Volume 25, Issue 3 - Special Issue: Israel Society for Auditory Research (ISAR) 2014 Annual Scientific Conference / Guest Editors: Karen B. Avraham and Karen Banai

Soft tissue conduction (STC) is a recently expounded mode of auditory stimulation in which the clinical bone vibrator delivers auditory frequency vibratory stimuli to skin sites on the head, neck, and thorax. Investigation of the mechanism of STC stimulation has served as a platform for the elucidation of the mechanics of cochlear activation, in general, and to a better understanding of several perplexing auditory phenomena. This review demonstrates that it is likely that the cochlear hair cells can be directly activated at low sound intensities by the fluid pressures initiated in the cochlea; that the fetus in utero, completely enveloped in amniotic fluid, hears by STC; that a speaker hears his/her own voice by air conduction and by STC; and that pulsatile tinnitus is likely due to pulsatile turbulent blood flow producing fluid pressures that reach the cochlea through the soft tissues.

Background: Active middle ear implants such as the vibrant sound bridge (VSB) have been placed on the round window (RW) in patients with conductive or mixed hearing loss, with satisfactory hearing results. Several observations show that the mechanism of RW stimulation is not completely understood. The purpose of the present study was to compare different coupling procedures between the transducer and the RW in order to contribute to an understanding of the mechanism of RW stimulation. Methods: Five fat sand rats underwent ablation of the left ear and opening of the right bulla, followed by baseline measurements of thresholds of auditory nerve brainstem evoked responses (ABR) to air and bone conduction click stimuli. Subsequently the malleus and incus were removed from the right middle ear, modeling a conductive hearing loss in which the VSB on the RW is indicated. In the next stage of the experiment, a rod attached to the bone vibrator was placed gently on the RW membrane and then on saline fluid applied to the RW niche. ABR thresholds were recorded following both placements. Results: Mean baseline ABR threshold in response to air conduction stimuli was 48±4 dB; mean ABR threshold when the rod was placed on the dry RW membrane was 99±12 dB; mean ABR threshold when the rod was in the saline on RW niche was 79±7 dB. Conclusions: ABR thresholds were better (lower) with stimulation of fluid on the RW membrane compared to direct stimulation of the RW, providing further evidence of a direct fluid pathway.

Background: The N1-P2 is an obligatory cortical response that can reflect the representation of spectral and temporal characteristics of an auditory stimulus. Traditionally, mean amplitudes and latencies of the prominent peaks in the averaged response are compared across experimental conditions. Analyses of the peaks in the averaged response only reflect a subset of the data contained within the electroencephalogram (EEG) signal. We used single-trial analyses techniques to identify the contribution of brain noise, neural synchrony, and spectral power to the generation of P2 amplitude and how these variables may change across age group. This information is important for appropriate interpretation of event-related potentials (ERPs) results and in understanding of age-related neural pathologies. Methods: EEG was measured from 25 younger and 25 older normal hearing adults. Age-related and individual differences in P2 response amplitudes, and variability in brain noise, phase locking value (PLV), and spectral power (4–8 Hz) were assessed from electrode FCz. Model testing and linear regression were used to determine the extent to which brain noise, PLV, and spectral power uniquely predicted P2 amplitudes and varied by age group. Results: Younger adults had significantly larger P2 amplitudes, PLV, and power compared to older adults. Brain noise did not differ between age groups. The results of regression testing revealed that brain noise and PLV, but not spectral power were unique predictors of P2 amplitudes. Model fit was significantly better in younger than in older adults. Conclusions: ERP analyses are intended to provide a better understanding of the underlying neural mechanisms that contribute to individual and group differences in behavior. The current results support that age-related declines in neural synchrony contribute to smaller P2 amplitudes in older normal hearing adults. Based on our results, we discuss potential models in which differences in neural synchrony and brain noise can account for associations with P2 amplitudes and behavior and potentially provide a better explanation of the neural mechanisms that underlie declines in auditory processing and training benefits.

Background: The ability of human listeners to comprehend rapid speech improves quickly with experience, a process known as adaptation. Whether inefficient adaptation to rapid speech partially accounts for the marked difficulties of older listeners with rapid speech is not clear. Methods: Two conditions of adaptation to time-compressed speech were used. A baseline condition intended to test the hypothesis that adaptation is different in older and younger listeners, and an interference condition in which sentences compressed to two different rates were interleaved. Identification accuracy was compared between two time points (before and after adaptation) and between older and younger listeners. Results: The effects of adaptation did not differ between younger and older listeners in either adaptation condition. Conclusions: It seems that once initial performance differences are taken into account, rapid adaptation to time-compressed speech is as effective and as immune to interference by competing speech rates in younger and older adults.

Background: Connexin 26 ( GJB2 ) mutations are associated with various types of hearing loss, either without associated symptoms or with skin disease, constituting a form of syndromic hearing loss. These mutations can lead to deafness in either a recessive or a dominant autosomal form of inheritance. Methods: Ascertainment of a Jewish Ashkenazi family with nonsyndromic hearing loss led to the construction of a pedigree for a four-generation family, with hearing loss detected in three successive generations. The entire coding region of the GJB2 gene was amplified and sequenced by Sanger sequencing. Results: Audiological analysis revealed that the age of onset and severity of hearing loss were earlier and more severe, respectively, in each successive generation of an Ashkenazi Jewish family. A mutation, c.224G>A, leading to missense p.Arg75Gln was detected only in the affected members of the family. Conclusions: The entire coding region of GJB2 should be checked in hearing-impaired patients by Sanger sequencing, rather than examination only of the two most prevalent mutations, regardless of mode of inheritance or ethnicity. Furthermore, predictions regarding phenotype based on genotype can be difficult to make due to clinical variability in multigenerational families, as demonstrated in the family presented in this study.

Background: Physiological and behavioral sex-related differences have been previously reported in the human auditory system, although data are limited to adults and are equivocal. While physiological evidence showed some advantage for females, psychophysical data tended to show greater sensitivity for males in several auditory tasks. Possible explanations for the gender effect in the auditory system include differences between the sexes in physical dimensions of the ear, brain anatomy, exposure to androgens prenatally and/or at puberty, and/or environmental factors (e.g., auditory experience). The purpose of the present study was to investigate sex-related differences in an auditory frequency discrimination task in children prior to puberty. Methods: A total of 24 normal-hearing children were divided into two age groups: 7- and 8-year-olds, with six girls and six boys in each age group. All children took part in a testing session that consisted of three Difference Limen for Frequency (DLF) measurements. Cognitive tests were also conducted. Results: Results showed that (a) boys outperformed the girls regardless of age; (b) age effect was significant, with older children performing better than the younger ones, irrespective of gender; (c) intrameasurement variance was smaller for the older children; and (d) age, gender, and auditory working memory and capacity explained over 65% of the variance in DLF thresholds. This is the first evidence of a gender effect in the auditory system in children prior to puberty. Conclusions: This evidence suggests that it is more likely that inherent physiological differences between the sexes influence the differential outcomes reported in the present study.

Background: The aim of this study was to describe the results of the Auditory Behavior in Everyday Life (ABEL) questionnaire adapted to Hebrew and to Arabic and its association to clinical test results in children with cochlear implants. As assessment of hearing by audiometry does not always adequately reflect performance in daily life, questionnaires have been developed to assess functioning in natural surroundings and to track progress. In order to evaluate cochlear-implanted children’s verbal and communicative abilities, the parental ABEL questionnaire was developed in 2002. The advantages of the ABEL questionnaire are that it is intended for a wide age range, is quick to administer, and is filled out by parents themselves. Methods: The ABEL questionnaire was translated into Hebrew and into Arabic and routinely used in the clinic. A total of 61 questionnaires were thus filled out by parents of children with cochlear implants (ages 3.9–14.3 years) when they came for routine mapping. Retrospectively, data were analyzed and questionnaire results were compared with performance with the implant on several clinical tests: audiometric thresholds, discrimination (percentage) of vowel-consonant-vowel nonsense syllables, and results of speech perception tests with monosyllabic and bisyllabic words and with sentences in quiet and in noise. Results: A correlation was found between the different sections of the questionnaire, and age at implantation had a significant effect on questionnaire scores. However, correlations between questionnaire score and clinical tests were found only for speech perception tests in noise and not in quiet or to audiogram and speech reception threshold. Conclusions: As has been reported previously, self-evaluation or parental evaluation does not always correlate with all measured results of hearing performance. However, the subjective information collected through questionnaires can be valuable for evaluation of progress, for counseling and rehabilitation training, as well as for mapping.

Background : Learning effect has been studied in the literature, but the learning done in short-term training has not been studied. Also, to date, the learning effect of different psychoacoustic measures has not been compared. In the current study, we compared the perceptual learning effect caused by performing four different auditory temporal processing (ATP) tasks in a short-term training design including two training sessions. Methods : A total of 74 young, normal-hearing participants each performed one of the following tasks: spectral temporal order judgment (TOJ), dichotic TOJ, gap detection, or duration discrimination. Each task was performed in two consecutive sessions. Results : A learning effect was observed only for the spectral TOJ task. The change from the first to the second session was larger in spectral TOJ (81%) than in dichotic TOJ (2%), gap detection (7%), and duration discrimination (5%). Conclusions : The difference in perceptual learning between spectral TOJ and other ATP tasks suggests that the performance of this task involves other cue(s) in addition to the temporal one.

Background: Perception of speech in the presence of competing multitalker noise is difficult for most individuals with sensory hearing loss, and in particular, for the elderly hearing impaired. Elderly people frequently report that these difficulties are poorly compensated for by hearing aids, albeit the algorithms and technologies aiming to improve speech perception in noise. The aim of the current study was therefore to assess competing speech signals processing by measuring the amount of signal to noise ratio (SNR) loss experienced by elderly hearing impaired individuals and their performance in dichotic listening tests. Methods: Speech in multitalker babble noise and dichotic listening were assessed in older hearing impaired individuals and in young normal-hearing adults. Results: The average dichotic scores in the elderly group were substantially and significantly lower compared with the scores of the younger group with a significant right ear advantage (higher accuracy in reporting words arriving at the right ear than words arriving at the left ear) in the elderly group. Speech identification in noise in the older group was significantly poorer than in the younger group (SNR loss: 10 dB). Conclusions: The poor performance in the elderly hearing impaired group highlights the difficulties faced by hearing impaired older adults in demanding listening environments. Our results suggest that it may be unreasonable to expect that elderly hearing impaired individuals may fully understand speech in multitalker environments even when hearing aids are used.