial configurations of speech and noise. Speech was always presented at 0° azimuth (the front) and noise at the front, 90° to the right, or 90° to the left. Results: Unilateral headphone SRTs for the LittleLINT were higher for children (−9 dB SNR) than for adults (−13 dB SNR) and were lower than those for the LINT (−10 dB SNR for adults). Slopes (12 to 14%/dB) were comparable with that of the LINT (15%/dB), suggesting equal efficiency for the limited set of numbers. Normal-hearing subjects demonstrated several benefits of two-ear listening in spatial configurations (spatial release from masking [SRM], head shadow, summation, and squelch). Only SRM was influenced by age. Implanted children clearly benefited from bilateral implantation, as shown by SRM (3 dB) and head shadow effects (4 to 6 dB) comparable with normal-hearing children, but no summation or binaural squelch was established. The first CI seemed to contribute most to spatial speech perception. Conclusions: The steep slope, the familiarity to children, and the repeatability of lists make the LittleLINT suitable for fast and accurate SRT estimation in children. Spatial speech perception benefits were observed in normal-hearing subjects from the age of 4 yrs. Cochlear-implanted children showed better-ear effects but there was no evidence of true binaural processing.