Juxtacellular Labeling of Stellate, Disk and Basket Neurons in the Central Nucleus of the Guinea Pig Inferior Colliculus.

We reconstructed the intrinsic axons of 32 neurons in the guinea pig inferior colliculus (IC) following juxtacellular labeling. Biocytin was injected into cells , after first analyzing physiological response properties. Based on axonal morphology there were two classes of neuron: (1) laminar cells (14/32, 44%) with an intrinsic axon and flattened dendrites confined to a single fibrodendritic lamina and (2) translaminar cells (18/32, 56%) with axons that terminated in two or more laminae in the central nucleus (ICc) or the surrounding cortex.

Salicylate decreases the spontaneous firing rate of guinea pig auditory nerve fibres.

Tinnitus has similarities to chronic neuropathic pain where there are changes in the firing rate of different types of afferent neurons. We postulated that one possible cause of tinnitus is a change in the distribution of spontaneous firing rates in at least one type of afferent auditory nerve fibre in anaesthetised guinea pigs. In control animals there was a bimodal distribution of spontaneous rates, but the position of the second mode was different depending upon whether the fibres responded best to high (> 4 kHz) or low (≤4 kHz) frequency tonal stimulation.

Nitric oxide increases gain in the ventral cochlear nucleus of guinea pigs with tinnitus.

Previous work has led to the hypothesis that, during the production of noise-induced tinnitus, higher levels of nitric oxide (NO), in the ventral cochlear nucleus (VCN), increase the gain applied to a reduced input from the cochlea. To test this hypothesis, we noise-exposed 26 guinea pigs, identified evidence of tinnitus in 12 of them and then compared the effects of an iontophoretically applied NO donor or production inhibitor on VCN single unit activity. We confirmed that the mean driven firing rate for the tinnitus and control groups was the same while it had fallen in the non-tinnitus group.

Does training with amplitude modulated tones affect tone-vocoded speech perception?

Temporal-envelope cues are essential for successful speech perception. We asked here whether training on stimuli containing temporal-envelope cues without speech content can improve the perception of spectrally-degraded (vocoded) speech in which the temporal-envelope (but not the temporal fine structure) is mainly preserved. Two groups of listeners were trained on different amplitude-modulation (AM) based tasks, either AM detection or AM-rate discrimination (21 blocks of 60 trials during two days, 1260 trials; frequency range: 4Hz, 8Hz, and 16Hz), while an additional control group did not undertake any training.

Nitric oxide regulates the firing rate of neuronal subtypes in the guinea pig ventral cochlear nucleus.

The gaseous free radical, nitric oxide (NO) acts as a ubiquitous neuromodulator, contributing to synaptic plasticity in a complex way that can involve either long term potentiation or depression. It is produced by neuronal nitric oxide synthase (nNOS) which is presynaptically expressed and also located postsynaptically in the membrane and cytoplasm of a subpopulation of each major neuronal type in the ventral cochlear nucleus (VCN). We have used iontophoresis in vivo to study the effect of the NOS inhibitor L-NAME (L-NG-Nitroarginine methyl ester) and the NO donors SIN-1 (3-Morpholinosydnonimine hydrochloride) and SNOG (S-Nitrosoglutathione) on VCN units under urethane anaesthesia.

Visual Speech Benefit in Clear and Degraded Speech Depends on the Auditory Intelligibility of the Talker and the Number of Background Talkers.

Perceiving speech in background noise presents a significant challenge to listeners. Intelligibility can be improved by seeing the face of a talker. This is of particular value to hearing impaired people and users of cochlear implants.

Standardized questions in English for estimating tinnitus prevalence and severity, hearing difficulty and usage of healthcare resources, and their translation into 11 European languages.

Introduction: Prevalence estimates depend largely on the nature of the question asked to define the presence of the health condition, and the literature on the population burden of tinnitus and hearing difficulties is no different in this respect. The lack of standardized questions for data collection limits comparison across studies and across countries. The purpose of this short Technical Note is to report the first attempt to establish a set of standard questions developed for use in population-based surveys, and their adaptation and translation from English into 11 European languages.

Visual Inhibition Measures Predict Speech-in-Noise Perception Only in People With Low Levels of Education.

Inhibition-the ability to suppress goal-irrelevant information-is thought to be an important cognitive skill in many situations, including speech-in-noise (SiN) listening. Both inhibition and SiN perception are thought to worsen with age, but attempts to connect age-related declines in these two abilities have produced mixed results even though a clear positive relationship has generally been hypothesized. We suggest that these inconsistencies may occur because listener-based demographic variables such as educational attainment modulate the relationship between inhibition and SiN perception.

Gap-induced inhibition of the post-auricular muscle response in humans and guinea pigs.

A common method for measuring changes in temporal processing sensitivity in both humans and animals makes use of GaP-induced Inhibition of the Acoustic Startle (GPIAS). It is also the basis of a common method for detecting tinnitus in rodents. However, the link to tinnitus has not been properly established because GPIAS has not yet been used to objectively demonstrate tinnitus in humans.

Revisiting Models of Concurrent Vowel Identification: The Critical Case of No Pitch Differences.

When presented with two vowels simultaneously, humans are often able to identify the constituent vowels. Computational models exist that simulate this ability, however they predict listener confusions poorly, particularly in the case where the two vowels have the same fundamental frequency. Presented here is a model that is uniquely able to predict the combined representation of concurrent vowels.

Is Human Auditory Cortex Organization Compatible With the Monkey Model? Contrary Evidence From Ultra-High-Field Functional and Structural MRI.

It is commonly assumed that the human auditory cortex is organized similarly to that of macaque monkeys, where the primary region, or "core," is elongated parallel to the tonotopic axis (main direction of tonotopic gradients), and subdivided across this axis into up to 3 distinct areas (A1, R, and RT), with separate, mirror-symmetric tonotopic gradients. This assumption, however, has not been tested until now. Here, we used high-resolution ultra-high-field (7 T) magnetic resonance imaging (MRI) to delineate the human core and map tonotopy in 24 individual hemispheres.

Listening in Naturalistic Scenes: What Can Functional Near-Infrared Spectroscopy and Intersubject Correlation Analysis Tell Us About the Underlying Brain Activity?

Listening to speech in the noisy conditions of everyday life can be effortful, reflecting the increased cognitive workload involved in extracting meaning from a degraded acoustic signal. Studying the underlying neural processes has the potential to provide mechanistic insight into why listening is effortful under certain conditions. In a move toward studying listening effort under ecologically relevant conditions, we used the silent and flexible neuroimaging technique functional near-infrared spectroscopy (fNIRS) to examine brain activity during attentive listening to speech in naturalistic scenes.

Mammalian behavior and physiology converge to confirm sharper cochlear tuning in humans.

Frequency analysis of sound by the cochlea is the most fundamental property of the auditory system. Despite its importance, the resolution of this frequency analysis in humans remains controversial. The controversy persists because the methods used to estimate tuning in humans are indirect and have not all been independently validated in other species.

The Association Between the Processing of Binaural Temporal-Fine-Structure Information and Audiometric Threshold and Age: A Meta-Analysis.

The ability to process binaural temporal fine structure (TFS) information, which influences the perception of speech in spatially distributed soundscapes, declines with increasing hearing loss and age. Because of the relatively small sample sizes used in previous studies, and the population-unrepresentative distribution of hearing loss and ages within study samples, it has been difficult to determine the relative and combined contributions of hearing loss and age. The aim of this study was to survey published and unpublished studies that assessed binaural TFS sensitivity using the TFS-low frequency (LF) test.

Association between subjective tinnitus and cognitive performance: protocol for systematic review and meta-analysis.

Introduction: Subjective tinnitus is very common and has a number of comorbid associations including depression, sleep disturbance and concentration difficulties. Concentration difficulties may be observable in people with tinnitus through poorer behavioural performance in tasks thought to measure specific cognitive domains such as attention and memory (ie, cognitive performance). Several reviews have discussed the association between tinnitus and cognition; however, none to date have investigated the association between tinnitus and cognitive performance through meta-analysis with reference to an established theoretical taxonomy.

Senescent Changes in Sensitivity to Binaural Temporal Fine Structure.

Differences in the temporal fine structure (TFS) of sounds at the two ears are used for sound localization and for the perceptual analysis of complex auditory scenes. The ability to process this binaural TFS information is poorer for older than for younger participants, and this may contribute to age-related declines in the ability to understand speech in noisy situations. However, it is unclear how sensitivity to binaural TFS changes across the older age range.

Sensitivity to Melody, Rhythm, and Beat in Supporting Speech-in-Noise Perception in Young Adults.

Objectives: Musicians appear to have an enhanced ability to perceive speech-in-noise, prompting suggestions that musical training could be used to help people who struggle to communicate in noisy environments. This study assessed the role of sensitivity to beat, rhythm, and melody in supporting speech-in-noise perception.

Design: This is an exploratory study based on correlation.

Hearing in Real-Life Environments (HERE): Structure and Reliability of a Questionnaire on Perceived Hearing for Older Adults.

Objectives: The ability to hear in a variety of social situations and environments is vital for social participation and a high quality of life. One way to assess hearing ability is by means of self-report questionnaire. For questionnaires to be useful, their measurement properties, based on careful validation, have to be known.

Refinement and Validation of the Social Participation Restrictions Questionnaire: An Application of Rasch Analysis and Traditional Psychometric Analysis Techniques.

Objectives: The primary aim of this research was to refine and validate the Social Participation Restrictions Questionnaire (SPaRQ). The SPaRQ is a hearing-specific, patient-reported outcome measure that was originally developed through consultation with adults with hearing loss, clinicians, and researchers. This research comprised two studies.

Communication calls produced by electrical stimulation of four structures in the guinea pig brain.

One of the main central processes affecting the cortical representation of conspecific vocalizations is the collateral output from the extended motor system for call generation. Before starting to study this interaction we sought to compare the characteristics of calls produced by stimulating four different parts of the brain in guinea pigs (Cavia porcellus). By using anaesthetised animals we were able to reposition electrodes without distressing the animals.

The Association Between Cognitive Performance and Speech-in-Noise Perception for Adult Listeners: A Systematic Literature Review and Meta-Analysis.

Published studies assessing the association between cognitive performance and speech-in-noise (SiN) perception examine different aspects of each, test different listeners, and often report quite variable associations. By examining the published evidence base using a systematic approach, we aim to identify robust patterns across studies and highlight any remaining gaps in knowledge. We limit our assessment to adult unaided listeners with audiometric profiles ranging from normal hearing to moderate hearing loss.

Gap-induced reductions of evoked potentials in the auditory cortex: A possible objective marker for the presence of tinnitus in animals.

Animal models of tinnitus are essential for determining the underlying mechanisms and testing pharmacotherapies. However, there is doubt over the validity of current behavioural methods for detecting tinnitus. Here, we applied a stimulus paradigm widely used in a behavioural test (gap-induced inhibition of the acoustic startle reflex GPIAS) whilst recording from the auditory cortex, and showed neural response changes that mirror those found in the behavioural tests.

Performance of the Tinnitus Functional Index as a diagnostic instrument in a UK clinical population.

Objectives: The Tinnitus Functional Index (TFI) has been optimised as a diagnostic tool for quantifying the functional impact of tinnitus in US veteran and civilian groups. However, the TFI has not been fully evaluated for use in other English-speaking clinical populations despite its increasingly popular uptake. Here, a prospective multi-site longitudinal validation study was conducted to evaluate psychometric properties relevant to the UK clinical population.

Quality of questionnaires for the assessment of otitis media with effusion in children.

Objectives: Audiometric tests provide information about hearing in otitis media with effusion (OME). Questionnaires can supplement this information by supporting clinical history-taking as well as potentially providing a standardized and comprehensive assessment of the impact of the disease on a child. There are many possible candidate questionnaires.