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Tabas A, von Kriegstein K. Multiple Concurrent Predictions Inform Prediction Error in the Human Auditory Pathway. J Neurosci 2024; 44:e2219222023. [PMID: 37949655 PMCID: PMC10851690 DOI: 10.1523/jneurosci.2219-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 09/08/2023] [Accepted: 09/16/2023] [Indexed: 11/12/2023] Open
Abstract
The key assumption of the predictive coding framework is that internal representations are used to generate predictions on how the sensory input will look like in the immediate future. These predictions are tested against the actual input by the so-called prediction error units, which encode the residuals of the predictions. What happens to prediction errors, however, if predictions drawn by different stages of the sensory hierarchy contradict each other? To answer this question, we conducted two fMRI experiments while female and male human participants listened to sequences of sounds: pure tones in the first experiment and frequency-modulated sweeps in the second experiment. In both experiments, we used repetition to induce predictions based on stimulus statistics (stats-informed predictions) and abstract rules disclosed in the task instructions to induce an orthogonal set of (task-informed) predictions. We tested three alternative scenarios: neural responses in the auditory sensory pathway encode prediction error with respect to (1) the stats-informed predictions, (2) the task-informed predictions, or (3) a combination of both. Results showed that neural populations in all recorded regions (bilateral inferior colliculus, medial geniculate body, and primary and secondary auditory cortices) encode prediction error with respect to a combination of the two orthogonal sets of predictions. The findings suggest that predictive coding exploits the non-linear architecture of the auditory pathway for the transmission of predictions. Such non-linear transmission of predictions might be crucial for the predictive coding of complex auditory signals like speech.Significance Statement Sensory systems exploit our subjective expectations to make sense of an overwhelming influx of sensory signals. It is still unclear how expectations at each stage of the processing pipeline are used to predict the representations at the other stages. The current view is that this transmission is hierarchical and linear. Here we measured fMRI responses in auditory cortex, sensory thalamus, and midbrain while we induced two sets of mutually inconsistent expectations on the sensory input, each putatively encoded at a different stage. We show that responses at all stages are concurrently shaped by both sets of expectations. The results challenge the hypothesis that expectations are transmitted linearly and provide for a normative explanation of the non-linear physiology of the corticofugal sensory system.
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Affiliation(s)
- Alejandro Tabas
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, United Kingdom
- Department of Psychology, Technische Universität Dresden, 01062 Dresden, Germany
- Max Planck Institute for Human Cognitive and Brain Sciences, 04103 Leipzig, Germany
| | - Katharina von Kriegstein
- Department of Psychology, Technische Universität Dresden, 01062 Dresden, Germany
- Max Planck Institute for Human Cognitive and Brain Sciences, 04103 Leipzig, Germany
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2
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Brennan MA, Svec A, Farhadi A, Maxwell BN, Carney LH. Inherent envelope fluctuations in forward masking: Effects of age and hearing loss. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 153:1994. [PMID: 37092921 PMCID: PMC10071988 DOI: 10.1121/10.0017724] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 05/03/2023]
Abstract
Forward masking is generally greater for Gaussian noise (GN) than for low-fluctuation noise maskers, i.e., GN disruption. Because the minimal hearing loss that is associated with older age may affect GN disruption differently than more significant hearing loss, the current study explored the contribution of minimal hearing loss associated with older age to GN disruption. GN disruption was measured using three masker-signal delays (25, 75, and 150 ms) for three adult groups: younger participants with normal hearing (NH), older participants with minimal hearing loss, and older participants with sensorineural hearing loss. The role of underlying mechanisms was tested using a computational model for midbrain neurons. The primary result suggests that older listeners with mild threshold elevations that typically occur with age may be more susceptible to the deleterious effects of masker envelope fluctuations than younger listeners with NH. Results from the computational model indicate that there may be a larger influence of efferent feedback and saturation of inner hair cells on forward masking and GN disruption than previously considered.
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Affiliation(s)
- Marc A Brennan
- University of Nebraska-Lincoln, Lincoln, Nebraska 68583, USA
| | - Adam Svec
- San José State University, San Jose, California 95192, USA
| | - Afagh Farhadi
- University of Rochester, Rochester, New York 14642, USA
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3
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Kumar S, Nayak S, Pitchai Muthu AN. Effect of selective attention on auditory brainstem response. HEARING, BALANCE AND COMMUNICATION 2023. [DOI: 10.1080/21695717.2023.2168413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Sathish Kumar
- Department of Audiology and Speech-Language Pathology, Kasturba Medical College, Mangalore, Manipal Academy of Higher Education, Mangalore, India
| | - Srikanth Nayak
- Department of Audiology and Speech-Language Pathology, Yenepoya Medical College, Yenepoya University (Deemed to be University), Mangalore, India
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4
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Stein J, von Kriegstein K, Tabas A. Predictive encoding of pure tones and FM-sweeps in the human auditory cortex. Cereb Cortex Commun 2022; 3:tgac047. [PMID: 36545253 PMCID: PMC9764222 DOI: 10.1093/texcom/tgac047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 11/05/2022] [Accepted: 11/10/2022] [Indexed: 11/17/2022] Open
Abstract
Expectations substantially influence perception, but the neural mechanisms underlying this influence are not fully understood. A prominent view is that sensory neurons encode prediction error with respect to expectations on upcoming sensory input. Although the encoding of prediction error has been previously demonstrated in the human auditory cortex (AC), previous studies often induced expectations using stimulus repetition, potentially confounding prediction error with neural habituation. These studies also measured AC as a single population, failing to consider possible predictive specializations of different AC fields. Moreover, the few studies that considered prediction error to stimuli other than pure tones yielded conflicting results. Here, we used functional magnetic resonance imaging (fMRI) to systematically investigate prediction error to subjective expectations in auditory cortical fields Te1.0, Te1.1, Te1.2, and Te3, and two types of stimuli: pure tones and frequency modulated (FM) sweeps. Our results show that prediction error is elicited with respect to the participants' expectations independently of stimulus repetition and similarly expressed across auditory fields. Moreover, despite the radically different strategies underlying the decoding of pure tones and FM-sweeps, both stimulus modalities were encoded as prediction error in most fields of AC. Altogether, our results provide unequivocal evidence that predictive coding is the general encoding mechanism in AC.
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Affiliation(s)
| | - Katharina von Kriegstein
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technical University Dresden, Bamberger Str. 7, Dresden 01187, Germany
| | - Alejandro Tabas
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technical University Dresden, Bamberger Str. 7, Dresden 01187, Germany
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5
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Harnessing the power of artificial intelligence to transform hearing healthcare and research. NAT MACH INTELL 2021. [DOI: 10.1038/s42256-021-00394-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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6
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Zimdahl JW, Thomas H, Bolland SJ, Leggett K, Barry KM, Rodger J, Mulders WHAM. Excitatory Repetitive Transcranial Magnetic Stimulation Over Prefrontal Cortex in a Guinea Pig Model Ameliorates Tinnitus. Front Neurosci 2021; 15:693935. [PMID: 34366777 PMCID: PMC8339289 DOI: 10.3389/fnins.2021.693935] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 07/01/2021] [Indexed: 11/13/2022] Open
Abstract
Tinnitus, a phantom auditory perception that can seriously affect quality of life, is generally triggered by cochlear trauma and associated with aberrant activity throughout the auditory pathways, often referred to as hyperactivity. Studies suggest that non-auditory structures, such as prefrontal cortex (PFC), may be involved in tinnitus generation, by affecting sensory gating in auditory thalamus, allowing hyperactivity to reach the cortex and lead to perception. Indeed, human studies have shown that repetitive transcranial magnetic stimulation (rTMS) of PFC can alleviate tinnitus. The current study investigated whether this therapeutic effect is achieved through inhibition of thalamic hyperactivity, comparing effects of two common clinical rTMS protocols with sham treatment, in a guinea pig tinnitus model. Animals underwent acoustic trauma and once tinnitus developed were treated with either intermittent theta burst stimulation (iTBS), 20 Hz rTMS, or sham rTMS (10 days, 10 min/day; weekdays only). Tinnitus was reassessed and extracellular recordings of spontaneous tonic and burst firing rates in auditory thalamus made. To verify effects in PFC, densities of neurons positive for calcium-binding proteins, calbindin and parvalbumin, were investigated using immunohistochemistry. Both rTMS protocols significantly reduced tinnitus compared to sham. However, spontaneous tonic firing decreased following 20 Hz stimulation and increased following iTBS in auditory thalamus. Burst rate was significantly different between 20 Hz and iTBS stimulation, and burst duration was increased only after 20 Hz treatment. Density of calbindin, but not parvalbumin positive neurons, was significantly increased in the most dorsal region of PFC indicating that rTMS directly affected PFC. Our results support the involvement of PFC in tinnitus modulation, and the therapeutic benefit of rTMS on PFC in treating tinnitus, but indicate this is not achieved solely by suppression of thalamic hyperactivity.
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Affiliation(s)
- Jack W Zimdahl
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Harrison Thomas
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Samuel J Bolland
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.,Perron Institute for Neurological and Translational Research, Crawley, WA, Australia
| | - Kerry Leggett
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Kristin M Barry
- School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Jennifer Rodger
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.,Perron Institute for Neurological and Translational Research, Crawley, WA, Australia
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Jennings SG. The role of the medial olivocochlear reflex in psychophysical masking and intensity resolution in humans: a review. J Neurophysiol 2021; 125:2279-2308. [PMID: 33909513 PMCID: PMC8285664 DOI: 10.1152/jn.00672.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 03/16/2021] [Accepted: 04/02/2021] [Indexed: 02/01/2023] Open
Abstract
This review addresses the putative role of the medial olivocochlear (MOC) reflex in psychophysical masking and intensity resolution in humans. A framework for interpreting psychophysical results in terms of the expected influence of the MOC reflex is introduced. This framework is used to review the effects of a precursor or contralateral acoustic stimulation on 1) simultaneous masking of brief tones, 2) behavioral estimates of cochlear gain and frequency resolution in forward masking, 3) the buildup and decay of forward masking, and 4) measures of intensity resolution. Support, or lack thereof, for a role of the MOC reflex in psychophysical perception is discussed in terms of studies on estimates of MOC strength from otoacoustic emissions and the effects of resection of the olivocochlear bundle in patients with vestibular neurectomy. Novel, innovative approaches are needed to resolve the dissatisfying conclusion that current results are unable to definitively confirm or refute the role of the MOC reflex in masking and intensity resolution.
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Affiliation(s)
- Skyler G Jennings
- Department of Communication Sciences and Disorders, The University of Utah, Salt Lake City, Utah
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8
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Tabas A, von Kriegstein K. Adjudicating Between Local and Global Architectures of Predictive Processing in the Subcortical Auditory Pathway. Front Neural Circuits 2021; 15:644743. [PMID: 33776657 PMCID: PMC7994860 DOI: 10.3389/fncir.2021.644743] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/16/2021] [Indexed: 11/13/2022] Open
Abstract
Predictive processing, a leading theoretical framework for sensory processing, suggests that the brain constantly generates predictions on the sensory world and that perception emerges from the comparison between these predictions and the actual sensory input. This requires two distinct neural elements: generative units, which encode the model of the sensory world; and prediction error units, which compare these predictions against the sensory input. Although predictive processing is generally portrayed as a theory of cerebral cortex function, animal and human studies over the last decade have robustly shown the ubiquitous presence of prediction error responses in several nuclei of the auditory, somatosensory, and visual subcortical pathways. In the auditory modality, prediction error is typically elicited using so-called oddball paradigms, where sequences of repeated pure tones with the same pitch are at unpredictable intervals substituted by a tone of deviant frequency. Repeated sounds become predictable promptly and elicit decreasing prediction error; deviant tones break these predictions and elicit large prediction errors. The simplicity of the rules inducing predictability make oddball paradigms agnostic about the origin of the predictions. Here, we introduce two possible models of the organizational topology of the predictive processing auditory network: (1) the global view, that assumes that predictions on the sensory input are generated at high-order levels of the cerebral cortex and transmitted in a cascade of generative models to the subcortical sensory pathways; and (2) the local view, that assumes that independent local models, computed using local information, are used to perform predictions at each processing stage. In the global view information encoding is optimized globally but biases sensory representations along the entire brain according to the subjective views of the observer. The local view results in a diminished coding efficiency, but guarantees in return a robust encoding of the features of sensory input at each processing stage. Although most experimental results to-date are ambiguous in this respect, recent evidence favors the global model.
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Affiliation(s)
- Alejandro Tabas
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany.,Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Katharina von Kriegstein
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Germany.,Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
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9
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Tabas A, von Kriegstein K. Neural modelling of the encoding of fast frequency modulation. PLoS Comput Biol 2021; 17:e1008787. [PMID: 33657098 PMCID: PMC7959405 DOI: 10.1371/journal.pcbi.1008787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 03/15/2021] [Accepted: 02/12/2021] [Indexed: 11/19/2022] Open
Abstract
Frequency modulation (FM) is a basic constituent of vocalisation in many animals as well as in humans. In human speech, short rising and falling FM-sweeps of around 50 ms duration, called formant transitions, characterise individual speech sounds. There are two representations of FM in the ascending auditory pathway: a spectral representation, holding the instantaneous frequency of the stimuli; and a sweep representation, consisting of neurons that respond selectively to FM direction. To-date computational models use feedforward mechanisms to explain FM encoding. However, from neuroanatomy we know that there are massive feedback projections in the auditory pathway. Here, we found that a classical FM-sweep perceptual effect, the sweep pitch shift, cannot be explained by standard feedforward processing models. We hypothesised that the sweep pitch shift is caused by a predictive feedback mechanism. To test this hypothesis, we developed a novel model of FM encoding incorporating a predictive interaction between the sweep and the spectral representation. The model was designed to encode sweeps of the duration, modulation rate, and modulation shape of formant transitions. It fully accounted for experimental data that we acquired in a perceptual experiment with human participants as well as previously published experimental results. We also designed a new class of stimuli for a second perceptual experiment to further validate the model. Combined, our results indicate that predictive interaction between the frequency encoding and direction encoding neural representations plays an important role in the neural processing of FM. In the brain, this mechanism is likely to occur at early stages of the processing hierarchy.
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Affiliation(s)
- Alejandro Tabas
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Saxony, Germany
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany
| | - Katharina von Kriegstein
- Chair of Cognitive and Clinical Neuroscience, Faculty of Psychology, Technische Universität Dresden, Dresden, Saxony, Germany
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany
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10
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Liu X, Zhang O, Chen A, Hu K, Ehret G, Yan J. Corticofugal Augmentation of the Auditory Brainstem Response With Respect to Cortical Preference. Front Syst Neurosci 2019; 13:39. [PMID: 31496941 PMCID: PMC6713121 DOI: 10.3389/fnsys.2019.00039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 08/02/2019] [Indexed: 11/30/2022] Open
Abstract
Physiological studies documented highly specific corticofugal modulations making subcortical centers focus processing on sounds that the auditory cortex (AC) has experienced to be important. Here, we show the effects of focal conditioning (FC) of the primary auditory cortex (FCAI) on auditory brainstem response (ABR) amplitudes and latencies in house mice. FCAI significantly increased ABR peak amplitudes (peaks I–V), decreased thresholds, and shortened peak latencies in responses to the frequency tuned by conditioned cortical neurons. The amounts of peak amplitude increases and latency decreases were specific for each processing level up to the auditory midbrain. The data provide new insights into possible corticofugal modulation of inner hair cell synapses and new corticofugal effects as neuronal enhancement of processing in the superior olivary complex (SOC) and lateral lemniscus (LL). Thus, our comprehensive ABR approach confirms the role of the AC as instructor of lower auditory levels and extends this role specifically to the cochlea, SOC, and LL. The whole pathway from the cochlea to the inferior colliculus appears, in a common mode, instructed in a very similar way.
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Affiliation(s)
- Xiuping Liu
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Oliver Zhang
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Amber Chen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Kaili Hu
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Günter Ehret
- Institute of Neurobiology, University of Ulm, Ulm, Germany
| | - Jun Yan
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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11
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Abstract
Cholinergic efferent neurons originating in the brainstem innervate the acoustico-lateralis organs (inner ear, lateral line) of vertebrates. These release acetylcholine (ACh) to inhibit hair cells through activation of calcium-dependent potassium channels. In the mammalian cochlea, ACh shunts and suppresses outer hair cell (OHC) electromotility, reducing the essential amplification of basilar membrane motion. Consequently, medial olivocochlear neurons that inhibit OHCs reduce the sensitivity and frequency selectivity of afferent neurons driven by cochlear vibration of inner hair cells (IHCs). The cholinergic synapse on hair cells involves an unusual ionotropic ACh receptor, and a near-membrane postsynaptic cistern. Lateral olivocochlear (LOC) neurons modulate type I afferents by still-to-be-defined synaptic mechanisms. Olivocochlear neurons can be activated by a reflex arc that includes the auditory nerve and projections from the cochlear nucleus. They are also subject to modulation by higher-order central auditory interneurons. Through its actions on cochlear hair cells, afferent neurons, and higher centers, the olivocochlear system protects against age-related and noise-induced hearing loss, improves signal coding in noise under certain conditions, modulates selective attention to sensory stimuli, and influences sound localization.
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Affiliation(s)
- Paul Albert Fuchs
- The Center for Hearing and Balance, Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195
| | - Amanda M Lauer
- The Center for Hearing and Balance, Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195
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12
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Lohse M, Bajo VM, King AJ. Development, organization and plasticity of auditory circuits: Lessons from a cherished colleague. Eur J Neurosci 2018; 49:990-1004. [PMID: 29804304 PMCID: PMC6519211 DOI: 10.1111/ejn.13979] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/11/2018] [Accepted: 05/23/2018] [Indexed: 12/20/2022]
Abstract
Ray Guillery was a neuroscientist known primarily for his ground-breaking studies on the development of the visual pathways and subsequently on the nature of thalamocortical processing loops. The legacy of his work, however, extends well beyond the visual system. Thanks to Ray Guillery's pioneering anatomical studies, the ferret has become a widely used animal model for investigating the development and plasticity of sensory processing. This includes our own work on the auditory system, where experiments in ferrets have revealed the role of sensory experience during development in shaping the neural circuits responsible for sound localization, as well as the capacity of the mature brain to adapt to changes in inputs resulting from hearing loss. Our research has also built on Ray Guillery's ideas about the possible functions of the massive descending projections that link sensory areas of the cerebral cortex to the thalamus and other subcortical targets, by demonstrating a role for corticothalamic feedback in the perception of complex sounds and for corticollicular projection neurons in learning to accommodate altered auditory spatial cues. Finally, his insights into the organization and functions of transthalamic corticocortical connections have inspired a raft of research, including by our own laboratory, which has attempted to identify how information flows through the thalamus.
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Affiliation(s)
- Michael Lohse
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Victoria M Bajo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Andrew J King
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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13
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Carney LH. Supra-Threshold Hearing and Fluctuation Profiles: Implications for Sensorineural and Hidden Hearing Loss. J Assoc Res Otolaryngol 2018; 19:331-352. [PMID: 29744729 PMCID: PMC6081887 DOI: 10.1007/s10162-018-0669-5] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 04/19/2018] [Indexed: 12/22/2022] Open
Abstract
An important topic in contemporary auditory science is supra-threshold hearing. Difficulty hearing at conversational speech levels in background noise has long been recognized as a problem of sensorineural hearing loss, including that associated with aging (presbyacusis). Such difficulty in listeners with normal thresholds has received more attention recently, especially associated with descriptions of synaptopathy, the loss of auditory nerve (AN) fibers as a result of noise exposure or aging. Synaptopathy has been reported to cause a disproportionate loss of low- and medium-spontaneous rate (L/MSR) AN fibers. Several studies of synaptopathy have assumed that the wide dynamic ranges of L/MSR AN fiber rates are critical for coding supra-threshold sounds. First, this review will present data from the literature that argues against a direct role for average discharge rates of L/MSR AN fibers in coding sounds at moderate to high sound levels. Second, the encoding of sounds at supra-threshold levels is examined. A key assumption in many studies is that saturation of AN fiber discharge rates limits neural encoding, even though the majority of AN fibers, high-spontaneous rate (HSR) fibers, have saturated average rates at conversational sound levels. It is argued here that the cross-frequency profile of low-frequency neural fluctuation amplitudes, not average rates, encodes complex sounds. As described below, this fluctuation-profile coding mechanism benefits from both saturation of inner hair cell (IHC) transduction and average rate saturation associated with the IHC-AN synapse. Third, the role of the auditory efferent system, which receives inputs from L/MSR fibers, is revisited in the context of fluctuation-profile coding. The auditory efferent system is hypothesized to maintain and enhance neural fluctuation profiles. Lastly, central mechanisms sensitive to neural fluctuations are reviewed. Low-frequency fluctuations in AN responses are accentuated by cochlear nucleus neurons which, either directly or via other brainstem nuclei, relay fluctuation profiles to the inferior colliculus (IC). IC neurons are sensitive to the frequency and amplitude of low-frequency fluctuations and convert fluctuation profiles from the periphery into a phase-locked rate profile that is robust across a wide range of sound levels and in background noise. The descending projection from the midbrain (IC) to the efferent system completes a functional loop that, combined with inputs from the L/MSR pathway, is hypothesized to maintain "sharp" supra-threshold hearing, reminiscent of visual mechanisms that regulate optical accommodation. Examples from speech coding and detection in noise are reviewed. Implications for the effects of synaptopathy on control mechanisms hypothesized to influence supra-threshold hearing are discussed. This framework for understanding neural coding and control mechanisms for supra-threshold hearing suggests strategies for the design of novel hearing aid signal-processing and electrical stimulation patterns for cochlear implants.
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Affiliation(s)
- Laurel H Carney
- Departments of Biomedical Engineering, Neuroscience, and Electrical & Computer Engineering, Del Monte Institute for Neuroscience, University of Rochester, 601 Elmwood Ave., Box 603, Rochester, NY, 14642, USA.
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14
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Terreros G, Delano PH. Corticofugal modulation of peripheral auditory responses. Front Syst Neurosci 2015; 9:134. [PMID: 26483647 PMCID: PMC4588004 DOI: 10.3389/fnsys.2015.00134] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 09/15/2015] [Indexed: 01/17/2023] Open
Abstract
The auditory efferent system originates in the auditory cortex and projects to the medial geniculate body (MGB), inferior colliculus (IC), cochlear nucleus (CN) and superior olivary complex (SOC) reaching the cochlea through olivocochlear (OC) fibers. This unique neuronal network is organized in several afferent-efferent feedback loops including: the (i) colliculo-thalamic-cortico-collicular; (ii) cortico-(collicular)-OC; and (iii) cortico-(collicular)-CN pathways. Recent experiments demonstrate that blocking ongoing auditory-cortex activity with pharmacological and physical methods modulates the amplitude of cochlear potentials. In addition, auditory-cortex microstimulation independently modulates cochlear sensitivity and the strength of the OC reflex. In this mini-review, anatomical and physiological evidence supporting the presence of a functional efferent network from the auditory cortex to the cochlear receptor is presented. Special emphasis is given to the corticofugal effects on initial auditory processing, that is, on CN, auditory nerve and cochlear responses. A working model of three parallel pathways from the auditory cortex to the cochlea and auditory nerve is proposed.
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Affiliation(s)
- Gonzalo Terreros
- Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Paul H Delano
- Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile Santiago, Chile ; Departamento de Otorrinolaringología, Hospital Clínico de la Universidad de Chile Santiago, Chile
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15
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Wu C, Stefanescu RA, Martel DT, Shore SE. Listening to another sense: somatosensory integration in the auditory system. Cell Tissue Res 2015; 361:233-50. [PMID: 25526698 PMCID: PMC4475675 DOI: 10.1007/s00441-014-2074-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 11/18/2014] [Indexed: 12/19/2022]
Abstract
Conventionally, sensory systems are viewed as separate entities, each with its own physiological process serving a different purpose. However, many functions require integrative inputs from multiple sensory systems and sensory intersection and convergence occur throughout the central nervous system. The neural processes for hearing perception undergo significant modulation by the two other major sensory systems, vision and somatosensation. This synthesis occurs at every level of the ascending auditory pathway: the cochlear nucleus, inferior colliculus, medial geniculate body and the auditory cortex. In this review, we explore the process of multisensory integration from (1) anatomical (inputs and connections), (2) physiological (cellular responses), (3) functional and (4) pathological aspects. We focus on the convergence between auditory and somatosensory inputs in each ascending auditory station. This review highlights the intricacy of sensory processing and offers a multisensory perspective regarding the understanding of sensory disorders.
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Affiliation(s)
- Calvin Wu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, 48109, USA
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Radtke-Schuller S, Seeler S, Grothe B. Restricted loss of olivocochlear but not vestibular efferent neurons in the senescent gerbil (Meriones unguiculatus). Front Aging Neurosci 2015; 7:4. [PMID: 25762929 PMCID: PMC4327622 DOI: 10.3389/fnagi.2015.00004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 01/11/2015] [Indexed: 11/19/2022] Open
Abstract
Degeneration of hearing and vertigo are symptoms of age-related auditory and vestibular disorders reflecting multifactorial changes in the peripheral and central nervous system whose interplay remains largely unknown. Originating bilaterally in the brain stem, vestibular and auditory efferent cholinergic projections exert feedback control on the peripheral sensory organs, and modulate sensory processing. We studied age-related changes in the auditory and vestibular efferent systems by evaluating number of cholinergic efferent neurons in young adult and aged gerbils, and in cholinergic trigeminal neurons serving as a control for efferents not related to the inner ear. We observed a significant loss of olivocochlear (OC) neurons in aged compared to young adult animals, whereas the overall number of lateral superior olive (LSO) cells was not reduced in aging. Although the loss of lateral and medial olivocochlear (MOC) neurons was uniform and equal on both sides of the brain, there were frequency-related differences within the lateral olivocochlear (LOC) neurons, where the decline was larger in the medial limb of the superior olivary nucleus (high frequency representation) than in the lateral limb (middle-to-low frequency representation). In contrast, neither the number of vestibular efferent neurons, nor the population of motor trigeminal neurons were significantly reduced in the aged animals. These observations suggest differential effects of aging on the respective cholinergic efferent brainstem systems.
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Affiliation(s)
- Susanne Radtke-Schuller
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University Munich, Germany ; IFB German Center for Vertigo and Balance Disorders Munich, Germany
| | - Sabine Seeler
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University Munich, Germany
| | - Benedikt Grothe
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University Munich, Germany ; IFB German Center for Vertigo and Balance Disorders Munich, Germany
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Abstract
To determine how expectations affect loudness and loudness difference, in two experiments we induced some subjects to expect loud sounds (condition L), some to expect soft sounds (condition S), and others to have no particular expectations (control). In Experiment 1, all subjects estimated the loudnesses of the same set of three moderately loud 1-kHz tones. Estimates were greatest for subjects in condition S and smallest for subjects in condition L. Control subjects' estimates were intermediate but closer to those of condition S subjects. In Experiment 2, subjects estimated the difference in loudness for pairs of moderately loud 1-kHz tones. Again, estimates were smallest for condition L subjects; estimates were greatest for control subjects, and condition S subjects' estimates were closer to control estimates than to condition L estimates. This pattern of results is explainable by a combination of (1) Parducci's (1995) range-frequency theory and (2) a gain control mechanism in the auditory system under top-down governance (Schneider, Parker, & Murphy, 2011).
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