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The Auditory Steady-State Response (ASSR) is a type of auditory evoked potential (AEP) generated in the auditory system that can be automatically detected by means of objective response detectors (ORDs). ASSRs are usually registered on the scalp using electroencephalography (EEG). ORD are univariate techniques, i.e. only uses one data channel. However, techniques involving more than one channel - multi-channel objective response detectors (MORDs) - have been showing higher detection rate (DR) when compared to ORD techniques. When ASSR is evoked by amplitude stimuli, the responses could be detected by analyzing the modulation frequencies and their harmonics. Despite this, ORD techniques are traditionally applied only in its first harmonic. This approach is known as one-sample test. The q-sample tests, however, considers harmonics beyond the first. Thus, this work proposes and evaluates the use of q-sample tests using a combination of multiple EEG channels and multiple harmonics of the stimulation frequencies and compare them with traditional one-sample tests. The database used consists of EEG channels from 24 volunteers with normal auditory threshold collected following a binaural stimulation protocol by amplitude modulated (AM) tone with modulating frequencies near 80 Hz. The best q-sample MORD result showed an increase in DR of 45.25% when compared with the best one-sample ORD test. Thus, it is recommended to use multiple channels and multiple harmonics, whenever available.

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An Auditory Steady-State Response (ASSR) is a valuable tool for determining auditory thresholds in individuals who are either unable or unwilling to cooperate with conventional behavioral testing methods. This study proposes a sequential test technique for automatic detection of ASSRs, incorporating a non-detection stopping criterion. The electrophysiological thresholds of a normal hearing volunteer were established using data collected from multichannel EEG signals. The detection probabilities and critical values were obtained via Monte Carlo simulations. Remarkably, application of the non-detection stopping criterion resulted in a 60% reduction in exam time in the absence of a response. These findings clearly demonstrate the significant potential of the sequential test in enhancing the performance of automatic audiometry.

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PURPOSE: In the present study, a new procedure to perform automatic audiometry using multifrequency Auditory Steady-State Response (ASSR) is proposed. METHODS: The automatic audiometry procedure consists of detecting the presence of multifrequency ASSR in real-time using the sequential test strategy and by adjusting the stimulus intensity independently. The ASSR audiometric thresholds of 18 adult volunteers with normal hearing were determined by automatically (four simultaneous frequencies per ear) at modulation frequencies in the 80 Hz range. The exam time and the difference between ASSR thresholds and pure-tone behavioural hearing thresholds were estimated as performance measures. RESULTS: The results showed that automatic audiometry can reduce the number of intensity levels used to obtain the ASSR threshold by up to 58% when compared to audiometry without using the techniques applied in automatic audiometry. In addition, the average of the difference between ASSR thresholds and Pure-Tone Behavioural Hearing thresholds was around 19 dB, which is similar to the results reported in similar studies. CONCLUSIONS: The audiometric procedure proposed in this study is fully automatic, i.e., does not require any human supervision throughout the exam, and is able to significantly reduce the conventional exam time.

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Auditory steady-state response (ASSR) is useful for hearing threshold estimation. The ASSR is usually detected with objective response detectors (ORD). The performance of these detectors depends on the signal-to-noise ratio (SNR) as well as the signal length. Since it is undesirable to increase the signal length, then, this work provides a multivariate technique for improving the SNR and consequently the detection power. We propose the insertion of a short calibration step before the detection protocol, in order to perform a search among the available electroencephalogram (EEG) derivations and select the derivation with the highest SNR. The ORD used in this work was the magnitude-squared coherence (MSC). The standard detection protocol is to use the same EEG derivation in all exams. Using 22-scalp positions, the new technique achieved a detection rate higher than that obtained in 99.13% of the standard detection protocol. When restrictions were applied to the search, a superior performance was achieved. Thus, the technique proposed was able to track the best EEG derivations before exams and seems to be able to deal with the variability between individuals and between sessions.

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Objective: Objective Response Detection (ORD) can be used for auditory steady-state response (ASSR) detection. In conventional ORD methods, the statistical tests are applied at the end of data collection ('single-shot tests'). In sequential ORD methods, statistical tests are applied repeatedly, while data is being collected. However, repeated testing can increase False Positive (FP) rates. One solution is to infer that response is present only after the test remains significant for a predefined number of consecutive detections (NCD). Thus, this paper describes a new method for finding the required NCD that control the FP rate for ASSR detection.Design: NCD values are estimated using Monte Carlo simulations.Study sample: ASSR signals were recorded from 8 normal-hearing subjects.Results: The exam time was reduced by up to 38.9% compared to the single-shot test with loss of approximately 5% in detection rate. Alternatively, lower gains in time were achieved for a smaller (non-significant) loss in detection rate. The FP rates at the end of the test were kept at the nominal level expected (1%).Conclusion: The sequential test strategy with NCD as the stopping criterion can improve the speed of ASSR detection and prevent higher than expected FP rates.

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Abstracts Objective: The detection of the auditory steady-state responses is usually performed by an appropriate objective response detector applied to stimulus-related epochs of the raw electroencephalogram (EEG). In order to improve the detection time, sequential detection strategies are usually used. These multiple tests strategies increase the probability of mistakenly detecting a response. The aim of this study was to develop strategies to determine the critical values for the sequential detection strategies based on constant significance level tests. Design: Extensive Monte Carlo simulations were used to test these strategies for the magnitude-squared coherence (MSC) detector. The performances of these strategies were compared with previous works found in the literature. Study sample: All strategies were applied to synthetic and real EEG datasets. Results: The strategies ensure the desired significance level at the end of the sequential detection strategy. The simulated results are in accordance with the real data results. Conclusions: For the MSC detector, where the critical value depends on the number of epochs, the proposed sequential detection strategies obtain better performance regarding test time and detection rate, but worse overall detection rate compared to applying a test only once.

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INTRODUCTION AND OBJECTIVE: Auditory steady state responses to continuous amplitude modulated tones at rates between 70 and 110Hz, have been proposed as a feasible alternative to objective frequency specific audiometry in cochlear implant subjects. The aim of the present study is to obtain physiological thresholds by means of auditory steady-state response in cochlear implant patients (Clarion HiRes 90K), with acoustic stimulation, on free field conditions and to verify its biological origin. METHODS: 11 subjects comprised the sample. Four amplitude modulated tones of 500, 1000, 2000 and 4000Hz were used as stimuli, using the multiple frequency technique. The recording of auditory steady-state response was also recorded at 0dB HL of intensity, non-specific stimulus and using a masking technique. RESULTS: The study enabled the electrophysiological thresholds to be obtained for each subject of the explored sample. There were no auditory steady-state responses at either 0dB or non-specific stimulus recordings. It was possible to obtain the masking thresholds. A difference was identified between behavioral and electrophysiological thresholds of -6±16, -2±13, 0±22 and -8±18dB at frequencies of 500, 1000, 2000 and 4000Hz respectively. CONCLUSIONS: The auditory steady state response seems to be a suitable technique to evaluate the hearing threshold in cochlear implant subjects.

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Epilepsy is a neurological disease related to the occurrence of pathological oscillatory activity, but the basic physiological mechanisms of seizure remain to be understood. Our working hypothesis is that specific sensory processing circuits may present abnormally enhanced predisposition for coordinated firing in the dysfunctional brain. Such facilitated entrainment could share a similar mechanistic process as those expediting the propagation of epileptiform activity throughout the brain. To test this hypothesis, we employed the Wistar audiogenic rat (WAR) reflex animal model, which is characterized by having seizures triggered reliably by sound. Sound stimulation was modulated in amplitude to produce an auditory steady-state-evoked response (ASSR; -53.71Hz) that covers bottom-up and top-down processing in a time scale compatible with the dynamics of the epileptic condition. Data from inferior colliculus (IC) c-Fos immunohistochemistry and electrographic recordings were gathered for both the control Wistar group and WARs. Under 85-dB SLP auditory stimulation, compared to controls, the WARs presented higher number of Fos-positive cells (at IC and auditory temporal lobe) and a significant increase in ASSR-normalized energy. Similarly, the 110-dB SLP sound stimulation also statistically increased ASSR-normalized energy during ictal and post-ictal periods. However, at the transition from the physiological to pathological state (pre-ictal period), the WAR ASSR analysis demonstrated a decline in normalized energy and a significant increase in circular variance values compared to that of controls. These results indicate an enhanced coordinated firing state for WARs, except immediately before seizure onset (suggesting pre-ictal neuronal desynchronization with external sensory drive). These results suggest a competing myriad of interferences among different networks that after seizure onset converge to a massive oscillatory circuit.

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Abstract Introduction The performance of auditory steady state response (ASSR) in threshold testing when recorded ipsilaterally and contralaterally, as well as at low and high modulation frequencies (MFs), has not been systematically studied. Objective To verify the influences of mode of recording (ipsilateral vs. contralateral) and modulation frequency (40 Hz vs. 90 Hz) on ASSR thresholds. Methods Fifteen female and 14 male subjects (aged 18–30 years) with normal hearing bilaterally were studied. Narrow-band CE-chirp® stimuli (centerd at 500, 1000, 2000, and 4000 Hz) modulated at 40 and 90 Hz MFs were presented to the participants' right ear. The ASSR thresholds were then recorded at each test frequency in both ipsilateral and contralateral channels. Results Due to pronounced interaction effects between mode of recording and MF (p < 0.05 by two-way repeated measures ANOVA), mean ASSR thresholds were then compared among four conditions (ipsi-40 Hz, ipsi-90 Hz, contra-40 Hz, and contra-90 Hz) using one-way repeated measures ANOVA. At the 500 and 1000 Hz test frequencies, contra-40 Hz condition produced the lowest mean ASSR thresholds. In contrast, at high frequencies (2000 and 4000 Hz), ipsi-90 Hz condition revealed the lowest mean ASSR thresholds. At most test frequencies, contra-90 Hz produced the highest mean ASSR thresholds. Conclusions Based on the findings, the present study recommends two different protocols for an optimum threshold testing with ASSR, at least when testing young adults. This includes the use of contra-40 Hz recording mode due to its promising performance in hearing threshold estimation.

Resumo Introdução O desempenho da resposta auditiva de estado estável (RAEE) em testes de limiar com registros ipsilateral e contralateral e modulações em frequências (MFs) não tem sido sistematicamente estudado. Objetivo Verificar a influência do modo de registro (ipsilateral vs. contralateral) e da modulação em frequências (40 Hz vs. 90 Hz) nos limiares de RAEE. Método Foram estudados 15 mulheres e 14 homens (18-30 anos) com audição bilateral normal. Estímulos CE-chirp® de banda estreita (centrados em 500, 1.000, 2.000 e 4.000 Hz) modulados em 40 e 90 Hz de MF foram apresentados à orelha direita dos participantes. Em seguida, os limiares de RAEE foram registrados em cada frequência de teste nos canais ipsilateral e contralateral. Resultados Devido aos pronunciados efeitos de interação entre o modo de registro e MF (p < 0,05 por variância com dois fatores para medidas repetidas – Anova duas vias), os limiares médios de RAEE foram então comparados entre quatro condições (Ipsi-40 Hz, Ipsi-90 Hz, Contra-40 Hz e Contra-90 Hz), com o uso de variância e com um fator para medidas repetidas (Anova uma via). Nas frequências de teste de 500 e 1.000 Hz, a condição Contra-40 Hz produziu os mais baixos limiares médios de RAEE. Em contraste, em altas frequências (2.000 e 4.000 Hz), a condição Ipsi-90 Hz revelou os mais baixos limiares médios de RAEE. Na maioria das frequências de teste, a condição Contra-90 Hz produziu os mais elevados limiares médios de RAEE. Conclusões Com base nos achados do presente estudo, os autores recomendam dois protocolos diferentes para um teste de limiares ideal com RAEE, pelo menos em adultos jovens. Isso inclui o uso do modo de registro Contra-40 Hz, devido ao seu desempenho promissor nas estimativas do limiar auditivo.

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INTRODUCTION: The performance of auditory steady state response (ASSR) in threshold testing when recorded ipsilaterally and contralaterally, as well as at low and high modulation frequencies (MFs), has not been systematically studied. OBJECTIVE: To verify the influences of mode of recording (ipsilateral vs. contralateral) and modulation frequency (40Hz vs. 90Hz) on ASSR thresholds. METHODS: Fifteen female and 14 male subjects (aged 18-30 years) with normal hearing bilaterally were studied. Narrow-band CE-chirp® stimuli (centerd at 500, 1000, 2000, and 4000Hz) modulated at 40 and 90Hz MFs were presented to the participants' right ear. The ASSR thresholds were then recorded at each test frequency in both ipsilateral and contralateral channels. RESULTS: Due to pronounced interaction effects between mode of recording and MF (p<0.05 by two-way repeated measures ANOVA), mean ASSR thresholds were then compared among four conditions (ipsi-40Hz, ipsi-90Hz, contra-40Hz, and contra-90Hz) using one-way repeated measures ANOVA. At the 500 and 1000Hz test frequencies, contra-40Hz condition produced the lowest mean ASSR thresholds. In contrast, at high frequencies (2000 and 4000Hz), ipsi-90Hz condition revealed the lowest mean ASSR thresholds. At most test frequencies, contra-90Hz produced the highest mean ASSR thresholds. CONCLUSIONS: Based on the findings, the present study recommends two different protocols for an optimum threshold testing with ASSR, at least when testing young adults. This includes the use of contra-40Hz recording mode due to its promising performance in hearing threshold estimation.

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OBJECTIVE: The aim of this study was to evaluate the potential interactions of the simultaneous presentation of air- and bone-conducted stimuli on auditory steady-state responses (ASSR) amplitude in newborns. DESIGN: Bone- and air-conducted stimuli were sinusoidal carrier tones of 500 and 2000 Hz respectively modulated in amplitude (95% depth). Air- and bone- conducted stimuli were either simultaneously recorded in the same ear using insert earphones and bone vibrator respectively, or recorded individually (single stimulation). STUDY SAMPLE: Sixty-nine well babies (135 ears) with ages ranging from 1 to 16 days (mean of 9.2 ± 7.9 days) were tested in this study. RESULTS: No significant changes in ASSR amplitude by air-conducted stimuli were observed when evoked by simultaneous or single stimulation. The same trend prevailed for ASSR amplitudes evoked by bone-conducted stimuli. CONCLUSIONS: The results of this study suggest that the simultaneous stimulation of air-and bone-conducted stimuli does not alter ASSR amplitude values in well babies. Therefore, the results support the use of this technique as a potential hearing screening tool to discriminate between conductive and sensorineural hearing loss.

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BACKGROUND: Auditory selective attention is the human ability of actively focusing in a certain sound stimulus while avoiding all other ones. This ability can be used, for example, in behavioral studies and brain-machine interface. NEW METHOD: In this work we developed an objective method - called Spatial Coherence - to detect the side where a subject is focusing attention to. This method takes into consideration the Magnitude Squared Coherence and the topographic distribution of responses among electroencephalogram electrodes. The individuals were stimulated with amplitude-modulated tones binaurally and were oriented to focus attention to only one of the stimuli. RESULTS: The results indicate a contralateral modulation of ASSR in the attention condition and are in agreement with prior studies. Furthermore, the best combination of electrodes led to a hit rate of 82% for 5.03 commands per minute. COMPARISON WITH EXISTING METHOD(S): Using a similar paradigm, in a recent work, a maximum hit rate of 84.33% was achieved, but with a greater a classification time (20s, i.e. 3 commands per minute). CONCLUSIONS: It seems that Spatial Coherence is a useful technique for detecting focus of auditory selective attention.

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UNLABELLED: Narrow band CE-chirps(®) were developed to provide a better synchronization of neural response due to the compensation of the traveling wave delay in the basilar membrane. These stimuli combined with a detection method that includes higher response harmonics on the auditory steady-state response (ASSR) recording was studied in this research. OBJECTIVE: (1) To establish air conduction thresholds for ASSR to narrow band CE-chirp(®) in normal hearing full-term neonates; (2) describe the test time needed for the above in one ear and (3) to compare the results in infants and normally hearing adults. METHOD: ASSR to air-conducted stimuli were obtained in 30 full-term neonates (14 girls and 16 boys) with an average age of 34.3h of life. All neonates were presented presence of transient-evoked otoacoustic emissions (TEOAE) and result "pass" in automatic ABR at 35dB nHL before ASSR test. ASSR thresholds of both ears of 10 normal hearing adults (5 girls and 5 boys) varied in age between 23 and 30 years and with hearing thresholds better than or equal to 15dB HL at all frequencies between 250 and 8000Hz were recorded to compare with the neonate data. RESULTS: The neonate ASSR thresholds estimated from 50% using cumulative distributions were 24.5, 13.5, 7.5 and 10dB nHL at 500, 1000, 2000, and 4000Hz, respectively. For the same frequency order, ASSR thresholds estimated from 90% of the neonates were 34.5, 28, 12.5 and 15dB nHL. It required 21.2 (±5)min on average to obtain threshold in each ear in neonates, with a range of 12-29min. When ASSR thresholds recorded in full-term neonates and adults were directly compared, the differences between these groups were not significant for 1000Hz (p=0.500), 2000Hz (p=0.610) and 4000Hz (p=0.362). However, at 500Hz, ASSR thresholds in neonates tend to be greater than in adults (p=0.001). CONCLUSION: In this study ASSR thresholds estimated from 90% of the neonates were 34.5, 28, 12.5 and 15dB nHL. It required 21.2 (±5)min on average to obtain threshold in each ear and ASSR thresholds to narrow band CE-chirp(®) in neonates are not significant for adults ASSR thresholds, except at 500Hz, when the ASSR thresholds in neonates tend to be greater than in adults.

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Introdução: A resposta auditiva de estado estável (RAEE) pode ser captada utilizando vários tipos de transdutores como fones supra-aurais, fones de inserção, vibrador ósseo e alto falante. A avaliação por meio de alto falante pode ser utilizada na determinação dos níveis mínimos de resposta em campo livre com e sem próteses auditivas. Objetivo: avaliar a aplicabilidade da RAEE em campo livre segundo a saída máxima do transdutor e tempo de exame. Métodos: Foram avaliadas 27 crianças com perda auditiva neurossensorial bilateral de grau moderado a profundo com faixa etária entre oito meses e 12 anos por meio da audiometria tonal e RAEE em campo livre, com e sem as próteses auditivas. Resultados: Na condição sem prótese auditiva, a presença de respostas na audiometria foi maior que na RAEE. Na condição com prótese auditiva, a presença de respostas na audiometria e na RAEE foi igual para as freqüências de 1000, 2000 e 4000 Hz. Não foi observada associação entre o tempo de exame e idade. O menor tempo médio de exame foi observado na perda auditiva de grau profundo, na condição sem prótese auditiva. Conclusões: Na condição com prótese auditiva, a presença de resposta tende a 100 % em ambos os procedimentos de avaliação nas diferentes freqüências. Não há associação entre o tempo de exame e variável idade. O tempo de exame nas crianças com perda auditiva de grau moderado e severo é maior do que no grau profundo, na condição sem prótese auditiva. Na condição com prótese auditiva, não há associação entre tempo de exame e o grau da perda auditiva.

Introduction : The auditory steady-state response (ASSR) can be recorded by the utilization of many kinds of transductors as supra-auricular phones, insertion phones, bone vibrator and loudspeaker. The assessment by loudspeaker may be used on the determination of minimal answer levels in free field with or without hearing aids. Objective : to evaluate the applicability of ASSR in free field according to maximum output of the transductor and the duration of the exam. Methods: 27 children aged from 8 months to 12 years, with bilateral neurossensorial hearing impairment from moderate to profound were evaluated by means of tonal audiometry and ASSR on soundfield with and without hearing aids. Results: In the condition without hearing aids, the answers presence in audiometry and ASSR was the same for frequencies of 1000, 2000 and 4000 Hz. No association was observed between the duration of the exam and age. The smallest time of duration of exam was observed with hearing impairment of profound degree, in the condition without hearing aid. Conclusions: In the condition with hearing aids, the answer presence tends towards 100% on both evaluation procedures on different frequencies. There is no association between duration of ASSR exam and age. The duration of the ASSR exam on children with moderate and severe hearing impairment is higher than with profound degree in condition without hearing aids. In the condition with hearing aids there is no association between duration of ASSR exam and hearing impairment degree.

Introduccion: La respuesta auditiva de estado estable (RAEE) se puede captar utilizando vários tipos de transdutores como auriculares supra-aurales, auriculares de inserción, vibrador oseo y altavoz. La evaluació por médio de altavoz puede ser usada para la derterminacíon de niveles mínimos de respuesta en campo libre con y sin audífonos. Objetivo: evaluar la aplicabildad de RAEE en campo libre de acuerdo con la salida máxima del transdutor y el tiempo de examen. Métodos: Se han evaluado 27 niños con perdida auditiva neurosensorial bilateral de grado moderado a profundo con edades entre ocho meses y 12 años por médio de la audiometria tonal y RAEE en compo libre con y sin audifonos. Resultados: En la condición sin uso de audifonos la presencia de respuesta en la audiometria fue maior que en la RAEE. En la condición con audifonos la presencia de respuestas en la audiomentria y en la RAEE fue igual para las frecuencias de 1000, 2000 y 4000 Hz. No se observó associación entre el tiempo de examen y la edad. El tiempo médio mas corto de examen fué observado para perdida de grado profundo, en la condición sin uso de audifono. Conclusión: En la condición con audifono la presencia de respuestas tiende a 100% en ambos procediemientos de evaluación en las diferentes frecuencias. No hay asociación entre tiempo de examen y la variable edad. El tiempo médio de examen para niños con perdida auditiva moderada y severa es maior que para niños con perdida profunda en la condición sin audifono. En la condición con audifono no hay asociación entre tiempo de examen y grado de perdida auditiva.

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