Characteristics of the Deconvolved Transient AEP from 80 Hz Steady-State Responses to Amplitude Modulation Stimulation.

This study aimed to validate the existence and investigate the characteristics of the transient responses from conventional auditory steady-state responses (ASSRs) using deconvolution methods capable of dealing with amplitude modulated (AM) stimulation. Conventional ASSRs to seven stimulus rates were recorded from 17 participants. A deconvolution method was selected and modified to accommodate the AM stimulation. The calculated responses were examined in terms of temporal features with respect to different combinations of stimulus rates. Stable transient responses consisting of early stage brainstem responses and middle latency responses were reconstructed consistently for all rate combinations, which indicates that the superposition hypothesis is applicable to the generation of approximately 80 Hz ASSRs evoked by AM tones (AM-ASSRs). The new transient responses are characterized by three pairs of peak-troughs named as n0p0, n1p1, and n2p2 within 40 ms. Compared with conventional ABR-MLRs, the n0p0 indicates the first neural activity where p0 might represent the main ABR components; the n1 is the counterpart of N10; the p2 is corresponding to the robust Pa at about 30 ms; the p1 and n2 are absent of real counterparts. The peak-peak amplitudes show a slight decrease with increasing stimulation rate from 75 to 95 Hz whereas the peak latencies change differently, which is consistent with the known rate-effect on AEPs. This is direct evidence for a transient response derived from AM-ASSRs for the first time. The characteristic components offer insight into the constitution of AM-ASSRs and may be promising in clinical applications and fundamental studies.

Auditory Deficits in Patients With Mild and Moderate Obstructive Sleep Apnea Syndrome: A Speech Syllable Evoked Auditory Brainstem Response Study.

OBJECTIVES: The energy consumption process of cochlea and neural signal transduction along the auditory pathway are highly dependent on blood oxygen supply. At present, it is under debate on whether the obstructive sleep apnea syndrome (OSAS) would affect the auditory function since the patients suffer from low oxygen saturation. Moreover, it is difficult to detect the functional state of auditory in less severe stage of OSAS. Recently, speech-evoked auditory brainstem response (speech-ABR) has been reported to be a new electrophysiological tool in characterizing the auditory dysfunction. The aim of the present study is to evaluate the auditory processes in adult patients with mild and moderate OSAS by speech-ABR. METHODS: An experimental group of 31 patients with mild to moderate OSAS, and a control group without OSAS diagnosed by apnea hypopnea index in polysomnogram were recruited. All participants underwent otologic examinations and tests of pure-tone audiogram, distortion product otoacoustic emissions, click-evoked auditory brainstem response (click-ABR) and speech-ABR, respectively. RESULTS: The results of pure-tone audiogram, distortion product otoacoustic emissions, and click-ABR in OSAS group showed no significant differences compared with the control group (P>0.05). Speech-ABRs for OSAS participants and controls showed similar morphological waveforms and typical peak structures. There were significant group differences for the onset and offset transient peaks (P<0.05), where OSAS group had longer latencies for peak V (6.69± 0.33 ms vs. 6.39±0.23 ms), peak C (13.48±0.30 ms vs. 13.31±0.23 ms), and peak O (48.27±0.39 ms vs. 47.60± 0.40 ms) compared to the control group. The latency of these peaks showed significant correlations with apnea hypopnea index for peak V (r=0.37, P=0.040), peak C (r=0.36, P=0.045), as well as peak O (r=0.55, P=0.001). CONCLUSION: These findings indicate that some auditory dysfunctions may be present in patients with mild and moderate OSAS, and the damages were aggravated with the severity of OSAS, which suggests that speech-ABR may be a potential biomarker in the diagnosis and evaluation at early stage of OSAS.

[Noise attenuation analysis on auditory evoked potential based on maximum length sequence].

The maximum length sequence (m-sequence) has been successfully used to study the linear/nonlinear components of auditory evoked potential (AEP) with rapid stimulation. However, more study is needed to evaluate the effect of the m-sequence order in terms of the noise attenuation performance. This study aimed to address this issue using response-free electroencephalogram (EEG) and EEGs with nonlinear AEPs. We examined the noise attenuation ratios to evaluate the noise variation for the calculations of superimposed averaging and cross-correlation, respectively, which constitutes the main process in the deconvolution method using the dataset of spontaneous EEGs to simulate the cases of different orders (order 5 to 12) of m-sequences. And an experiment using m-sequences of order 7 and 9 was performed in true cases with substantial linear and nonlinear AEPs. The results demonstrate that the noise attenuation ratio is well agreed with the theoretical value derived from the properties of m-sequences on the random noise condition. The comparison of waveforms for AEP components from two m-sequences showed high similarity suggesting the insensitivity of AEP to the m-sequence order. This study provides a more comprehensive solution to the selection of m-sequences which will facilitate the feasible application on the nonlinear AEP with m-sequence method.

Improved Transient Response Estimations in Predicting 40 Hz Auditory Steady-State Response Using Deconvolution Methods.

The auditory steady-state response (ASSR) is one of the main approaches in clinic for health screening and frequency-specific hearing assessment. However, its generation mechanism is still of much controversy. In the present study, the linear superposition hypothesis for the generation of ASSRs was investigated by comparing the relationships between the classical 40 Hz ASSR and three synthetic ASSRs obtained from three different templates for transient auditory evoked potential (AEP). These three AEPs are the traditional AEP at 5 Hz and two 40 Hz AEPs derived from two deconvolution algorithms using stimulus sequences, i.e., continuous loop averaging deconvolution (CLAD) and multi-rate steady-state average deconvolution (MSAD). CLAD requires irregular inter-stimulus intervals (ISIs) in the sequence while MSAD uses the same ISIs but evenly-spaced stimulus sequences which mimics the classical 40 Hz ASSR. It has been reported that these reconstructed templates show similar patterns but significant difference in morphology and distinct frequency characteristics in synthetic ASSRs. The prediction accuracies of ASSR using these templates show significant differences (p < 0.05) in 45.95, 36.28, and 10.84% of total time points within four cycles of ASSR for the traditional, CLAD, and MSAD templates, respectively, as compared with the classical 40 Hz ASSR, and the ASSR synthesized from the MSAD transient AEP suggests the best similarity. And such a similarity is also demonstrated at individuals only in MSAD showing no statistically significant difference (Hotelling's T2 test, T2 = 6.96, F = 0.80, p = 0.592) as compared with the classical 40 Hz ASSR. The present results indicate that both stimulation rate and sequencing factor (ISI variation) affect transient AEP reconstructions from steady-state stimulation protocols. Furthermore, both auditory brainstem response (ABR) and middle latency response (MLR) are observed in contributing to the composition of ASSR but with variable weights in three templates. The significantly improved prediction accuracy of ASSR achieved by MSAD strongly supports the linear superposition mechanism of ASSR if an accurate template of transient AEPs can be reconstructed. The capacity in obtaining both ASSR and its underlying transient components accurately and simultaneously has the potential to contribute significantly to diagnosis of patients with neuropsychiatric disorders.

[Progress of generation mechanisms of auditory steady-state response].

The scalp-recorded auditory steady-state response (ASSR) is a periodically evoked potential in response to the stimulation with the acoustical property in the same period. The ASSR can be readily induced in comparison with transient responses for specific conditions. The clinical utility of ASSR may be unjustified for the ambiguity of the genesis. With the advance of relevant research, it is considered that the main generation hypotheses of the ASSR are conceived to be pertinent with the linear superposition or neural entrainment mechanism. Based on current findings and our contributions in this field, we introduce recent progresses of the two mechanisms with comments, and suggest the benefit of the rapid stimulation technology in this regard.

[Effectiveness of cisplatin on the expressions of Bcl-2 and Bax in cochlea and spiral ganglion cells of guinea pigs].

OBJECTIVE: To investigate the effectiveness of cisplatin on the expressions of Bcl-2 and Bax in cochlea and spiral ganglion cells (SGC) of guinea pigs. METHOD: Twenty guinea pigs were randomly divided into cisplatin (n = 10) and control groups (n = 10). Cisplatin group were administrated with a dose of intraperitoneal injection of 16 mg/kg, while the control group were received intraperitoneal injection of normal saline as placebo. Before and 7 days following injections, the ototoxic effect was measured with distortion product otoacoustic emission (DPOAE). Bcl-2, Bax in cochlea were detected by Western Blot. Immunohistochemical staining was used to detect the protein levels of Bcl-2 and Bax in spiral ganglion cells. RESULT: In control and cisplatin group, Bcl-2 protein levels were 0.727 8 ± 0.016 9 and 0.467 6 ± 0.020 1, Bax protein levels were 0.384 8 ± 0. 0217 and 0.735 6 ± 0.022 3 in cochlea respectively, both P < 0.01. In Control and cisplatin group, the grey values of Bcl-2 in SGC were 99.00 ± 2.42 and 149.80 ± 2.37 respectively, the grey values of Bax were 154.50 ± 2.80 and 104.50 ± 3.09 respectively, both P < 0.05. CONCLUSION: Decreased expression of Bcl-2 and increased expression of Bax may be involved in cisplatin-induced apoptosis in cochlea and SGC of guinea pigs.

[Relationships of electrophysiological characteristic between speech evoked auditory brainstem response and auditory mismatch negativity].

OBJECTIVE: To investigate the relationships of electrophysiological characteristics between speech evoked auditory brainstem response (s-ABR) and auditory mismatch negativity (MMN), so as to provide more clues for the mechanism of speech cognitive behavior. METHOD: Thirty-three ears in 33 normal hearing adults were included in this study. Their s-ABR were recorded with speech syllables /da/ at 80 dB HL intensity. Meanwhile, two MMNs were recorded with 1 kHz frequency deviant extent and 40 dB intensity deviant extent in them. The electrophysiological characteristics of s-ABRs and MMNs, as well as the relationships of MMN latencies between s-ABR parameters including latencies in time domain, fundamental frequency(F0) and first formants(F1) in frequency domain were analyzed statistically. RESULT: MMN latency of frequency deviance showed a negative correlation tendency with s-ABR transient components, and it showed a positive trend with sustained components of s-ABR. While MMN latency of intensity deviance showed a positive correlation with s-ABR latency of peak V, A and D respectively, and it negatively showed a correlation with s-ABR latency of other peak s and amplitude of F0 and FI respectively. Only the s-ABR latency of peak F and MMN latency of frequency deviance, and the F0 amplitude of s-ABR and MMN latency of intensity deviance were moderate correlation statistically. CONCLUSION: It was probably the neurons of frequency deviant MMN unmatched the characteristics of frequency with the neurons of s-ABR transient component, but well matched the characteristics of frequency with the neurons of s-ABR sustained component. Similarly, the neurons of intensity deviant MMN probably matched the characteristics of intensity with neurons of different components of s-ABR or not. These results may formed as a valuable clue for further investigation of speech perception and temporal processing abilities.

[The effectiveness of endoscopic tragus cartilage-perichondrium myringoplasty in the treatment of large tympanic membrane perforations].

OBJECTIVE: To evaluate effectiveness of endoscopic tragus cartilage-perichondrium in the treatment of large tympanic membrane perforations. METHOD: Patients with large tympanic membrane perfortations who had underwent cartilage-perichondrium myringoplasty were retrospectively retrieved from our department. Those with a follow-up of equal to or greater than 12 months after surgery were included in the study. Hearing test results were reported using a four-frequency air conduction and bone-air conduction gap. Patients were labeled as treatment success if the tympanic membrane was intact without lateralization or anterior blunting after surgery. RESULT: Of the 35 patients with large tympanic membrane perforations treated by endoscopic tragus cartilage-perichondrium, 33 (94.3%) were treatment success. There was no graft lateralization, anterior blunting, neocholesteatoma, and sensorineural hearing loss in these patients after surgery. The air conduction and bone-air conduction gap before surgery in the study cohort were (43.8 ± 5.7) dB and (28.5 ± 3.1) dB, respectively. Postoperative air conduction and bone-air conduction gap of the cohort were (31.4 ± 6.4) dB HL and (16.2 ± 4.1) dB, respectively. The postoperative air conduction and bone-air conduction gap decreased significantly after surgery (P < 0.01). Overall postoperative air-bone gap in 27 of the 35 patients (77%) were less than 20 dB after surgery. CONCLUSION: Endoscopic cartilage-perichondrium myringoplasty is an effective procedure in the treatment of large tympanic membrane perforations.

[Instantaneous energy spectrum analysis for frequency following response of speech evoked brainstem response].

Speech evoked brainstem responses (s-ABRs) elicited by a speech syllable /da/ are composed of four parts: onset response (OR), transitional response, frequency following response (FFR) and offset response. FFR elicited by periodic events behaves like a quasi-periodic waveform corresponding to the stimulus sounds. The fast Fourier transform based spectra are commonly used to exam the characteristics of s-ABR in practice, which is, however, unable to trace the occurrence of the main components of s-ABR. The FFR is usually not obvious in the original individual s-ABR waveform. In this paper, we proposed a novel approach to observe the FFR by an instantaneous energy spectrum performed on the intrinsic mode functions (IMFs) after empirical mode decomposition (EMD) of the s-ABR. We demonstrated that the FFR is most pronounced on the second layer of IMFs. This finding suggests a new way which may be available to characterize and to detect the FFR better. This will benefit the clinic applications of s-ABRs.

[Comparison of the efficiency of techniques for deconvolving auditory-evoked potentials with high rate stimulation].

In some auditory evoked potential (AEP) examinations, high rate stimulation paradigms deliver more stimuli with the same period of time, which might lead to overlapping responses. At present, several established techniques can be proposed to address such problem, thus the research scope in both scientific and clinical applications is expanded. In this study, the restoring efficiency of evoked responses is investigated using a simulation strategy. We examined the AEPs derived from three paradigms--conventional ensemble averaging, continuous loop averaging deconvolution (CLAD) and maximum length sequence (MLS). Their performances were evaluated by correlation coefficients and Euclidean distances between ideal and the derived responses. We found that MLS can only slightly enhance the performance at the cost of larger stimulus jitter and much more stimulus numbers; while CLAD method with lower jittering even degenerates the quality, suggesting that, in practical use, the recording efficiency will not be significantly improved by simply using high rate stimulation with overlapping responses introduced.

[Comparison of auditory brainstem responses to speech from bilateral ears with ipsilateral recordings].

OBJECTIVE: To compare the time domain and the frequency domain of speech-evoked auditory brain-stem response measured by stimulation of left and right ears, and to explore the difference and possible reasons of neural coding for speech from different ears in auditory brainstem. METHOD: Speech-ABRs to syllable /da/ of 31 healthy adults were recorded. Statistical analysis was performed on time-domain parameters, such as latencies and amplitudes of featured peaks, and frequency-domain ones, such as amplitudes of the fundamental frequency and the first formant of speech-ABRs ranging from 20-50 ms. A scoring criterion to grade the appearance of featured waves was proposed for waveform evaluation. RESULT: There were no significant difference for the latencies of binaural featured peaks and amplitudes of feature peaks (except peaks A and O). The waveform .scores of right ear were greater than that of left ear. The amplitudes of fundamental frequency of binaural waves were both greater than that of the first formant. There was no significant difference of amplitudes of fundamental frequency and the first formant between two ears. CONCLUSION: The origins and distributions of speech-ABR are essentially symmetrical in brainstem in contrast with the hemisphere asymmetry of speech.

[Components and characteristics of speech-ABR from healthy young adults.].

OBJECTIVE: To determine the electrophysiological characteristics of speech evoked-ABR, which are then related to the acoustic properties of stimulus sound in terms of the latencies of the main components, and moreover compared to the conventional click-ABR to explore their underlying relationships. METHODS: The speech-ABR and click-ABR were recorded from 31 healthy young adults without any hearing problem examined by audiometric screen processes. The speech syllable/da/was synthesized by Klatt method. The ABRs recorded by the same clinic certificated instrument following established protocols and the stimulus sound was processed and analyzed in both time and frequency domain by a software package developed on Matlab platform. RESULTS: The main components of speech-ABR were clearly identified, and were categorized into onset response, frequency following response, transitional response and offset response in responding to the stimulus sound structure involving consonant and vowel portions. The latency of peak A significantly correlated with that of peaks V, C, D, E and F respectively (P < 0.05), especially with V. Furthermore, the latencies of peak D, E, and F are significantly correlated with each other (P < 0.01). Transitional component peak C was only correlated with peak V and A (P < 0.05); and offset wave O was independent to all the other peaks (P > 0.05). The latencies of speech-V and peak III were significantly delayed in comparison with their counterparts of click-ABR (P < 0.01). It was observed that the appearance rate of wave III was significantly lower than that of click-III (P < 0.01), while there was no significant delay and low appearance rate for wave-I observed in speech-ABR (P > 0.05). CONCLUSIONS: This study verified the clear patterns of speech-ABR from healthy adults, the main components of which are closely related and analogues to the combination of the main waves of click-ABR, SN10 and FFR evoked by low-frequency tone. It offers a promising tool in the study of speech coding and processing mechanism.