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Background Audiologists often lack confidence in results produced by current protocols for diagnostic electrophysiologic testing of infants. This leads to repeat testing appointments and slow protocols which extend the time needed to complete the testing and consequently delay fitting of amplification. A recent publication (Sininger et al50) has shown how new technologies can be applied to electrophysiologic testing systems to improve confidence in results and allow faster test protocols. Average test times for complete audiogram predictions when using new technologies and protocols were found to be just over 32 minutes using auditory brainstem response (ABR) and just under 20 minutes using auditory steady-state response (ASSR) technology. Purpose The purpose of this manuscript is to provide details of expedited test protocols for infant and toddler diagnostic electrophysiologic testing. Summary Several new technologies and their role in test speed and confidence are described including CE-Chirp stimuli, automated detection of ABRs using a technique called F MP, Bayesian weighting which is an alternative to standard artifact rejection and Next-Generation ASSR with improved response detection and chirp stimuli. The test protocol has the following features: (1) preliminary testing includes impedance measures and otoacoustic emissions, (2) starting test levels are based on Broad-Band CE-Chirp thresholds in each ear, (3) ABRs or ASSRs are considered present based on automated detection rather than on replication of responses, (4) number of test levels is minimized, (5) ASSR generally evaluates four frequencies in each ear simultaneously with flexibility to change all test levels independently. Conclusions Combining new technologies with common-sense strategies has been shown to substantially reduce test times for predicting audiometric thresholds in infants and toddlers (Sininger et al50). Details and rationales for changing test strategies and protocols are given and case examples are used to illustrate.

Background: Audiologists often lack confidence in results produced by current protocols for diagnosticelectrophysiologic testing of infants. This leads to repeat testing appointments and slow protocols whichextend the time needed to complete the testing and consequently delay fitting of amplification. A recentpublication (Sininger et al, 2018) has shown how new technologies can be applied to electrophysiologictesting systems to improve confidence in results and allow faster test protocols. Average test times forcomplete audiogram predictions when using new technologies and protocols were found to be just over32 minutes using auditory brainstem response (ABR) and just under 20 minutes using auditory steadystateresponse (ASSR) technology.Purpose: The purpose of this manuscript is to provide details of expedited test protocols for infant andtoddler diagnostic electrophysiologic testing.Summary: Several new technologies and their role in test speed and confidence are described includingCE-Chirp stimuli, automated detection of ABRs using a technique called FMP, Bayesian weighting which isan alternative to standard artifact rejection and Next-Generation ASSR with improved response detectionand chirp stimuli. The test protocol has the following features: (1) preliminary testing includes impedancemeasures and otoacoustic emissions, (2) starting test levels are based on Broad-Band CE-Chirp thresholdsin each ear, (3) ABRs or ASSRs are considered present based on automated detection rather thanon replication of responses, (4) number of test levels is minimized, (5) ASSR generally evaluates fourfrequencies in each ear simultaneously with flexibility to change all test levels independently.Conclusions: Combining new technologies with common-sense strategies has been shown to substantiallyreduce test times for predicting audiometric thresholds in infants and toddlers (Sininger et al, 2018).Details and rationales for changing test strategies and protocols are given and case examples are used toillustrate.

This article describes the audiologic findings and medical status of infants who were found to have hearing loss, detected as part of the Identification of Neonatal Hearing Impairment (INHI) project. In addition, the neonatal and maternal health variables for the group of infants who could not be tested with visual reinforcement audiometry (VRA) due to developmental and visual disability are presented.The overall goal of the INHI project was to evaluate the test performance of auditory brain stem response and evoked otoacoustic emission (OAE) tests given in the newborn period. These tools were evaluated on the basis of the infants' hearing when tested behaviorally with VRA at 8 to 12 mo corrected age. The neonatal test results, VRA results, medical history information and a record of intercurrent events occurring between the neonatal period and the time of VRA were collated and reviewed. The purpose of this article is to review the characteristics of those infants who were found to have hearing loss.Of 2995 infants who had VRA tests judged to be of good or fair reliability, 168 had a finding of hearing loss for at least one ear, an incidence of 5.6%. Sixty-six infants had bilateral losses, an incidence of 2%, and 22 infants had bilateral hearing losses in the moderate to profound range, an incidence 0.7%. The prevalence of middle ear problems was greater than 50% among these infants with hearing loss. From the larger group of 168 infants with hearing loss, a group of 56 infants (86 ears) was chosen as those with a low probability that the hearing loss was due to transient middle ear pathology and was more likely hearing loss of a permanent nature. These were the infants used for the analyses of neonatal test performance (Norton et al., 2000). In this selected group there were 30 infants with bilateral impairment of at least mild degree, which is an incidence of 1%. There were approximately equal numbers of ears in the mild, moderate, severe and profound range of hearing loss. Risk factors associated with hearing loss were reviewed for the total sample of infants tested with VRA and for those infants with hearing loss. A history of treatment with aminoglycosides was the risk factor most often reported in the entire sample; however, there was no difference in prevalence of this risk factor for the normal-hearing and hearing-impaired groups. The risk factor associated with the highest incidence of hearing loss was stigmata of syndromes associated with sensorineural hearing loss and other neurosensory disorders. Sixty-seven infants who returned for follow-up could not be tested with VRA due to severe developmental delay or visual disability. Many of these infants had medical histories indicating the sequelae of extreme prematurity and/or very low birthweight.Most of the hearing losses found in this study were mild and, based on clinical history and tympanometry tests, many of the mild and some of the moderate impairments may have been acquired in early infancy due to middle ear effusion. In the group of infants used for determination of neonatal test performance there were approximately equal numbers of mild, moderate, severe and profound losses. Only a small percentage of infants with a conventional risk indicator for hearing loss actually had a hearing loss, and there were a significant number of infants with hearing loss who did not have a risk indicator. These findings support the need for an early identification program based on universal neonatal hearing screening rather than by targeted testing of those with risk indicators.

The purpose of this study was to compare the performance of transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), and auditory brain stem responses (ABRs) as tools for identification of neonatal hearing impairment.A total of 4911 infants including 4478 graduates of neonatal intensive care units, 353 well babies with one or more risk factors for hearing loss (Joint Committee on Infant Hearing, 1994) and 80 well babies without risk factor who did not pass one or more neonatal test were targeted as the potential subject pool on which test performance would be assessed. During the neonatal period, they were evaluated using TEOAEs in response to an 80 dB pSPL click, DPOAE responses to two stimulus conditions (L1 = L2 = 75 dB SPL and L1 = 65 dB SPL L2 = 50 dB SPL), and ABR elicited by a 30 dB nHL click. In an effort to describe test performance, these "at-risk" infants were asked to return for behavioral audiologic assessments, using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age, regardless of neonatal test results. Sixty-four percent of these subjects returned and reliable VRA data were obtained on 95.6% of these returnees. This approach is in contrast to previous studies in which, by necessity, efforts were made to follow only those infants who "failed" the neonatal screening tests. The accuracy of the neonatal measures in predicting hearing status at 8 to 12 mo corrected age was determined. Only those infants who provided reliable, monaural VRA test results were included in the analysis. Separate analyses were performed without regard to intercurrent events (i.e., events between the neonatal and VRA tests that could cause their results to disagree), and then after accounting for the possible influence of intercurrent events such as otitis media and late-onset or progressive hearing loss.Low refer rates were achieved for the stopping criteria used in the present study, especially when a protocol similar to the one recommended in the National Institutes of Health (1993) Consensus Conference Report was followed. These analyses, however, do not completely describe test performance because they did not compare neonatal screening test results with a gold standard test of hearing. Test performance, as measured by the area under a relative operating characteristic curve, were similar for all three neonatal tests when neonatal test results were compared with VRA data obtained at 8 to 12 mo corrected age. However, ABRs were more successful at determining auditory status at 1 kHz, compared with the otoacoustic emission (OAE) tests. Performance was more similar across all three tests when they were used to identify hearing loss at 2 and 4 kHz. No test performed perfectly. Using either the two- or three-frequency pure-tone average (PTA), with a fixed false alarm rate of 20%, hit rates for the neonatal tests, in general, exceeded 80% when hearing impairment was defined as behavioral thresholdsor =30 dB HL. All three tests performed similarly when a two-frequency (2 and 4 kHz) PTA was used as the gold standard; OAE test performance decreased when a three-frequency PTA (adding 1 kHz) was used as the gold standard definition. For both PTA and all three neonatal screening measures, however, hit rate increased as the magnitude of hearing loss increased.Singly, all three neonatal hearing screening tests resulted in low refer rates, especially if referrals for follow-up were made only for the cases in which stopping criteria were not met in both ears. Following a protocol similar to that recommended in the National Institutes of Health (1993) Consensus Conference report resulted in refer rates that were less than 4%. TEOAEs at 80 dB pSPL, DPOAE at L1 = 65, L2 = 50 dB SPL and ABR at 30 dB nHL measured during the neonatal period, and as implemented in the current study, performed similarly at predicting behavioral hearing status at 8 to 12

The objective of this study was to describe the demographic data, medical status, and incidence of risk factors for hearing impairment in the neonatal intensive care unit (NICU) and well-baby populations in a multicenter prospective study designed to assess neonatal hearing impairment and to evaluate factors that might affect neonatal hearing test performance.This was a prospective multicenter study funded by the National Institutes of Health-National Institute on Deafness and Other Communication Disorders to evaluate the effectiveness of auditory brain stem response, transient evoked otoacoustic emissions, and distortion product otoacoustic emissions for newborn hearing screening. Research staff at each site obtained informed consent and detailed demographic and medical data, including information on established risk factors for hearing loss on 4478 high-risk infants cared for in the NICU, 2348 infants from the well-baby nurseries with no risk factor, and 353 infants from the well-baby nurseries with risk factors. For follow-up purposes the sample was divided further to include a subgroup called selects. Selects were either infants from the well-baby nursery who had an established risk factor for hearing impairment (N = 353) or did not pass the neonatal hearing screen protocol (N = 80). In this study, we focus on the distribution of infants by nursery and risk factors only. Particular effort was made to enroll infants with risk factors for hearing loss in both the NICU and well-baby nurseries. Descriptive analyses are used to describe characteristics of this sample.All 10 of the risk factors established by the Joint Committee on Infant Hearing in 1994 were identified in the NICU population. The four most common were ototoxic medications (44.4%), very low birth weight (17.8%), assisted ventilation5 days (16.4%), and low Apgar scores at 1 or 5 min (13.9%). In contrast, only six risk factors were present in the well-baby nurseries: family history (6.6%), craniofacial abnormalities (3.4%), low Apgar scores (2.8%), syndromes (0.5%), ototoxic medications (0.2%), and congenital infection (0.1%).These descriptive risk factor data reflect both the newborn populations at the study sites and the bias for enrolling infants at risk for hearing loss. The high-risk NICU sample reflects the characteristics typically found in graduates of the NICU. The data summarized in this study will be used to assess the relationships between risk factor and hearing test outcome.

Objectives 1) To describe transient evoked otoacoustic emission (TEOAE) levels, noise levels and signal to noise ratios (SNRs) for a range of frequency bands in three groups of neonates who were tested as a part of the Identification of Neonatal Hearing Impairment multi-center consortium project. 2) To describe the relations between these TEOAE measurements and age, test environment, baby state, and test time. Design TEOAEs were measured in 4478 graduates of neonatal intensive care units (NICUs), 353 well babies with at least one risk indicator, and 2348 well babies without risk factors. TEOAE and noise levels were measured for frequency bands centered at 1.0, 1.5, 2.0, 3.0, and 4.0 kHz for a click stimulus level of 80 dB SPL. For those ears not meeting “passing” stopping criteria at 80 dB pSPL, a level of 86 dB pSPL was included. Measurement-based stopping rules were used such that a test did not terminate unless the response revealed a criterion SNR in four out of five frequency bands or no response occurred after a preset number of averages. Baby state, test environment, and other test factors were captured at the time of test. Results: TEOAE levels, noise levels and SNRs were similar for NICU graduates, well babies with risk factors and well babies without risk factors. There were no consistent differences in response quality as a function of test environment, i.e., private room, unit, open crib, nonworking isolette, or working isolette. Noise level varied little across risk group, test environment, or infant state other than crying, suggesting that the primary source of noise in TEOAE measurements is infant noise. The most significant effect on response quality was center frequency. Responses were difficult to measure in the half-octave band centered at 1.0 kHz, compared with higher frequencies. Reliable responses were measured routinely at frequencies of 1.5 kHz and higher. Conclusions TEOAEs are easily measured in both NICU graduates and well babies with and without risk factors for hearing loss in a wide variety of test environments. Given the difficulties encountered in making reliable measurements for a frequency band centered at 1.0 kHz, its inclusion in a screening program may not be justified.

Objective: The purpose of this study is to describe the recruitment and retention strategies as well as the sample demographics for families with infants completing the neonatal examination and returning for follow-up. These data are compared to those infants inactivated from the study. Design: This study was a prospective, randomized clinical study. All infants who were confined to the neonatal intensive care unit (NICU) and well babies with at least one risk indicator were targeted for behavioral audiometric follow-up testing. In addition, infants without risk factors from the well-baby nursery, but who failed a newborn test, were also followed. Several variables were evaluated to determine those factors, if any, that might predict which families returned for follow-up testing. Results: Recruitment was achieved as per study design with 4911 high-risk infants and 2348 well-baby nursery infants (without risk indicators for hearing) enrolled. Of the 4911 high-risk infants enrolled, 64% were successfully recruited into the follow-up portion of the study. This was less than the projected rate of 80%. Factors predicting non-compliance with the study protocol for follow-up were predominantly sociodemographic and included nonwhite race, no insurance, substance abuse, young maternal age, more than two children at home, and late onset of prenatal care. Conclusions: Factors related to low socioeconomic status and increased social risk were the strongest predictors of poor study protocol compliance. Despite retention challenges, 64% of the targeted, high-risk infants subsequently returned for the 8-to 12-months behavioral hearing assessment protocols for validation purposes.

Objectives 1) To describe the auditory brain stem response (ABR) measurement system and optimized methods used for study of newborn hearing screening. 2) To determine how recording and infant factors related to the screening, using well-defined, specific ABR outcome measures. Design Seven thousand one hundred seventy-nine infants, 4478 from the neonatal intensive care unit (NICU) and the remaining from the well-baby nursery, were evaluated with an automated ABR protocol in each ear. Two channel recordings were obtained (vertex to mastoid or channel A and vertex to nape of neck or channel B) in response to click stimuli of 30 and 69 dB nHL in all infants as well as 50 dB nHL in infants who did not meet criteria for response at 30 dB. Criteria for response included F(SP) > or =3.1 and a tester-judgment of response. Criteria could be met in the first or repeat test with a maximum of 6144 accepted sweeps per test. Results More than 99% of infants could complete the ABR protocol. More than 90% of NICU and well-baby nursery infants "passed" given the strict criteria for response, whereas 86% of those with high risk factors met criterion for ABR response detection. The number of infants who did not meet ABR response criteria in one or both ears was systematically related to stimulus level with the largest group not meeting criteria at 30 dB followed by 50 and 69 dB nHL. Meeting criteria on the ABR was positively correlated with the amplitude of wave V, with low noise and low electrode impedance. Factors that predicted how many sweeps would be needed to reach criterion F(SP) included noise level of the test site, state of the baby (for example, quiet sleep versus crying), recording noise, electrode impedance and response latency. Channel A (vertex to mastoid) reached criterion more often than channel B (vertex to nape of neck) due to higher noise in channel B. Average total test time for 30 dB nHL screening in both ears was under 8 minutes. Well babies with risk factors took slightly longer to evaluate than other groups with this automated ABR procedure and have higher noise levels. Conclusions ABR implemented with an automated detection algorithm using a 30 dB nHL click stimulus is reliable technique for rapid assessment of auditory status in newborns. Factors other than hearing loss that influenced the test result include infant state, electrode location and impedance, testing site, and infant risk status. Even so, ABRs were reliably recorded in the vast majority of babies under circumstances in which most babies are found in the perinatal period.

1) To describe the hearing status of the at-risk infants in the National Institutes of Health-Identification of Neonatal Hearing Impairment study sample at 8 to 12 mo corrected age (chronologic age adjusted for prematurity). 2) To describe the visual reinforcement audiometry (VRA) protocol that was used to obtain monaural behavioral data for the sample.All neonatal intensive care unit infants and well babies with risk factors (including well babies who failed neonatal tests) were targeted for follow-up behavioral evaluation once they had reached 8 mo corrected age. Three thousand one hundred and thirty-four (64.4%) of the 4868 surviving infants returned for at least one behavioral hearing evaluation, which employed a well-defined VRA protocol. VRA thresholds or minimum response levels (MRLs) were determined for speech and pure tones of 1.0, 2.0, and 4.0 kHz for each ear using insert earphones.More than 95% of the infants were reliably tested with the VRA protocol; 90% provided complete tests (four MRLs for both ears). Ninety-four percent of the at-risk infants were found to have normal hearing sensitivity (MRLs of 20 dB HL) at 1.0, 2.0, and 4.0 kHz in both ears. Of the infants, 2.2% had bilateral hearing impairment, and 3.4% had impairment in one ear only. More than 80% of the impaired ears had losses of mild-to-moderate degree.This may be the largest study to attempt to follow all at-risk infants with behavioral audiometric testing, regardless of screening outcome, in an effort to validate the results of auditory brain stem response, distortion product otoacoustic emission, and transient evoked otoacoustic emission testing in the newborn period. It is one of only a few studies to report hearing status of infants at 1 yr of age, using VRA on a clinical population. Successful testing of more than 95% of the infants who returned for the VRA follow-up documents the feasibility of obtaining monaural behavioral data in this population.

Objectives: 1) To describe distortion product otoacoustic emission (DPOAE) levels, noise levels and signal to noise ratios (SNRs) for a wide range of frequencies and two stimulus levels in neonates and infants. 2) To describe the relations between these DPOAE measurements and age, test environment, baby state, and test time. Design: DPOAEs were measured in 2348 well babies without risk indicators, 353 well babies with at least one risk indicator, and 4478 graduates of neonatal intensive care units (NICUs). DPOAE and noise levels were measured at f 2 frequencies of 1.0, 1.5, 2.0, 3.0, and 4.0 kHz, and for primary levels (L 1 /L 2 ) of 65/50 dB SPL and 75/75 dB SPL. Measurement-based stopping rules were used such that a test did not terminate unless the response was at least 3 dB above the mean noise floor + 2 SDs (SNR) for at least four of five test frequencies. The test would terminate, however, if these criteria were not met after 360 sec. Baby state, test environment, and other test factors were captured at the time of each test. Results: DPOAE levels, noise levels and SNRs were similar for well babies without risk indicators, well babies with risk indicators, and NICU graduates. There was a tendency for larger responses at f 2 frequencies of 1.5 and 2.0 Hz, compared with 3.0 and 4.0 kHz; however, the noise levels systematically decreased as frequency increased, resulting in the most favorable SNRs at 3.0 and 4.0 kHz. Response levels were least and noise levels highest for an f 2 frequency of 1.0 kHz. In addition, test time to achieve automatic stopping criteria was greatest for 1.0 kHz. With the exception of active/alert and crying babies, baby state had little influence on DPOAE measurements. Additionally, test environment had little impact on these measurements, at least for the environments in which babies were tested in this study. However, the lowest SNRs were observed for infants who were tested in functioning isolettes. Finally, there were some subtle age affects on DPOAE levels, with the infants born most prematurely producing the smallest responses, regardless of age at the time of test. Conclusions: DPOAE measurements in neonates and infants result in robust responses in the vast majority of ears for f 2 frequencies of at least 2.0, 3.0 and 4.0 kHz. SNRs decrease as frequency decreases, making the measurements less reliable at 1.0 kHz. When considered along with test time, there may be little justification for including an f 2 frequency at 1.0 kHz in newborn screening programs. It would appear that DPOAEs result in reliable measurements when tests are conducted in the environments in which babies typically are found. Finally, these data suggest that babies can be tested in those states of arousal that are most commonly encountered in the perinatal period.

Objectives This article describes the design of a multicenter study sponsored by the National Institutes of Health. The purpose of this study was to determine the accuracy of three measures of peripheral auditory system status (transient evoked otoacoustic emissions, distortion product otoacoustic emissions, and auditory brain stem responses) applied in the perinatal period for predicting behavioral hearing status at 8 to 12 mo corrected age. The influences of the infant’s medical status, the test environment, and test and response parameters on test performance were e-amined. Design Seven institutions participated in this study. There were 7179 infants evaluated in the perinatal period. All graduates of the neonatal intensive care unit (4478) and well babies with one or more risk factor for hearing loss (353) were targeted for follow-up testing using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age. Well babies without any risk indicators (N = 2348) were not targeted for follow-up VRA testing. However, 80 of these well babies did not pass the screening protocol and thus were targeted for follow-up VRA testing as well. Perinatal test performance was evaluated using the VRA data as the “gold standard.” Results The results of this study are described in a series of 11 articles following this introductory article. Conclusions The evaluation of newborn hearing tests required a longitudinal study in which newborn test results were compared with a gold standard based on behavioral audiometric assessment. Such an evaluation was possible because all newborns, passes as well as refers, were followed up long enough to permit reliable behavioral measurements. In addition, prenatal, perinatal, and maternal history information, test environment, and test parameter information were collected to provide data that led to a complete description of factors affecting test outcomes. All of these data were obtained in a sample of sufficient ethnic, medical, and geographic diversity in efforts to increase the generalizability of the results. Finally, the data were combined in a relational data base to e-amine the factors that influence test performance. Specific information related to these issues is presented in the articles that follow.

Auditory neuropathy (AN) is a hearing disorder that presents with a grossly abnormal or absent neural response as measured by evoked potentials in the presence of normal outer hair cell function evidenced by present otoacoustic emissions or cochlear microphonics. Rehabilitation for patients with AN is challenging due to abnormal temporal encoding at the auditory nerve leading to severely impaired speech perception. Although patients with AN may demonstrate improvement in thresholds with amplification, temporal encoding dysfunction, and consequently speech perception degradation, is not alleviated by amplification. Another issue is the heterogeneity of the AN population in terms of audiologic and neurologic findings, in addition to uncertain etiology and pathophysiology. For children with prelingual onset of AN, development of auditory and oral communication skills is particularly compromised. All children with hearing loss in the severe-to-profound range who do not benefit from conventional amplification can be considered candidates for a cochlear implant (CI). This paper presents a case study of a child with AN who received a CI. Whereas no synchronous neural response auditory brainstem response could be elicited to acoustic stimuli, an electrically evoked auditory nerve action potential was evident following implantation, suggesting restoration to some degree of neural synchrony. Significant improvement in speech perception was found post-CI. Recommendation to implant all patients with AN would be premature, but these findings suggest that electrical stimulation in some cases of auditory neuropathy can be a viable option. Abbreviations: AN = auditory neuropathy, CI = cochlear implant, CM = cochlear microphonic, DSL = desired sensation level, EAP = electrically evoked compound action potential, ESP = Early Speech Perception test, IHC = inner hair cells, LTASS = long-term average speech spectrum, NRT = neural response telemetry, OAE = otoacoustic emission, TAC = Test of Auditory Comprehension, TEOAE = transient evoked otoacoustic emission

Otoacoustic emissions are typically reduced in amplitude when broadband noise is presented to the contralateral ear. This contralateral suppression is attributed to activation of the medial olivocochlear system, which has an inhibitory effect on outer hair-cell activity. By studying the effects of contralateral noise on cochlear output at different stages of auditory maturation in human neonates, it is possible to describe the timecourse for development of medial efferent system function in humans. The present study recorded 2 f1-f2 distortion product otoacoustic emissions (DPOAE) in human adults, term and premature neonates at three f2 frequencies: 1500, 3000, and 6000 Hz, using fixed primary tone frequency ratio (f2/f1 = 1.2) and level separation (10 dB, L1L2). Average DPOAE growth functions were recorded with and without contralateral broadband noise. Results indicate that contralateral suppression of DPOAEs is absent at 6000 Hz, but present at 1500 and 3000 Hz for all ages. However, DPOAE amplitude from premature neonates was not altered by noise in an adult-like manner; in this age group, DPOAE amplitude was equally likely to by suppressed or enhanced by noise presented contralaterally. Contralateral enhancement may reflect a temporary stage of immaturity in outer hair cell-medial efferent fiber synapses just prior to term birth.

Objectives: Auditory neuropathy is a recently described disorder in which patients demonstrate hearing loss for pure tones, impaired word discrimination out of proportion to pure tone loss, absent or abnormal auditory brainstem responses, and normal outer hair cell function as measured by otoacoustic emissions and cochlear microphonics. We have identified eight pediatric patients having hearing deficits that are most likely due to a neuropathy of the eighth nerve. In this study, the results of audiologic testing performed with these eight children are described. Study Design: Retrospective review of audiologic findings in eight children with auditory neuropathy. Methods. Each subject was tested with pure tone and speech audiologic testing, auditory brainstem response, and click-evoked otoacoustic emissions. Results of these tests were tabulated and summarized. Results: Pure tone audiologic testing revealed five children with upsloping sensorineural hearing loss, two with high frequency loss, and one with a mild, flat configuration. Six children demonstrated poor word discrimination scores, and the other two had fair to good word discrimination. All eight subjects had normal distortion product and transient otoacoustic emissions. All eight children demonstrated absent or marked abnormalities of brainstem auditory evoked potentials. These findings suggest that while cochlear outer hair cell function is normal, the lesion is located at the eighth nerve. Conclusions: Recent advances in otoacoustic emissions testing permit differentiation of neural deafness from sensory deafness. This paper describes the clinical presentation and audiologic findings in pediatric auditory neuropathy, as well as the recommended management of these patients. Otolaryngologists should be aware of this disorder and implications for its management, which differs from treatment of sensorineural hearing loss.

The absolute auditory sensitivity of the human newborn infant was investigated using auditory brainstem response thresholds (ABR). ABRs were elicited with clicks and tone-bursts of 0.5, 1.5, 4.0 and 8.0 kHz, embedded in notched noise, in healthy, full-term human neonates and young adults with known, normal-hearing sensitivity. Stimuli were calibrated using a probe microphone positioned near the tympanic membrane in the ear canal of each subject to control for differences in resonance characteristics of infant and adult ear canals. ABR thresholds were also characterized relative to group psychophysical thresholds (nHL) and relative to individual psychophysical threshold or sensation level (SL) for the adult subjects. Infant ABR thresholds measured in p.e. SPL for all stimuli are elevated by to 3-25 dB relative to adult thresholds. Threshold elevation is greatest for the high-frequency stimuli. Result are consistent with neural immaturity for high-frequency stimuli in the auditory system of human neonates.

Objectives: This article evaluates the concept of auditory threshold and discusses the limitations of assessing threshold in human neonates. The advantages and limitations of assessing neonatal threshold by means of auditory brain stem response (ABR) are discussed, and data from several studies of newborn ABR threshold are compared. The authors report data from their own study designed to compare adult and neonatal ABR threshold using tonal stimuli. Experimental Design: Several studies are compared. Data from the authors are ABR thresholds for tone bursts of 0.5, 1.5, 4, and 8 kHz, determined from 2-channel recordings in full-term neonates and adults. Stimuli were calibrated in SPL by means of a probe microphone inserted into the ear canal along with the insert transducer of each subject. Results: All studies find a degree of threshold elevation in neonates relative to adult threshold. Neonatal ABR thresholds from our laboratory for stimuli from 500 through 8000 Hz are elevated relative to adult thresholds by 5 to 25 dB. Threshold elevation in our data and in other studies has found that neonatal ABR thresholds to high-frequency stimuli show the largest elevation relative to adults and low-frequency stimuli the most mature. Conclusions: Thresholds of neonates, as measured by the ABR, are immature especially for high-frequency stimuli. Proper stimulus calibrations, which removes the influence of ear canal resonance, are important for comparisons of data across age groups. Developmental differences in the conductive mechanism and neural immaturity are the most harmonious explanations for elevation of neonatal ABR thresholds.

Filtering of electrode‐recorded activity before averaging is used in evoked‐potential measurements to reduce background noise under the assumption that unwanted spectral components will be suppressed without substantially altering neural activity. Desired filter characteristics depend on signal and noise spectra and filter choice can affect the validity and efficiency of ABR measurement. Spectral characteristics of the human auditory brain‐stem response (ABR) change with subject age and state and with the level and spectrum of the stimulus. Brain‐stem evoked potentials from infants comprise greater low‐frequency spectral components than do adult ABRs. Physiologic noise can also change with age of the subject. This study compares the effects of 30‐ and 100‐Hz high‐pass filters on ABR amplitude and response F sp in full‐term infants. Stimuli used to elicit ABRs are moderate‐ and low‐level clicks and 500‐Hz tone bursts. Spectral characteristics of the averaged ABR and the no‐stimulus background noise from full‐term infants are also characterized. Results indicate that (1) energy in the infant ABR is concentrated below 100 Hz and (2) a high‐pass recording filter of 30 Hz reveals a larger‐amplitude ABR and enhances the overall signal‐to‐noise ratio as measured by F sp as compared to a 100‐Hz high pass.

Auditory neuropathy (AN) is a term used to describe an auditory disorder in which there is evidence of normal outer hair cell function (otoacoustic emissions and/or cochlear microphonics) and poor function of the auditory nerve (absent or highly distorted auditory brain stem response starting with wave I). Many of these patients have evidence of generalized peripheral nerve disease, leading to an assumption that the peripheral portion of the auditory nerve is the most likely site of lesion. A small group of these patients has received cochlear implants, and the majority of them achieve average to above-average performance. Although this outcome may seem incongruous with neural disease, average performance by patients with AN may be a result of the reintroduction of neural synchrony by electrical stimulation and/or the fact that most deaf patients have poor nerve survival. Although cochlear implants are promising for deaf patients with AN, more study of the disorder is needed.

Objective: To define both auditory nerve and cochlear receptor functions in subjects with auditory neuropathy (AN). Design: We tested 33 AN subjects (66 ears) and compared them with 21 healthy subjects (28 ears). In AN subjects, the average pure-tone (1, 2, and 4 kHz) threshold loss was 57 dB HL. Click stimuli were used to elicit transient evoked otoacoustic emissions (TEOAEs), cochlear microphonics (CMs), and auditory brain stem responses (ABRs). Both cochlear and ABR potentials were recorded from surface electrodes (vertex-ipsilateral mastoid) using averaging procedures. The amplitudes and latencies of CMs and ABRs and the amplitude of the TEOAEs were analyzed. Results: CM amplitudes recorded from normal ears decreased as a function of subject age. CMs recorded from AN subjects fell within the normal age-adjusted range in 60% of the subjects and were >2 SEEs (standard error of estimate) above the age-adjusted normal regression in 40% of the subjects. TEOAEs were absent in 19 (30%) AN ears (bilaterally in eight, and unilaterally in three subjects) and were present in 44 ears. In AN subjects, correlations among CM amplitude, TEOAE amplitude, and pure-tone average thresholds were not significantly related. CM amplitudes were not significantly different whether TEOAEs or ABRs were present or absent. The ABR was present in 21% of AN subjects and consisted of a low-amplitude Wave V without a preceding Wave I. Measures of CM amplitude and PTA hearing loss were not significantly different in those AN ears with a preserved ABR compared with ears with absent ABRs. Summating potentials to transient click stimuli were of small amplitude (

Objective The purposes of this article are to describe the overall protocol for the Identification of Neonatal Hearing Impairment (INHI) project and to describe the management of the data collected as part of this project. A well-defined protocol and database management techniques were needed to ensure that data were 1) collected accurately and in the same way across sites; 2) maintained in a database that could be used to provide feedback to individual sites regarding enrollment and the extent to which the protocol was complete on individual subjects; and 3) available to answer project questions. This article describes techniques that were used to meet these needs. Design This study was a prospective, randomized study that was designed to evaluate auditory brain stem responses, transient evoked otoacoustic emissions, and distortion product otoacoustic emissions as hearing-screening tools, and to relate neonatal test findings to hearing status, defined by visual reinforcement audiometry at 8 to 12 mo of age. Measures of middle-ear function also were obtained at some sites as part of the neonatal test battery. In addition, other clinical and demographic data were gathered to determine the extent to which factors, other than auditory status, influenced test behavior. Three groups were evaluated: neonatal intensive care unit (NICU) infants (those who spent 3 or more days in a NICU), well babies with risk factors for hearing loss, and well babies without risk factors. Six centers participated in the trial. The testers for the project included audiologists, technicians, audiology graduate students, and medical research staff. The same computerized neonatal test program was applied at each center. This program generated the neonatal test database automatically. Clinical and demographic data were collected by means of concise data collection forms and were entered into a database at each site. After the neonatal test, subjects from the NICU and at-risk well babies were evaluated with visual reinforcement audiometry starting at 8 to 12 mo of age. All data were electronically transmitted to the core site where they were merged into one overall database. This database was exercised to provide feedback and to identify discrepancies throughout the course of the study. In its final form, it served as the database on which all analyses were performed. Results and conclusion The protocol was a departure from typical hearing screening procedures in terms of 1) its regimented application of three screening measures; 2) the detailed information that was obtained regarding subject clinical and demographic factors; and 3) its application of the same procedures across six centers having diverse geographic location and subject demographics. A learning curve for successfully executing the study protocols was observed. Throughout the study, monthly reports were generated to monitor subject enrollment, check for data completeness, and to perform data integrity checks. In combination with monthly data reports and checks that occurred throughout the progression of the study, miscellaneous data audits were performed to check accuracy of neonatal testing programs and to cross-check information entered in the clinical and demographic database. The data management techniques used in this project helped to ensure the quality of the data collection process and also allowed for detailed analyses once data were collected. This was particularly important because it enabled us to evaluate not only the performance of individual measures as screening tools, but also permitted an evaluation of the influence of other variables on screening test results.

This article summarizes the results of a multi-center study, "Identification of Neonatal Hearing Impairment," sponsored by the National Institutes of Health. The purpose of this study was to determine the performance characteristics of three measures of peripheral auditory system status, transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), and auditory brain stem responses (ABR), applied in the neonatal period in predicting hearing status at 8 to 12 mo corrected age.The design and implementation of this study are described in the first two articles in this series. Seven institutions participated in this study; 7179 infants were evaluated. Graduates of the neonatal intensive care unit and well babies with one or more risk factors for hearing loss were targeted for follow-up testing using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age. Neonatal test performance was evaluated using the VRA data as the "gold standard."The major results of the study are described in the nine articles preceding this summary article. TEOAEs in response to an 80 dB pSPL click, DPOAEs in response to L1 = 65 and L2 = 50 dB SPL and ABR in response to a 30 dB nHL click performed well as predictors of permanent hearing loss of 30 dB or greater at 8 to 12 mo corrected age. All measures were robust with respect to infant state, test environment and infant medical status. No test performed perfectly.Based on the data from this study, the 1993 National Institutes of Health Consensus Conference-recommended protocol-an OAE test followed by an ABR test for those infants failing the OAE test-would result in low referral rate (96 to 98%). TEOAEs for 80 dB pSPL, ABR for 30 dB nHL and DPOAEs for L1 = 65 dB SPL and L2 = 50 dB SPL perform well in predicting hearing status based on the area under the relative operating characteristic curve. Accuracy for the OAE measurements are best when the speech awareness threshold or the pure-tone average for 2.0 kHz and 4 kHz are used as the gold standard. ABR accuracy varies little as a function of the frequencies included in the gold standard. In addition, 96% of those infants returning for VRA at 8 to 12 mo corrected age were able to provide reliable ear-specific behavioral thresholds using insert earphones and a rigorous psychophysical VRA protocol.

Auditory neuropathy (AN) was initially described as impairment of auditory neural function, with preserved cochlear hair cell function. In this report, 67 patients with audiological and neurophysiological criteria for hearing loss due to auditory neuropathy are described. Reviewing this large body of patients, AN appears to consist of a number of varieties, with different etiologies and sites affected. All varieties share a relatively spared receptor function, and an impaired neural response, with diminished ability to follow fast temporal changes in the stimulus, but different varieties in this general scheme can be distinguished. Analyses of the clinical features indicate that auditory neuropathies vary in several measures including age of onset, presence of peripheral neuropathy, etiology, and behavioral and physiological measures of auditory function. The sites affected along the peripheral auditory pathway may include dysfunction of the outer hair cells, the synapse between hair cell and auditory nerve, and the auditory nerve fibers, with myelin as well as axonal impairments contributing to the disorder.

Author(s): Abdala, C; Sininger, YS; Starr, A | Abstract: ObjectiveThe objective of this experiment was to address: 1) whether normal efferent system function is required for normal cochlear tuning as measured by distortion product otoacoustic emission (DPOAE) suppression in humans and 2) whether cochlear function, assessed by DPOAE suppression tuning, is normal in a small group of patients with auditory neuropathy.DesignDPOAE suppression tuning curves (STCs) are similar to other physiologic measures of tuning. They are generated by evoking a DPOAE with two simultaneously presented pure tones and then suppressing the distortion product with a third tone of varying frequency and level. In this study, DPOAE STCs were generated with f2 frequencies of 1500, 3000, and 6000 Hz in 15 normal-hearing adults and four subjects with documented auditory neuropathy. Tuning curve width, slope and tip characteristics, as well as rate of suppression growth were measured in each group. Contralateral suppression of otoacoustic emissions (OAEs) was also recorded as an index of medial efferent function.ResultsResults show that the four subjects with auditory neuropathy lacked efferent suppression of OAEs. However, these four subjects showed normal estimates of cochlear tuning as measured by DPOAE suppression results.ConclusionsThis finding suggests that normal efferent system function is not required at the time of test for normal DPOAE suppression tuning. It also suggests that cochlear function as evaluated by detailed measures of DPOAE suppression, is normal in these "typical" patients with auditory neuropathy.

Auditory neuropathy affects the normal synchronous activity in the auditory nerve, without affecting the amplification function in the inner ear. Patients with auditory neuropathy often complain that they can hear sounds, but cannot understand speech. Here we report psychophysical tests indicating that these patients' poor speech recognition is due to a severe impairment in their temporal processing abilities. We also simulate this temporal processing impairment in normally hearing listeners and produce similar speech recognition deficits. This study demonstrates the importance of neural synchrony for auditory perceptions including speech recognition in humans. The results should contribute to better diagnosis and treatment of auditory neuropathy.

Members of a Roma (Gypsy) family with hereditary motor and sensory peripheral neuropathy (HMSN) and concomitant auditory and vestibular cranial neuropathies were identified in Kocevje, Slovenia. The illness begins in childhood with a severe and progressive motor disability and the deafness is delayed until the second decade. There are no symptoms of vestibular dysfunction. The family structure is consistent with an autosomal recessive pattern of inheritance and the genetic locus for the disorder is linked to the same region of chromosome 8q24 as other Roma families with HMSN and deafness from Lom, Bulgaria (HMSN-Lom). The present study shows that the deafness is caused by a neuropathy of the auditory nerve with preserved measures of cochlear outer hair cell function (otoacoustic emissions and cochlear microphonics) but absent neural components of auditory brainstem potentials. The hearing loss affects speech comprehension out of proportion to the pure tone loss. Vestibular testing showed absence of caloric responses. Physiological and neuropathological studies of peripheral nerves were compatible with the nerve disorder contemporaneously affecting Schwann cells and axons resulting in both slowed nerve conduction and axonal loss. Genetic linkage studies suggest a refinement of the 8q24 critical region containing the HMSN-Lom locus that affects peripheral motor and sensory nerves as well as the cranial auditory and vestibular nerves.

Threshold measures of auditory brainstem response (ABR) were generated in 72 full-term newborn infants in response to clicks and tone burst stimuli between 500 and 8000 Hz as detailed in a previous study. These results were further analyzed for differences in response related to ear (lateral asymmetry) and subject gender. Thresholds obtained in male infants were significantly lower than those of females (P = 0.0485). The greatest differences in threshold between male and female infants occurs in the right ear (7.45 dB) as opposed to the left ear (1.56 dB). Both male and female infants have significantly larger wave V amplitude elicited from the right ear than the left (P = 0.0002) using low-level stimuli. Also, as has been noted in adults, female infants have larger amplitude ABRs than males (P = 0.0018), but amplitude differences across gender are significant only in the right ear (ear by gender interaction P = 0.0278). Results of this study indicate that gender differences and lateral asymmetry in auditory function are not a result of gender bias for or unbalanced auditory trauma, but a biologically significant phenomenon that is present at birth. The argument is made that superior right ear performance may be part of cerebral laterality in auditory function.

To define mechanisms accounting for transient deafness in three children (two siblings, ages 3 and 6, and an unrelated child, age 15) when they become febrile.Audiometric tests (pure-tone audiometry, speech and sentence comprehension), tympanometry, middle ear muscle reflex thresholds, otoacoustic emissions (OAEs), and electrophysiological methods (auditory brain stem responses [ABRs], sensory evoked potentials, peripheral nerve conduction velocities) were used to test the children when they were afebrile and febrile.ABRs, when afebrile, were abnormal with a profound delay of the IV-V and absence of waves I-III. The ABR in one of the children, tested when febrile, showed no ABR components. Measures of cochlear receptor function using OAEs were normal in both febrile and afebrile states. Cochlear microphonic potentials were present in the three children, and a summating potential was likely present in two. When afebrile, there was a mild threshold elevation for all frequencies in the 15-yr-old and a mild elevation of thresholds for just low frequencies in the two siblings. Speech comprehension in quiet was normal but impaired in noise. One of the siblings tested when febrile had a profound elevation (80 dB) of pure-tone thresholds and speech comprehension was absent. Acoustic reflexes subserving middle ear muscles and olivocochlear bundle were absent when febrile and when afebrile. No other peripheral or cranial nerve abnormalities were found in any of the children. Sensory nerve action potentials from median nerve in one of the children showed no abnormalities on warming of the hand to 39 degrees C.These children have an auditory neuropathy manifested by a disorder of auditory nerve function in the presence of normal cochlear outer hair cell functions. They develop a conduction block of the auditory nerves when their core body temperature rises due, most likely, to a demyelinating disorder of the auditory nerve. The auditory neuropathy in the two affected siblings is likely to be inherited as a recessive disorder.

Distortion product otoacoustic emission (DPOAE) iso-suppression tuning curves (STC) were generated in 15 normal-hearing adults and 16 healthy term-born neonates for three f2 frequencies. The 2f1-f2 DPOAE was elicited using f2/f1 = 1.2, LI = 1.2, LI = 65 and L2 = 50 dB SPL. A suppressor tone was presented at frequencies ranging from 1 octave below to 1/4 octave above f2 and varied in level until DPOAE amplitude was reduced by 6 dB. The suppressor level required for 6 dB suppression was plotted as function of suppressor frequency to generate a DPOAE STC. Forward-masked psychoacoustic tuning curves (PTC) were obtained for three of the adult subjects. Results indicate that DPOAE STCs are stable and show minimal inter- and intra-subject variability. The tip of the STC is consistently centered around the f2 region and STCs are similar in shape, width (Q10) and slope to VIIIth-nerve TCs. PTCs and STCs measured in the same subject showed similar trends, although PTCs had narrower width and steeper slope. Neonatal STCs were recorded at 3000 and 6000 Hz only and were comparable in shape, width and slope to adult STCs. Results suggest: (1) suppression of the 2f1-f2 DPOAE may provide an indirect measure of cochlear frequency resolution in humans and (2) cochlear tuning, and associated active processes in the cochlea, are mature by term birth for at least mid- and high-frequencies. These results provide significant impetus for continued study of DPOAE suppression as a means of evaluating cochlear frequency resolution in humans.

The auditory brain stem response (ABR) is felt to be an objective technique for predicting hearing thresholds because a voluntary response is not required from the subject. However, determination of ABR threshold can be a subjective process. This article discusses a technique, termed Fsp, which adds objectivity to ABR threshold detection by creating a ratio of signal plus averaged background noise over an estimate of the averaged background noise for any given averaged ABR. Fsp values have an F distribution. Consequently, the confidence of true detection for a given ABR can be determined by comparing its calculated Fsp value to statistical tables. Using a technique such as Fsp not only adds objectivity to ABR threshold detection, but also optimizes test time by allowing the averaging process to stop as soon as the background noise has been reduced and the true neural potential can be judged to be present. The estimate of the background noise can be used as a weighting factor to reduce the influence of noisy segments during the averaging process as well. Using this technique, we have found ABR threshold to be within 5 or 6 dB of psychophysical threshold for like (click) stimuli and, in our pediatric clinic, ABR click thresholds are within 10 dB of puretone average for children with losses ranging from mild to profound.

A vertical recording montage (C z to the seventh cervical vertebra or C 7 ) has been shown to yield significantly lower auditory brainstem response (ABR) threshold when compared with a horizontal or anterior-posterior montage (Sininger & Don, 1989). The present study further examines the relationship between electrode placement and the amplitude of the ABR to low-level stimuli. Four electrode arrays were compared—the commonly-used clinical configuration of forehead to ipsilateral mastoid, the vertical array from the previous study (C z to C 7 ), and two additional montages employing linked mastoids as reference to either the vertex or forehead electrode. ABRs were recorded simultaneously in four channels in response to 8000 click stimuli at 10, 20, and 30 dB SL from 9 male and 9 female adult subjects with normal hearing. The effect of electrode channel was significant at

An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing. © 1991 Oxford University Press.

This study investigated the effects of click polarity on threshold detectability (threshold level in dB SL) of the auditory brain stem response (ABR). ABRs were obtained from 10 normally hearing adult subjects in response to rarefaction and condensation clicks presented from 0 to 10 dB SL in 2 dB steps. An objective response signal-to-noise estimator, known as Fsp, was the dependent variable. ABR detectability functions (Fsp by dB SL) were not significantly influenced by click polarity. Conclusions can only be drawn for normally hearing adults. For this population, click polarity does not affect threshold detection with the ABR.

Auditory brain-stem response (ABR) recorded from 3 orthogonally placed electrode pairs reveals a voltage-voltage-voltage plot of activity known as the 3-channel Lissajous' trajectory (3-CLT). ABR 3-CLT responses have been recorded from 9 human subjects in response to monaural, 70 dB nHL clicks. Responses were simultaneously recorded from 3 electrode channels in the vertical, horizontal and anterior-posterior plane. These 3 channels were combined to form human ABR 3-CLTs. Analysis of data included inspection of single-channel data, determination of segments along the trajectory which fall into distinct planes, and derivation of overall amplitude by time measures known as vector amplitude plots. Depending upon definition, 9 or 10 sequential, overlapping planar segments are found in the ABR 3-CLT of human subjects. Measures of planar apex latency and duration of planar segments were found to be reasonably consistent between subjects as were the orientations of planar segments. Vector amplitude plots (absolute amplitude of 3-channel recordings over time) derived from the human 3-CLT demonstrate 8 fast peaks which appear to be superimposed upon slow wave activity. These plots are shown to be potentially useful in determining optimal electrode orientations for single-channel recording of various ABR peaks. It was concluded that planar-segment formation in the ABR 3-CLT is a consistent finding in human subjects and that this technique is a promising clinical and research tool.

Two discrete studies of lesions (sectioning the auditory nerve and mid-sagittal brain-stem) were performed in 5 adult cats to determine the relationship between planar-segment formation and underlying generator activity. The experiments gave 2 major results: (1) Section of the VIII nerve at the brain-stem resulted in loss of potentials after wave II and almost total loss of wave II in most traces. In the time interval of planar segments a1, a2 and b1, only a single planar loop remained after sectioning the VIII nerve, and its orientation corresponded to that of the pre-surgical planar segment a1. (2) Whereas mid-sagittal sectioning of the brain-stem considerably reduced waves 4, 5 and 7 in vector amplitude plots, planar analysis showed that planar segments c2, c3, c4 and d1 were reduced to the simpler configuration of a line in voltage-space, and that planar segments d2, d3 and d4 were reduced in size and shifted in orientation. These results suggest the following hypotheses: (1) planar segment a1 must represent activity arising from the VIII nerve peripheral to its entry point into the brain; (2) VIII nerve activity can extend into the time that the cochlear nuclear complex is active; (3) an additional generator, probably the cochlear nuclear complex, contributes to the negativity observed after wave I; (4) planar segments c2, c3, c4 and d1 represent activity from generators whose input is from the contralateral ear. Some of the contributors to planar segments d2, d3 and d4 are activated by pathways ipsilateral to the stimulated ear, while the remaining portion is contralaterally activated.

This study evaluated the effects of stimulus presentation rate and electrode orientation on ABR threshold. Six normal-hearing adults served as subjects. ABRs were recorded from three orthogonal electrode pairs in response to click stimuli at rates of 48 and 21/s. Psychophysical thresholds were determined for each of these stimuli, and ABRs were recorded with stimuli between 0 and 10 dB SL in 2-dB steps. A ratio of ABR signal strength to noise variance (F sp ) was the criterion used to define threshold. Specifically, an F sp value of 2.25, equivalent to a 95% response confidence using 5 and 250 degrees of freedom, was the criterion used to determine response presence within a maximum of 10,000 sweeps per average. Results revealed that, for normal-hearing adult subjects, click rate up to 48/s does not influence the sensation level at which a detectable response can be found, and a nearly vertical electrode orientation is optimal for recording the response at low levels. The predicted difference between psychophysical and ABR thresholds with a vertical electrode orientation, using 10,000 sweeps per average, up to 48 clicks per second, and an F sp criterion of 2.25 is 4.4 dB.

Twelve students from classrooms for children with severe language disorders and 12 age-matched controls were evaluated for short-term memory scanning speed using the Sternberg task. Sets of two, three, and four digits were presented via earphones as memory sets, followed by single-probe digits. Reaction time was measured for a verbal response of "yes" or "no" indicating whether the probe was a member of the initial set. Average per-item scanning speed for the normal children was 66 ms, which was significantly different from the 253-ms average scanning speed of the language-disordered group. Many similarities were noted in the performance of the two groups on the memory scanning task. No differences were found in estimates of encoding and response speed, in percentage of errors or in serial or numerical position effects across groups. Results indicate that children with developmental language disorders may demonstrate reduced processing speed or memory retrieval time, which could contribute to linguistic deficits.

The etiology of an incidentally discovered temporary threshold shift observed in an experimental animal (Harley guinea pig) is discussed with its potential implications for auditory research.