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PubMed1992

Adaptation to auditory motion in the horizontal plane: effect of prior exposure to motion on motion detectability.

Thresholds for auditory motion detectability were measured in a darkened anechoic chamber while subjects were adapted to horizontally moving sound sources of various velocities. All stimuli were 500-Hz lowpass noises presented at a level of 55 dBA. The threshold measure employed was the minimum audible movement angle (MAMA)--that is, the minimum angle a horizontally moving sound must traverse to be just discriminable from a stationary sound. In an adaptive, two-interval forced-choice procedure, trials occurred every 2-5 sec (Experiment 1) or every 10-12 sec (Experiment 2). Intertrial time was "filled" with exposure to the adaptor--a stimulus that repeatedly traversed the subject's front hemifield at ear level (distance: 1.7 m) at a constant velocity (-150 degrees/sec to +150 degrees/sec) during a run. Average MAMAs in the control condition, in which the adaptor was stationary (0 degrees/sec,) were 2.4 degrees (Experiment 1) and 3.0 degrees (Experiment 2). Three out of 4 subjects in each experiment showed significantly elevated MAMAs (by up to 60%), with some adaptors relative to the control condition. However, there were large intersubject differences in the shape of the MAMA versus adaptor velocity functions. This loss of sensitivity to motion that most subjects show after exposure to moving signals is probably one component underlying the auditory motion aftereffect (Grantham, 1989), in which judgments of the direction of moving sounds are biased in the direction opposite to that of a previously presented adaptor.

Adult↗
PubMed1982

Noise impairment in the guinea pig. II. Changes of single unit responses in the inferior colliculus.

Spontaneous and evoked activity of neurons in the inferior colliculus of guinea pigs was recorded before and after exposure to noise (continuous or intermittent white noise, 115 dB SPL for 30 min). A single unit was investigated in each animal, and its activity was monitored for several hours. Exposure to noise elevated the threshold of the tip of the tuning curve, resulting in a broadening of the tuning curve. Threshold elevation at the characteristic frequency was greater after exposure to intermittent noise (200 ms noise and 200 ms pause), reaching values of 22.8 +/- 3.7 dB (means +/- S.E.) than it was after exposure to continuous noise (threshold elevation of 13.1 +/- 1.7 dB). The average threshold shift was 17.1 +/- 2 dB. Neither the shape of the poststimulus histograms nor the slope of the spike-intensity curves changed with the noise exposure. The total number of spikes during the response was, however, reduced, and the reduction was in proportion to the threshold elevation. Monaural noise exposure had no effect on the neuronal activity evoked by stimulation of the opposite, nonexposed ear. The latencies of responses recorded after exposure to noise were also longer than the latencies at the same absolute intensity recorded before the exposure. Thus the latencies during the original pre-exposure and acquired postexposure thresholds were practically identical.

Action Potentials↗
PubMed1992

[Normative parameter characterization for the auditory brainstem response of the normal newborn].

The auditory brainstem response generated by clicks was studied in 119 normal newborns. One ear was studied in detail at 20, 40 and 60 dBnHL, the other at 20 and 30 dBnHL, increasing the intensity if no response was found. The latency for waves I, III and V in the detailed studied ear was 2.7 +/- .39, 5.4 +/- .44 and 7.7 +/- .48, respectively. 85% of newborns had thresholds for auditory brainstem response less than 40 dBnHL, 54% less than 20 dBnHL and 15% between 40 and 60 dBnHL. These findings are compatible with conductive loss in the higher threshold group and support data from Stockard, regarding high risk groups. Additionally, our data suggests that an adequate level to screen for hearing loss in newborns is between 30 and 40 dBnHL.

Auditory Threshold↗
PubMed1987

Self-reported disability and handicap in the population in relation to pure-tone threshold, age, sex and type of hearing loss.

A self-administered questionnaire concerning auditory disability and handicap was completed by 1691 subjects who were part of a two-stage random sample of the UK adult population. A principal components analysis of questionnaire replies identified four components. They were interpreted as (a) disability for everyday speech, (b) disability for speech-in-quiet, (c) localisation, and (d) hearing handicap. Components (a) and (d) were the strongest, accounting for 68% of the variance. Subjects also performed pure-tone audiometry amongst other tests. Audiometric information was well described by a two-parameter model characterised by low-to-mid-frequency loss and high-frequency slope. All four components increased progressively with increasing low-to-mid-frequency loss, independent of high-frequency slope. They were best correlated with a binaural average over 0.5, 1 and 2 kHz weighted 4:1 in favour of the better ear, out of several audiometric descriptors examined. Sex and socio-economic group did not generally affect disability or handicap, but people of similar hearing impairment reported less disability and handicap as age increased. This is interpreted as over-compensation for the effects of age in self-report. There were three unexpected findings which may entail some changes in current thinking on the relationship between auditory impairment and self-perceived disability/handicap. Hearing losses incorporating a conductive component in the better ear were more disabling and handicapping than sensorineural losses of equal magnitude. Localisation ability and, to a lesser extent, general hearing handicap were more highly correlated with measures of impairment in the worse ear than in the better ear. There was little evidence for the concept of a 'low fence' in the relationship between impairment and either disability or handicap.

Adolescent↗
PubMed1988

Modification of spontaneous and evoked otoacoustic emissions and associated psychoacoustic microstructure by aspirin consumption.

The discovery that aspirin consumption can abolish spontaneous otoacoustic emissions [D. McFadden and H.S. Plattsmier, J. Acoust. Soc. Am. 76, 443-448 (1984)] provides a technique for further exploring the relation between otoacoustic emissions (spontaneous and evoked) and psychoacoustic threshold microstructure. Spontaneous emissions, delayed evoked emissions, synchronous evoked emissions, and threshold microstructure in four subjects were monitored before, during, and after consumption of 3.9 g of aspirin per day (three 325-mg tablets every 6 h) for 3 or 4 days. The changes in spontaneous emissions are consistent with the findings of McFadden and Plattsmier except that one spontaneous emission appeared to plateau at a reduced level above the noise floor during the last day and a half of the 3-day period of aspirin consumption. Evoked emissions and threshold microstructure were also reduced by aspirin consumption but persisted longer and recovered sooner. In most instances, the initial change in threshold microstructure was a trend to increased sensitivity (reduced thresholds), with a greater increase near threshold maxima than at threshold minima. Further reduction in the levels of the evoked emissions was accompanied by the eventual decrease in sensitivity (elevation of all thresholds).

Adult↗
PubMed1998

Gender distinctions and lateral asymmetry in the low-level auditory brainstem response of the human neonate.

Threshold measures of auditory brainstem response (ABR) were generated in 72 full-term newborn infants in response to clicks and tone burst stimuli between 500 and 8000 Hz as detailed in a previous study. These results were further analyzed for differences in response related to ear (lateral asymmetry) and subject gender. Thresholds obtained in male infants were significantly lower than those of females (P = 0.0485). The greatest differences in threshold between male and female infants occurs in the right ear (7.45 dB) as opposed to the left ear (1.56 dB). Both male and female infants have significantly larger wave V amplitude elicited from the right ear than the left (P = 0.0002) using low-level stimuli. Also, as has been noted in adults, female infants have larger amplitude ABRs than males (P = 0.0018), but amplitude differences across gender are significant only in the right ear (ear by gender interaction P = 0.0278). Results of this study indicate that gender differences and lateral asymmetry in auditory function are not a result of gender bias for or unbalanced auditory trauma, but a biologically significant phenomenon that is present at birth. The argument is made that superior right ear performance may be part of cerebral laterality in auditory function.

Acoustics↗
PubMed2005

Auditory gap detection in the early blind.

For blind individuals, audition provides critical information for interacting with the environment. Individuals blinded early in life (EB) typically show enhanced auditory abilities relative to sighted controls as measured by tasks requiring complex discrimination, attention and memory. In contrast, few deficits have been reported on tasks involving auditory sensory thresholds (e.g., Yates, J.T., Johnson, R.M., Starz, W.J., 1972. Loudness perception of the blind. Audiology 11(5), 368-376; Starlinger, I., Niemeyer, W., 1981. Do the blind hear better? Investigations on auditory processing in congenital or early acquired blindness. I. Peripheral functions. Audiology 20(6), 503-509). A study of gap detection stands at odds with this distinction [Muchnik, C., Efrati, M., Nemeth, E., Malin, M., Hildesheimer, M., 1991. Central auditory skills in blind and sighted subjects. Scand. Audiol. 20(1), 19-23]. In the current investigation we re-examined gap detection abilities in the EB using a single-interval, yes/no method. A group of younger sighted control individuals (SCy) was included in the analysis in addition to EB and sighted age matched control individuals (SCm) in order to examine the effect of age on gap detection performance. Estimates of gap detection thresholds for EB subjects were nearly identical to SCm subjects and slightly poorer relative to the SCy subjects. These results suggest some limits on the extent of auditory temporal advantages in the EB.

Adult↗
PubMed1993

Vascular decompression surgery for severe tinnitus: selection criteria and results.

Seventy-four patients were operated on within a period of 10 years to treat incapacitating tinnitus; 72 underwent microvascular decompression (MVD) of the intracranial portion of the auditory nerve, and 2 underwent section of the eighth nerve close to the brain stem. Of those who underwent MVD, 2 had no change in symptoms and later also underwent section of the eighth nerve near the brain stem. Two patients did not return for follow-up. Of the 72 remaining patients, 13 (18.1%) experienced total relief from tinnitus, 16 (22.2%) showed marked improvement, 8 (11.1%) showed slight improvement, 33 (45.8%) had no improvement, and 2 (2.8%) became worse. The patients who experienced total relief and those who showed marked improvement had experienced their tinnitus for an average of 2.9 years and 2.7 years, respectively; those who showed slight improvement and those who had no improvement had experienced their tinnitus for a longer time before the operation (mean, 5.2 and 7.9 years, respectively). Of the 72 patients who were operated on and followed, 32 were women. Of these, 54.8% experienced total relief from tinnitus or marked improvement, while only 29.3% of the men showed such relief or improvement. Selection of the patients for operation was mainly based on patient history and, to some extent, on auditory test results (brainstem auditory evoked potentials [BAEP], acoustic middle ear reflexes, and audiometric data).

Adolescent↗
PubMed1986

Masking and the perception of stop consonants: psychoacoustical and electrophysiological experiments.

Naturally spoken German words Stahl [Sta:1] and Spott [Spot] were prepared with gaps (silent intervals) of different lengths between the fricative (S) and the corresponding stop consonant [t] or [p], and with various fricative sound pressure levels. Reduction of the normally occurring pause between the fricative and the stop consonant [t] or [p] to less than 10 ms or 20 ms, respectively, leads to "suppression" of the acoustically present stop, e.g. Spott [Spot] is heard as Schott [Sot]. We compare the results of single neuron recordings from animals to results from psychophysical tests on humans, since animal experiments exclude the effects of possible speech-specific perceptual processes. The animal experiments were done on anesthetized cats, from which we recorded single unit activity in the medial geniculate body (MGB). For neurons which represented the stop consonant by a discharge increase, we varied the gap between the fricative and its following stop from 0 up to 120 ms. For all neurons the responses to the stop consonant were positively correlated with gap length and always showed a minimum for gaps of 30 ms or less. This critical interval for minimum responses matches that found in the human psychophysical measurements of stop consonant "suppression". The time course of the interval dependence of neural responses follows the pattern of the psychoacoustical measurements in humans. Suppression of neural responses to the stop did not depend on whether the neuron responded to either the preceding fricative or the following vowel. Neural (animal experiment) and perceptual (human experiment) responses to the stop consonant show the same dependence on the fricative sound pressure level. The results are interpreted as forward masking. The neurophysiological data correspond well to experiments in which discharge reduction is elicited with simple signals ("forward masking"). Our experiments are evidence that auditory masking plays a role in the suppression of stop consonants and that this phenomenon can be explained without assuming phonetic processes in speech perception at a higher level or specific for humans.

Animals↗
PubMed1980

Age-related changes in the auditory evoked brainstem potentials of albino and pigmented guinea pigs.

The auditory evoked brainstem responses of guniea pigs in two age groups were recorded and examined for evidence of age-dependent changes at peripheral stations in the auditory pathway. Because pigmented guinea pigs have been found to be less sensitive to sounds than albinos, both groups were included in this study. Old and young animals did not differ in response latency or in the conduction times associated with the individual potentials. By contrast, the amplitudes of the brainstem responses to high-frequency stimuli were distinctly reduced in old guinea pigs, with no difference in the dynamic of the amplitude between the two age groups. Within each age group, albino and pigmented animals resembled one another in all parameters studied. The effect of the aging process at the peripheral stations of the auditory pathway is discussed in the light of these results.

Aging↗
PubMed1989

Characteristics of auditory brainstem responses in ground squirrels.

Auditory brainstem responses (ABRs) were characterized at 37 degrees C in ground squirrels (Citellus lateralis) which were implanted with recording screws to record ABRs, and a thermistor to record brain temperature. After two weeks ground squirrels were reanesthetized and tone pips and clicks were delivered through a TDH-49 headphone. Recorded ABRs were found to vary in a predictable manner as a function of stimulus frequency and intensity. At intensities above 50 dB SPL, ABRs could be recorded over the range tested (2-32 kHz). An 8 kHz tone pip was the best frequency for recording ABRs at the lowest stimulus intensities. Latencies decreased as stimulus frequencies increased from 4 kHz to 32 kHz.

Acoustic Stimulation↗
PubMed1994

Effects of acoustic overstimulation on cochlear evoked potentials.

Guinea pigs were exposed to 2 kHz pure-tone or octave-band pass noise at an intensity of 100 dBSPL for 30 min. The effects of sound exposure on cochlear microphonics (CM) and compound action potential (AP) were studied using a test condition devised to complete the measurement of the sensitivity of both potentials for the frequency from 1 to 7 kHz within several minutes. The loss of CM sensitivity was limited to around 5 dB for all test frequencies in animals exposed either to pure-tone or band noise. In contrast, the loss of AP in both exposure conditions was significantly greater than that of the CM, and the magnitude of the AP losses reflected the frequency characteristics of the exposure sounds. From these observations, the AP is considered to be a more sufficient index than the CM in studying the effects of acoustic overstimulation.

Animals↗
PubMed2005

Auditory brainstem responses to airborne sounds in the aquatic frog Xenopus laevis: correlation with middle ear characteristics.

In this study we recorded auditory brainstem responses to airborne sounds to determine the hearing sensitivity of Xenopus laevis frogs and correlated their hearing profiles with middle ear characteristics. In newly metamorphosed frogs (body mass 0.5-0.76 gm, snout-vent length 17-20 mm) best hearing sensitivities were measured in the 2.4-2.8 kHz range, whereas optimal hearing sensitivity of older adults (body mass 18-90 gm; snout-vent length 57-100 mm) ranged from 1.0 to 1.2 kHz. Middle ear volumes reconstructed from serial sections showed approximate volume of 0.002 cc and 0.04-0.07 cc in newly metamorphosed and older frogs, respectively. This inverse frequency-volume relationship is consistent with the properties of an acoustic resonator indicating that differences in best hearing sensitivity are at least in part correlated to variation in middle ear volumes for airborne sounds. These results are consistent with peak frequency vibrational velocity profiles of Xenopus tympanic disk that have been shown to be dependent on underlying middle ear volumes and corroborate the occurrence of peak amplitudes of otoacoustic emissions in the 1.0-1.2 kHz region in adult Xenopus frogs.

Aging↗
PubMed2006

FM signals produce robust paradoxical latency shifts in the bat's inferior colliculus.

Previous studies in echolocating bats, Myotis lucifugus, showed that paradoxical latency shift (PLS) is essential for neural computation of target range and that a number of neurons in the inferior colliculus (IC) exhibit unit-specific PLS (characterized by longer first-spike latency at higher sound levels) in response to tone pulses at the unit's best frequency. The present study investigated whether or not frequency-modulated (FM) pulses that mimic the bat's echolocation sonar signals were equally effective in eliciting PLS. For two-thirds of PLS neurons in the IC, both FM and tone pulses could elicit PLS, but only FM pulses consistently produced unit-specific PLS. For the remainder of PLS neurons, only FM pulses effectively elicited PLS; these cells showed either no PLS or no response, to tone pulses. PLS neurons generally showed more pronounced PLS in response to narrow-band FM (each sweeping 20 kHz in 2 ms) pulse that contained the unit's best frequency. In addition, almost all PLS neurons showed duration-independent PLS to FM pulses, but the same units exhibited duration-dependent PLS to tone pulses. Taken together, when compared to tone pulses, FM stimuli can provide more reliable estimates of target range.

Acoustic Stimulation↗
PubMed2006

Distribution of pendrin in the organ of Corti of mice observed by electron immunomicroscopy.

The distribution of pendrin, which is encoded by the Pendred syndrome gene, has been investigated immunohistochemically in the inner ear. In the cochlea, pendrin has been found in the spiral prominence, external sulcus cells, Hensen's cells and Claudius cells, but its expression in the organ of Corti remains unclear. We examined whether pendrin localizes in the organ of Corti by postembedding immunogold analysis. In the organ of Corti, gold particles were clearly observed in outer and inner hair cells, including the stereocilia. The density of the particles was especially high in the cuticular plates of the hair cells. Gold particles were also detected in the external sulcus, in part of the spiral ligament adjacent to the external sulcus, in supporting cells, and in the spiral ganglion of the cochlea. Our study revealed that pendrin occurs in the organ of Corti. The role of pendrin in the organ of Corti and its association with the Cl- or pH regulation of neurotransmission require further study.

Analysis of Variance↗
PubMed1990

The utility of the auditory brainstem response as a screening procedure.

A population of very low birthweight infants consisting of 41 infants (24 female) less than 1000 g birthweight and 108 infants (63 female) 1000-1499 g birthweight received auditory brainstem response audiometry (ABR) before initial discharge from hospital and were subsequently monitored via behavioural audiometry and tympanometry as part of their pediatric medical team follow-up assessment at age 7 months. Results support the use of ABR but indicate that its diagnostic yield was enhanced by the use of multiple ABR parameters in combination with basic audiological techniques. The commonly used single-value ABR pass/fail criterion was not found to be clinically practical.

Acoustic Impedance Tests↗