Determination of Hearing Threshold for Single Frequencies From the Acoustic Reflex

With preactivation, the threshold of stapedial reflex activity can be lowered by 20–30 dB. From these measures of the normal and reduced reflex threshold, an extrapolation may be performed down to the hearing threshold. Thus, the hearing threshold can be determined for every single frequency from 0.125 to 4 kHz if the reflex is elicitable up to 8 kHz.

Résumé

Graˇce à une pré-stimulation, le seuil du réflexe stapédien peut ětre réduit de 20 à 30 dB. Afin de déterminer le seuil d'audition, nous faisons une extrapolation à partir du seuil classique et du seuil réduit du réflexe. Il est ainsi possible de déterminer objectivement le seuil d'audition pour chaque fréquence entre 0.125 et 4 kHz, à condition que le réflexe stapédien puisse ětre obtenu jusqu'à 8 kHz.     

Phase Reversal in Brain Stem Responses: Its Use in the Detection of Asymmetry in the Auditory Pathways

Electrode placement is an important consideration in the recording of a large-amplitude stable response. In this study, brain stem auditory-evoked potentials (BAEP) were obtained from subjects and patients under two electrode configurations, namely ‘vertex-mastoid’ and ‘mastoid-mastoid’. The BAEP waveforms to ipsilateral, contralateral and binaural stimulation were examined for their phase relation with respect to stimulation. In the mastoid-mastoid recording mode, a complete polarity reversal was shown upon changing stimulation from the ipsilateral (with respect to the active input) to the contralateral ear. On simultaneous binaural stimulation, the response was shown to summate to zero. This observation has led to the objective assessment of asymmetry of hearing. Several patients exhibiting recruitment were tested under the mastoid-mastoid recording configuration with binaural stimulation. The results show that a summated ‘null’ response only occurs at an intensity level where loudness equality is attained at the two ears and recruitment is complete. Applied in this way the technique has promising application in the determination of the presence or absence of recruitment and hence in the differential diagnosis of cochlear and retrocochlear lesions.

La position de l'électrode est d'une grande importance pour l'enregistrement d'une réponse stable et de grande amplitude. Dans cette étude, les potentiels évoqués du tronc cérébral ont été obtenus chez des sujets normaux et des malades dans deux conditions: électrodes vertex-mastoïde et électrodes mastoïde-mastoïde. Notre attention s'est portée sur les rapports entre les phases des réponses et la stimulation: homolatérale, contralatérale, binaurale. Lorsque l'enregistrement est fait entre les deux mastoïdes nous observons: 1) un changement de polarité de 180° en appliquant séparément le stimulus à l'une ou l'autre oreille; 2) une annulation des réponses si le stimulus est présenté de façon binaurale.

Nous disposons de la sorte d'un moyen objectif pour évaluer la symétrie de l'audition. Plusieurs malades présentant un recrutement ont été examinés; les résultats indiquent que Ton ne trouve l'annulation binaurale qu'aux niveaux sonores où le recrutement est complet. Ces observations nous conduisent à proposer notre épreuve comme un test objectif de recrutement complet et par conséquent un test pour le diagnostic des lésions cochléaires et rétrocochléaires.     

Pitch and loudness information encoded in auditory imagery as revealed by event‐related potentials

Two experiments using the ERP method and a task that involved comparing an imagined‐S1 (the first stimulus) with a perceived‐S2 (the second stimulus) were conducted to investigate whether imagined auditory representations encode pitch and loudness information. It was found that the amplitude of the imagery‐related late positive complex (LPC) decreased with pitch but increased with loudness of the imagined sound, which was consistent with amplitude modulations of the auditory perception‐related N1 component, thereby providing the first neural evidence that auditory imagery encodes perceptual attributes of auditory experiences.     

Aspects cliniques de quelques formes pathologiques particulières des réponses du nerf auditif chez l'homme

Clinical, audiometric and electro-cochleographic data in typical pathological conditions of the inner ear, eighth nerve and central nervous system are presented and discussed. The occurrence of the different types of electro-cochleographic responses in routine clinical investigations is underlined. Their significance for the differential diagnosis of deafness and otological disorders is temptatively presented.     

Variation in preferred gain with experience for hearing-aid users

This study aimed to determine whether gain adaptation occurs, and at which frequency bands, among new hearing aid (HA) users. Fifty new and 26 experienced HA users were fitted with three listening programs (NAL-NL1 and NAL-NL1 with low- and high-frequency cuts) in the same hearing instrument family. Real-life gain preferences and comfortable loudness levels were measured one, four, and 13 months post-fitting for the new HA users, and one month post-fitting for the experienced HA users. Relative to experienced HA users, new HA users preferred progressively less overall gain than prescribed as the hearing loss became more severe. Gain adaptation occurred in new HA users with greater hearing loss, but was not complete 13 months post-fitting, and was not explained by changes in loudness perception. Preferences for a high-frequency gain cut by half of all study participants could not be predicted from audiological data. Gain adaptation management is recommended for new HA users with more than a mild hearing loss.     

High-dose glycine inhibits the loudness dependence of the auditory evoked potential (LDAEP) in healthy humans

Rationale The loudness dependence of the auditory evoked Potential (LDAEP) has been suggested to be a putative marker of central serotonin function, with reported abnormalities in clinical disorders presumed to reflect serotonin dysfunction. Despite considerable research, very little is known about the LDAEP’s sensitivity to other neurotransmitter systems. Objectives Given the role of N-methyl-d-aspartate (NMDA) receptors in modulating pyramidal cell activity in cortico-cortico and thalamo-cortical loops, we examined the effect of targeting the glycine modulatory site of the NMDA receptor with high-dose glycine on the LDAEP in healthy subjects. Materials and methods The study was a double-blind, placebo-controlled repeated-measures design in which 14 healthy participants were tested under two acute treatment conditions, placebo and oral glycine (0.8 g/kg). Changes in the amplitude of the N1/P2 at varying intensities (60, 70, 80, 90, 100 dB) were examined at C_Z. Results Compared to placebo, high-dose glycine induced a weaker LDAEP (a pronounced decrease in the slope of the N1/P2 with increasing tone loudness; p < 0.02). Conclusion While the exact mechanism responsible for the effects of glycine on the LDAEP are not known, the findings suggest an inhibitory effect in the cortex, possibly via activation of NMDA receptors on GABA interneurons or inhibitory glycine receptors. The findings add to the growing literature exhibiting modulation of the LDAEP by multiple neurochemical systems in addition to the serotonergic system.     

Serotonergic functioning as measured by the loudness dependence of auditory evoked potentials is related to a haplotype in the brain-derived neurotrophic factor (BDNF) gene

Objectives

The serotonergic system plays an important pathophysiological role in various psychiatric disorders. Brain-derived neurotrophic factor (BDNF) is involved in the differentiation and survival of serotonergic neurons. A previous study showed that low serum BDNF levels were associated with strong loudness dependence of auditory evoked potentials (LDAEP) as a reflection of low central serotonergic activity. To evaluate the genetic basis of this relationship, we studied whether the LDAEP is correlated with genetic variants within the BDNF gene.

Methods

Ninety five healthy subjects (41 males, 54 females) received electrophysiological recording of LDAEP and blood drawing for BDNF genotyping. Three BDNF markers (including the single nucleotide polymorphism rs6265(Val66Met)) were analyzed.

Results

Haplotype analysis revealed stronger LDAEP values in carriers of the G(Val)-C-T [rs6265(Val66Met)-rs2030324-rs1491850] haplotype within the BDNF gene in comparison to other haplotype carriers. These findings were demonstrated for the LDAEP of both left and right primary auditory cortices as well as for the vertex electrode (Cz).

Conclusion

Subjects with the BDNF haplotype G(Val)-C-T seem to be characterized by low serotonergic activity as well as possibly by low serum BDNF levels. These findings need replication in independent samples.     

耳鸣掩蔽治疗结合心理治疗的疗效观察

目的 通过比较单纯耳鸣掩蔽治疗与耳鸣掩蔽治疗结合心理治疗的疗效,探讨耳鸣掩蔽治疗结合心理治疗的临床意义.方法 对158例耳鸣患者先进行耳鸣响度匹配后行掩蔽治疗,其中79例患者辅以心理治疗,比较单纯掩蔽治疗组与掩蔽治疗结合心理治疗组耳鸣残疾度量化表(tinnitus handicapinventory,THI)疗效评分.结果 治疗后单纯掩蔽治疗组(79例)THI得分42.8±23.1,耳鸣治疗结合心理治疗组(79例)THI得分28.3±22.5;两组THI评分结果差异有统计学意义(P=0.019).结论 耳鸣掩蔽治疗结合心理治疗较单纯耳鸣掩蔽治疗可以获得更好的临床效果.     

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus™ systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to “very soft” and “too loud”. Within this dynamic range, the stimulus strength intervals associated to the verbal categories “soft”, “medium”, “loud” and “very loud” were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems. Parts of this paper were presented at the 76th annual meeting of the Deutsche Gesellschaft für HNO-Heilkunde, Kopf- und Hals-Chirurgie in Erfurt on 8 May 2005.     

Gender and Oral Contraceptive Effects on Temporary Auditory Effects of Noise

The first experiment examined thresholds at 4 and 8 kHz and the threshold of octave masking at 4 kHz before and after noise for males, females, and females using oral contraceptives. Females using oral contraceptives evidenced greater threshold shifts at 4 kHz than either of the other two groups. The second experiment examined thresholds and the loudness discrimination index at 4 kHz for males and females before and after noise exposure. Females evidenced greater loudness discrimination index changes both with and without noise exposure than did males. In addition, females responded to the noise with cutaneous vasodilation while males evidenced vasoconstriction.