Multiple Auditory Steady-state Responses Research Articles

Audiological Characteristics of Vestibular Schwannoma Patients With Normal Pure-Tone Audiometry.

To investigate the audiological characteristics of vestibular schwannoma (VS) patients with normal pure-tone audiometry (PTA) results. A retrospective study. Forty-two VS patients with normal PTA results from October 2016 to October 2022 were included. Normal PTA was defined when the hearing threshold is ≤25 dB hearing loss (HL) in each test frequency and the PTA is ≤25 dB HL. Results of multiple audiological tests such as the auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), multiple auditory steady-state responses threshold (ASSR), and speech discrimination score were retrospectively reviewed. Demographic data of these patients were also been collected. According to our results, the ABR and average ASSR threshold of the affected side were statistically significantly higher in VS patients with normal PTA. ABR waveforms on the affected side also showed more abnormalities. The DPOAE pass rates of the affected side were lower than the unaffected side while the amplitude and signal-to-noise ratio rate was also lower. In addition, we used magnetic resonance imaging 3-dimensional reconstruction images to measure the volume of tumors in these patients. We also found that higher ABR threshold means lager tumor size in patients with normal PTA. VS patients with normal PTA result cannot be assumed to have no impairment of hearing function. ABR, DPOAE, and ASSR results showed the characteristic changes in the affect ear. ABR threshold has the highest sensitivity for hearing abnormalities and is strong relative with tumor size in patients with normal PTA.

Reliability and Accuracy of Chirp Based Multiple Auditory Steady State Response (MSSR) and Auditory Brainstem Response (ABR) in Children.

The purpose of this study was to compare the reliability and accuracy of chirp-based Multiple Auditory Steady State Response (MSSR) and Auditory Brainstem Response (ABR) in children. The prospective clinical study was conducted at Selayang Hospital (SH) and Hospital Canselor Tuanku Muhriz (HCTM) within one year. A total of 38 children ranging from 3 to 18 years old underwent hearing evaluation using ABR tests and MSSR under sedation. The duration of both tests were then compared. The estimated hearing threshold of frequency specific chirp MSSR showed good correlation with ABR especially in higher frequencies such as 2000 Hz and 4000Hz with the value of cronbach alpha of 0.890, 0.933, 0.970 and 0.969 on 500Hz, 1000Hz, 2000Hz and 4000Hz. The sensitivity of MSSR is 0.786, 0.75, 0.957 and 0.889 and specificity is 0.85, 0.882, 0.979 and 0.966 over 500Hz, 1000Hz, 2000Hz and 4000Hz. The duration of MSSR tests were shorter than ABR tests in normal hearing children with an average of 35.3 minutes for MSSR tests and 46.4 minutes for ABR tests. This can also be seen in children with hearing loss where the average duration for MSSR tests is 40.0 minutes and 52.0 minutes for ABR tests. MSSR showed good correlation and reliability in comparison with ABR especially on higher frequencies. Hence, MSSR is a good clinical test to diagnose children with hearing loss.

Flexible Silver/Carbon Nanotube‐Graphene Oxide‐Polydimethylsiloxane Electrode Patch for Electroencephalography Language

A flexible silver/carbon nanotube‐graphene oxide‐polydimethylsiloxane (Ag/CNT‐GO‐PDMS) patch electrode for recording electroencephalography (EEG) signals and recognizing words is prepared. These patches record EEG signals under the synergistic sensing mechanism of the noncontact capacitance mode of the CNT‐GO‐PDMS patch and contact current mode of the Ag claws, with low scalp contact resistance of 6.4 kΩ. In the occipital region, the signal‐to‐noise ratios (SNR) are ≈90 dB for α‐waves and 9 dB for visual‐evoked signals; the SNR of auditory‐evoked EEG signals in the temporal region is ≈10 dB. The EEG cap comprises seven Ag/CNT‐GO‐PDMS patches to record EEG signals in steady‐state visual‐evoked potentials (SSVEP) and multiple auditory steady‐state response (MASSR). These patches can recognize nine words (“one” to “nine”) in the SSVEP–MASSR paradigm, with a visual accuracy of 90.4% and auditory accuracy of 54.0%. The statistical analysis also shows that the stimulation frequency and scalp channel are significant influencing factors for the accuracy of word recognition. We developed a standardized process of flexible Ag/CNT‐GO‐PDMS patches and herein propose a new strategy to identify words, which is of great significance for the establishment of the EEG language database and the application of EEG in the field of information transmission.

Chirp-Evoked Auditory Steady-State Response: The Effect of Repetition Rate.

The auditory steady-state response (ASSR) is commonly used in clinical pediatric audiology in order to provide an electrophysiological estimate of hearing threshold, and has the potential to be used in unsupervised mobile EEG applications. Enhancement of the ASSR amplitude through optimization of the stimulation and recording methods shortens the required testing time or reduce the offset between the electrophysiological and behavioral thresholds. Here, we investigate the spatial distribution of the ASSR to broadband chirp stimuli across a wide range of repetition rates on the scalp and in the ears. Moreover, the ASSR amplitude is compared across repetition rates for commonly used electrode configurations. ASSR to chirp stimuli with repetition rates from 6-198 Hz was recorded using scalp EEG and high-density ear-EEG. The distributions of the ASSR amplitude and phase were found to be dependent on the chirp repetition rate across the scalp, but independent of repetition rate in the ears. The normal drop in ASSR SNR for high repetition rates seen for click and pure tone stimuli was not found for chirp stimuli. Instead, the ASSR SNRs for chirp stimuli at high repetition rates (95-198 Hz) were found to be comparable to that found at 40 Hz for scalp EEG and even higher than 40 Hz ASSR for ear-EEG. Based on the results, use of chirp stimuli with high repetition rates (95-198 Hz) is advantageous for multiple stimulus ASSR recording in both clinical practice and mobile real-life applications.

Classification of Schizophrenia EEG Based on Gamma-Band Brain Network

Gamma-band (40-Hz) activity is critical for cortico-cortical transmission and the integration of information across neural networks during sensory and cognitive processing. Patients with schizophrenia show selective reductions in the capacity to support synchronized gamma-band oscillations in response to auditory stimulation presented 40-Hz. Despite widespread application of this 40-Hz auditory steady-state response (ASSR) as a translational electroencephalographic biomarker for therapeutic development for neuropsychiatric disorders, the spatiotemporal dynamics underlying the ASSR have not been fully characterized. In this study, a novel Granger causality analysis was applied to assess the propagation of gamma oscillations in response to 40-Hz steady-state stimulation across cortical sources in schizophrenia patients (n = 426) and healthy comparison subjects (n = 293). Both groups showed multiple ASSR source interactions that were broadly distributed across brain regions. Schizophrenia patients showed distinct, hierarchically sequenced connectivity abnormalities. During the response onset interval, patients exhibited abnormal increased connectivity from the inferior frontal gyrus to the superior temporal gyrus, followed by decreased connectivity from the superior temporal to the middle cingulate gyrus. In the later portion of the ASSR response (300–500 ms), patients showed significantly increased connectivity from the superior temporal to the middle frontal gyrus followed by decreased connectivity from the left superior frontal gyrus to the right superior and middle frontal gyri. These findings highlight both the orchestration of distributed multiple sources in response to simple gamma-frequency stimulation in healthy subjects as well as the patterns of deficits in the generation and maintenance of gamma-band oscillations across the temporo-frontal sources in schizophrenia patients.

Neural network dynamics underlying gamma synchronization deficits in schizophrenia

Gamma-band (40-Hz) activity is critical for cortico-cortical transmission and the integration of information across neural networks during sensory and cognitive processing. Patients with schizophrenia show selective reductions in the capacity to support synchronized gamma-band oscillations in response to auditory stimulation presented 40-Hz. Despite widespread application of this 40-Hz auditory steady-state response (ASSR) as a translational electroencephalographic biomarker for therapeutic development for neuropsychiatric disorders, the spatiotemporal dynamics underlying the ASSR have not been fully characterized. In this study, a novel Granger causality analysis was applied to assess the propagation of gamma oscillations in response to 40-Hz steady-state stimulation across cortical sources in schizophrenia patients (n = 426) and healthy comparison subjects (n = 293). Both groups showed multiple ASSR source interactions that were broadly distributed across brain regions. Schizophrenia patients showed distinct, hierarchically sequenced connectivity abnormalities. During the response onset interval, patients exhibited abnormal increased connectivity from the inferior frontal gyrus to the superior temporal gyrus, followed by decreased connectivity from the superior temporal to the middle cingulate gyrus. In the later portion of the ASSR response (300–500 ms), patients showed significantly increased connectivity from the superior temporal to the middle frontal gyrus followed by decreased connectivity from the left superior frontal gyrus to the right superior and middle frontal gyri. These findings highlight both the orchestration of distributed multiple sources in response to simple gamma-frequency stimulation in healthy subjects as well as the patterns of deficits in the generation and maintenance of gamma-band oscillations across the temporo-frontal sources in schizophrenia patients.

Characterization of interstimulus interaction in the multiple auditory steady-state responses at high sound levels.

Multiple auditory steady-state response (MASSR) is recommended to estimate hearing thresholds in difficult-to-test individuals. The multiple stimuli that evoke MASSR may present an interstimulus interaction (ISI) that is able to distort the generation of responses. No consensus exists on the effects of the ISI in MASSR when dealing with high sound level stimuli or cases of sensorineural hearing loss. This study investigated the effects of ISI on the amplitude and detectability of auditory steady-state responses, with a focus at and above 65 dB sound pressure level (SPL). Normal hearing (NH) and sensorineural hearing impaired (SNHI) adults were tested with different stimulus types [amplitude modulation (AM) One octave chirp (OC), and a weighted OC (WOC)], stimulus levels, and modalities (single or multiple stimuli). ISI typically attenuated response amplitude of a control stimulus caused by an interference stimulus one octave above the control stimulus. At and above 80 dB SPL, attenuations of around 50% decreased the number of detectable responses near SNHI thresholds, especially for OC and WOC. AM stimuli obtained a higher detection rate than OC and WOC when presented 10 dB above the behavioral hearing threshold of SNHI participants. Using OC in MASSR when assessing elevated thresholds might diminish accuracy on threshold estimation, and extend test duration.

Correlation between Preoperative Auditory Steady-State Response and Postoperative Electrically Evoked Auditory Brainstem Response and T Level in Cochlear Implantation for Child Patients with Inner-Ear Malformations

Objective: This study aims to investigate the correlation between thresholds of preoperative multiple auditory steady-state response (ASSR) and electrically evoked auditory brainstem response (EABR) and the behavioral threshold. Methods: A total of 72 patients were elected to receive a multichannel cochlear implant. According to the residual hearing determined in a preoperative test using high-, moderate-, and low-frequency ASSR, these patients were divided into the following 2 groups: residual hearing and hearing loss. The EABR and behavioral thresholds 1 year after implantation were assayed, and differences between these 2 parameters were compared. Results: Among the high-, moderate-, and low-frequency residual hearing groups, the EABR and behavioral thresholds of patients 1 year after implantation were significantly lower than those in the hearing loss group, and the differences were statistically significant (p < 0.01). Conclusion: Before the operation, ASSR results can be used to predict the efficacy of cochlear implantation in patients, and they serve as one of the reference conditions for choosing the ear for implantation. However, the threshold of ASSR is not equivalent to the actual auditory threshold of patients after implantation, and the deviation between these 2 thresholds is more significant at low frequencies.

74. Screening high risk babies with Auditory Brainstem Responses and Multiple Auditory Steady State Responses

Objective Evaluate the results of the hearing screening program organized and applied in the “William Soler” Paediatric Hospital, targeting multiple high-risk groups. Material and methods The children were evaluated using click Auditory Brainstem Responses (ABR with Multiple Auditory Steady State Responses (MSSR) (0.5 and 2 kHz). The possible causes of hearing impairment were examined comparatively. Results The results shows an overall incidence of permanent hearing losses of 3,3% in the high risk population with referral rates of around 10%. The common perinatal causes of hearing losses were low birth weight; foetal suffering and the use of ototoxic drugs have remained very frequent. Conclusions The incidence of hearing impairment and the referral rates were quite comparable to those reported in the high risk population by similar screening protocols. It is found some variations in the current causes of hearing losses when comparing the early and late periods (before and after 1990) of the screening program. Significance This hearing screening program with Auditory Brainstem Responses (ABR) and Multiple Auditory Steady State Responses (MSSR) shows a high grade of efficiency and sensibility in programs to early detection of hearing deafness.

40-Hz multiple auditory steady-state responses to narrow-band chirps in sedated and anaesthetized infants

ObjectiveThe general consensus to date has been that a stimulus repetition rate of 40Hz is not appropriate for the recording of auditory steady-state responses (ASSR) in sedated or anaesthetized infants. The aim of this study was to investigate whether reliable 40-Hz ASSR thresholds can be obtained in sedated infants using narrow-band chirp stimuli in the clinical routine. Methods40-Hz auditory brainstem responses (ABR) and 40-Hz ASSR were recorded in 34 infants below the age of 48 months under sedation or under general anaesthesia. ABR were evoked by broad-band chirp stimuli with a flat amplitude spectrum. ASSR were recorded simultaneously from both ears with an adaptive multiple stimulus paradigm using four narrow-band chirps centred at 500, 1000, 2000 and 4000Hz. ABR and ASSR thresholds were evaluated to determine differences between the estimates from the two methods. ResultsDespite of sedation and anaesthesia, large wave V amplitudes of the chirp evoked 40-Hz ABR were found at levels as low as 10dB above the individual ABR threshold. ASSR thresholds for stimulus repetition rates of 40Hz could be consistently estimated in all 34 infants. Thresholds estimated from the ASSR for the four frequencies of the narrow-band chirps and the threshold derived from the broad-band chirp ABR differ, on average by 3.7dB for the frequency range of 1000–2000Hz and 7.1dB for the frequency range from 2000 to 4000Hz. ConclusionIn contrast to the general assumption that 40-Hz ASSR are not appropriate for threshold estimation in infants our results demonstrate that multiple ASSR with a stimulus repetition rate of 40Hz can be recorded in sedated and anaesthetized infants using narrow-band chirps. Threshold estimates obtained with 40-Hz ASSR are, on average, slightly higher than those obtained with chirp evoked ABR but allow for a frequency specific characterisation of the hearing ability.

Objective Response Detection of Multiple Auditory Steady-State Responses: Rice Detector vs Component Synchrony Measure

Multiple auditory steady state responses (MASSR) is used to assess the integrity auditory pathways for different frequencies applied simultaneously without significant increases in exam time. Objective Response Detection (ORD) techniques have been employed for hearing screening since it conducts to response identification with statistical basis. This work aims at comparing time and detection rate of two ORD, Rice detector (RD) and Component Synchrony Measure (CSM). The binaural auditory stimulation was applied to 21 normal hearing infants and consisted of four amplitude-modulated (AM) tones presented simultaneously on each ear with the carriers 500, 1000, 2000 and 4000 Hz, and at 50 and 40 dBSPL intensity levels. The CSM presented higher detection rates than RD for all carriers, both intensities and ears (statistical difference, assessed by proportion test with significance level of alfa=0.05, only for 500 Hz in both ears and for 1000 Hz in the left ear). Moreover, detection times were lower for CSM compared to RD (unpaired Wilcoxon rank-sum test with alfa=0.05 indicated statistical difference for 1000 Hz at 50 dBSPL and 2000 Hz at 50 dBSPL both for the left ear). Hence, the CSM could be considered more effective for hearing screening purposes.

Monotic Versus Dichotic Multiple-Stimulus Auditory Steady State Responses in Young Children

In their recent study on infant multiple auditory steady state responses (ASSR), the authors found that ASSR amplitudes unexpectedly decreased when switching from 1-ear stimulation to 2-ear stimulation, a result not present in adults. In addition, residual EEG noise levels increased in the 2-ear condition. In the present study, to determine whether to use 1-ear or 2-ear multiple ASSR Protocols clinically, the authors tested a new group of 19 young children to determine whether these unexpected findings could be replicated. ASSR amplitude and EEG noise were compared for 1-ear (4 stimuli) versus 2-ear (8 stimuli) multiple stimuli presented at 60 dBHL. Results indicated a small but significant decrease in amplitudes going from 1-ear (40.1 nV) to 2-ear (37.9 nV) multiple stimuli. EEG noise was not significantly different between the 2 conditions. Despite small amplitude decreases, the 2-ear stimulus condition was more efficient for infants and young children with normal hearing.

Ipsi- and contralateral interaction in the 40 Hz auditory steady state responses (ASSRs) with two carriers at 60 dB SPL

Objective: Auditory steady state responses have been suggested for simultaneous threshold assessment using the multiple ASSR (MASSR) technique. However, at least at high stimulation levels, strong interactions reduce response amplitudes. The present study investigates ASSR interaction at a moderate stimulus level. Design: Sinusoidal carriers modulated at rates near 40 Hz were used as probe. Unmodulated and modulated interferers were presented ipsi- or contralaterally. Study sample: Twenty normal-hearing subjects participated. Results: Unmodulated interferers did not significantly change ASSR amplitudes. Modulated interferers, presented ipsilaterally or contralaterally, both significantly reduced the ASSR SNR by 13% and 8%, respectively. Conclusions: To compensate for the average SNR reduction would require a 32% and 18% longer measurement time for ipsi- and contralateral interferers, respectively, far less than the doubling of measurement time for two single measurements, emphasizing the MASSR technique advantage. However, the largest reduction for a single subject was 22% for the amplitude and 28% for the SNR, almost completely undoing the benefit in measurement time in MASSR. The individually varying interaction effects even at 60 dB SPL clearly limits the advantage of using the MASSR for modulation rates near 40 Hz over corresponding single ASSR measurements, at least for two simultaneous carriers.

Air-bone gap estimated with multiple auditory steady-state response in young children with otitis media with effusion

Multiple auditory steady-state responses (ASSRs) to air- and bone-conduction stimuli were recorded in young children with otitis media with effusion (OME). After treatment for OME, differences between pre-treatment bone-conduction ASSR levels and post-treatment conditioned orientation reflex (COR) or air-conduction ASSR levels were examined, and compared with ASSR-estimated air-bone gap (ABG) before treatment. Navigator Pro with Master was used to assess the threshold of air- and bone-conduction ASSR in both ears at 500Hz, 1000Hz, 2000Hz and 4000Hz. For bone-conduction ASSR, RadioEar B-71 bone-vibrator placed on the mastoid was used with white-noise masking on the contralateral ear. After ventilation tube placement, the thresholds of COR got closer to those of pre-treatment bone-conduction ASSR in young children with OME. Moreover, post-treatment air-conduction ASSR thresholds also got closer to those of pre-treatment bone-conduction ASSR. The differences between pre-treatment bone-conduction ASSR thresholds and post-treatment COR or air-conduction ASSR thresholds became much smaller than ASSR-estimated ABG before treatment. These findings suggest that bone-conduction ASSR can assess the normal or near normal cochlear sensitivity in young children with conductive hearing loss. It is also suggested that ASSR-estimated ABG can be used clinically to predict their accurate ABG.

Comparing statistics for objective detection of transient and steady-state evoked responses in newborns

Objective: Receiver operating characteristic (ROC) methodology was used to compare the performance of different statistics in the automatic detection of multiple auditory steady-state responses (MSSR) and click auditory brainstem responses (cABR). Study sample: Thirty-five healthy newborns tested within the first two weeks of birth. Design: In each case cABR and MSSR (0.5 and 2 kHz) were recorded with and without acoustic stimulation, using AUDIX equipment. With this test sample of recordings, ROC curves were evaluated separately for each statistic evaluated: (1) the standard deviation ratio (SDR) and the correlation coefficient ratio (CCR) for the cABR; (2) the Hotelling T2 (HT2) and circular T2 (CT2) for the MSSR. Results: All objective detection methods performed well (areas under ROC (AUC) > 0.9). The MSSR statistics showed significantly larger AUCs at both frequencies (HT2: 0.98 and 1; CT2: 0.96 and 0.99) than the cABR measures (SDR: 0.91 and CCR: 0.92). The HT2 hits rate was the highest (97–100% at 0.5 and 2 kHz) for fixed false alarms rates of both 10 and 20%. Conclusions: This superiority of performance of T2-like statistics, reflecting inherent advantages of MSSR analysis for automation, warrants serious consideration for further development of newborn screening technology.

Multiple-ASSR Interactions in Adults with Sensorineural Hearing Loss

The multiple auditory steady-state response (multiple-ASSR) technique, where thresholds for up to 8 frequencies (4 in each ear) are obtained simultaneously, is currently of great interest for audiometric assessment of infants. Although threshold estimates using the multiple-ASSR appear to be reasonably accurate, it is not currently known whether it is more efficient to use multiple stimuli or single stimuli when testing individuals with sensorineural hearing loss (SNHL). The current study investigated the effect of single versus multiple simultaneous stimuli on the 80- and 40-Hz ASSRs in adults with normal hearing or SNHL. Results showed significant interactions (i.e., decreased amplitudes) for both ASSRs going from single to multiple stimuli in one ear. Going from multiple one ear to multiple two ears did not further reduce the amplitude of the 80-Hz ASSR. At the 40-Hz rate, however, there was a further amplitude decrease going from one-ear multiple to two-ear multiple stimuli. Importantly, these interactions did not differ between the normal-hearing and SNHL groups. Although supportive of the multiple-ASSR technique, there are likely situations where it is more efficient to use single stimuli. Future studies are required to assess these interactions in infants with varying degrees and configurations of hearing loss.

The effect of varying stimulus phase between frequency and amplitude modulation on auditory steady-state responses in neonates

Objective: To compare auditory steady-state responses (ASSRs) to air-conducted amplitude, frequency, and mixed modulated stimuli (AM, FM, and MM, respectively) in neonates. Design: Multiple ASSRs to AM, FM, and MM to 0.5, 1, 2, and 4 kHz tones modulated between 0.078 and 0.092 kHz were recorded and compared. MM phase settings across the cycle at 45° intervals were used and optimum phase settings were predicted using a sinusoidal model. Study sample: Twenty neonates with click ABR thresholds of ≤ 40 dB nHL. Results: ASSR amplitudes were significantly larger to AM than FM stimuli. MM phase setting had a significant effect on amplitude at 1, 2, and 4 kHz but not 0.5 kHz. MM phase settings (± 95% confidence intervals) of 276° (± 9.5°) and 270° (± 19.1°) were predicted for 1 and 2 kHz, respectively. The 0.5 and 4 kHz data were not sufficient to model any effect of phase. MM and AM response latencies increased with decreasing carrier frequency. Some MM response latencies were significantly different from AM response latencies, however no consistent trend was apparent. Test times were significantly affected by phase setting. Conclusions: MM phase settings have a significant effect on ASSR response amplitude and latencies in neonates.

Phase Stability of Auditory Steady State Responses in Newborn Infants

This study examined the phases of auditory steady state responses (ASSRs) evoked by exponentially amplitude-modulated (AM) tones in 44 newborn infants (within 3 days of birth) and in 15 older infants (within 3 to 15 wks of birth). Our hypothesis was that the phases of the ASSRs would show orderly changes with modulation rate/carrier frequency and that this stability could be used with phase-biasing statistical techniques to augment response detection. Multiple ASSRs were recorded to four modulated tonal carriers with intensities of 50 dB SPL, which were combined and presented simultaneously. The carriers of 0.5, 1, 2, and 4 kHz were modulated at rates between 78 and 95 Hz. Recordings lasted 12.3 mins. Data were analyzed offline with particular attention to phase and its possible exploitation in response detection using a phase-weighted t test (PWT). Population normative phase values were compared with self-normative values. The latter uses phase estimates from ASSRs that are detected at an earlier time to estimate expected phases of ASSRs, which have not yet been detected. This was implemented as an interstimulus phase-weighted t test (iPWT). A secondary analysis compared using fixed test durations where data were evaluated once at the end of the recording with variable test durations where data were evaluated after every sweep. Average phases were not statistically different between the newborn and older infants. The mean ASSR phases across both infant groups were 10°, 36°, 83°, and 110° in the left ear and 78°, 97°, 135°, and 138° in the right ear for the four modulated carriers, respectively. Of a total of 172 detected ASSRs across the four carriers, 63% (109/172), 84% (144/172), and 99% (170/172) of the phase values fell within ±30°, ±45°, and ±90° of the population mean values, respectively. Self-normative phase values were slightly closer to actual measured phases, than population normative values. Compared with the F test, with a fixed duration, the iPWT technique did slightly better (71.7% versus 77.1% detected). Compared with the F test, with variable test duration, test time was reduced using the iPWT technique for normal and weighted averaging by 4 and 2.9 sweeps (66 and 48 secs), respectively, while false-positive rates were maintained. Compared with tests that relied on the F-ratio and a fixed time of 12.3 mins, using variable test times and the iPWT approach resulted in a halving of test time, while slightly improving comparable ASSR detection rates (66.7% versus 72.5%). An inter-ear average phase difference of 52° was found, which was not accounted for by modulation rates used for left/right ears. Converting phase to latency yielded similar results to prior studies. The phase responses of ASSRs evoked by AM tones are stable in newborn and young infants. When using the multiple auditory steady state response (MASTER) technique, it is possible to employ phase-biasing methods to reduce test time and increase detection rates. Using self-normative intrastimulus phase difference values provides better estimated phases than average population phases for purposes of response detection.

Bone-Conducted Hearing Assessment with 80-Hz Multiple Auditory Steady-State Responses to Brief Tones in Adults with Normal Hearing

Objective: To investigate interactions (if any) in the bone-conduction auditory steady-state response (BC ASSR) between multiple brief tones presented simultaneously. Methods: 500-, 1,000-, 2,000-, and 4,000-Hz brief tones, repeated at a rate of 77–101 Hz, were presented using a B-71 vibrator. BC ASSR thresholds and amplitudes at 50 dB nHL were measured in two conditions where the stimulus was either presented alone or together with other stimuli. Results: Significantly larger amplitudes in the single-stimulus condition were found at 50 dB nHL. However, there was no significant threshold difference between single- and multiple-stimulus conditions. The BC ASSR thresholds (means ± SD) at 500, 1,000, 2,000, and 4,000 Hz were 96.7 ± 9.7, 75.3 ± 11.5, 65.6 ± 7.4, and 57.8 ± 7.2 dB re 1 µN ppe, respectively. Conclusion: Interactions occurred in the multiple-stimulus condition at high presentation levels, but not at threshold levels. The results of the present study imply that BC ASSR thresholds to multiple brief-tone stimuli can be assessed at the same time, at least in normal-hearing adults.

Prognostic validity of dichotic multiple frequencies auditory steady-state responses versus distortion product otoacoustic emissions in hearing screening of high risk neonates

Objective To determine the validity of dichotic multiple frequencies auditory steady-state responses (ASSR) as a hearing screening technique versus using distortion product otoacoustic emissions (DPOAEs) among high-risk neonates. Methods A cross sectional study was performed on 118 high-risk neonates by means of dichotic multiple frequencies ASSR and DPOAE for hearing screening. DPOAE results were used as the standard for hearing screening in parallel with ASSR. Dichotic multiple frequencies ASSR results were analyzed by means of F-value of less or greater than 0.05 criteria as a pass–fail for the responses. Dichotic multiple ASSR hearing screening technique was considered in two intensity levels at 40 and 70 dB HL. The ASSRs thresholds were measured in high risk neonates with and without hearing deficits as determined by DPOAES. The results of ASSR and DPOAE were compared to be gathered by contingency table in order to obtain sensitivity, specificity and other different statistical values. Average performing times for the tests were analyzed. Results The specificity of dichotic multiple ASSR was 92.6%, 93.8% and the sensitivity was 71.6%, 62.2% at the 70 and 40 dB hearing levels, respectively. Mean ASSR thresholds for normal-hearing infants at an average corrected age of 6 days were 32.2 ± 12.2, 29.8 ± 10.2, 26.2 ± 11.4 and 30.4 ± 10.8 dB HL for 0.5, 1, 2 and 4 kHz, respectively. The average times for performing the tests were 18.7 and 32.9 min respectively. Conclusions ASSR with this special paradigm is a fairly desirable method for hearing screening of high-risk neonates. There is good concordance between ASSRs and DOPAEs results among high risk neonates referred for hearing screening. The sensitivity and specificity of this test is sufficient for hearing screening in high risk neonates. This test could be valuable for rapid confirmation of normal thresholds. As long as further research have not been conducted on ASSR, great caution should be made to interpret the results of ASSR as a hearing screening technique in young infants and also additional techniques such as the tone-evoked ABRs should be used to cross-check results. It's still too soon to recommend ASSRs as a standalone electrophysiologic measure of hearing thresholds in infants.