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New objective and accurate feedback detection method, transfer function variation criterion (TVC), has been developed for evaluating the performance of feedback cancellation techniques. The proposed method is able to classify stable, unstable, and sub-oscillatory stages of feedback in hearing aids. The sub-oscillatory stage is defined as a state where the hearing aid user may perceive distortion of sound quality without the occurrence of oscillation. This detection algorithm focuses on the transfer function variation of hearing aids and the relationship between system stability and feedback oscillation. The transfer functions are obtained using the FIR Wiener filtering algorithm off-line. An anechoic test box is used for the exact and reliable evaluation of different hearing aids. The results are listed and compared with the conventional power concentration ratio (PCR), which has been generally adopted as a feedback detection method for the performance evaluation of hearing aids. The possibility of real-time implementation is discussed in terms of a more convenient and exact performance evaluation of feedback cancellation techniques.

Objective This study explored the feasibility of measuring electrically evoked cortical auditory event-related potentials (eERPs) in children with auditory brainstem implants (ABIs). Design Five children with unilateral ABIs ranging in age from 2.8 to 10.2 years (mean: 5.2 years) participated in this study. The stimulus was a 100-msec biphasic pulse train that was delivered to individual electrodes in a monopolar stimulation mode. Electrophysiological recordings of the onset eERP were conducted in all subjects. Results The onset eERP was recorded in four subjects who demonstrated auditory perception. These eERP responses showed variations in waveform morphology across subjects and stimulating electrode locations. No eERPs were observed in one subject who received no auditory sensation from ABI stimulation. Conclusions eERPs can be recorded in children with ABIs who develop auditory perception. The morphology of the eERP can vary across subjects and also across stimulating electrode locations within subjects.

Objectives The overall aim of the study was to evaluate the feasibility of using electrophysiological measures of the auditory change complex (ACC) to identify candidates for cochlear implantation in children with auditory neuropathy spectrum disorder (ANSD). To achieve this overall aim, this study (1) assessed the feasibility of measuring the ACC evoked by temporal gaps in a group of children with ANSD across a wide age range and (2) investigated the association between gap detection thresholds (GDTs) measured by the ACC recordings and open-set speech-perception performance in these subjects. Design Nineteen children with bilateral ANSD ranging in age between 1.9 and 14.9 years (mean: 7.8 years) participated in this study. Electrophysiological recordings of the auditory event-related potential (ERP), including the onset ERP response and the ACC, were completed in all subjects and open-set speech perception was evaluated for a subgroup of 16 subjects. For the ERP recordings, the stimulus was a Gaussian noise presented through ER-3A insert earphones to the test ear. Two stimulation conditions were used. In the "control condition," the stimulus was an 800-msec Gaussian noise. In the "gapped condition," the stimuli were two noise segments, each being 400 msec in duration, separated by one of five gaps (i.e., 5, 10, 20, 50, or 100 msec). The interstimulation interval was 1200 msec. The aided open-set speech perception ability was assessed using the Phonetically Balanced Kindergarten (PBK) word lists presented at 60 dB SPL using recorded testing material in a sound booth. For speech perception tests, subjects wore their hearing aids at the settings recommended by their clinical audiologists. For a subgroup of five subjects, psychophysical GDTs for the Gaussian noise were also assessed using a three-interval, three-alternative forced-choice procedure. Results Responses evoked by the onset of the Gaussian noise (i.e., onset responses) were recorded in all stimulation conditions from all subjects tested in this study. The presence/absence, peak latency and amplitude, and response width of the onset response did not correlate with aided PBK word scores. The objective GDTs measured with the ACC recordings from 17 subjects ranged from 10 to 100 msec. The ACC was not recorded from two subjects for any gap durations tested in this study. There was a robust negative correlation between objective GDTs and aided PBK word scores. In general, subjects with prolonged objective GDTs showed low-aided PBK word scores. GDTs measured using electrophysiological recordings of the ACC correlated well with those measured using psychophysical procedures in four of five subjects who were evaluated using both procedures. Conclusions The clinical application of the onset response in predicting open-set speech-perception ability is relatively limited in children with ANSD. The ACC recordings can be used to objectively evaluate temporal resolution abilities in children with ANSD having no severe comorbidities, and who are older than 1.9 years. The ACC can potentially be used as an objective tool to identify poor performers among children with ANSD using properly fit amplification, and who are thus, cochlear implant candidates.

OBJECTIVES This study aimed to (1) determine the sensitivity of the electrically evoked auditory change complex (eACC) to changes in stimulating electrode position; and (2) investigate the association between results of eACC measures and behavioral electrode discrimination and their association with speech-perception performance in pediatric cochlear implant (CI) users who have auditory neuropathy spectrum disorder (ANSD). DESIGN Fifteen children with ANSD ranging in age between 5.4 and 18.6 years participated in this study. All subjects used Cochlear Nucleus devices. For each subject, open-set speech-perception ability was assessed using the Phonetically Balanced Kindergarten word lists presented at 60 dB SPL, using monitored live voice in a sound booth. Behavioral and objective measures of electrode discrimination were assessed in a nonclinical test environment. The stimuli used to elicit these measures were 800 msec biphasic pulse trains delivered by a direct interface to the CI. Data were collected from two basic stimulation conditions. In the standard condition, the entire pulse train was delivered to a mid-array electrode (electrode 11 or 12) at the maximum comfortable level (C level). In the change condition, the stimulus was split into two 400 msec pulse train segments presented sequentially on two different electrodes. The stimulation level of the second 400 msec pulse train was loudness balanced to the C level of the mid-array electrode used in the standard condition. The separation between the pair of stimulating electrodes was systematically varied. For behavioral electrode-discrimination measures, each subject was required to determine whether he or she heard one or two sounds for stimuli presented in different stimulation conditions. For the eACC measures, two replicates of 100 artifact-free sweeps were recorded for each stimulation condition. RESULTS The eACC in response to changes in stimulating electrode position was recorded from all subjects with ANSD using direct electrical stimulation. Electrode-discrimination thresholds determined with the eACC and behavioral measures were consistent. Children with ANSD using CIs who showed poorer speech performance also required larger separations between the stimulating electrode pair to reliably elicit the eACC than subjects with better speech-perception performance. There was a robust correlation between electrode-discrimination capacities and speech-perception performances in subjects tested in this study. The effect of electrode separation on eACC amplitudes was not monotonic. CONCLUSIONS These results demonstrate the feasibility of using eACC to evaluate electrode-discrimination capacities in children with ANSD. These results suggest that the eACC elicited by changes in stimulating electrode position holds great promise as an objective tool for evaluating spectral-pattern detection in such subjects, which may be predictive of their potential speech-perception performance.

Auditory neuropathy spectrum disorder (ANSD) is a clinical syndrome characterized by evidence of cochlear function in conjunction with an aberrant auditory neural system. The auditory brainstem response (ABR) cannot be recorded or is grossly abnormal in ANSD patients. Consequently, the fitting of amplification is delayed until behavioral testing is possible. For some ANSD children, behavioral testing is infeasible despite advanced age due to other comorbidities. Therefore, it is crucial to identify a reliable measure of auditory thresholds for ANSD children in order to provide appropriate and timely intervention. Despite an absent ABR, the cortical auditory evoked potential (CAEP) can be recorded from ANSD patients1-4. Previous studies have also shown that hearing thresholds can be reliably measured with the CAEP response in SNHL children5 and its accuracy is as good as or better than that of the ABR6. This report demonstrates the feasibility of using the CAEP to estimate hearing thresholds in ANSD children.

OBJECTIVES This study aimed (1) to investigate the feasibility of recording the electrically evoked auditory event-related potential (eERP), including the onset P1-N1-P2 complex and the electrically evoked auditory change complex (EACC) in response to temporal gaps, in children with auditory neuropathy spectrum disorder (ANSD); and (2) to evaluate the relationship between these measures and speech-perception abilities in these subjects. DESIGN Fifteen ANSD children who are Cochlear Nucleus device users participated in this study. For each subject, the speech-processor microphone was bypassed and the eERPs were elicited by direct stimulation of one mid-array electrode (electrode 12). The stimulus was a train of biphasic current pulses 800 msec in duration. Two basic stimulation conditions were used to elicit the eERP. In the no-gap condition, the entire pulse train was delivered uninterrupted to electrode 12, and the onset P1-N1-P2 complex was measured relative to the stimulus onset. In the gapped condition, the stimulus consisted of two pulse train bursts, each being 400 msec in duration, presented sequentially on the same electrode and separated by one of five gaps (i.e., 5, 10, 20, 50, and 100 msec). Open-set speech-perception ability of these subjects with ANSD was assessed using the phonetically balanced kindergarten (PBK) word lists presented at 60 dB SPL, using monitored live voice in a sound booth. RESULTS The eERPs were recorded from all subjects with ANSD who participated in this study. There were no significant differences in test-retest reliability, root mean square amplitude or P1 latency for the onset P1-N1-P2 complex between subjects with good (>70% correct on PBK words) and poorer speech-perception performance. In general, the EACC showed less mature morphological characteristics than the onset P1-N1-P2 response recorded from the same subject. There was a robust correlation between the PBK word scores and the EACC thresholds for gap detection. Subjects with poorer speech-perception performance showed larger EACC thresholds in this study. CONCLUSIONS These results demonstrate the feasibility of recording eERPs from implanted children with ANSD, using direct electrical stimulation. Temporal-processing deficits, as demonstrated by large EACC thresholds for gap detection, might account in part for the poor speech-perception performances observed in a subgroup of implanted subjects with ANSD. This finding suggests that the EACC elicited by changes in temporal continuity (i.e., gap) holds promise as a predictor of speech-perception ability among implanted children with ANSD.

This study aims to objectively evaluate temporal processing capabilities using the electrically evoked auditory change complex (eACC) in patients with auditory brainstem implants (ABIs). Study participants include seven Cochlear Nucleus 24M ABI recipients (six children and one adult). All children received ABIs due to cochlear nerve deficiency and the adult recipient was diagnosed with neurofibromatosis type II (NF-2). The speech processor was bypassed and electrical stimulus was a biphasic pulse train directly sent through individual electrodes of the ABI. Gap durations tested in this study ranged from 4 to 256 ms. Amplitude modulation frequency was 10 Hz. Modulation depths tested in this study ranged from 1% to 99%. Behavioral gap detection thresholds were also obtained for two participants. The eACCs were evoked by temporal gaps and amplitude modulations. The shortest gap duration and the smallest amplitude modulation depth that can be used to evoke the eACC vary across study participants and across st...

Acoustically evoked neural and hair cell potentials can be measured from the round window (RW) intraoperatively in the general population of cochlear implant recipients.Cochlear implant performance varies greatly among patients. Improved methods to assess and monitor functional hair cell and neural substrate before and during implantation could potentially aid in enhanced nontraumatic intracochlear electrode placement and subsequent improved outcomes.Subjects (1-80 yr) undergoing cochlear implantation were included. A monopolar probe was placed at the RW after surgical access was obtained. The cochlear microphonic (CM), summating potential (SP), compound action potential (CAP), and auditory nerve neurophonic (ANN) were recorded in response to tone bursts at frequencies of 0.25 to 4 kHz at various levels.Measurable hair cell/neural potentials were detected to 1 or more frequencies in 23 of 25 subjects. The greatest proportion and magnitude of cochlear responses were to low frequencies (1,000 Hz). At these low frequencies, the ANN, when present, contributed to the ongoing response at the stimulus frequency. In many subjects, the ANN was small or absent, whereas hair cell responses remained.In cochlear implant recipients, acoustically evoked cochlear potentials are detectable even if hearing is extremely limited. Sensitive measures of cochlear and neural status can characterize the state of hair cell and neural function before implantation. Whether this information correlates with speech performance outcomes or can help in tailoring electrode type, placement or audiometric fitting, can be determined in future studies.

This study aimed to (1) investigate the relationship between the acoustic change complex (ACC) and perceptual measures of frequency and intensity discrimination, and gap detection; and (2) examine the effects of acoustic change on the amplitudes and latencies of the ACC.Psychophysical thresholds for frequency and intensity discrimination and gap detection, as well as ACCs elicited by stimuli containing increments in frequency, or intensity or gaps, were recorded from the same group of subjects. The magnitude of the acoustic change was systematically varied for the ACC recording.Twenty-six adults with normal hearing, ranging in age between 19 and 39 years.Electrophysiological and psychophysical measures for frequency and intensity discrimination were significantly correlated. Electrophysiological thresholds were comparable to psychophysical thresholds for intensity discrimination but were higher than psychophysical thresholds for gap detection and frequency discrimination. Increasing the magnitude of acoustic change increased the ACC amplitude but did not show consistent effects across acoustic dimensions for ACC latency.The ACC can be used as an objective index of auditory discrimination in frequency and intensity. The ACC amplitude is a better indicator for auditory processing than the ACC latency.

Objective: Compare electrocochleography (ECochG) recordings obtained simultaneously at the round window (RW) and tympanic membrane (TM) in patients with auditory neuropathy spectrum disorder (ANSD) in order to validate a noninvasive method for assessing site of lesion in these patients. Better understanding of site of lesion may help optimize intervention strategy and ultimately, performance among ANSD children.Method: ECochG responses were recorded simultaneously at the TM and RW using single pulse and trains of clicks and tone-burst stimuli during cochlear implantation in ANSD children. Recorded potentials included the cochlear microphonic (CM) and nerve compound action potential (CAP). Correlation between RW and TM ECochG recordings were analyzed using Pearson correlation test.Results: ECochG responses were successfully recorded at both the TM and RW simultaneously from 7 ANSD patients using all 4 paradigms. Both sites (TM and RW) revealed similar response patterns although RW responses were at least 1...

This study used two paradigms to investigate the development of temporal integration and temporally selective listening. Experiment 1 measured detection as a function of duration for a pure tone at 1625 or 6500 Hz. At both frequencies thresholds of children younger than 7 years old were higher than those for older children and adults. The pattern of temporal integration was similar across groups for the 6500-Hz signal, but younger children showed relatively more temporal integration for the 1625-Hz signal due to high thresholds for the briefest 1625-Hz signal. Experiment 2 measured detection thresholds for one or for three brief tone pips presented in a noise masker. In one set of conditions, the noise masker consisted of 100-ms steady bursts interleaved with 10-ms temporal gaps. In other conditions, the level of the central 50 ms of the 100-ms masking noise bursts was adjusted by either +6 or −6 dB. Children showed higher thresholds but similar temporal integration compared with adults. Overall, these data suggest that children are less efficient than adults in weighting the output of the monaural temporal window at 1625 but not 6500 Hz. Children are efficient in combining energy from brief temporal epochs that are separated by noise.

The purpose of this study was to investigate the effects of stimulation level and electrode pairing on the binaural interaction component (BIC) of the electrically evoked auditory brain stem response (EABR) in Nucleus cochlear implant (CI) users.Ten postlingually deafened adult CI users participated in this study. EABRs were measured using loudness balanced, biphasic current pulses presented in the left monaural, right monaural, and bilateral stimulation conditions. BICs were computed based on measures of the EABR obtained for each subject by pairing the electrode 12 (of 22 intracochlear electrodes) in the right ear with each of 11 electrodes spaced across the electrode array in the left ear. The effect of stimulation level on the amplitude of the BIC was investigated by measuring growth functions of the BIC from six subjects. The effect of electrode pairing on the amplitude of the BIC was studied at high stimulation levels in 10 subjects and at low stimulation levels in seven subjects. The high stimulation level was chosen as the 90% point of the subject's dynamic range (DR) or the highest stimulation level in which the electrophysiologic recordings were not contaminated by muscle artifacts. The low stimulation level was chosen as a level that was 10% point of subject's DR higher than the BIC threshold for six of these seven subjects. For one subject, BIC thresholds were not available and the low stimulation level was referred to the 70% point of subject's DR.BICs were successfully recorded from all 11 interaural electrode pairs for a majority of subjects tested at both stimulation levels. BIC amplitudes increased with stimulation level. The effect of stimulation level on latencies of the BIC was less robust. At high stimulation levels, BIC amplitudes did not change significantly as the stimulating electrode used in the left ear was systematically varied. When low stimulation levels were used, BIC amplitude was maximal for interaural electrode pairs with similar intracochlear positions and decreased when the offset between interaural electrodes increased.This study demonstrates that stimulation level affects amplitudes of the BIC response. It is possible to record the BIC of the EABR in bilateral CI users even from interaural electrode pairs that have large interaural offsets. This finding suggests that when high-level stimuli are used, there is a broad pattern of current spread within the two cochleae. At lower stimulation levels, the spread of excitation within the cochlea is reduced making the effect of electrode pairing on the amplitude of the BIC more pronounced.

The purpose of this study was to determine if changes in the position of the stimulating electrode in the cochlea could be used to elicit the electrically evoked auditory change complex (EACC) from Nucleus cochlear implant users.Nine postlingually deafened adults participated in this study. Each study participant had been using his or her Nucleus CI24 cochlear implant for at least 3 mos before testing. The speech processor was bypassed and the output of the implanted receiver/stimulator was controlled directly. The stimulus was a 600 msec burst of a biphasic pulse train (1000 pps). In control conditions, the stimulating electrode was held constant and stimulation continued throughout the 600 msec recording interval. In experimental conditions, the EACC was elicited by introducing a change in the stimulating electrode 300 msec after the onset of the pulse train. The EACC was recorded using surface electrodes. Three recordings of 100 sweeps each were obtained for each stimulus condition. Bandpass filtering (1-100 Hz) was used to minimize contamination of the recordings by stimulus artifact. Averaged responses were then smoothed using a 40-msec wide boxcar filter and standard peak picking procedures were used to analyze these responses in the time domain.In each case, a clear onset response (P1-N1-P2) was recorded. In the experimental conditions, a second evoked potential, the EACC, was also recorded after the change in stimulating electrode. This second response had general morphological characteristics that were very similar to those of the onset response. Increasing the separation between the two stimulating electrodes in the experimental conditions resulted in a general trend toward increased EACC amplitudes.This report describes results of a set of experiments in which the speech processor of the cochlear implant was bypassed and the EACC was recorded in response to a change in stimulating electrode position. EACC amplitude was shown to increase as the separation between the two stimulating electrodes increased. Although preliminary in nature, these results demonstrate the feasibility of recording the EACC in response to changes in stimulating electrode position from individual cochlear implant users.