Prudence Allen

Contralateral inhibition of distortion product otoacoustic emissions in children with auditory processing disorders

Abstract Objective: The purpose of this study was to evaluate changes in distortion product otoacoustic emission (DPOAE) level elicited by contralateral noise in children with normal hearing, and those with auditory processing disorders (APD) whose audiometric thresholds were normal. It was hypothesized that children with APD would demonstrate smaller changes. Design: Levels of DPOAEs were recorded for f2 stimulus tones fixed at 2, 3, and 4 kHz while the f1 tone was ramped around nominal stimulus frequency ratios of f2/f1 = 1.22 and 1.10. Mean and maximum absolute changes resulting from contralateral broadband noise presented at 60 dB SPL were evaluated across the DPOAE frequency bands for each individual and for both groups of subjects. Study sample: Eight normal-hearing children and eight children with APD whose audiometric thresholds were normal participated. Results: There were no significant differences in DPOAE inhibition between normal hearing and APD groups, or previously recorded adult data. Mean absolute changes were typically near 1 dB, except for f2 = 4 kHz and the stimulus frequency ratio 1.22 where inhibition was only 0.5 dB. However, there were individual children in both groups who demonstrated larger DPOAE changes for some stimulus parameters. Conclusions: The inhibition of otoacoustic emissions requires further study in APD children. Sumario Objetivo: El propósito de este estudio fue evaluar los cambios en el nivel de las emisiones otoacústicas por productos de distorsión (DPOAE) generados por ruido contralateral, en niños con audición normal y en aquellos con trastornos de procesamiento auditivo (APD), cuyos umbrales audiométricos era normales. Se planteó la hipótesis que los niños con ADP demostrarían cambios menores. Diseño: Se registraron los niveles de DPOAE para tonos de estímulo f2 fijos a 2, 3 y 4 KHz, mientras que el f1 fue colocado cercano a tasas nominales de frecuencia del estímulo f1/f2 = 1.22 y 1.10. Los cambios medios y máximos absolutos que resultaron del ruido de banda ancha contralateral a 60 dB SPL fueron evaluados en todas las bandas de frecuencias de las DPOAE para cada individuo y para ambos grupos de sujetos. Muestra del Estudio: Participaron ocho niños con audición normal y ocho niños con APD, cuyos umbrales audiométricos eran normales. Resultados: No hubo diferencias significativas en la inhibición de las DPOAE entre los grupos con audición normal y con APD, o con información de adultos previamente registrada. Los cambios medios absolutos estuvieron típicamente cerca de 1 dB, excepto para f2 = 4 kHz, para la tasa de frecuencia del estímulo de 1.22, donde la inhibición fue solo 0.5 dB. Sin embargo, hubo niños individuales en ambos grupos que demostraron cambios mayores en DPOAE para algunos parámetros de estímulo. Conclusiones: La inhibición de las emisiones otoacústicas requiere de más estudio en niños con APD.

Multidimensional scaling of complex sounds by school-aged children and adults

A paired-comparisons procedure was used to evaluate the processing of complex, nonspeech sounds by 7- and 10-year-old children and adults. Stimuli were brief duration and included pure tones, harmonic complexes, and bands of noise. From their similarity ratings, a three-dimensional multidimensional scaling solution was derived. Results suggested that listeners classified the stimuli into clusters based upon periodicity and the number of spectral peaks. Within each cluster, the stimuli were ordered according to frequency. Because individual differences in the overall weightings of features were large, separate solutions were derived for two subgroups of listeners, formed based upon similarities in the pattern of dimension weights obtained in the group analysis. One subgroup, for whom the full group analysis captured a large proportion of the variance in the ratings, included the adults, many of the 10-year-olds, and a few of the 7-year-olds. The solution derived for this subgroup suggested that spectral and temporal information were weighted equally and integrated into all dimension weights. Frequency information was coded but given less weight and was not used for stimulus classification. A second subgroup of listeners included most of the 7-year-old and some of the 10-year-old children. Examination of their data suggested that they relied heavily on an analysis of the signals according to periodicity as was reflected in their temporal fine structure. Also encoded but of lesser importance were aspects of spectral shape and absolute frequency.

Development of auditory information integration abilities

The ability of normal-hearing children (aged 4 through 7 years) and adults to integrate information was measured in an auditory sample discrimination task. On each trial a pair of tonal sequences was played whose component frequencies were randomly drawn from two equal-variance, Gaussian distributions with different means. The listeners task was to identify the sequence drawn from the distribution with the higher mean frequency. Performance was first evaluated as a function of the number of components in each sequence. Results showed that discrimination accuracy improved with increasing age until age 7, at which time performance was adult-like. The 7-year-olds and the adults discriminated the sequences with increasing accuracy as the sequence length was increased, but the 4-to 6-year-old listeners, as a group, did not. Data were fitted with a model with two free parameters, one representing resolution of the components and presumed to reflect peripheral processing, and another representing central noise added to the decision process after the component information is combined [R. Lutfi, J. Acoust. Soc. Am. 86, 934-944 (1989)]. On average, both parameters showed gradual changes as age increased, with adult-like values by 7 years of age. Individual data however suggest that the changes in central noise with age may be less gradual than the changes in peripheral resolution. In a second condition, increases in component duration produced improved performance for the 7-year-olds and the adults, while that of the younger listeners remained the same. Fitted parameters suggested improvements in component resolution for the older children, with no changes in central noise levels. In a third condition, reducing the overlap in the distributions improved performance for only a few of several younger children. This improvement was attributable to lower levels of central noise. Overall, these results suggest that with increasing age children are better able to discriminate between sounds that are variable and have overlapping acoustic characteristics. This age-related improvement may be attributed both to improvements in the ability to resolve the components and to reductions in central noise.

Temporal resolution in preschool children

An adaptive three‐alternative forced‐choice paradigm, in the form of a video game, was used to test auditory temporal processing skills in young children. Thirty children between the ages of three and seven were asked to detect a temporal gap in a burst of octave band noise, centered at 400 or 2000 Hz. The minimum detectable gap (gap threshold) was estimated by taking the median of the threshold estimates from at least three 20‐trial adaptive runs. While the variability in the median threshold estimates was substantial, the data suggest that low‐frequency gap thresholds were higher for the children than for adults, with the younger children producing higher thresholds. High‐frequency gap thresholds were comparable to adult values for all children. All the individual adaptive runs were “adult‐like,” suggesting that the subjects were concentrating on the task. However, run‐to‐run variability, as well as subject‐to‐subject variability, was high. It seemed that the children had “good days” and “bad days,” and that the younger children were more influenced by these variations than their older colleagues. [Work supported by NICHD Grant 5 P30 HD03352.]

Auditory processing disorders: Relationship to cognitive processes and underlying auditory neural integrity

BACKGROUND Auditory processing disorder (APD) in children has been reported and discussed in the clinical and research literature for many years yet there remains poor agreement on diagnostic criteria, the relationship between APD and cognitive skills, and the importance of assessing underlying neural integrity. PURPOSE The present study used a repeated measures design to examine the relationship between a clinical APD diagnosis achieved with behavioral tests used in many clinics, cognitive abilities measured with standardized tests of intelligence, academic achievement, language, phonology, memory and attention and measures of auditory neural integrity as measured with acoustic reflex thresholds and auditory brainstem responses. METHOD Participants were 63 children, 7-17 years of age, who reported listening difficulties in spite of normal hearing thresholds. Parents/guardians completed surveys about the childs auditory and attention behavior while children completed an audiologic examination that included 5 behavioral tests of auditory processing ability. Standardized tests that examined intelligence, academic achievement, language, phonology, memory and attention, and objective tests auditory function included crossed and uncrossed acoustic reflex thresholds and auditory brainstem responses (ABR) were also administered to each child. RESULTS Forty of the children received an APD diagnosis based on the 5 behavioral tests and 23 did not. The groups of children performed similarly on intelligence measures but the children with an APD diagnosis tended to perform more poorly on other cognitive measures. Auditory brainstem responses and acoustic reflex thresholds were often abnormal in both groups of children. SUMMARY Results of this study suggest that a purely behavioral test battery may be insufficient to accurately identify all children with auditory processing disorders. Physiologic test measures, including acoustic reflex and auditory brainstem response tests, are important indicators of auditory function and may be the only indication of a problem. The results also suggest that performance on behavioral APD tests may be strongly influenced by the childs language levels.

Distortion product otoacoustic emission contralateral suppression functions obtained with ramped stimuli

The purpose of this research was to investigate the changes that occur in human distortion product otoacoustic emission (DPOAE) level functions over continuous frequency bands in response to activation of the medial olivocochlear (MOC) efferent system by contralateral broadband noise. DPOAEs were obtained using continuous upward ramps of the lower frequency tone (f(1)) while the higher frequency tone (f(2)) was fixed. These ramps were designed to change the stimulus frequency ratio f(2)/f(1) over a fixed range for each fixed f(2) value of 2, 3, and 4 kHz. Contralateral noise was presented on alternating ramps and the DPOAEs with and without contralateral noise were averaged separately. Stimulus frequency ratios of 1.10 and 1.22, and noise levels of 60 and 50 dB sound pressure level (SPL) were employed. Changes in DPOAE level were generally suppression (a reduction in DPOAE magnitude), but enhancement was also observed. For most participants, changes were evident for much of the frequency ranges tested. Average absolute changes for 60 dB SPL noise were 0.95, 0.81, and 0.42 dB for the wider stimulus frequency ratios and f(2) of 2, 3, and 4 kHz, respectively. For the narrower ratio and 60 dB SPL noise, the changes were larger with average absolute changes of 1.33, 1.09, and 0.87 dB. For the narrower ratio and 50 dB SPL noise, the changes were 1.08, 0.78, and 0.55 dB with f(2) of 2, 3, and 4 kHz, respectively. DPOAE nulls were observed and a common response pattern was a shift of emission morphology to higher frequencies with contralateral acoustic stimulation. The method appears promising for relatively rapid evaluation of the MOC efferent system in humans and offers information complementary to measurement strategies that explore the effects of stimulus level.

Cochlear Delay and Medial Olivocochlear Functioning in Children with Suspected Auditory Processing Disorder

Behavioral manifestations of processing deficits associated with auditory processing disorder (APD) have been well documented. However, little is known about their anatomical underpinnings, especially cochlear processing. Cochlear delays, a proxy for cochlear tuning, measured using stimulus frequency otoacoustic emission (SFOAE) group delay, and the influence of the medial olivocochlear (MOC) system activation at the auditory periphery was studied in 23 children suspected with APD (sAPD) and 22 typically developing (TD) children. Results suggest that children suspected with APD have longer SFOAE group delays (possibly due to sharper cochlear tuning) and reduced MOC function compared to TD children. Other differences between the groups include correlation between MOC function and SFOAE delay in quiet in the TD group, and lack thereof in the sAPD group. MOC-mediated changes in SFOAE delay were in opposite directions between groups: increase in delay in TD vs. reduction in delay in the sAPD group. Longer SFOAE group delays in the sAPD group may lead to longer cochlear filter ringing, and potential increase in forward masking. These results indicate differences in cochlear and MOC function between sAPD and TD groups. Further studies are warranted to explore the possibility of cochlea as a potential site for processing deficits in APD.

Stimulus set effects in the similarity ratings of unfamiliar complex sounds

This study examined the effect of the distribution of values for various acoustic properties on the similarity ratings obtained in a paired-comparison study of complex sounds. Listeners rated the similarity of tones and tone complexes in one of four sets. Across the four sets both component frequency and the number of components in the stimuli were drawn from distributions that were either categorical or noncategorical. Other acoustic properties were distributed similarly in all sets. Solutions suggested that frequency was most important to the ratings, followed by the number of components in each critical band. Results suggest that when the values of an acoustic property are distributed categorically, its importance to similarity ratings increases relative to that observed with a less categorical distribution.

Impact of classroom noise on reading and vocabulary skills in elementary school‐aged children

Classroom noise levels often exceed recommendations and, in large scale retrospective studies, it has been suggested that higher noise levels often correlate significantly with poorer academic performance [e.g., Shield., et al. (2002)]. However, experimental data on the performance of individual children are limited. This study therefore examined the effect of noise on the performance of children in grades 3–4 and 7–8 on standardized tests of oral reading, silent reading, and vocabulary (the Gray Oral Reading Test, the Gray Silent Reading Test, and the Peabody Picture Vocabulary Test). Each child completed parallel forms of a test in quiet and in classroom noise presented at 60 dB SPL. Required speech was presented at +10 S/N. Results from grouped data showed significantly reduced performance in noise only on the silent reading task and only for the older group of children. However, across tasks, when the effects of noise were evaluated as a function of childrens quiet performance levels, the noise effect...

Spectral pattern discrimination in children

This research measured the ability of 47 children, aged 4-9 years, to use spectral shape cues to discriminate among random-intensity sounds. The children were tested in forced-choice paradigms that were embedded in a video game format. Two classes of sounds were studied: tonal complexes with sinusoidally rippled amplitude spectra, and synthetic speech sounds (isolated vowels and consonants). The discriminability of the sounds was measured both in quiet and in a background of wide-band noise. Although the intersubject variability in performance was high, especially among the youngest children, the results revealed a substantial age effect. For both classes of sounds, the performance of the younger children was significantly poorer than the performance of an adult control group. However, there was no evidence in the data that the masking effect of the noise was greater for the children than for the adults.