Total remission or persistence of tinnitus and decreased sound level tolerance in adolescents with normal audiograms: A follow-up study.

Background: Tinnitus may reflect hidden cochlear synaptic injury that does not express in the audiogram, but leads to neuroplastic changes in auditory pathways that, in turn, reduce tolerance to sounds. Such injury may follow the exposure to loud sounds. The aim of this study was to follow-up adolescents enrolled in a private school to evaluate the prevalence of tinnitus and reduced sound level tolerance (SLT) with 1-year interval, as well as to observe rates of tinnitus persistence, remission and incidence of new cases by repeat measurements.

Envelope following responses, noise exposure, and evidence of cochlear synaptopathy in humans: Correction and comment.

A correction and comment are provided for a recent article by Paul, Waheed, Bruce, and Roberts [(2017). J. Acoust.

Auditory-somatosensory bimodal stimulation desynchronizes brain circuitry to reduce tinnitus in guinea pigs and humans.

The dorsal cochlear nucleus is the first site of multisensory convergence in mammalian auditory pathways. Principal output neurons, the fusiform cells, integrate auditory nerve inputs from the cochlea with somatosensory inputs from the head and neck. In previous work, we developed a guinea pig model of tinnitus induced by noise exposure and showed that the fusiform cells in these animals exhibited increased spontaneous activity and cross-unit synchrony, which are physiological correlates of tinnitus.

Subcortical amplitude modulation encoding deficits suggest evidence of cochlear synaptopathy in normal-hearing 18-19 year olds with higher lifetime noise exposure.

Noise exposure and aging can damage cochlear synapses required for suprathreshold listening, even when cochlear structures needed for hearing at threshold remain unaffected. To control for effects of aging, behavioral amplitude modulation (AM) detection and subcortical envelope following responses (EFRs) to AM tones in 25 age-restricted (18-19 years) participants with normal thresholds, but different self-reported noise exposure histories were studied. Participants with more noise exposure had smaller EFRs and tended to have poorer AM detection than less-exposed individuals.

Evidence that hidden hearing loss underlies amplitude modulation encoding deficits in individuals with and without tinnitus.

Damage to auditory nerve fibers that expresses with suprathreshold sounds but is hidden from the audiogram has been proposed to underlie deficits in temporal coding ability observed among individuals with otherwise normal hearing, and to be present in individuals experiencing chronic tinnitus with clinically normal audiograms. We tested whether these individuals may have hidden synaptic losses on auditory nerve fibers with low spontaneous rates of firing (low-SR fibers) that are important for coding suprathreshold sounds in noise while high-SR fibers determining threshold responses in quiet remain relatively unaffected. Tinnitus and control subjects were required to detect the presence of amplitude modulation (AM) in a 5 kHz, suprathreshold tone (a frequency in the tinnitus frequency region of the tinnitus subjects, whose audiometric thresholds were normal to 12 kHz).

Tinnitus is associated with reduced sound level tolerance in adolescents with normal audiograms and otoacoustic emissions.

Recent neuroscience research suggests that tinnitus may reflect synaptic loss in the cochlea that does not express in the audiogram but leads to neural changes in auditory pathways that reduce sound level tolerance (SLT). Adolescents (N = 170) completed a questionnaire addressing their prior experience with tinnitus, potentially risky listening habits, and sensitivity to ordinary sounds, followed by psychoacoustic measurements in a sound booth. Among all adolescents 54.

Maladaptive plasticity in tinnitus--triggers, mechanisms and treatment.

Tinnitus is a phantom auditory sensation that reduces quality of life for millions of people worldwide, and for which there is no medical cure. Most cases of tinnitus are associated with hearing loss caused by ageing or noise exposure. Exposure to loud recreational sound is common among the young, and this group are at increasing risk of developing tinnitus.

Achieving across-laboratory replicability in psychophysical scaling.

It is well known that, although psychophysical scaling produces good qualitative agreement between experiments, precise quantitative agreement between experimental results, such as that routinely achieved in physics or biology, is rarely or never attained. A particularly galling example of this is the fact that power function exponents for the same psychological continuum, measured in different laboratories but ostensibly using the same scaling method, magnitude estimation, can vary by a factor of three. Constrained scaling (CS), in which observers first learn a standardized meaning for a set of numerical responses relative to a standard sensory continuum and then make magnitude judgments of other sensations using the learned response scale, has produced excellent quantitative agreement between individual observers' psychophysical functions.

Evidence for differential modulation of primary and nonprimary auditory cortex by forward masking in tinnitus.

It has been proposed that tinnitus is generated by aberrant neural activity that develops among neurons in tonotopic of regions of primary auditory cortex (A1) affected by hearing loss, which is also the frequency region where tinnitus percepts localize (Eggermont and Roberts 2004; Roberts et al., 2010, 2013). These models suggest (1) that differences between tinnitus and control groups of similar age and audiometric function should depend on whether A1 is probed in tinnitus frequency region (TFR) or below it, and (2) that brain responses evoked from A1 should track changes in the tinnitus percept when residual inhibition (RI) is induced by forward masking.

Tinnitus: animal models and findings in humans.

Chronic tinnitus (ringing of the ears) is a medically untreatable condition that reduces quality of life for millions of individuals worldwide. Most cases are associated with hearing loss that may be detected by the audiogram or by more sensitive measures. Converging evidence from animal models and studies of human tinnitus sufferers indicates that, while cochlear damage is a trigger, most cases of tinnitus are not generated by irritative processes persisting in the cochlea but by changes that take place in central auditory pathways when auditory neurons lose their input from the ear.

Modulation of electrocortical brain activity by attention in individuals with and without tinnitus.

Age and hearing-level matched tinnitus and control groups were presented with a 40 Hz AM sound using a carrier frequency of either 5 kHz (in the tinnitus frequency region of the tinnitus subjects) or 500 Hz (below this region). On attended blocks subjects pressed a button after each sound indicating whether a single 40 Hz AM pulse of variable increased amplitude (target, probability 0.67) had or had not occurred.

Underlying mechanisms of tinnitus: review and clinical implications.

Background: The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus.

Computer-automated tinnitus assessment: noise-band matching, maskability, and residual inhibition.

Background: Psychoacoustic measures of tinnitus typically include loudness and pitch match, minimum masking level (MML), and residual inhibition (RI). We previously developed and documented a computer-automated tinnitus evaluation system (TES) capable of subject-guided loudness and pitch matching. The TES was further developed to conduct computer-aided, subject-guided testing for noise-band matching (NBM), MML, and RI.

Role of attention in the generation and modulation of tinnitus.

Neural mechanisms that detect changes in the auditory environment appear to rely on processes that predict sensory state. Here we propose that in tinnitus there is a disparity between what the brain predicts it should be hearing (this prediction based on aberrant neural activity occurring in cortical frequency regions affected by hearing loss and underlying the tinnitus percept) and the acoustic information that is delivered to the brain by the damaged cochlea. The disparity between the predicted and delivered inputs activates a system for auditory attention that facilitates through subcortical neuromodulatory systems neuroplastic changes that contribute to the generation of tinnitus.

Neural plasticity expressed in central auditory structures with and without tinnitus.

Sensory training therapies for tinnitus are based on the assumption that, notwithstanding neural changes related to tinnitus, auditory training can alter the response properties of neurons in auditory pathways. To assess this assumption, we investigated whether brain changes induced by sensory training in tinnitus sufferers and measured by electroencephalography (EEG) are similar to those induced in age and hearing loss matched individuals without tinnitus trained on the same auditory task. Auditory training was given using a 5 kHz 40-Hz amplitude-modulated (AM) sound that was in the tinnitus frequency region of the tinnitus subjects and enabled extraction of the 40-Hz auditory steady-state response (ASSR) and P2 transient response known to localize to primary and non-primary auditory cortex, respectively.

Re-examining the relationship between audiometric profile and tinnitus pitch.

Objective: We explored the relationship between audiogram shape and tinnitus pitch to answer questions arising from neurophysiological models of tinnitus: 'Is the dominant tinnitus pitch associated with the edge of hearing loss?' and 'Is such a relationship more robust in people with narrow tinnitus bandwidth or steep sloping hearing loss?'

Design: A broken-stick fitting objectively quantified slope, degree and edge of hearing loss up to 16 kHz. Tinnitus pitch was characterized up to 12 kHz. We used correlation and multiple regression analyses for examining relationships with many potentially predictive audiometric variables.

Ringing ears: the neuroscience of tinnitus.

Tinnitus is a phantom sound (ringing of the ears) that affects quality of life for millions around the world and is associated in most cases with hearing impairment. This symposium will consider evidence that deafferentation of tonotopically organized central auditory structures leads to increased neuron spontaneous firing rates and neural synchrony in the hearing loss region. This region covers the frequency spectrum of tinnitus sounds, which are optimally suppressed following exposure to band-limited noise covering the same frequencies.

Development of auditory phase-locked activity for music sounds.

The auditory cortex undergoes functional and anatomical development that reflects specialization for learned sounds. In humans, auditory maturation is evident in transient auditory-evoked potentials (AEPs) elicited by speech or music. However, neural oscillations at specific frequencies are also known to play an important role in perceptual processing.

Understanding the benefits of musical training: effects on oscillatory brain activity.

A number of studies suggest that musical training has benefits for other cognitive domains, such as language and mathematics, and studies of children and adults indicate structural as well as functional differences between the brains of musicians and nonmusicians. The induced gamma-band response has been associated with attentional, expectation, memory retrieval, and integration of top-down, bottom-up, and multisensory processes. Here we report data indicating that the induced gamma-band response to musical sounds is larger in adult musicians than in nonmusicians and that it develops in children after 1 year of musical training beginning at age 4.

Frequency-specific modulation of population-level frequency tuning in human auditory cortex.

Background: Under natural circumstances, attention plays an important role in extracting relevant auditory signals from simultaneously present, irrelevant noises. Excitatory and inhibitory neural activity, enhanced by attentional processes, seems to sharpen frequency tuning, contributing to improved auditory performance especially in noisy environments. In the present study, we investigated auditory magnetic fields in humans that were evoked by pure tones embedded in band-eliminated noises during two different stimulus sequencing conditions (constant vs.

Residual inhibition functions overlap tinnitus spectra and the region of auditory threshold shift.

Animals exposed to noise trauma show augmented synchronous neural activity in tonotopically reorganized primary auditory cortex consequent on hearing loss. Diminished intracortical inhibition in the reorganized region appears to enable synchronous network activity that develops when deafferented neurons begin to respond to input via their lateral connections. In humans with tinnitus accompanied by hearing loss, this process may generate a phantom sound that is perceived in accordance with the location of the affected neurons in the cortical place map.

Music training leads to the development of timbre-specific gamma band activity.

Oscillatory gamma band activity (GBA, 30-100 Hz) has been shown to correlate with perceptual and cognitive phenomena including feature binding, template matching, and learning and memory formation. We hypothesized that if GBA reflects highly learned perceptual template matching, we should observe its development in musicians specific to the timbre of their instrument of practice. EEG was recorded in adult professional violinists and amateur pianists as well as in 4- and 5-year-old children studying piano in the Suzuki method before they commenced music lessons and 1 year later.

Residual inhibition.

Following offset of an appropriate masking stimulus, tinnitus may remain suppressed for a period, typically less than a minute. This phenomenon is known as "residual inhibition" (RI). This chapter reviews the psychoacoustic properties of RI and their relation to hearing impairment, tinnitus spectra, and the spectra of masking stimuli.