Influence of click polarity on the brain-stem auditory evoked response (BAER) revisited

Brain-stem auditory evoked responses (BAERs) were recorded both to rarefaction and condensation click stimulation in 92 normal hearers and 78 patients with varying degrees of cochlear hearing loss (N = 340 ears). Frequency distributions of rarefaction minus condensation (R - C) latency and amplitude differences revealed clinically significant polarity effects in a substantial percentage of the patients studied. Bivariate plots of R - C latency and amplitude differences versus average high frequency hearing loss (PTA 3) demonstrated that the magnitude of the R - C latency and amplitude differences also seemed to be influenced by degree of high frequency hearing loss. Results are discussed relative to the phase-locking properties of the afferent auditory nerve fibers and the possible electrodiagnostic consequences of recording the BAER either to alternating or condensation clicks.     

诱发性耳声发射的掩蔽

３４例听觉正常受试者（共４８耳）进行疏波短声诱发性耳声发射（ＥＯＡＥ）掩蔽实验,项目包括同侧同时掩蔽、同侧后掩蔽和对倒后掩蔽。同时掩蔽的掩蔽声是稳态白噪声,后掩蔽的掩蔽声是宽带噪声。同侧同时掩蔽强度达３０ｄＢＳＬ时,未观察到对ＥＯＡＥ的掩蔽效应,但对主观听觉感受有掩蔽作用,表明ＥＯＡＥ的客观属性反映听觉行为有其局限性、同侧及对侧后掩蔽出现掩蔽效应时的掩蔽强度分别为３０和５０ｄＢＳＬ,掩蔽阈约分别为５９和６８ｄＢＳＬ。耳蜗的机械特性－非线性或耳蜗内存在的某种功能性的反馈调节系统可能是同侧后掩蔽的作用机理。下行的对侧橄榄耳蜗内侧束对外毛细胞主动收缩的抑制性作用,可有效解释对倒后掩蔽的ＥＯＡＥ变化。     

Three-channel Lissajous' trajectory of the binaural interaction components in human auditory brain-stem evoked potentials

The 3-channel Lissajous' trajectory (3-CLT) of the binaural interaction components (BI) in auditory brain-stem evoked potentials (ABEPs) was derived from 17 normally hearing adults by subtracting the response to binaural clicks (B) from the algebraic sum of monaural responses (L + R). ABEPs were recorded in response to 65 dB nHL, alternating polarity clicks, presented at a rate of 11/sec. A normative set of BI 3-CLT measures was calculated and compared with the corresponding measures of simultaneously recorded, single-channel vertex-left mastoid and vertex-neck derivations of BI and of ABEP L+R and B. 3-CLT measures included: apex latency, amplitude and orientation, as well as planar segment duration and orientation.The results showed 3 apices and associated planar segments (“Bd_II,” “Be” and “Bf”) in the 3-CLT of BI which corresponded in latency to the vertex-mastoid and vertex-neck peaks IIIn, V and VI of ABEP L + R and B. These apices corresponded in latency and orientation to apices of the 3-CLT of ABEP L + R and ABEP B. This correspondence suggests generators of the BI components between the trapezoid body and the inferior colliculus output. Durations of BI planar segments were approximately 1.0 msec. Apex amplitudes of BI 3-CLT were larger than the respective peak amplitudes of the vertex-mastoid and vertex-neck recorded BI, while their intersubject variabilities were comparable.     

Investigation of electrical responses recorded from the fenestra cochleae in cats

Electrical responses of the fenestra cochleae to stimulation by clicks of different intensity, polarity, and frequency, were studied in anesthetized cats. The absolute values of amplitude and latent period of the neural component of the response reflect the physiological state of the auditory nerve. Besides ordinary potentials characterized by peaks N1 and N2, specific responses were observed when clicks with an intensity of 85 dB or "rarefaction" clicks were used. Dependence of the amplitude of these responses on the intensity of acoustic stimuli of different polarity was investigated during a change in the rhythm of the stimulation; the effect of different rhythms of stimulation on the gradient of the curve reflecting this relationship was examined. The possible mechanisms of the effect of stimulus frequency are discussed.Scientific-Research Institute of Otolaryngology, Ministry of Health of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 151–157, March–April, 1979.     

The interaction between sex and click polarity in brain-stem auditory potentials evoked from control subjects of Oriental and Caucasian origin

Brain-stem auditory evoked potentials (BAEPs) were performed on 30 male and 30 female young normal Oriental subjects, using both condensation and rarefaction stimulation. The effects of sex and click polarity on the BAEP latencies and amplitudes were studied. Females had shorter absolute and interpeak latencies and higher absolute amplitudes than the males. These sex-related BAEP differences were independent of the click polarity. Rarefaction clicks produced shorter wave I latency and longer I–III interpeak latency, but the differences were significant in the female only. The polarity-related BAEP amplitude differences were essentially independent of the sex. BAEPs performed on 60 sex- and age-matched young Caucasian subjects produced similar results. The importance of establishing control BAEP values according to the sex and click polarity is emphasised.     

A Quantitative Analysis of the Sounds of Hector's Dolphin

We developed an automatic, computer-based system in which digital signal processing techniques were used to measure 31 variables from digitized Hector's dolphin (Cephalorhynchus hectori) sounds. Principal component analyses of these data were used to investigate the relationships between sounds. Hector's dolphins make only a very few types of pulsed “clicks”, most of which are centred around 125 kHz. None of these had an average frequency of less than 82 kHz, and the only audible sounds were made up of high-frequency clicks repeated at such high rates that the repetition rate was audible to us as a tonal “cry” or “squeal”. In comparison to signal levels recorded from other cetaceans, all the Hector's dolphin signals were low-level; the maximum received sound pressure level was 163 dB (re 1μPa).     

Short-latency auditory evoked potentials during change in the physical parameter of a sound stimulus

The amplitude-temporal and spectral characteristics of the short-latency auditory evoked potentials (SLAEP) recorded under conditions of monoaural stimulation with sound clicks with initial phase of rarefaction followed by compression and alteration, with the intensity of 60 dB and frequency of 11.1 Hz, were studied in ipsi- and contralateral derivations. Substantial changes in SLAEP morphology in response to polarity inversion of the acoustic stimulus were found. Waves II, IV, VI, and VII changed to the greatest extent. The spectral analysis detected three main SLAEP components: low- (LF), medium- (MF), and high-frequency (HF) components as well as the respective frequency bands. Change in the click phase from rarefaction to compression resulted in bilateral redistribution of power between the MF and HF components. This was expressed as a decrease in the HF peak power and simultaneous rise of MF power. Selective effects of the polarity inversion of the sound stimulus on the MF and HF components support the finding that the activity of SLAEP-generating structures are mainly reflected in the mentioned components. It is suggested that two populations of phase-sensitive units are represented in the auditory analyzer. These populations determine the characteristic changes in SLAEP morphology and spectral characteristics.     

Dynamic changes in hair cell stereocilia and cochlear transduction after noise exposure

The structures of cochlear transduction include stereocilia at the apical surface of hair cells and their connection to the tectorial membrane. The transduction site is one of the loci for noise-induced cochlear damage. Although stereocilia are susceptible to noise, it has been found that in the inner ears of avians, this fragile structure is largely self-repairing and is associated with recovery of hearing sensitivity after noise exposure, as observed in the difference between the temporal threshold shift (TTS) and the permanent threshold shift (PTS). In the mammalian cochleae, however, threshold shifts measured in the auditory brainstem responses (ABR) did not parallel the chronological changes in the stereocilia on hair cells. It is unclear how the morphological recovery of the stereocilia on the mammalian hair cells is correlated with the changes in cochlear transduction that can be assessed by measuring receptor potential. In the present study, guinea pigs were exposed to a broadband noise of 110 dB SPL for 2 h. Auditory sensitivity was evaluated using ABR and cochlear transduction was assessed using cochlear microphonics (CM). Stereocilia morphology was quantified at different time points after the noise and compared with the control. The noise produced a TTS of 55.69 ± 14.13 dB in frequency-averaged ABR thresholds. The threshold shift was reduced to 9.58 ± 11.75 dB SPL 1 month later with virtually no loss of hair cells. Damage to the stereocilia immediately after noise exposure was found to be associated with depression of CM amplitude. Virtually no abnormal stereocilia were observed 1 month after the noise in association with a fully recovered CM.     

白噪声对听觉脑干电反应(ABR)和耳蜗电图(ECochG)的影响

本文通过20例听力正常人和10例听力正常豚鼠研究了白噪声对耳蜗电图(ECochG)和听觉脑干电反应(ABR)的干涉作用。实验结果表明,白噪声比短声(信号)的声强级低30dB(SL)以上时,ECochG和ABR的振幅仅轻微减小。白噪声与短声的声强级相等时,ECochG与ABR的振幅和出现率会明显受到干涉而减小,甚至完全消失。但是,此时的耳蜗微音器电位(CM)并未观察到有明显的变化。这意味着白噪声对ECochG和ABR的干涉作用主要与围绕毛细胞基底部的突触产生的抑制密切相关。由于白噪声对ABR各波的干涉有些差异,所以认为这种抑制,可能既包括脑中抑制也包括侧方抑制。     

Auditory brain stem responses in characterization of dolphin hearing

Summary Auditory brain stem responses (ABR) were recorded from the head surface of non-anesthetized and non-relaxed bottle-nosed dolphins, Tursiops truncatus. The region of best ABR recording was shown to be located 6–9 cm caudal to the blowhole. The threshold values were about 1 mPa for noise bursts and –3 dB re 1 mPa for tone bursts of the optimal frequency (80 kHz). The maximum frequency at which ABR could be evoked was 140 kHz. The duration of temporal summation reached 0.5 ms at intensities near the threshold and decreased with an increase in intensity. When the stimuli were paired clicks of the same intensity, the time to complete recovery from the second response was about 5 ms, while that to its 50% recovery was 0.7 ms. When the conditioning click exceeded the testing one in intensity, prolongation of the recovery period was observed. A 40-dB intensity difference led to an approximately 10-fold prolongation of this period.Abbreviations ABR auditory brain stem response - EP evoked potential     

Hearing sensation levels of emitted biosonar clicks in an echolocating Atlantic bottlenose dolphin

Emitted biosonar clicks and auditory evoked potential (AEP) responses triggered by the clicks were synchronously recorded during echolocation in an Atlantic bottlenose dolphin (Tursiops truncatus) trained to wear suction-cup EEG electrodes and to detect targets by echolocation. Three targets with target strengths of -34, -28, and -22 dB were used at distances of 2 to 6.5 m for each target. The AEP responses were sorted according to the corresponding emitted click source levels in 5-dB bins and averaged within each bin to extract biosonar click-related AEPs from noise. The AEP amplitudes were measured peak-to-peak and plotted as a function of click source levels for each target type, distance, and target-present or target-absent condition. Hearing sensation levels of the biosonar clicks were evaluated by comparing the functions of the biosonar click-related AEP amplitude-versus-click source level to a function of external (in free field) click-related AEP amplitude-versus-click sound pressure level. The results indicated that the dolphin's hearing sensation levels to her own biosonar clicks were equal to that of external clicks with sound pressure levels 16 to 36 dB lower than the biosonar click source levels, varying with target type, distance, and condition. These data may be assumed to indicate that the bottlenose dolphin possesses effective protection mechanisms to isolate the self-produced intense biosonar beam from the animal's ears during echolocation.     

AEPs at the onset and offset of repetitive sound modulation,due to mismatch with the contents of an auditory sensory store

Long latency auditory evoked potentials (AEPs), chiefly consisting of a negative peak at about 150 msec and a positivity at 250 msec, were recorded at the beginning and end of periods during which the interaural time difference of binaural noise was switched between 0.0 and 0.8 msec at a fast rate (ISI = 50 or 25 msec) or the frequency of continuous binaural clicks was switched between 167 and 200 Hz every 80, 50 or 25 msec. In the latter case the offset responses occurred later than onset by a mean of 89, 47 and 27 msec respectively, suggesting they were probably generated at the moment the next switch was expected but failed to occur.The offset responses must be non-specific with respect to the interaural delay or the frequency of clicks, since neurones which respond to particular delays or frequencies and are made refractory by a rapid rate of stimulation should not suddenly become less so at the last in a series of identical stimuli, or be activated by the absence of a further event. It is proposed that the potentials are due to a higher order of neurone which automatically responds to the occurrence of a “mismatch” between the immediate sound and an image of that which was previously present, encoded in a short-term sensory store. In addition to frequency content and interaural delay, the image must contain information about the temporal modulation pattern of the sound over the previous few seconds.     

甲状腺激素对豚鼠卡那霉素中毒性耳聋的预防作用

卡那霉素、庆大霉素等抗生素常引起耳聋,目前尚无较好的防治方法。卡那霉素对内耳的毒性作用,主要先影响有关的酶功能,继而破坏毛细胞而致聋。甲状腺激素具有促进蛋白质合成、增强细胞生物氧化的功能。因此可能具有减轻卡那霉素耳毒性的作用。本实验以耳廓反射、内耳生物电及耳蜗铺片为指标,观察甲状腺激素对卡那霉素耳中毒的预防。实验豚鼠分两组,各13只,对照组每天注射卡那霉素300mg/kg,共10天;甲状腺素组先隔天服甲状腺片20mg共四次,以后给予与对照组相同剂量卡那霉素,同时仍隔天服甲状腺片20mg直至停药后16天,前后总共服17次。结果:(1)耳廓反射阈变化,对8、4、2KHz三个频率听力均下降的耳,对照组为11只耳,甲状腺素组为3只耳,两者差异显著。听力下降的频率范围及程度,对照组比甲状腺素组更大。对照组听力下降开始出现的时间明显早于甲状腺素组;(2)内耳生物电,0～80dβ不同程度短声引起的耳蜗微音器电位与听神经动作电位幅值甲状腺素组动物均高于对照组;(8)耳蜗铺片,对照组大部分动物耳蜗各回的毛细胞严重变性缺损,甲状腺素组耳蜗病变仅局限在底回。以上结果表明甲状腺激素能减轻卡那霉素的耳毒性,为耳毒性抗生素致聋的防治提供了一条新的研究途径。     

The recovery of the reactivity of the auditory system in the dolphin Tursiops truncatus to paired acoustic stimuli with different spectra]

Recovery cycles of the auditory brainstem responses were studied in the bottle-nosed dolphin, Tursiops truncatus, using paired acoustic clicks. The recovery time was longer if both clicks had identical spectra (50% recovery at 0.9 ms), as compared with that of different spectra (50% recovery at 0.35 ms). These results can explain a different recovery time of evoked responses after an artificial sound and after own locating one.     

Evoked potentials of the auditory cortex of the porpoise,Phocoena phocoena

Summary Evoked potential (EP) recordings in the auditory cortex of the porpoise,Phocoena phocoena, were used to obtain data characterizing the auditory perception of this dolphin. The frequency threshold curves showed that the lowest EP thresholds were within 120–130 kHz. An additional sensitivity peak was observed between 20 and 30 kHz. The minimal EP threshold to noise burst was 3·10^–4–10^/s-3 Pa. The threshold for response to modulations in sound intensity was below 0.5 dB and about 0.1% for frequency modulations. Special attention was paid to the dependence of the auditory cortex EP on the temporal parameters of the acoustic stimuli: sound burst duration, rise time, and repetition rate. The data indicate that the porpoise auditory cortex is adapted to detect ultrasonic, brief, fast rising, and closely spaced sounds like echolocating clicks.Abbreviation EP evoked potential     

Voltage responses to tones of outer hair cells in the basal turn of the guinea-pig cochlea: significance for electromotility and desensitization.

Voltage responses were recorded from outer hair cells (OHCS) in the basal coil of the guinea-pig cochlea in response to tones at frequencies above the characteristic frequency (CF) presented together with a 100 Hz tone at 80 dB or 85 dB sound pressure level (SPL). The amplitude and polarity of voltage responses to a 100 Hz, 85 dB SPL tone were altered when presented together with tones at frequencies above CF according to the frequency and level of the high-frequency tone, OHC phasic (ac) (greater than 500 microV) but not tonic (dc) voltage responses were elicited by the high-frequency tone. Thus the responses of OHCS to low-frequency tones can be altered when presented together with a high-frequency tone without an apparent dc change in membrane potential. Recordings were made from an OHC during cochlear desensitization through exposure to an intense tone. The maximum voltage response to high-level low-frequency tones remained unchanged, although the OHC response to high-frequency tones became less sensitive to low-level stimuli and more linear as a function of level. It is suggested that desensitization is associated with a change in the mechanical properties of the cochlea, possibly associated with the OHCS themselves, and not with inactivation of the transducer channels. The amplitude of the OHC ac voltage response was measured at neural threshold, and the consequences of these measurements on hair cell electromotility are considered.     

Apoptosis of inner hair cells caused by laser ablation of their spiral ganglion neurons in cultures of the mouse organ of Corti

Laser beam ablation of spiral ganglion neurons was performed in seven organotypic cultures of the newborn mouse cochlea between 5 and 8 days in vitro, with a recovery period of from 18 hours to 3 days. Direct somatic injury (laser or mechanical) inflicted on hair cells does not necessarily cause their death; many of them survive, repair damage and re-establish their neurosensory connections. By contrast, laser irradiation and ablation of their afferent spiral ganglion neurons causes a most spectacular degeneration of sensory cells within 18–48 hours after the insult. Ultrastructurally, the degenerated hair cells—characteristically the inner hair cells—display “dark-cell vacuolar degeneration” that combines the signs of apoptotic death (the peripheral condensation of nuclear chromatin and nuclear pyknosis) with signs of cell edema, vacuolization and necrosis. The ultimate condensation of the cytoplasm gives the dead cells a jet black appearance. The irradiated spiral ganglion neurons die displaying similar pathological characteristics. The extent and locus of inner hair cell degeneration correspond to that of ablated spiral ganglion neurons: ultimately the ablation of one neuron causes degeneration of a single inner hair cell within the closest radial segment of the afferent innervation. The elimination of spiral ganglion neurons by mechanical means does not affect hair cell survival. It is inferred that the laser pulse acts as a stimulus depolarizing the neuronal membrane of the spiral ganglion neurons and their radial fibers and causing the excitotoxic death of their synaptic sensory cells through excessive stimulation of the glutamatergic receptors. Reciprocal pre-and postsynaptic synapses between the afferent dendrites and inner hair cells in culture could possibly serve as entryways of the stimulus. The pathogenesis of this apparent transsynaptically-induced apoptotic death of inner hair cells will be further examined in culture.     

Energy detection and temporal integration in the noctuid A1 auditory receptor

The temporal integration of the A1 auditory receptor of two species of noctuid moths (Lepidoptera, Noctuidae) was investigated. Tympanal nerve spikes were recorded while stimulating the ear with broad band clicks. Thresholds were measured for single clicks, pairs of clicks with a separation of 1–20 ms, and trains of up to 8 clicks at separations of 1–2 ms. The average threshold for single clicks was 52.9 dB peSPL (SD 1.7 dB, n = 40) for Noctua pronuba and 50.1 dB peSPL (SD 4.0 dB, n = 27) for Spodoptera littoralis. The thresholds for double clicks with a 1 ms separation were lower than the thresholds for single clicks. The difference decreased as the separation between the clicks was increased. The results were fully consistent with an energy detector model (a leaky integrator with an exponential decay) with a time constant of about 4 ms.The results are compared to previously published results with pure tone intensity/duration trading. A common underlying mechanism is suggested, based on the passive electric properties of the receptor cell membrane.It is suggested, that the time constant revealed in the present study characterizes auditory receptors in general, and is related to the short time constants in vertebrate audition.Abbreviations peSPL peak equivalent sound pressure level - SD standard deviation - time constant     

Vestibular-dependent spinal reflexes evoked by brief lateral accelerations of the heads of standing subjects

An impulsive acceleration stimulus, previously shown to activate vestibular afferents, was applied to the mastoid. Evoked EMG responses from the soleus muscles in healthy subjects (n = 10) and patients with bilateral vestibular dysfunction (n = 3) were recorded and compared with the effects of galvanic stimulation (GVS). Subjects were stimulated while having their eyes closed, head rotated, and while tonically activating their soleus muscles. Rectified EMG responses were recorded from the leg contralateral to the direction of head rotation. Responses were characterized by triphasic potentials that consisted of short-latency (SL), medium-latency (ML), and long-latency (LL) components beginning at (mean ± SD) 54.2 ± 4.8, 88.4 ± 4.7, and 121 ± 7.1 ms, respectively. Mean amplitudes for the optimum stimulus rise times were 9.05 ± 3.44% for the SL interval, 16.70 ± 4.41% for the ML interval, and 9.75 ± 4.89% for the LL interval compared with prestimulus values. Stimulus rise times of 14 and 20 ms evoked the largest ML amplitudes. GVS evoked biphasic responses (SL and ML) with similar latencies. Like GVS, the polarity of the initial interval was determined by the polarity of the stimulus and the evoked EMG response was attenuated when subjects were seated. There was no significant EMG response evoked when subjects were stimulated using 500-Hz vibration or in patients with bilateral vestibular dysfunction. Our study demonstrates that a brief lateral acceleration, likely to activate the utricle, can evoke spinal responses with properties similar to those previously shown for vestibular activation by GVS. The triphasic nature of the responses may allow the nervous system to respond differently to short compared with long-duration linear accelerations, consistent with their differing significance.     

The effect of stimulus type and background noise on hearing abilities of the round goby Neogobius melanostomus

The auditory abilities of the round goby Neogobius melanostomus were quantified using auditory evoked potential recordings, using tone bursts and conspecific call stimuli. Fish were tested over a range of sizes to assess effects of growth on hearing ability. Tests were also run with and without background noise to assess the potential effects of masking in a natural setting. Neogobius melanostomus detected tone bursts from 100 to 600 Hz with no clear best frequency in the pressure domain but were most sensitive to 100 Hz tone stimuli when examined in terms of particle acceleration. Responses to a portion of the N. melanostomus call occurred at a significantly lower threshold than responses to pure tone stimulation. There was no effect of size on N. melanostomus hearing ability, perhaps due to growth of the otolith keeping pace with growth of the auditory epithelium. Neogobius melanostomus were masked by both ambient noise and white noise, but not until sound pressure levels were relatively high, having a 5-10 dB threshold shift at noise levels of 150 dB re 1 μPa and higher but not at lower noise levels.