Group Of Normal-hearing Subjects Research Articles

Vestibular Function in Children With a Congenital Cytomegalovirus Infection: 3 Years of Follow-Up.

Congenital cytomegalovirus (cCMV) infection is the most common nongenetic cause of sensorineural hearing loss in children. Due to the close anatomical relationship between the auditory and the vestibular sensory organs, cCMV can also be an important cause of vestibular loss. However, the prevalence and nature of cCMV-induced vestibular impairment is still underexplored. The aim of this study was to investigate the occurrence and characteristics of vestibular loss in a large group of cCMV-infected children, representative of the overall cCMV-population. Ninety-three children (41 boys, 52 girls) with a confirmed diagnosis of cCMV were enrolled in this prospective longitudinal study. They were born at the Ghent University Hospital or referred from another hospital for multidisciplinary follow-up in the context of cCMV. The test protocol consisted of regular vestibular follow-up around the ages of 6 months, 1 year, 2 years, and 3 years with the video Head Impulse Test, the rotatory test, and the cervical Vestibular Evoked Myogenic Potential test. On average, the 93 patients (52 asymptomatic, 41 symptomatic) were followed for 10.2 months (SD: 10.1 mo) and had 2.2 examinations (SD: 1.1). Seventeen (18%) patients had sensorineural hearing loss (7 unilateral, 10 bilateral). Vestibular loss was detected in 13 (14%) patients (7 unilateral, 6 bilateral). There was a significant association between the occurrence of hearing loss and the presence of vestibular loss (p < 0.001), with 59% (10/17) vestibular losses in the group of hearing-impaired children compared to 4% (3/76) in the group of normal-hearing subjects. In the majority of the cases with a vestibular dysfunction (85%, 11/13), both the semicircular canal system and the otolith system were affected. The remaining subjects (15%, 2/13) had an isolated semicircular canal dysfunction. Sixty-one patients already had at least one follow-up examination. Deterioration of the vestibular function was detected in 6 of them (10%, 6/61). cCMV can impair not only the auditory but also the vestibular function. Similar to the hearing loss, vestibular loss in cCMV can be highly variable. It can be unilateral or bilateral, limited or extensive, stable or progressive, and early or delayed in onset. As the vestibular function can deteriorate over time and even normal-hearing subjects can be affected, vestibular evaluation should be part of the standard otolaryngology follow-up in all children with cCMV.

Different perception of musical stimuli in patients with monolateral and bilateral cochlear implants.

The aim of the present study is to measure the perceived pleasantness during the observation of a musical video clip in a group of cochlear implanted adult patients when compared to a group of normal hearing subjects. This comparison was performed by using the imbalance of the EEG power spectra in alpha band over frontal areas as a metric for the perceived pleasantness. Subjects were asked to watch a musical video clip in three different experimental conditions: with the original audio included (Norm), with a distorted version of the audio (Dist), and without the audio (Mute). The frontal EEG imbalance between the estimated power spectra for the left and right prefrontal areas has been calculated to investigate the differences among the two populations. Results suggested that the perceived pleasantness of the musical video clip in the normal hearing population and in the bilateral cochlear implanted populations has similar range of variation across the different stimulations (Norm, Dist, and Mute), when compared to the range of variation of video clip's pleasantness for the monolateral cochlear implanted population. A similarity exists in the trends of the perceived pleasantness across the different experimental conditions in the mono- and bilaterally cochlear implanted patients.

Discrimination of envelope statistics reveals evidence of sub-clinical hearing damage in a noise-exposed population with ‘normal’ hearing thresholds

Noise exposure can affect the functioning of inner hair cells (IHC) within the cochlea, leading to a ‘noisy’ representation of the properties of sounds even when absolute thresholds are normal. This may lead to a reduced ability to discriminate sounds based on their statistical properties, especially for narrowband sounds presented at low levels, since such sounds excite only a small proportion of the IHCs. This idea was tested by requiring subjects to discriminate a Gaussian noise from a ‘low-noise noise’ with minimal envelope fluctuations. The noises were centred at 2, 3, or 4kHz. The stimulus duration required for threshold was measured as a function of sensation level (SL) for two groups of normal-hearing subjects, one rarely exposed to high-noise events (control group, C) and one frequently exposed to high-noise events (experimental group, X). For group X, threshold consistently rose for SLs below about 20dB, while for group C the threshold did not consistently rise at low SLs (although it did for a minority of subjects). The worsening in performance with decreasing level was significantly greater for group X than for group C.

Late auditory evoked response components investigated in a large group of normal hearing subjects

The temporal dynamics and the underlying sources of the late auditory transient components, the sustained field and steady-state responses were successfully investigated using single complex auditory stimulus type.

Level dependence of auditory filters in nonsimultaneous masking as a function of frequency

Auditory filter bandwidths were measured using nonsimultaneous masking, as a function of signal level between 10 and 35 dB SL for signal frequencies of 1, 2, 4, and 6 kHz. The brief sinusoidal signal was presented in a temporal gap within a spectrally notched noise. Two groups of normal-hearing subjects were tested, one using a fixed masker level and adaptively varying signal level, the other using a fixed signal level and adaptively varying masker level. In both cases, auditory filters were derived by assuming a constant filter shape for a given signal level. The filter parameters derived from the two paradigms were not significantly different. At 1 kHz, the equivalent rectangular bandwidth (ERB) decreased as the signal level increased from 10 to 20 dB SL, after which it remained roughly constant. In contrast, at 6 kHz, the ERB increased consistently with signal levels from 10 to 35 dB SL. The results at 2 and 4 kHz were intermediate, showing no consistent change in ERB with signal level. Overall, the results suggest changes in the level dependence of the auditory filters at frequencies above 1 kHz that are not currently incorporated in models of human auditory filter tuning.

Auditory temporal processes in normal-hearing individuals and in patients with auditory neuropathy

Objective To study objectively auditory temporal processing in a group of normal hearing subjects and in a group of hearing-impaired individuals with auditory neuropathy (AN) using electrophysiological and psychoacoustic methods. Methods Scalp recorded evoked potentials were measured to brief silent intervals (gaps) varying between 2 and 50 ms embedded in continuous noise. Latencies and amplitudes of N100 and P200 were measured and analyzed in two conditions: (1) active, when using a button in response to gaps; (2) passive, listening, but not responding. Results In normal subjects evoked potentials (N100/P200 components) were recorded in response to gaps as short as 5 ms in both active and passive conditions. Gap evoked potentials in AN subjects appeared only with prolonged gap durations (10–50 ms). There was a close association between gap detection thresholds measured psychoacoustically and electrophysiologically in both normals and in AN subjects. Conclusions Auditory cortical potentials can provide objective measures of auditory temporal processes. Significance The combination of electrophysiological and psychoacoustic methods converged to provide useful objective measures for studying auditory cortical temporal processing in normals and hearing-impaired individuals. The procedure used may also provide objective measures of temporal processing for evaluating special populations such as children who may not be able to provide subjective responses.

Frequency-specificity of auditory brainstem responses elicited by 500 Hz tone-pip with Gaussian envelope in normal hearing and sensorineural hearing loss

The purpose of this study was to determine the frequency specificity of auditory brainstem responses elicited by 500 Hz tone pips with the Gaussian envelope. The latency–intensity functions of wave V for click and 500 Hz tone-pip were analyzed in a group of normal hearing subjects and in large group of patients with different levels and configurations of sensorineural hearing loss. Tone-pip was digitally synthesized using a Gaussian envelope with a rise/fall time of 2 ms. In both groups of subjects the highest differences between the latencies of wave V for tone pip and click were observed near the threshold of wave V. The latency–intensity functions in the group of patients with hearing loss show an approximately parallel course that indicates the response to be more frequency–specific than in normal hearing subjects. The responses to 500 Hz tone-pip in the group of patients with sensorineural hearing loss are more frequency specific than in normal hearing subjects.

Registrierung ereigniskorrelierter auditorischer Potentiale (P300) bei Patienten mit einem Cochlear Implant

Event-related auditory evoked potentials can contribute to the evaluation of discrimination abilities of cochlear implant users. Auditory P300 potentials to a frequency contrast were obtained in six post-lingually deaf adults using a cochlear implant and in a control group of normal hearing subjects. The aim of this study was to investigate how these potentials were determined by the stimulation pattern of the cochlear implant. To visualise these stimulation patterns colour-coded plots (stimulograms) were calculated based on the stimulus and the fitting file of the individual subject as inputs. These stimulograms were used to evaluate the influence of various stimulation parameters on the stimulation contrast used in an oddball paradigm. The influence of discrimination difficulty on the P300 response is demonstrated.

The contribution of visual areas to speech comprehension: a PET study in cochlear implants patients and normal-hearing subjects

Early visual cortex can be recruited by meaningful sounds in the absence of visual information. This occurs in particular in cochlear implant (CI) patients whose dependency on visual cues in speech comprehension is increased. Such cross-modal interaction mirrors the response of early auditory cortex to mouth movements (speech reading) and may reflect the natural expectancy of the visual counterpart of sounds, lip movements. Here we pursue the hypothesis that visual activations occur specifically in response to meaningful sounds. We performed PET in both CI patients and controls, while subjects listened either to their native language or to a completely unknown language. A recruitment of early visual cortex, the left posterior inferior temporal gyrus (ITG) and the left superior parietal cortex was observed in both groups. While no further activation occurred in the group of normal-hearing subjects, CI patients additionally recruited the right perirhinal/fusiform and mid-fusiform, the right temporo-occipito-parietal (TOP) junction and the left inferior prefrontal cortex (LIPF, Broca’s area). This study confirms a participation of visual cortical areas in semantic processing of speech sounds. Observation of early visual activation in normal-hearing subjects shows that auditory-to-visual cross-modal effects can also be recruited under natural hearing conditions. In cochlear implant patients, speech activates the mid-fusiform gyrus in the vicinity of the so-called face area. This suggests that specific cross-modal interaction involving advanced stages in the visual processing hierarchy develops after cochlear implantation and may be the correlate of increased usage of lip-reading.

Verbal Information-processing Capabilities and Cochlear Implants: Implications for Preoperative Predictors of Speech Understanding

In this study, we examined preoperative verbal cognitive capacity in 11 deafened adults who were cochlear implant candidates and reexamined level of speech understanding after 6-8 months' experience with the implant. Verbal cognitive performance in the implant group was compared in a group of normal hearing subjects and in nonimplanted group of deafened adults. The three groups performed on par with each other with an exception: The individuals in the cochlear implant group and the nonimplanted group of deafened adults performed significatly worse than those of normal hearing in tasks in which use of internal speech is a key feature (i.e., rhyme judgement and lexical decision tasks). Postoperative observations of the implanted individuals' level of speech understanding suggest that it is possible to predict the level of speech understanding by means of a properative cognitive assessment. The characteristics of three verbal cognitive abilities prove to be critical indicators of 6 - 8 months' postoperative outcome: internal speech functioning, speed of verval information processing, and working memory capacity - the first factor proved the most decisive. We discuss the results with respect to direct versus indirect predictors of outcomes from cochlear implant operations and the effect of auditory deprivation on deafened adults' capability to process auditory information.

The effects on transient evoked otoacoustic emissions following changes in external auditory canal acoustic impedance.

The form of the transient evoked otoacoustic emission (TEOAE) generated by an acoustic impulse and recorded in the external auditory canal is dependent on many factors. Of these, the acoustic impedance of the external canal is possibly the most important. The effect of a change of acoustic impedance on the TEOAEs, induced by filling the external canal with helium or sulphur hexafluoride gas, is measured in a group of normal hearing subjects. The fundamental frequency of the TEOAEs is found to depend upon the density of the gas in the external canal. Compared to that of air (density 1.29 g/l) the frequency increased with helium (density 0.178 g/l) and decreased with sulphur hexafluoride (density 6.6 g/l). The amplitude of the TEOAEs was also found to depend upon the density of the gas in the canal, decreasing with helium and increasing with sulphur hexafluoride. These results suggest that the TEOAEs observed in the group of subjects tested arose within the external auditory canal. This does not imply that cochlear emissions are not generated in response to transient acoustic impulses, rather it implies that this study failed to show the presence of a cochlear-mediated emission.

Fine structure of 2f1−f2 acoustic distortion product: Effect of L1/L2 ratio

The fine structure of the 2f1−f2 acoustic distortion product (ADP) was measured in a group of normal-hearing subjects with different combinations of primary levels (L1 and L2). The frequency ratio (f2/f1,f2≳f1) was 1.2, and the f2 frequency was swept from 1781 to 2300 Hz in 1/32 octave steps. In condition 1, L1 was fixed at 50 dB SPL while L2 varied from 30 to 75 dB SPL in 5-dB steps. In condition 2, L2 was fixed at 50 dB SPL and L1 was varied as in condition 1. For a fixed L1, an upward frequency shift was evident in the ADP fine structure as the L2 level increased, whereas for fixed L2, a downward frequency shift in the ADP pattern was observable with an increasing L1. These results support a vector sum computer model for the ADP fine structure [Sun et al., 2166–2174, 2175–2183 (1994)], suggesting that ADP fine structure is largely generated in the overlap area of the traveling waves for the primary tones, and the effects of reemissions from the 2f1−f2 area are minimal. A large variance was observed in the best L1/L2 ratio, ranging from −7.5 to 20 dB both across and within subjects. [Work supported by NIDCD.]

EVALUATION OF AN EARPHONE-SUPPORT DEVICE FOR MEASURING EARPLUG ATTENUATION

A new procedure for determining the attenuation of earplugs with a standard audiometric headset was evaluated. The procedure utilized a device that supports a conventional supraaural earphone cushion (MX-41/AR) such that it does not contact the pinna or the earplug during threshold measurement. The attenuation provided by a foam earplug was estimated on a group of normal-hearing subjects using this method. The resulting attenuation values were compared to data obtained using sound field (ANSI S12.6-1984) methods, and to values obtained by simply placing the earphone on the pinna. Results suggest that the test re-test reliabilities of both the earphone-support method and the earphone-only method were comparable to that of the sound field procedure. Also, of the four test frequencies employed (1, 2, 3 and 4 kHz), the closet correspondence between attenuation estimates obtained using the ANSI procedures and estimates obtained with the support device occurred at 1 and 2 kHz.

Preparing for Communication Interactions

Some people with hearing impairment may use anticipatory strategies to prepare for an upcoming communication interaction, such as a doctor's appointment. They may consider vocabulary and statements that might occur, and they may practice speechreading a partner saying the items. Experiment 1 evaluated the effectiveness of two types of anticipatory strategies: workbook activities and situation-specific lipreading practice. Two groups of normal-hearing subjects were asked to prepare for a communication interaction in a bank setting where they would be required to recognize speech using only the visual signal. Each group was assigned to one type of anticipatory strategy. A third group served as a control group. Experiment 2 evaluated whether multifaceted anticipatory practice improved cochlear implant users' ability to recognize statements and words audiovisually that might occur in a doctor's office, bank, movie theater, and gas station. One group of implanted subjects received 4 days of training, 1 day for each setting, and a second group served as a control group. In both experiments, subjects who used anticipatory strategies did not improve their performance on situation-specific sentence tests more than the control subjects.

Stimulus repetition rate effect on the auditory brainstem response in systemic lupus erythematosus.

Neuropsychiatric involvement is common in systemic lupus erythematosus (SLE), but, in early half of cases, indications are not present on examination. Auditory brainstem response (ABR) measures using differential stimulus repetition rates have been reported as sensitive indicators of subclinical central nervous system (CNS) disorders associated with SLE. In the present study, ABRs were measured in a group of normal-hearing subjects with SLE, as well as in a group of subject controls. Differences in interpeak latency (IPL) measures obtained using low- and high-stimulus repetition rates did not reach statistical significance (P greater than .05). Clinical utility of ABRs using high- and low-stimulus repetition rates for the identification of occult CNS disorder in patients with SLE was not demonstrated.

Effect of Noise on Word Discrimination by Subjects with Impaired Hearing, Compared with Those with Normal Hearing

A comparison was made of the discrimination ability of different groups of hearing-impaired and normal-hearing subjects in noisy conditions. Four groups of subjects having a sensorineural hearing loss with various audiogram configurations, one group of subjects having a conductive hearing loss and one group of normal-hearing subjects were chosen. The submaster tapes were recorded in quiet and in pink noise with signal-to-noise ratios of -3, -8, and -13 dB. The test subjects heard the test words monaurally via earphones. The best speech discrimination was achieved in quiet, anechoic conditions. As the noise level increased, speech discrimination decreased. Subjects with sensorineural hearing loss were more adversely affected by noise than subjects with normal hearing or with conductive hearing loss. However, at high noise levels, their speech discrimination was poorer than that of normal-hearing subjects. Persons with a high-frequency hearing loss, cut-off point 1 kHz, suffered in noise similarly to those with sloping or flat hearing losses. In quiet and in moderate noise, the speech discrimination of subjects with a conductive hearing loss and subjects with normal hearing was similar, while at high noise levels, subjects with conductive hearing losses achieved better discrimination than normal-hearing subjects.

Reproducibility of Hearing Threshold MeasurementsSupplementary Data on Bone-conduction and Speech Audiometry

The reproducibility of bone-conduction pure-tone audiometry and speech recognition thresholds has been tested in groups of normal-hearing subjects. Each person was tested twice during the same day, and the test-retest difference was calculated. The reproducibility is presented as the standard deviation of this difference. Bone-conduction threshold measurements have a high degree of test-retest precision, whereas air-bone gaps show a large range of distribution in these normal-hearing subjects. This makes the interpretation of such gaps spurious when values are below 20-30 dB. Speech recognition threshold has the highest degree of test-retest precision of all audiometric tests, and this is probably due to the steep slope of the psychometric function at 50% intelligibility. A more detailed graphic presentation of the 50% point of intersection will bring the reproducibility down to less than 2.5 dB.

Functional Changes in the Brainstem Auditory Pathways following Open-Heart Surgery

Measurements of the auditory brainstem responses (ABR) were used to assess the functional integrity of the brainstem auditory pathways following open-heart surgery. Recording of ABR was performed in 31 patients before and after open-heart surgery. The values of ABR measurements were compared to those of a control group of normal-hearing subjects. Postoperative aberrations in ABR were observed in 12 patients. Brainstem transmission time measured as wave I to wave V interpeak latency (I-V IPL) was prolonged in 6 patients and shortened in 8 patients. Concomitant impairment in hearing function was not present, and therefore, these changes most probably reflected a functional alteration in the neurological status of the brainstem. Possible explanations of the postoperative changes in I-V IPL are discussed, however, further studies are needed to clarify the pathogenesis of these changes. Measurement of ABR may prove to be an important adjunct in the overall assessment of the neurological status following open-heart surgery.

Excess masking among listeners with a sensorineural hearing loss.

Three experiments were conducted to determine whether listeners with a sensorineural hearing loss exhibited greater than normal amounts of masking at frequencies above the frequency of the masker. Excess masking was defined as the difference (in dB) between the masked thresholds actually obtained from a hearing-impaired listener and the expected thresholds calculated for the same individual. The expected thresholds were the power sum of the listener's thresholds in quiet and the average masked thresholds obtained from a group of normal-hearing subjects at the test frequency. Hearing-impaired listeners, with thresholds in quiet ranging from approximately 35-70 dB SPL (at test frequencies between 500-3000 Hz), displayed approximately 12-15 dB of maximum excess masking. The maximum amount of excess masking occurred in the region where the threshold in quiet of the hearing-impaired listener and the average normal masked threshold were equal. These findings indicate that listeners with a sensorineural hearing loss display one form of reduced frequency selectivity (i.e., abnormal upward spread of masking) even when their thresholds in quiet are taken into account.

刺激音間隔短縮による臨床か電図ＡＰの変化

The effect of the changes of interstimulus interval (ISI) was compared among the four groups consiting of normal hearing subjects sensorineural deafness due to hair cells damage, due to endolymphatic hydrops and cerebello-pontine angle lesion.The click sound stimulation was used for measurement of the auditory whole nerve action potential (AP), using the transtympanic technique in electrocochleography.A moderate decrease in similar manner was shown in two groups of normal hearing subjects and sensorineural hearing loss with hair cells damage. On the other hand, a remarkable decrease was shown in order two groups of sensorineural hearing loss with endolymphatic hydrops and with cerebello-pontine angle lesion.It is suggested that a remarkable decrease in amplitude of AP with shortening of ISI is due to abnormal function in synaptic junction between the cochlear hair cell and the first auditory neuron and/or abnormal function in the post synaps.