Hearing threshold estimation in infants using auditory steady-state responses

Successful early intervention in children with permanent hearing loss requires assessment techniques that can accurately reflect the behavioral audiogram in infancy. This retrospective study compared auditory steady-state response (ASSR) findings from subjects tested in the first three months of life with subsequently obtained behavioral hearing levels. ASSR audiograms were established using amplitude and frequency modulated tones at octave frequencies (500 Hz to 4 kHz). Results obtained from 575 subjects including 285 with normal hearing, 271 with sensorineural hearing loss, and 19 with auditory neuropathy-type hearing loss are presented. ASSR and behavioral hearing thresholds for subjects in the normal and sensorineural groups were highly correlated, with Pearson r values exceeding 0.95 at each of the test frequencies. In contrast, ASSR thresholds in children with AN-type hearing loss did not accurately reflect the behavioral audiogram. Overall, the findings indicate that ASSR testing can offer useful insights into the hearing acuity of children tested in infancy.     

Automated cortical auditory evoked potentials threshold estimation in neonates

Introduction

The evaluation of cortical auditory evoked potential has been the focus of scientific studies in infants. Some authors have reported that automated response detection is effective in exploring these potentials in infants, but few have reported their efficacy in the search for thresholds.

Objective auditory threshold estimation using sine-wave derived responses.

A derived response method of acquiring frequency specific auditory evoked potentials that utilizes a pure tone in combination with a toneburst is applied to the measurement of hearing sensitivity in guinea pigs, chinchillas and pocket gophers. Two experiments which demonstrate that thresholds acquired via tone-derived responses are 10 to 15 dB more sensitive than thresholds to solitary tonebursts are described. The derived potentials approximate behaviorally acquired thresholds at frequencies of 0.5 kHz and above. This technique may provide a more rapid means of assessing hearing sensitivity in laboratory animals than by behavioral means.     

The estimation of hearing threshold for high frequencies in children from the Upper Silesia

Study was carried out in frequency range 8-18 kHz with audiometer AS 10 HF. Lack of internationally accepted reference value of the hearing threshold of air conduction at extended frequency range resulted in own evaluation of the audiometric zero point for air conduction at the range 8-18 kHz in "otologically healthy" subjects younger than 20 years. They were divided into subgroup A and B according to age. Investigation of the threshold values for air conduction at extended range of high frequencies were base for evaluation of the audiometric zero value for the used equipment.     

Objective determination of auditory threshold in the child

In children who are difficult to test with dubious behavioural-audiometric results, brainstem electric response audiometry (BERA) is today the method of choice for accurate determination of hearing threshold. Oral sedation with the shortacting neuroleptic chloroprothixene allows BERA to be performed on an outpatient basis. Thirty-six girls and 41 boys aged between 11 weeks and 12 years (median age 40 months) with inconsistent behavioural-audiometric findings were examined. Frequency-following responses were searched for in flat fast response curves. BERA proved to be a very sensitive method compared with behavioural audiometry and was reliable even for children who are difficult to evaluate clinically, and for asymmetrical auditory thresholds. In conjunction with the standard pedaudiological test battery, BERA improves diagnostic accuracy and causes little disturbance as an outpatient procedure.     

Pure-tone auditory threshold in school children

To determine pure-tone auditory thresholds, 197 screened children at a typical primary school in a German town (~70,000 inhabitants) were examined. All children underwent a tympanometry and an audiometry at 17 frequencies from 125 to 16 kHz. Regarding age effects, two groups (6–8 and 9–12 years) were analyzed. The cross-sectional research was supplemented by a follow-up study with 35 children of the first graders 3 years later. School children have the poorest hearing sensitivity at low frequencies (below 1 kHz) and the best sensitivity at the extended high frequencies above 8 kHz. Hearing thresholds are rising significantly with age. Through all frequencies, averaged improvements were 3.8 dB (right ear) and 3.7 dB (left ear) at the cross-sectional study and 3.7 dB (right ear) and 5.1 dB (left ear) at the longitudinal study. The overall deviation (left and right) from the standard thresholds for adults were 7.4 and 3.6 dB for the younger and older age groups, respectively. The ear canal volume (ECV) measured by tympanometric tests was at mean with 1.06 cm³ for the 6- to 8-year age group significantly lower (p < 0.001) in comparison with 1.18 cm³ for the 9- to 12-year age group. Also, girls had significant (p < 0.001) smaller ECV (mean 1.07 cm³) than boys (1.17 cm³). Auditory performance improves with rising age in school children.     

Rapid threshold estimation using the "chained-stimuli" technique for auditory brain stem response measurement.

The "chained-stimuli" technique for rapid auditory brain stem response (ABR) threshold estimation involves lengthening the averaging time window and presenting a series ("chain") of click stimuli. Each stimulus chain contains, in addition to a silent interval, click stimuli of 10, 20, 30, 40, 50, 60, and 70 dB nHL that are separated by 10 msec intervals. Using this method, the single averaged response to the chained-stimulus contains up to seven individual ABRs. The responses elicited by each level of click stimulus within the chain can be analyzed separately. In this study, chained-stimuli ABR threshold estimations for normal hearers were essentially equivalent to those obtained using an automated conventional ABR method. The data for a seven point latency-intensity function using the chained-stimuli technique were obtained in a mean time of only 8 min per ear.     

Low-frequency auditory brainstem response threshold

Auditory brainstem thresholds have been determined in 35 non-cooperative, anaesthetized children using a 'two-point audiogram' paradigm. The high-frequency point was found with a 2 kHz tone-burst without masking, and the low-frequency with a 0.5 kHz tone-burst together with 1 kHz high-pass noise masking. Great variability was found in the low-frequency thresholds, and only 3 of 18 ears with normal high-frequency thresholds had low-frequency thresholds below 70 dB nHL. It is concluded that the 0.5 kHz tone-burst with 1 kHz high-pass noise masking is not a reliable method for routine assessment of low-frequency auditory threshold at the brainstem level.     

The estimation of air--conduction threshold in extended range of high frequencies in young adult patients suffering from primary arterial hypertension

The aim of the study was evaluation of the hearing ability on the base of air conduction threshold at extended range of high frequencies in young subjects with primary arterial hypertension. Lack of internationally accepted reference value of air conduction hearing threshold at extended frequency range resulted in own evaluation of the audiometric zero point for air conduction at the range 8-18 kHz in "otologically healthy" subjects younger than 20 years. Detection of impaired hearing of the extended high frequencies range in young subjects with primary arterial hypertension may be useful in diagnostics of hypertension as well as in prophylactic examinations in the group of individuals with high risk of primary hypertension. Evaluation of air conduction threshold at extended frequency range allows to detect sensorineural hearing impairment undetectable with application of conventional frequency range.     

Meta-analysis of variables that affect accuracy of threshold estimation via measurement of the auditory steady-state response (ASSR)

Reported are the results of meta-analyses of data derived collectively from a sample of 56 published research studies on electric response audiometry (ERA) using auditory steady-state responses (ASSRs). Several specific methodological issues were examined and hypotheses were posited to rigorously test common conclusions drawn from the ASSR literature on the accuracy of ASSR-ERA. Explanatory variables for analyses were type of population (normally hearing and hearing-impaired), type of modulation, number of sweeps acquired during response analysis, electrode montage, and modulation rate (80 vs. 40 Hz). No explanatory variables were found to be significantly related to the degree of disparity between thresholds obtained by ASSR-ERA versus behavioral audiometry in the normally hearing population. Conversely, all but one explanatory variable (i.e. electrode montage) was found to be significantly related to mean threshold differences in the hearing-impaired and combined populations. Results both substantiate some of common conclusions drawn from the literature but call others into question, helping to identify those methodological issues which appear to, or not to, significantly affect the accuracy of estimating threshold using ASSR measurement. In addition to these findings, another practical outcome of this study was the development of various summary tables of the data analysed from the literature sampled.     

Meta-analysis of variables that affect accuracy of threshold estimation via measurement of the auditory steady-state response (ASSR)

Reported are the results of meta-analyses of data derived collectively from a sample of 56 published research studies on electric response audiometry (ERA) using auditory steady-state responses (ASSRs). Several specific methodological issues were examined and hypotheses were posited to rigorously test common conclusions drawn from the ASSR literature on the accuracy of ASSR-ERA. Explanatory variables for analyses were type of population (normally hearing and hearing-impaired), type of modulation, number of sweeps acquired during response analysis, electrode montage, and modulation rate (80 vs. 40 Hz). No explanatory variables were found to be significantly related to the degree of disparity between thresholds obtained by ASSR-ERA versus behavioral audiometry in the normally hearing population. Conversely, all but one explanatory variable (i.e. electrode montage) was found to be significantly related to mean threshold differences in the hearing-impaired and combined populations. Results both substantiate some of common conclusions drawn from the literature but call others into question, helping to identify those methodological issues which appear to, or not to, significantly affect the accuracy of estimating threshold using ASSR measurement. In addition to these findings, another practical outcome of this study was the development of various summary tables of the data analysed from the literature sampled.     

Auditory brainstem response threshold estimation: subjective threshold estimation by experienced clinicians in a computer simulation of the clinical test

Little research has been undertaken into the extent to which auditory brainstem response (ABR) threshold estimation varies between experienced professionals. In this paper, results are presented for 16 professionals who estimated ABR threshold for 12 sets of data in a computer simulation of the clinical test. The design differs from previous research in this area in that subjects had control over the creation of the set of traces from which they would estimate threshold, much as they would in the clinical situation. No agreement for threshold was found for any of the 12 sets of test data across the 16 subjects, and for nine of the sets, the difference between highest and lowest estimated threshold was 40 dB or greater. The maximum difference between highest and lowest estimated threshold was 60dB. It is argued that the variability is not accounted for by experimental design. The implications for clinical practice are discussed.     

Auditory brainstem response threshold estimation: subjective threshold estimation by experienced clinicians in a computer simulation of the clinical test

Little research has been undertaken into the extent to which auditory brainstem response (ABR) threshold estimation varies between experienced professionals. In this paper, results are presented for 16 professionals who estimated ABR threshold for 12 sets of data in a computer simulation of the clinical test. The design differs from previous research in this area in that subjects had control over the creation of the set of traces from which they would estimate threshold, much as they would in the clinical situation. No agreement for threshold was found for any of the 12 sets of test data across the 16 subjects, and for nine of the sets, the difference between highest and lowest estimated threshold was 40 dB or greater. The maximum difference between highest and lowest estimated threshold was 60 dB. It is argued that the variability is not accounted for by experimental design. The implications for clinical practice are discussed.     

The accuracy of objective threshold determination at low frequencies: comparison of different auditory brainstem response (ABR) and auditory steady state response (ASSR) methods

Objective: The hearing threshold at 500?Hz was estimated using five methods which are suitable for the low frequency range: Low-Chirp BERA (LCBERA), Notched-noise BERA (NNBERA), Narrow band CE-Chirp BERA (NBCBERA) and Narrow band CE-Chirp ASSR (NBCASSR) (40/90?Hz). The slope of the discrimination function of each method was used for determination of the most efficient method. The threshold values were compared and the corresponding odds ratios (OR) were calculated. Design: All methods were applied to each subject. Stimulus levels were arranged individually. Response detection was carried out by visual inspection of the records in case of BERA and automatically in case of ASSR. Each individual series of recordings was converted to a dichotomous function indicating whether or not a response was discernible and a continuous method-specific discrimination function was constructed. This function was realised by a Boltzmann function whose slope in the inflection point serves as quality measure. Additionally, an OR evaluation was carried out in order to validate the significance of results. Study sample: Twenty five normal hearing adults (aged 18–30 years) were tested. Results: LCBERA proved to have the highest reliability according to the slope of the Boltzmann function, the comparison of threshold values and OR. Conclusions: The LCBERA is recommended for use in routine clinical practice.     

Normative auditory brainstem response data for hearing threshold in the rabbit

In an experimental study, we determined the physiological hearing threshold of the rabbit in order to use these data as normative values for further experimental investigations. The aim was to use different acoustic stimuli (click and tone-pip stimuli) with different frequency spectra for air and bone conduction (BC) in order to obtain further information about the optimal form of stimulus when recording auditory evoked potentials in the rabbit. For the investigation, we used 46 female New Zealand rabbits weighing 3.2-4.4 kg and aged 6 months. The equipment used to record brainstem auditory evoked potentials was the Nicolet Viking IV P System (Nicolet Biomedical, Inc.). In accordance with the experimental set-up, the measurements took place under intubation anesthesia, with a total of four repeat measurements performed on each ear at different times. Tone-pip and click stimuli with varying intensities of stimulus, transmitted via air conduction and BC, were applied. The I-IV waves proved the most stable for both stimulus modalities. They were registrable in 98.7% of cases, whereas only 30.2% of the V waves could be recorded. Values averaged from all measurements made throughout the study yielded a potential threshold of 34.8 dB peak equivalent (p.e.) SPL for the click stimulus, 13.8 dB p.e. SPL for the tone-pip stimulus at 8 kHz and 34.2 dB p.e. SPL for the click stimulus transmitted via BC. With regard to latencies, the results indicated a good reproducibility through different stimuli with acceptable standard deviations. The values for physiological hearing threshold obtained here can serve as normative data in subsequent experimental animal studies.     

Interlaminar differences of spike activation threshold in the auditory cortex of the rat

The neural circuits of the auditory cortex are a substrate for the dual purpose of representing and storing the auditory signal on one hand, and sending its relevant features to other cortical and subcortical areas on the other hand. The ability to process and transform the signal crucially depends on achievement of the neuronal spike threshold following spatiotemporal summation of the synaptic signals. We used patch-clamp recording in a thin slice preparation to compare neuronal responses to current injection of layer II/III and layer V neurons. We found that while the two classes of neurons do not differ in passive neuronal properties, layer II/III neurons possess a lower firing threshold relative to layer V neurons (-44.8 +/- 2.4 mV vs. -34.3 +/- 4.0 mV). We speculate that a lower spiking threshold in layer II/III neurons might favor local intracolumnar activation for representation and storage of the auditory information whereas a more positive spiking threshold for layer V neurons may prevent unnecessary cortical spread of a scarcely processed signal.