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Nature Reviews. Neurology Mar 2016Tinnitus 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... (Review)
Review
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. Head or neck injuries can also trigger the development of tinnitus, as altered somatosensory input can affect auditory pathways and lead to tinnitus or modulate its intensity. Emotional and attentional state could be involved in the development and maintenance of tinnitus via top-down mechanisms. Thus, military personnel in combat are particularly at risk owing to combined risk factors (hearing loss, somatosensory system disturbances and emotional stress). Animal model studies have identified tinnitus-associated neural changes that commence at the cochlear nucleus and extend to the auditory cortex and other brain regions. Maladaptive neural plasticity seems to underlie these changes: it results in increased spontaneous firing rates and synchrony among neurons in central auditory structures, possibly generating the phantom percept. This Review highlights the links between animal and human studies, and discusses several therapeutic approaches that have been developed to target the neuroplastic changes underlying tinnitus.
Topics: Animals; Auditory Cortex; Auditory Pathways; Cochlear Nucleus; Humans; Neuronal Plasticity; Noise; Tinnitus; Treatment Outcome
PubMed: 26868680
DOI: 10.1038/nrneurol.2016.12 -
Hearing Research Nov 2022Sensory processing is frequently conceptualized as a linear flow of information from peripheral receptors through hierarchically organized brain regions, ultimately... (Review)
Review
Sensory processing is frequently conceptualized as a linear flow of information from peripheral receptors through hierarchically organized brain regions, ultimately reaching the cortex. In reality, this ascending stream is accompanied by massive descending connections that cascade from the cortex toward more peripheral subcortical structures. In the central auditory system, these feedback connections influence information processing at virtually every level of the pathway, including the thalamus, midbrain, and brainstem, and exert influence even at the level of the cochlea. The auditory cortico-collicular system, which connects the auditory cortex to the auditory midbrain, mediates manifold functions ranging from tuning shifts to defense behavior. In this review, we first summarize recent findings regarding the anatomical organization and physiological properties of the auditory cortico-collicular pathway. We then highlight several new studies that show that this projection system mediates high-level cognitive processes, acoustico-motor behaviors, and auditory plasticity, and discuss the circuit mechanisms through which they are mediated. Finally, we discuss remaining unanswered questions regarding cortico-collicular circuitry and function and potential avenues for future exploration.
Topics: Acoustic Stimulation; Auditory Cortex; Auditory Pathways; Inferior Colliculi
PubMed: 35351323
DOI: 10.1016/j.heares.2022.108488 -
Annual Review of Neuroscience Jul 2018Hearing is often viewed as a passive process: Sound enters the ear, triggers a cascade of activity through the auditory system, and culminates in an auditory percept. In... (Review)
Review
Hearing is often viewed as a passive process: Sound enters the ear, triggers a cascade of activity through the auditory system, and culminates in an auditory percept. In contrast to a passive process, motor-related signals strongly modulate the auditory system from the eardrum to the cortex. The motor modulation of auditory activity is most well documented during speech and other vocalizations but also can be detected during a wide variety of other sound-generating behaviors. An influential idea is that these motor-related signals suppress neural responses to predictable movement-generated sounds, thereby enhancing sensitivity to environmental sounds during movement while helping to detect errors in learned acoustic behaviors, including speech and musicianship. Findings in humans, monkeys, songbirds, and mice provide new insights into the circuits that convey motor-related signals to the auditory system, while lending support to the idea that these signals function predictively to facilitate hearing and vocal learning.
Topics: Acoustic Stimulation; Animals; Auditory Pathways; Hearing; Humans; Movement; Vocalization, Animal
PubMed: 29986164
DOI: 10.1146/annurev-neuro-072116-031215 -
Cold Spring Harbor Perspectives in... Aug 2019When hearing fails, cochlear implants (CIs) provide open speech perception to most of the currently half a million CI users. CIs bypass the defective sensory organ and... (Review)
Review
When hearing fails, cochlear implants (CIs) provide open speech perception to most of the currently half a million CI users. CIs bypass the defective sensory organ and stimulate the auditory nerve electrically. The major bottleneck of current CIs is the poor coding of spectral information, which results from wide current spread from each electrode contact. As light can be more conveniently confined, optical stimulation of the auditory nerve presents a promising perspective for a fundamental advance of CIs. Moreover, given the improved frequency resolution of optical excitation and its versatility for arbitrary stimulation patterns the approach also bears potential for auditory research. Here, we review the current state of the art focusing on the emerging concept of optogenetic stimulation of the auditory pathway. Developing optogenetic stimulation for auditory research and future CIs requires efforts toward viral gene transfer to the neurons, design and characterization of appropriate optogenetic actuators, as well as engineering of multichannel optical implants.
Topics: Animals; Auditory Pathways; Cochlear Implantation; Cochlear Implants; Deafness; Humans; Optogenetics; Prosthesis Design; Speech Perception
PubMed: 30323016
DOI: 10.1101/cshperspect.a033225 -
Neuroscience May 2019Many, or most, tinnitus models rely on increased central gain in the auditory pathway as all or part of the explanation, in that central auditory neurones deprived of... (Review)
Review
Many, or most, tinnitus models rely on increased central gain in the auditory pathway as all or part of the explanation, in that central auditory neurones deprived of their usual sensory input maintain homeostasis by increasing the rate at which they fire in response to any given strength of input, including amplifying spontaneous firing which forms the basis of tinnitus. However, dramatic gain changes occur in response to damage to the auditory periphery, irrespective of whether tinnitus occurs. This article considers gain in its broadest sense, summarizes its contributory processes, neural manifestations, behavioral effects, techniques for its measurement, pitfalls in attributing gain changes to tinnitus, a discussion of the minimum evidential requirements to implicate gain as a necessary and/or sufficient basis to explain tinnitus, and the extent of existing evidence in this regard. Overall there is compelling evidence that peripheral auditory insults induce changes in neuronal firing rates, synchrony and neurochemistry and thus increase gain, but specific attribution of these changes to tinnitus is generally hampered by the absence of hearing-matched human control groups or insult-exposed non-tinnitus animals. A few studies show changes specifically attributable to tinnitus at group level, but the limited attempts so far to classify individual subjects based on gain metrics have not proven successful. If gain turns out to be unnecessary or insufficient to cause tinnitus, candidate additional mechanisms include focused attention, resetting of sensory predictions, failure of sensory gating, altered sensory predictions, formation of pervasive memory traces and/or entry into global perceptual networks. This article is part of a Special Issue entitled: Hearing Loss, Tinnitus, Hyperacusis, Central Gain.
Topics: Acoustic Stimulation; Animals; Auditory Pathways; Cochlea; Hearing; Humans; Hyperacusis; Tinnitus
PubMed: 30690137
DOI: 10.1016/j.neuroscience.2019.01.027 -
Neurobiology of Learning and Memory Mar 2022Increasing evidence has shown that noise overexposure could lead to impaired hippocampal function. Hippocampal alteration is also observed in several auditory deficits,... (Review)
Review
Increasing evidence has shown that noise overexposure could lead to impaired hippocampal function. Hippocampal alteration is also observed in several auditory deficits, including hearing loss, and tinnitus. Therefore, the functions of hearing and cognition interact with each other. Here, we summarize the evidence that noise affects the hippocampus from aspects of behavior, neurogenesis, ultrastructure, neurotransmission, other biomarkers, and electrophysiology. We also address hippocampal alterations in auditory disorders, including hearing loss and tinnitus. Based on the current state of the field, we point out several aspects that need further investigation. This review is not only to provide a comprehensive summary of the current state of the field but to emphasize that hearing matters in cognition and pave the way for future research.
Topics: Auditory Pathways; Hippocampus; Humans; Neurogenesis; Noise; Tinnitus
PubMed: 35124220
DOI: 10.1016/j.nlm.2022.107589 -
Nature Reviews. Neuroscience Oct 2019Humans and other animals use spatial hearing to rapidly localize events in the environment. However, neural encoding of sound location is a complex process involving... (Review)
Review
Humans and other animals use spatial hearing to rapidly localize events in the environment. However, neural encoding of sound location is a complex process involving the computation and integration of multiple spatial cues that are not represented directly in the sensory organ (the cochlea). Our understanding of these mechanisms has increased enormously in the past few years. Current research is focused on the contribution of animal models for understanding human spatial audition, the effects of behavioural demands on neural sound location encoding, the emergence of a cue-independent location representation in the auditory cortex, and the relationship between single-source and concurrent location encoding in complex auditory scenes. Furthermore, computational modelling seeks to unravel how neural representations of sound source locations are derived from the complex binaural waveforms of real-life sounds. In this article, we review and integrate the latest insights from neurophysiological, neuroimaging and computational modelling studies of mammalian spatial hearing. We propose that the cortical representation of sound location emerges from recurrent processing taking place in a dynamic, adaptive network of early (primary) and higher-order (posterior-dorsal and dorsolateral prefrontal) auditory regions. This cortical network accommodates changing behavioural requirements and is especially relevant for processing the location of real-life, complex sounds and complex auditory scenes.
Topics: Acoustic Stimulation; Animals; Auditory Cortex; Auditory Pathways; Hearing; Humans; Sound Localization
PubMed: 31467450
DOI: 10.1038/s41583-019-0206-5 -
International Journal of Molecular... Mar 2021Growth hormone (GH) plays an important role in auditory development during the embryonic stage. Exogenous agents such as sound, noise, drugs or trauma, can induce the... (Review)
Review
Growth hormone (GH) plays an important role in auditory development during the embryonic stage. Exogenous agents such as sound, noise, drugs or trauma, can induce the release of this hormone to perform a protective function and stimulate other mediators that protect the auditory pathway. In addition, GH deficiency conditions hearing loss or central auditory processing disorders. There are promising animal studies that reflect a possible regenerative role when exogenous GH is used in hearing impairments, demonstrated in in vivo and in vitro studies, and also, even a few studies show beneficial effects in humans presented and substantiated in the main text, although they should not exaggerate the main conclusions.
Topics: Animals; Auditory Cortex; Auditory Pathways; Cochlea; Cochlear Nerve; Gene Expression Regulation; Growth Hormone; Hearing Loss, Functional; Hearing Loss, Sensorineural; Hippocampus; Humans; Insulin-Like Growth Factor I; Nerve Regeneration; Noise
PubMed: 33799503
DOI: 10.3390/ijms22062829 -
Hearing Research Apr 2017The circadian system integrates environmental cues to regulate physiological functions in a temporal fashion. The suprachiasmatic nucleus, located in the hypothalamus,... (Review)
Review
The circadian system integrates environmental cues to regulate physiological functions in a temporal fashion. The suprachiasmatic nucleus, located in the hypothalamus, is the master clock that synchronizes central and peripheral organ clocks to orchestrate physiological functions. Recently, molecular clock machinery has been identified in the cochlea unravelling the potential involvement in the circadian regulation of auditory functions. Here, we present background information on the circadian system and review the recent findings that introduce circadian rhythms to the auditory field. Understanding the mechanisms by which circadian rhythms regulate auditory function will provide fundamental knowledge on the signalling networks that control vulnerability and resilience to auditory insults.
Topics: Acoustic Stimulation; Animals; Auditory Pathways; Auditory Perception; Circadian Clocks; Circadian Rhythm; Circadian Rhythm Signaling Peptides and Proteins; Cochlea; Cues; Hearing; Humans; Signal Transduction
PubMed: 27665709
DOI: 10.1016/j.heares.2016.08.018 -
Developmental Neurobiology Jul 2021The auditory system detects and encodes sound information with high precision to provide a high-fidelity representation of the environment and communication. In mammals,... (Review)
Review
The auditory system detects and encodes sound information with high precision to provide a high-fidelity representation of the environment and communication. In mammals, detection occurs in the peripheral sensory organ (the cochlea) containing specialized mechanosensory cells (hair cells) that initiate the conversion of sound-generated vibrations into action potentials in the auditory nerve. Neural activity in the auditory nerve encodes information regarding the intensity and frequency of sound stimuli, which is transmitted to the auditory cortex through the ascending neural pathways. Glial cells are critical for precise control of neural conduction and synaptic transmission throughout the pathway, allowing for the precise detection of the timing, frequency, and intensity of sound signals, including the sub-millisecond temporal fidelity is necessary for tasks such as sound localization, and in humans, for processing complex sounds including speech and music. In this review, we focus on glia and glia-like cells that interact with hair cells and neurons in the ascending auditory pathway and contribute to the development, maintenance, and modulation of neural circuits and transmission in the auditory system. We also discuss the molecular mechanisms of these interactions, their impact on hearing and on auditory dysfunction associated with pathologies of each cell type.
Topics: Acoustic Stimulation; Animals; Auditory Pathways; Axons; Cochlea; Humans; Mammals; Neuroglia
PubMed: 33561889
DOI: 10.1002/dneu.22813