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Purpose: This study examined the ability of listeners using cochlear implants (CIs) and listeners with normal hearing (NH) to identify silent gaps of different duration and the relation of this ability to speech understanding in CI users. Method: Sixteen NH adults and 11 postlingually deafened adults with CIs identified synthetic vowel-like stimuli that were either continuous or contained an intervening silent gap ranging from 15 ms to 90 ms. Cumulative d', an index of discriminability, was calculated for each participant. Consonant and consonant-nucleus-consonant (CNC) word identification tasks were administered to the CI group. Results: Overall, the ability to identify stimuli with gaps of different duration was better for the NH group than for the CI group. Seven CI users had cumulative d' scores that were no higher than those of any NH listener, and their CNC word scores ranged from 0% to 30%. The other 4 CI users had cumulative d' scores within the range of the NH group, and their CNC word scores ranged from 46% to 68%. For the CI group, cumulative d' scores were significantly correlated with their speech testing scores. Conclusions: The ability to identify silent gap duration may help explain individual differences in speech perception by CI users.

Purpose: This study examined the ability of listeners using cochlear implants (CIs) and listeners with normal hearing (NH) to identify silent gaps of different duration and the relation of this ability to speech understanding in CI users. Method: Sixteen NH adults and 11 postlingually deafened adults with CIs identified synthetic vowel-like stimuli that were either continuous or contained an intervening silent gap ranging from 15 ms to 90 ms. Cumulative d', an index of discriminability, was calculated for each participant. Consonant and consonant--nucleus--consonant (CNC) word identification tasks were administered to the CI group. Results: Overall, the ability to identify stimuli with gaps of different duration was better for the NH group than for the CI group. Seven CI users had cumulative d' scores that were no higher than those of any NH listener, and their CNC word scores ranged from 0% to 30%. The other 4 CI users had cumulative d' scores within the range of the NH group, and their CNC word scores ranged from 46% to 68%. For the CI group, cumulative d' scores were significantly correlated with their speech testing scores. Conclusions: The ability to identify silent gap duration may help explain individual differences in speech perception by CI users. KEY WORDS: gap duration identification, cochlear implants, speech perception, Cochlear implants (CIs) are electronic devices that have enabled individuals with severe-to-profound hearing loss to regain some hearing. Nearly all of those individuals who receive CIs regain the sensation of [...]

It is well known that discrimination response variability increases with stimulus intensity, closely related to Weber's Law. It is also an axiom that sensation magnitude increases with stimulus intensity. Following earlier researchers such as Thurstone, Garner, and Durlach and Braida, we explored a new method of exploiting these relationships to estimate the power function exponent relating sound pressure level to loudness, using the accuracy with which listeners could identify the intensity of pure tones. The log standard deviation of the normally distributed identification errors increases linearly with stimulus range in decibels, and the slope, a, of the regression is proportional to the loudness exponent, n. Interestingly, in a demonstration experiment, the loudness exponent estimated in this way is greater for females than for males. Il est bien connu que la variabilite de la reponse de discrimination augmente avec l'intensite du stimulus, liee de pres a la loi de Weber. Aussi, que l'amplitude de la sensation augmente avec l'intensite du stimulus est un axiome. Dans la foulee de chercheurs comme Thurstone, Garner et Durlach et Braida, nous explorons une nouvelle methode d'exploitation de ces relations afin d'evaluer l'exposant de la fonction puissance du niveau de pression acoustique relativement a la sonie, en utilisant l'exactitude a laquelle les auditeurs peuvent identifier l'intensite des sons purs. La valeur logarithmique de l'ecart-type des erreurs d'identification normalement reparties augmente de fagon lineaire avec la gamme de stimuli (exprimee en decibels), et la pente de regression, a, est proportionnelle a l'exposant de la sonie, n. A titre de demonstration, une experience permet de constater que l'exposant pour la sonie evalue de cette facon est plus eleve chez les femmes que chez les hommes. DOI: 10.1037/cjep2007007

Experiments on the absolute identification of pure tones were conducted at a single frequency in order to explore several effects. We measured the change in transmitted information as the stimulus range was varied, and we also measured the change in transmitted information as the number of categories within a fixed range was increased. In the former case, we found that information increased with increasing range. In the latter case, we found that information increased with increasing number of categories, but the increase was due to a purely mathematical effect. Transmitted information was estimated by means of computer simulation designed to overcome, in part, small sample bias. This simulator is of potential use to others by helping them calculate transmitted or mutual information accurately using a minimum number of experimental trials. The graph of calculated information against number of trials was found to assume a characteristic shape.

Even though speech signals trigger coding in the cochlea to convey speech information to the central auditory structures, little is known about the neural mechanisms involved in such processes. The purpose of this study was to understand the encoding of formant cues and how it relates to vowel recognition in listeners. Neural representations of formants may differ across listeners; however, it was hypothesized that neural patterns could still predict vowel recognition. To test the hypothesis, the frequency-following response (FFR) and vowel recognition were obtained from 38 normal-hearing listeners using four different vowels, allowing direct comparisons between behavioral and neural data in the same individuals. FFR was employed because it provides an objective and physiological measure of neural activity that can reflect formant encoding. A mathematical model was used to describe vowel confusion patterns based on the neural responses to vowel formant cues. The major findings were (1) there were large variations in the accuracy of vowel formant encoding across listeners as indexed by the FFR, (2) these variations were systematically related to vowel recognition performance, and (3) the mathematical model of vowel identification was successful in predicting good vs poor vowel identification performers based exclusively on physiological data. [ABSTRACT FROM AUTHOR]

Objectives: To provide a level-adjusted correction to the current standard relating anatomical cochlear place to characteristic frequency in humans, and to re-evaluate anatomical frequency mismatch in cochlear implant (CI) recipients considering this correction. It is hypothesized that a level-adjusted place-frequency function may represent a more accurate tonotopic benchmark for CIs in comparison to the current standard., Design: The present analytical study compiled data from fifteen previous animal studies that reported iso-intensity responses from cochlear structures at different stimulation levels. Extracted outcome measures were characteristic frequencies and centroid-based best frequencies at 70 dB SPL input from 47 specimens spanning a broad range of cochlear locations. A simple relationship was used to transform these measures to human estimates of characteristic and best frequencies, and non-linear regression was applied to these estimates to determine how the standard human place-frequency function should be adjusted to reflect best frequency rather than characteristic frequency. The proposed level-adjusted correction was then compared to average place-frequency positions of commonly used CI devices when programmed with clinical settings., Results: The present study showed that the best frequency at 70 dB SPL (BF70) tends to shift away from characteristic frequency (CF). The amount of shift was statistically significant (signed-rank test z = 5.143, p < 0.001), but the amount and direction of shift depended on cochlear location. At cochlear locations up to 600° from the base, BF70 shifted downwards in frequency relative to CF by about 4 semitones on average. Beyond 600° from the base, BF70 shifted upwards in frequency relative to CF by about 6 semitones on average. In terms of spread (90% prediction interval), the amount of shift between CF and BF70 varied from relatively no shift to nearly an octave of shift. With the new level-adjusted frequency-place function, the amount of anatomical frequency mismatch for devices programmed with standard of care settings is less extreme than originally thought, and may be nonexistent for all but the most apical electrodes., Conclusions: The present study validates the current standard for relating cochlear place to characteristic frequency, and introduces a level-adjusted correction for how best frequency shifts away from characteristic frequency at moderately loud stimulation levels. This correction may represent a more accurate tonotopic reference for CIs. To the extent that it does, its implementation may potentially enhance perceptual accommodation and speech understanding in CI users, thereby improving CI outcomes and contributing to advancements in the programming and clinical management of CIs.

Acoustic models have been used in numerous studies over the past thirty years to simulate the percepts elicited by auditory neural prostheses. In these acoustic models, incoming signals are processed the same way as in a cochlear implant speech processor. The percepts that would be caused by electrical stimulation in a real cochlear implant are simulated by modulating the amplitude of either noise bands or sinusoids. Despite their practical usefulness these acoustic models have never been convincingly validated. This study presents a tool to conduct such validation using subjects who have a cochlear implant in one ear and have near perfect hearing in the other ear, allowing for the first time a direct perceptual comparison of the output of acoustic models to the stimulation provided by a cochlear implant.