1
|
Wu PZ, Liberman LD, Liberman MC. Noise-induced synaptic loss and its post-exposure recovery in CBA/CaJ vs. C57BL/6J mice. Hear Res 2024; 445:108996. [PMID: 38547565 PMCID: PMC11024800 DOI: 10.1016/j.heares.2024.108996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/11/2024] [Accepted: 03/22/2024] [Indexed: 04/07/2024]
Abstract
Acute noise-induced loss of synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) has been documented in several strains of mice, but the extent of post-exposure recovery reportedly varies dramatically. If such inter-strain heterogeneity is real, it could be exploited to probe molecular pathways mediating neural remodeling in the adult cochlea. Here, we compared synaptopathy repair in CBA/CaJ vs. C57BL/6J, which are at opposite ends of the reported recovery spectrum. We evaluated C57BL/6J mice 0 h, 24 h, 2 wks or 8 wks after exposure for 2 h to octave-band noise (8-16 kHz) at either 90, 94 or 98 dB SPL, to compare with analogous post-exposure results in CBA/CaJ at 98 or 101 dB. We counted pre- and post-synaptic puncta in immunostained cochleas, using machine learning to classify paired (GluA2 and CtBP2) vs. orphan (CtBP2 only) puncta, and batch-processing to quantify immunostaining intensity. At 98 dB, both strains show ongoing loss of ribbons and synapses between 0 and 24 h, followed by partial recovery, however the extent and degree of these changes were greater in C57BL/6J. Much of the synaptic recovery is due to transient reduction in GluA2 intensity in synaptopathic regions. In contrast, CtBP2 intensity showed only transient increases (at 2 wks). Neurofilament staining revealed transient extension of ANF terminals in C57BL/6J, but not in CBA/CaJ, peaking at 24 h and reverting by 2 wks. Thus, although interstrain differences in synapse recovery are dominated by reversible changes in GluA2 receptor levels, the neurite extension seen in C57BL/6J suggests a qualitative difference in regenerative capacity.
Collapse
Affiliation(s)
- Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
2
|
Moverman DJ, Liberman LD, Kraemer S, Corfas G, Liberman MC. Ultrastructure of noise-induced cochlear synaptopathy. Sci Rep 2023; 13:19456. [PMID: 37945811 PMCID: PMC10636047 DOI: 10.1038/s41598-023-46859-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 11/06/2023] [Indexed: 11/12/2023] Open
Abstract
Acoustic overexposure can eliminate synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs), even if hair-cell function recovers. This synaptopathy has been extensively studied by confocal microscopy, however, understanding the nature and sequence of damage requires ultrastructural analysis. Here, we used focused ion-beam scanning electron microscopy to mill, image, segment and reconstruct ANF terminals in mice, 1 day and 1 week after synaptopathic exposure (8-16 kHz, 98 dB SPL). At both survivals, ANF terminals were normal in number, but 62% and 53%, respectively, lacked normal synaptic specializations. Most non-synapsing fibers (57% and 48% at 1 day and 1 week) remained in contact with an IHC and contained healthy-looking organelles. ANFs showed a transient increase in mitochondrial content (51%) and efferent innervation (34%) at 1 day. Fibers maintaining synaptic connections showed hypertrophy of pre-synaptic ribbons at both 1 day and 1 week. Non-synaptic fibers were lower in mitochondrial content and typically on the modiolar side of the IHC, where ANFs with high-thresholds and low spontaneous rates are normally found. Even 1 week post-exposure, many ANF terminals remained in IHC contact despite loss of synaptic specializations, thus, regeneration efforts at early post-exposure times should concentrate on synaptogenesis rather than neurite extension.
Collapse
Affiliation(s)
- Daniel J Moverman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA
| | - Stephan Kraemer
- Center for Nanoscale Systems, Harvard College, Cambridge, MA, 02138, USA
| | - Gabriel Corfas
- Department of Otolaryngology-Head and Neck Surgery, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, 243 Charles St., Boston, MA, 02114-3096, USA.
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA.
| |
Collapse
|
3
|
Wu PZ, O'Malley JT, Liberman MC. Neural Degeneration in Normal-Aging Human Cochleas: Machine-Learning Counts and 3D Mapping in Archival Sections. J Assoc Res Otolaryngol 2023; 24:499-511. [PMID: 37957485 PMCID: PMC10695900 DOI: 10.1007/s10162-023-00909-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 09/03/2023] [Indexed: 11/15/2023] Open
Abstract
Quantifying the survival patterns of spiral ganglion cells (SGCs), the cell bodies of auditory-nerve fibers, is critical to studies of sensorineural hearing loss, especially in human temporal bones. The classic method of manual counting is tedious, and, although stereology approaches can be faster, they can only be used to estimate total cell numbers per cochlea. Here, a machine-learning algorithm that automatically identifies, counts, and maps the SGCs in digitized images of semi-serial human temporal-bone sections not only speeds the analysis, with no loss of accuracy, but also allows 3D visualization of the SGCs and fine-grained mapping to cochlear frequency. Applying the algorithm to 62 normal-aging human ears shows significantly faster degeneration of SGCs in the basal than the apical half of the cochlea. Comparison to fiber counts in the same ears shows that the fraction of surviving SGCs lacking a peripheral axon steadily increases with age, reaching more than 50% in the apical cochlea and almost 66% in basal regions.
Collapse
Affiliation(s)
- Pei-Zhe Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA.
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Jennifer T O'Malley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114-3096, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, 02115, USA
| |
Collapse
|
4
|
Hughes ML. Electrically evoked compound action potential polarity sensitivity, refractory-recovery, and behavioral multi-pulse integration as potential indices of neural health in cochlear-implant recipients. Hear Res 2023; 433:108764. [PMID: 37062161 PMCID: PMC10322179 DOI: 10.1016/j.heares.2023.108764] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 03/26/2023] [Accepted: 04/05/2023] [Indexed: 04/18/2023]
Affiliation(s)
- Michelle L Hughes
- University of Nebraska-Lincoln, Dept. of Special Education and Communication Disorders, 276 Barkley Memorial Center, 4072 East Campus Loop, Lincoln, NE, 68583, USA.
| |
Collapse
|
5
|
Comparison of response properties of the electrically stimulated auditory nerve reported in human listeners and in animal models. Hear Res 2022; 426:108643. [PMID: 36343534 PMCID: PMC9986845 DOI: 10.1016/j.heares.2022.108643] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/29/2022] [Accepted: 10/20/2022] [Indexed: 11/04/2022]
Abstract
Cochlear implants (CIs) provide acoustic information to implanted patients by electrically stimulating nearby auditory nerve fibers (ANFs) which then transmit the information to higher-level neural structures for further processing and interpretation. Computational models that simulate ANF responses to CI stimuli enable the exploration of the mechanisms underlying CI performance beyond the capacity of in vivo experimentation alone. However, all ANF models developed to date utilize to some extent anatomical/morphometric data, biophysical properties and/or physiological data measured in non-human animal models. This review compares response properties of the electrically stimulated auditory nerve (AN) in human listeners and different mammalian models. Properties of AN responses to single pulse stimulation, paired-pulse stimulation, and pulse-train stimulation are presented. While some AN response properties are similar between human listeners and animal models (e.g., increased AN sensitivity to single pulse stimuli with long interphase gaps), there are some significant differences. For example, the AN of most animal models is typically more sensitive to cathodic stimulation while the AN of human listeners is generally more sensitive to anodic stimulation. Additionally, there are substantial differences in the speed of recovery from neural adaptation between animal models and human listeners. Therefore, results from animal models cannot be simply translated to human listeners. Recognizing the differences in responses of the AN to electrical stimulation between humans and other mammals is an important step for creating ANF models that are more applicable to various human CI patient populations.
Collapse
|
6
|
Signatures of cochlear processing in neuronal coding of auditory information. Mol Cell Neurosci 2022; 120:103732. [PMID: 35489636 DOI: 10.1016/j.mcn.2022.103732] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 04/19/2022] [Accepted: 04/21/2022] [Indexed: 11/22/2022] Open
Abstract
The vertebrate ear is endowed with remarkable perceptual capabilities. The faintest sounds produce vibrations of magnitudes comparable to those generated by thermal noise and can nonetheless be detected through efficient amplification of small acoustic stimuli. Two mechanisms have been proposed to underlie such sound amplification in the mammalian cochlea: somatic electromotility and active hair-bundle motility. These biomechanical mechanisms may work in concert to tune auditory sensitivity. In addition to amplitude sensitivity, the hearing system shows exceptional frequency discrimination allowing mammals to distinguish complex sounds with great accuracy. For instance, although the wide hearing range of humans encompasses frequencies from 20 Hz to 20 kHz, our frequency resolution extends to one-thirtieth of the interval between successive keys on a piano. In this article, we review the different cochlear mechanisms underlying sound encoding in the auditory system, with a particular focus on the frequency decomposition of sounds. The relation between peak frequency of activation and location along the cochlea - known as tonotopy - arises from multiple gradients in biophysical properties of the sensory epithelium. Tonotopic mapping represents a major organizational principle both in the peripheral hearing system and in higher processing levels and permits the spectral decomposition of complex tones. The ribbon synapses connecting sensory hair cells to auditory afferents and the downstream spiral ganglion neurons are also tuned to process periodic stimuli according to their preferred frequency. Though sensory hair cells and neurons necessarily filter signals beyond a few kHz, many animals can hear well beyond this range. We finally describe how the cochlear structure shapes the neural code for further processing in order to send meaningful information to the brain. Both the phase-locked response of auditory nerve fibers and tonotopy are key to decode sound frequency information and place specific constraints on the downstream neuronal network.
Collapse
|
7
|
Perks KE, Sawtell NB. Neural readout of a latency code in the active electrosensory system. Cell Rep 2022; 38:110605. [PMID: 35354029 PMCID: PMC9045710 DOI: 10.1016/j.celrep.2022.110605] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/03/2022] [Accepted: 03/10/2022] [Indexed: 11/29/2022] Open
Abstract
The latency of spikes relative to a stimulus conveys sensory information across modalities. However, in most cases, it remains unclear whether and how such latency codes are utilized by postsynaptic neurons. In the active electrosensory system of mormyrid fish, a latency code for stimulus amplitude in electroreceptor afferent nerve fibers (EAs) is hypothesized to be read out by a central reference provided by motor corollary discharge (CD). Here, we demonstrate that CD enhances sensory responses in postsynaptic granular cells of the electrosensory lobe but is not required for reading out EA input. Instead, diverse latency and spike count tuning across the EA population give rise to graded information about stimulus amplitude that can be read out by standard integration of converging excitatory synaptic inputs. Inhibitory control over the temporal window of integration renders two granular cell subclasses differentially sensitive to information derived from relative spike latency versus spike count.
Collapse
Affiliation(s)
- Krista E Perks
- Department of Biology, Wesleyan University, Middletown, CT 06459, USA; Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | - Nathaniel B Sawtell
- Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
8
|
Marchetta P, Eckert P, Lukowski R, Ruth P, Singer W, Rüttiger L, Knipper M. Loss of central mineralocorticoid or glucocorticoid receptors impacts auditory nerve processing in the cochlea. iScience 2022; 25:103981. [PMID: 35281733 PMCID: PMC8914323 DOI: 10.1016/j.isci.2022.103981] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/26/2022] [Accepted: 02/21/2022] [Indexed: 02/08/2023] Open
Abstract
The key auditory signature that may associate peripheral hearing with central auditory cognitive defects remains elusive. Suggesting the involvement of stress receptors, we here deleted the mineralocorticoid and glucocorticoid receptors (MR and GR) using a CaMKIIα-based tamoxifen-inducible CreERT2/loxP approach to generate mice with single or double deletion of central but not cochlear MR and GR. Hearing thresholds of MRGRCaMKIIαCreERT2 conditional knockouts (cKO) were unchanged, whereas auditory nerve fiber (ANF) responses were larger and faster and auditory steady state responses were improved. Subsequent analysis of single MR or GR cKO revealed discrete roles for both, central MR and GR on cochlear functions. Limbic MR deletion reduced inner hair cell (IHC) ribbon numbers and ANF responses. In contrast, GR deletion shortened the latency and improved the synchronization to amplitude-modulated tones without affecting IHC ribbon numbers. These findings imply that stress hormone-dependent functions of central MR/GR contribute to “precognitive” sound processing in the cochlea. Top-down MR/GR signaling differentially contributes to cochlear sound processing Limbic MR stimulates auditory nerve fiber discharge rates Central GR deteriorates auditory nerve fiber synchrony
Collapse
Affiliation(s)
- Philine Marchetta
- University of Tübingen, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| | - Philipp Eckert
- University of Tübingen, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| | - Robert Lukowski
- University of Tübingen, Institute of Pharmacy, Pharmacology, Toxicology and Clinical Pharmacy, 72076 Tübingen, Germany
| | - Peter Ruth
- University of Tübingen, Institute of Pharmacy, Pharmacology, Toxicology and Clinical Pharmacy, 72076 Tübingen, Germany
| | - Wibke Singer
- University of Tübingen, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| | - Lukas Rüttiger
- University of Tübingen, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| | - Marlies Knipper
- University of Tübingen, Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| |
Collapse
|
9
|
Rattay F, Tanzer T. Impact of electrode position on the dynamic range of a human auditory nerve fiber. J Neural Eng 2022; 19. [PMID: 35105835 DOI: 10.1088/1741-2552/ac50bf] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 02/01/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrodes of a cochlear implant generate spikes in auditory nerve fibers (ANFs). While the insertion depth of each of the electrodes is linked to a frequency section of the acoustic signal, the amplitude of the stimulating pulses controls the loudness of the related frequency band. However, in comparison to acoustic stimulation the dynamic range of an electrically stimulated ANF is quite small. APPROACH The dynamic range of an electrically stimulated ANF is defined as the interval of stimulus amplitudes that causes firing probabilities between 10% and 90%. A compartment model that includes sodium ion current fluctuations as the stochastic key component for spiking was evaluated for different electrode placements and fiber diameters. MAIN RESULTS The dynamic range is reversely related to ANF diameter. An increased dynamic range is expected to improve the quality of auditory perception for cochlear implant users. Electrodes are often placed as close to the center axis of the cochlea as possible. The analysis of the simulated auditory nerve firing showed that this placement is disadvantageous for the dynamic range of a selected ANF. SIGNIFICANCE Five times larger dynamic ranges are expected for electrodes close to the terminal of the dendrite or at mid-dendritic placement as opposed to electrodes close to the modiolus.
Collapse
Affiliation(s)
- Frank Rattay
- Institut fuer Analysis und Scientific Computing, Technische Universitaet Wien, Wiedner Hauptstr. 8-10, 1040 Wien, Vienna, 1040, AUSTRIA
| | - Thomas Tanzer
- Institute of Analysis and Scientific Computing, Vienna University of Technology, Wiedner Hauptstrasse 8, Vienna, 1040, AUSTRIA
| |
Collapse
|
10
|
Panganiban CH, Barth JL, Tan J, Noble KV, McClaskey CM, Howard BA, Jafri SH, Dias JW, Harris KC, Lang H. Two distinct types of nodes of Ranvier support auditory nerve function in the mouse cochlea. Glia 2021; 70:768-791. [DOI: 10.1002/glia.24138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 11/12/2021] [Accepted: 12/17/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Clarisse H. Panganiban
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
- Wolfson Centre for Age‐Related Diseases King's College London London UK
| | - Jeremy L. Barth
- Department of Regenerative Medicine and Cell Biology Medical University of South Carolina Charleston South Carolina USA
| | - Junying Tan
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Kenyaria V. Noble
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Carolyn M. McClaskey
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Blake A. Howard
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - Shabih H. Jafri
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| | - James W. Dias
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Kelly C. Harris
- Department of Otolaryngology & Head and Neck Surgery Medical University of South Carolina Charleston South Carolina USA
| | - Hainan Lang
- Department of Pathology and Laboratory Medicine Medical University of South Carolina Charleston South Carolina USA
| |
Collapse
|
11
|
Navntoft CA, Landsberger DM, Barkat TR, Marozeau J. The Perception of Ramped Pulse Shapes in Cochlear Implant Users. Trends Hear 2021; 25:23312165211061116. [PMID: 34935552 PMCID: PMC8724057 DOI: 10.1177/23312165211061116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The electric stimulation provided by current cochlear implants (CI) is not power
efficient. One underlying problem is the poor efficiency by which information
from electric pulses is transformed into auditory nerve responses. A novel
stimulation paradigm using ramped pulse shapes has recently been proposed to
remedy this inefficiency. The primary motivation is a better biophysical fit to
spiral ganglion neurons with ramped pulses compared to the rectangular pulses
used in most contemporary CIs. Here, we tested the hypotheses that ramped pulses
provide more efficient stimulation compared to rectangular pulses and that a
rising ramp is more efficient than a declining ramp. Rectangular, rising ramped
and declining ramped pulse shapes were compared in terms of charge efficiency
and discriminability, and threshold variability in seven CI listeners. The tasks
included single-channel threshold detection, loudness-balancing, discrimination
of pulse shapes, and threshold measurement across the electrode array. Results
showed that reduced charge, but increased peak current amplitudes, was required
at threshold and most comfortable levels with ramped pulses relative to
rectangular pulses. Furthermore, only one subject could reliably discriminate
between equally-loud ramped and rectangular pulses, suggesting variations in
neural activation patterns between pulse shapes in that participant. No
significant difference was found between rising and declining ramped pulses
across all tests. In summary, the present findings show some benefits of charge
efficiency with ramped pulses relative to rectangular pulses, that the direction
of a ramped slope is of less importance, and that most participants could not
perceive a difference between pulse shapes.
Collapse
Affiliation(s)
- Charlotte Amalie Navntoft
- Hearing Systems Group, Department of Health Technology, 5205Technical University of Denmark, Kgs. Lyngby, Denmark.,Brain and Sound Lab, Department of Biomedicine, 27209Basel University, Basel, Switzerland
| | - David M Landsberger
- Department of Otolaryngology, 12296New York University School of Medicine, New York, USA
| | - Tania Rinaldi Barkat
- Brain and Sound Lab, Department of Biomedicine, 27209Basel University, Basel, Switzerland
| | - Jeremy Marozeau
- Hearing Systems Group, Department of Health Technology, 5205Technical University of Denmark, Kgs. Lyngby, Denmark
| |
Collapse
|
12
|
Liu W, Liu Q, Crozier RA, Davis RL. Analog Transmission of Action Potential Fine Structure in Spiral Ganglion Axons. J Neurophysiol 2021; 126:888-905. [PMID: 34346782 DOI: 10.1152/jn.00237.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Action potential waveforms generated at the axon initial segment (AIS) are specialized between and within neuronal classes. But is the fine structure of each electrical event retained when transmitted along myelinated axons or is it rapidly and uniformly transmitted to be modified again at the axon terminal? To address this issue action potential axonal transmission was evaluated in a class of primary sensory afferents that possess numerous types of voltage-gated ion channels underlying a complex repertoire of endogenous firing patterns. In addition to their signature intrinsic electrophysiological heterogeneity, spiral ganglion neurons are uniquely designed. The bipolar, myelinated somata of type I neurons are located within the conduction pathway, requiring that action potentials generated at the first heminode must be conducted through their electrically excitable membrane. We utilized this unusual axonal-like morphology to serve as a window into action potential transmission to compare locally-evoked action potential profiles to those generated peripherally at their glutamatergic synaptic connections with hair cell receptors. These comparisons showed that the distinctively-shaped somatic action potentials were highly correlated with the nodally-generated, invading ones for each neuron. This result indicates that the fine structure of the action potential waveform is maintained axonally, thus supporting the concept that analog signaling is incorporated into each digitally-transmitted action potential in the specialized primary auditory afferents.
Collapse
Affiliation(s)
- Wenke Liu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Institute for System Genetics, New York University School of Medicine, New York, NY, United States
| | - Qing Liu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Inscopix, Inc., Palo Alto, California, United States
| | - Robert A Crozier
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.,Synergy Pharmaceuticals Inc., New York, NY, United States
| | - Robin L Davis
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
| |
Collapse
|
13
|
Macrostructural Changes of the Acoustic Radiation in Humans with Hearing Loss and Tinnitus Revealed with Fixel-Based Analysis. J Neurosci 2021; 41:3958-3965. [PMID: 33795427 DOI: 10.1523/jneurosci.2996-20.2021] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 02/08/2021] [Accepted: 03/02/2021] [Indexed: 12/13/2022] Open
Abstract
Age-related hearing loss is the most prevalent sensory impairment in the older adult population and is related to noise-induced damage or age-related deterioration of the peripheral auditory system. Hearing loss may affect the central auditory pathway in the brain, which is a continuation of the peripheral auditory system located in the ear. A debilitating symptom that frequently co-occurs with hearing loss is tinnitus. Strikingly, investigations into the impact of acquired hearing loss, with and without tinnitus, on the human central auditory pathway are sparse. This study used diffusion-weighted imaging (DWI) to investigate changes in the largest central auditory tract, the acoustic radiation, related to hearing loss and tinnitus. Participants with hearing loss, with and without tinnitus, and a control group were included. Both conventional diffusion tensor analysis and higher-order fixel-based analysis were applied. The fixel-based analysis was used as a novel framework providing insight into the axonal density and macrostructural morphologic changes of the acoustic radiation in hearing loss and tinnitus. The results show tinnitus-related atrophy of the left acoustic radiation near the medial geniculate body. This finding may reflect a decrease in myelination of the auditory pathway, instigated by more profound peripheral deafferentation or reflecting a preexisting marker of tinnitus vulnerability. Furthermore, age was negatively correlated with the axonal density in the bilateral acoustic radiation. This loss of fiber density with age may contribute to poorer speech understanding observed in older adults.SIGNIFICANCE STATEMENT Age-related hearing loss is the most prevalent sensory impairment in the older adult population. Older individuals are subject to the cumulative effects of aging and noise exposure on the auditory system. A debilitating symptom that frequently co-occurs with hearing loss is tinnitus: the perception of a phantom sound. In this large DWI-study, we provide evidence that in hearing loss, the additional presence of tinnitus is related to degradation of the acoustic radiation. Additionally, older age was related to axonal loss in the acoustic radiation. It appears that older adults have the aggravating circumstances of age, hearing loss, and tinnitus on central auditory processing, which may partly be because of the observed deterioration of the acoustic radiation with age.
Collapse
|
14
|
Hintze A, Gültas M, Semmelhack EA, Wichmann C. Ultrastructural maturation of the endbulb of Held active zones comparing wild-type and otoferlin-deficient mice. iScience 2021; 24:102282. [PMID: 33851098 PMCID: PMC8022229 DOI: 10.1016/j.isci.2021.102282] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 01/18/2021] [Accepted: 03/03/2021] [Indexed: 11/13/2022] Open
Abstract
Endbulbs of Held are located in the anteroventral cochlear nucleus and present the first central synapses of the auditory pathway. During development, endbulbs mature functionally to enable rapid and powerful synaptic transmission with high temporal precision. This process is accompanied by morphological changes of endbulb terminals. Loss of the hair cell-specific protein otoferlin (Otof) abolishes neurotransmission in the cochlea and results in the smaller endbulb of Held terminals. Thus, peripheral hearing impairment likely also leads to alterations in the morphological synaptic vesicle (SV) pool size at individual endbulb of Held active zones (AZs). Here, we investigated endbulb AZs in pre-hearing, young, and adult wild-type and Otof−/− mice. During maturation, SV numbers at endbulb AZs increased in wild-type mice but were found to be reduced in Otof−/− mice. The SV population at a distance of 0–15 nm was most strongly affected. Finally, overall SV diameters decreased in Otof−/− animals during maturation. Maturation of wt endbulb of Held active zones leads to more synaptic vesicles At endbulbs of otoferlin knockout mice, synaptic vesicles decline with age Mainly two distinct synaptic vesicle populations are affected Synaptic vesicles sizes are reduced in six-month-old otoferlin knockout animals
Collapse
Affiliation(s)
- Anika Hintze
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Mehmet Gültas
- Breeding Informatics Group, Department of Animal Sciences, Georg-August-University Göttingen, Göttingen, Germany
| | - Esther A Semmelhack
- Developmental, Neural, and Behavioral Biology MSc/PhD Program, University of Göttingen, Göttingen, Germany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075 Göttingen, Germany.,Collaborative Research Center 1286, University of Göttingen, Göttingen, Germany
| |
Collapse
|
15
|
Resnick JM, Rubinstein JT. Simulated auditory fiber myelination heterogeneity desynchronizes population responses to electrical stimulation limiting inter-aural timing difference representation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:934. [PMID: 33639812 PMCID: PMC7872716 DOI: 10.1121/10.0003387] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 12/22/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
Auditory nerve responses to electrical stimulation exhibit aberrantly synchronous response latencies to low-rate pulse trains, nevertheless, cochlear implant users generally have elevated inter-aural timing difference detection thresholds. These findings present an apparent paradox in which single units are unusually precise but downstream within the auditory pathway access to this precision is lost. Auditory nerves innervating a region of cochlea exhibit natural heterogeneity in their diameter, myelination, and other structural properties; a key question is whether this diversity may contribute to the loss of temporal fidelity. In this work, responses of simulated auditory neuron populations with realistic intrinsic diameter and myelination heterogeneity to low-rate pulse trains were produced. By performing a receiver operating characteristic analysis on response latency distributions, ideal-observer interaural timing difference (ITD) detection limits were produced for each population. Fiber heterogeneity produced dispersion of inter-fiber latencies that produced ITD thresholds like that observed in the best performing cochlear implant users. Incorporation of myelin loss into these populations further increased inter-fiber latency variance and elevated ITD detection limits. These findings suggest that the interaction of applied currents with fibers' specific intrinsic properties may introduce fundamental limits on presentation of fine temporal structure in electrical stimulation.
Collapse
Affiliation(s)
- Jesse M Resnick
- Department of Otolaryngology-Head and Neck Surgery/Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, Washington 98195-7923, USA
| | - Jay T Rubinstein
- Department of Otolaryngology-Head and Neck Surgery/Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, Washington 98195-7923, USA
| |
Collapse
|
16
|
Wang M, Zhang C, Lin S, Wang Y, Seicol BJ, Ariss RW, Xie R. Biased auditory nerve central synaptopathy is associated with age-related hearing loss. J Physiol 2021; 599:1833-1854. [PMID: 33450070 DOI: 10.1113/jp281014] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 01/03/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Sound information is transmitted by different subtypes of spiral ganglion neurons (SGN) from the ear to the brain. Selective damage of SGN peripheral synapses (cochlear synaptopathy) is widely recognized as one of the primary mechanisms of hearing loss, whereas the mechanisms at the SGN central synapses remain unclear. We report that different subtypes of SGN central synapses converge at different ratios onto individual target cochlear nucleus neurons with distinct physiological properties, and show biased morphological and physiological changes during age-related hearing loss (ARHL). The results reveal a new dimension in cochlear nucleus neural circuitry that systematically reassembles and processes auditory information from different SGN subtypes, which is altered during ageing and probably contributes to the development of ARHL. In addition to known cochlear synaptopathy, the present study shows that SGN central synapses are also pathologically changed during ageing, which collectively helps us better understand the structure and function of SGNs during ARHL. ABSTRACT Sound information is transmitted from the cochlea to the brain by different subtypes of spiral ganglion neurons (SGN), which show varying degrees of vulnerability under pathological conditions. Selective cochlear synaptopathy, the preferential damage of certain subtypes of SGN peripheral synapses, has been recognized as one of the main mechanisms of hearing loss. The organization and function of the auditory nerve (AN) central synapses from different subtypes of SGNs remain unclear, including how different AN synapses reassemble onto individual neurons in the cochlear nucleus, as well as how they differentially change during hearing loss. Combining immunohistochemistry with electrophysiology, we investigated the convergence pattern and subtype-specific synaptopathy of AN synapses at the endbulb of Held, as well as the response properties of their postsynaptic bushy neurons in CBA/CaJ mice of either sex under normal hearing and age-related hearing loss (ARHL). We found that calretinin-expressing (type Ia ) and non-calretinin-expressing (type Ib /Ic ) endbulbs converged along a continuum of different ratios onto individual bushy neurons with varying physiological properties. Endbulbs degenerated during ageing in parallel with ARHL. Furthermore, the degeneration was more severe in non-calretinin-expressing synapses, which correlated with a gradual decrease in bushy neuron subpopulation predominantly innervated by these inputs. These synaptic and cellular changes were profound in middle-aged mice when their hearing thresholds were still relatively normal and prior to severe ARHL. Our findings suggest that biased AN central synaptopathy and the correlated shift in cochlear nucleus neuronal composition play significant roles in weakened auditory input and altered central auditory processing during ARHL.
Collapse
Affiliation(s)
- Meijian Wang
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA
| | - Chuangeng Zhang
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA
| | - Shengyin Lin
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA
| | - Yong Wang
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA
| | - Benjamin J Seicol
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA.,Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Robert W Ariss
- College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA
| | - Ruili Xie
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, OH, USA.,Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| |
Collapse
|
17
|
Budak M, Grosh K, Sasmal A, Corfas G, Zochowski M, Booth V. Contrasting mechanisms for hidden hearing loss: Synaptopathy vs myelin defects. PLoS Comput Biol 2021; 17:e1008499. [PMID: 33481777 PMCID: PMC7857583 DOI: 10.1371/journal.pcbi.1008499] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 02/03/2021] [Accepted: 11/06/2020] [Indexed: 11/18/2022] Open
Abstract
Hidden hearing loss (HHL) is an auditory neuropathy characterized by normal hearing thresholds but reduced amplitudes of the sound-evoked auditory nerve compound action potential (CAP). In animal models, HHL can be caused by moderate noise exposure or aging, which induces loss of inner hair cell (IHC) synapses. In contrast, recent evidence has shown that transient loss of cochlear Schwann cells also causes permanent auditory deficits in mice with similarities to HHL. Histological analysis of the cochlea after auditory nerve remyelination showed a permanent disruption of the myelination patterns at the heminode of type I spiral ganglion neuron (SGN) peripheral terminals, suggesting that this defect could be contributing to HHL. To shed light on the mechanisms of different HHL scenarios observed in animals and to test their impact on type I SGN activity, we constructed a reduced biophysical model for a population of SGN peripheral axons whose activity is driven by a well-accepted model of cochlear sound processing. We found that the amplitudes of simulated sound-evoked SGN CAPs are lower and have greater latencies when heminodes are disorganized, i.e. they occur at different distances from the hair cell rather than at the same distance as in the normal cochlea. These results confirm that disruption of heminode positions causes desynchronization of SGN spikes leading to a loss of temporal resolution and reduction of the sound-evoked SGN CAP. Another mechanism resulting in HHL is loss of IHC synapses, i.e., synaptopathy. For comparison, we simulated synaptopathy by removing high threshold IHC-SGN synapses and found that the amplitude of simulated sound-evoked SGN CAPs decreases while latencies remain unchanged, as has been observed in noise exposed animals. Thus, model results illuminate diverse disruptions caused by synaptopathy and demyelination on neural activity in auditory processing that contribute to HHL as observed in animal models and that can contribute to perceptual deficits induced by nerve damage in humans.
Collapse
Affiliation(s)
- Maral Budak
- Biophysics Program, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Karl Grosh
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Aritra Sasmal
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Gabriel Corfas
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Otolaryngology Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Michal Zochowski
- Biophysics Program, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Physics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Victoria Booth
- Departments of Mathematics & Anesthesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| |
Collapse
|
18
|
Guérit F, Marozeau J, Epp B, Carlyon RP. Effect of the Relative Timing between Same-Polarity Pulses on Thresholds and Loudness in Cochlear Implant Users. J Assoc Res Otolaryngol 2020; 21:497-510. [PMID: 32833160 PMCID: PMC7644659 DOI: 10.1007/s10162-020-00767-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/31/2020] [Indexed: 12/21/2022] Open
Abstract
The effect of the relative timing between pairs of same-polarity monophasic pulses has been studied extensively in single-neuron animal studies and has revealed fundamental properties of the neurons. For human cochlear implant listeners, the requirement to use charge-balanced stimulation and the typical use of symmetric, biphasic pulses limits such measures, because currents of opposite polarities interact at the level of the neural membrane. Here, we propose a paradigm to study same-polarity summation of currents while keeping the stimulation charge-balanced within a short time window. We used pairs of mirrored pseudo-monophasic pulses (a long-low phase followed by a short-high phase for the first pulse and a short-high phase followed by a long-low phase for the second pulse). We assumed that most of the excitation would stem from the two adjacent short-high phases, which had the same polarity. The inter-pulse interval between the short-high phases was varied from 0 to 345 μs. The inter-pulse interval had a significant effect on the perceived loudness, and this effect was consistent with both passive (membrane-related) and active (ion-channel-related) neuronal mechanisms contributing to facilitation. Furthermore, the effect of interval interacted with the polarity of the pulse pairs. At threshold, there was an effect of polarity, but, surprisingly, no effect of interval nor an interaction between the two factors. We discuss possible peripheral origins of these results.
Collapse
Affiliation(s)
- François Guérit
- Hearing Systems Group, Department of Health Technology, Technical University of Denmark, 352 Ørsteds Plads, 2800, Kgs. Lyngby, Denmark.
- Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, United Kingdom.
| | - Jeremy Marozeau
- Hearing Systems Group, Department of Health Technology, Technical University of Denmark, 352 Ørsteds Plads, 2800, Kgs. Lyngby, Denmark
| | - Bastian Epp
- Hearing Systems Group, Department of Health Technology, Technical University of Denmark, 352 Ørsteds Plads, 2800, Kgs. Lyngby, Denmark
| | - Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, United Kingdom
| |
Collapse
|
19
|
Yang H, Won JH, Choi I, Woo J. A computational study to model the effect of electrode-to-auditory nerve fiber distance on spectral resolution in cochlear implant. PLoS One 2020; 15:e0236784. [PMID: 32745116 PMCID: PMC7398541 DOI: 10.1371/journal.pone.0236784] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 07/15/2020] [Indexed: 11/24/2022] Open
Abstract
Spectral ripple discrimination (SRD) has been widely used to evaluate the spectral resolution in cochlear implant (CI) recipients based on its strong correlation with speech perception performance. However, despite its usefulness for predicting speech perception outcomes, SRD performance exhibits large across-subject variabilities even among subjects implanted with the same CIs and sound processors. The potential factors of this observation include current spread, nerve survival, and CI mapping. Previous studies have found that the spectral resolution reduces with increasing distance of the stimulation electrode from the auditory nerve fibers (ANFs), attributable to increasing current spread. However, it remains unclear whether the spread of excitation is the only cause of the observation, or whether other factors such as temporal interaction also contribute to it. In this study, we used a computational model to investigate channel interaction upon non-simultaneous stimulation with respect to the electrode–ANF distance, and evaluated the SRD performance for five electrode–ANF distances. The SRD performance was determined based on the similarity between two neurograms in response to standard and inverted stimuli and used to evaluate the spectral resolution in the computational model. The spread of excitation was observed to increase with increasing electrode–ANF distance, consistent with previous findings. Additionally, the preceding pulses delivered from neighboring channels induced a channel interaction that either inhibited or facilitated the neural responses to subsequent pulses depending on the electrode–ANF distance. The SRD performance was also found to decrease with increasing electrode–ANF distance. The findings of this study suggest that variation of the neural responses (inhibition or facilitation) with the electrode–ANF distance in CI users may cause spectral smearing, and hence poor spectral resolution. A computational model such as that used in this study is a useful tool for understanding the neural factors related to CI outcomes, such as cannot be accomplished by behavioral studies alone.
Collapse
Affiliation(s)
- Hyejin Yang
- Department of Biomedical Engineering, School of Electrical Engineering, University of Ulsan, Ulsan, Republic of Korea
| | - Jong Ho Won
- Division of ENT, Sleep Disordered Breathing, Respiratory, and Anesthesia, Office of Product Evaluation and Quality, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, United States of America
| | - Inyong Choi
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States of America
| | - Jihwan Woo
- Department of Biomedical Engineering, School of Electrical Engineering, University of Ulsan, Ulsan, Republic of Korea
- * E-mail:
| |
Collapse
|
20
|
Markowitz AL, Kalluri R. Gradients in the biophysical properties of neonatal auditory neurons align with synaptic contact position and the intensity coding map of inner hair cells. eLife 2020; 9:e55378. [PMID: 32639234 PMCID: PMC7343388 DOI: 10.7554/elife.55378] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/24/2020] [Indexed: 02/07/2023] Open
Abstract
Sound intensity is encoded by auditory neuron subgroups that differ in thresholds and spontaneous rates. Whether variations in neuronal biophysics contributes to this functional diversity is unknown. Because intensity thresholds correlate with synaptic position on sensory hair cells, we combined patch clamping with fiber labeling in semi-intact cochlear preparations in neonatal rats from both sexes. The biophysical properties of auditory neurons vary in a striking spatial gradient with synaptic position. Neurons with high thresholds to injected currents contact hair cells at synaptic positions where neurons with high thresholds to sound-intensity are found in vivo. Alignment between in vitro and in vivo thresholds suggests that biophysical variability contributes to intensity coding. Biophysical gradients were evident at all ages examined, indicating that cell diversity emerges in early post-natal development and persists even after continued maturation. This stability enabled a remarkably successful model for predicting synaptic position based solely on biophysical properties.
Collapse
Affiliation(s)
- Alexander L Markowitz
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
| | - Radha Kalluri
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
| |
Collapse
|
21
|
Reijntjes DOJ, Köppl C, Pyott SJ. Volume gradients in inner hair cell-auditory nerve fiber pre- and postsynaptic proteins differ across mouse strains. Hear Res 2020; 390:107933. [PMID: 32203820 DOI: 10.1016/j.heares.2020.107933] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 02/12/2020] [Accepted: 02/26/2020] [Indexed: 02/04/2023]
Abstract
In different animal models, auditory nerve fibers display variation in spontaneous activity and response threshold. Functional and structural differences among inner hair cell ribbon synapses are believed to contribute to this variation. The relative volumes of synaptic proteins at individual synapses might be one such difference. This idea is based on the observation of opposing volume gradients of the presynaptic ribbons and associated postsynaptic glutamate receptor patches in mice along the pillar modiolar axis of the inner hair cell, the same axis along which fibers were shown to vary in their physiological properties. However, it is unclear whether these opposing gradients are expressed consistently across animal models. In addition, such volume gradients observed for separate populations of presynaptic ribbons and postsynaptic glutamate receptor patches suggest different relative volumes of these synaptic structures at individual synapses; however, these differences have not been examined in mice. Furthermore, it is unclear whether such gradients are limited to these synaptic proteins. Therefore, we analyzed organs of Corti isolated from CBA/CaJ, C57BL/6, and FVB/NJ mice using immunofluorescence, confocal microscopy, and quantitative image analysis. We find consistent expression of presynaptic volume gradients across strains of mice and inconsistent expression of postsynaptic volume gradients. We find differences in the relative volume of synaptic proteins, but these are different between CBA/CaJ mice, and C57BL/6 and FVB/NJ mice. We find similar results in C57BL/6 and FVB/NJ mice when using other postsynaptic density proteins (Shank1, Homer, and PSD95). These results have implications for the mechanisms by which volumes of synaptic proteins contribute to variations in the physiology of individual auditory nerve fibers and their vulnerability to excitotoxicity.
Collapse
Affiliation(s)
- Daniël O J Reijntjes
- University of Groningen, University Medical Center Groningen, Groningen, Department of Otorhinolaryngology and Head/Neck Surgery, 9713 GZ, Groningen, the Netherlands.
| | - Christine Köppl
- Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, Germany
| | - Sonja J Pyott
- University of Groningen, University Medical Center Groningen, Groningen, Department of Otorhinolaryngology and Head/Neck Surgery, 9713 GZ, Groningen, the Netherlands
| |
Collapse
|
22
|
Brooks PM, Rose KP, MacRae ML, Rangoussis KM, Gurjar M, Hertzano R, Coate TM. Pou3f4-expressing otic mesenchyme cells promote spiral ganglion neuron survival in the postnatal mouse cochlea. J Comp Neurol 2020; 528:1967-1985. [PMID: 31994726 DOI: 10.1002/cne.24867] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 01/13/2020] [Accepted: 01/16/2020] [Indexed: 12/20/2022]
Abstract
During inner ear development, primary auditory neurons named spiral ganglion neurons (SGNs) are surrounded by otic mesenchyme cells, which express the transcription factor Pou3f4. Mutations in Pou3f4 are associated with DFNX2, the most common form of X-linked deafness and typically include developmental malformations of the middle ear and inner ear. It is known that interactions between Pou3f4-expressing mesenchyme cells and SGNs are important for proper axon bundling during development. However, Pou3f4 continues to be expressed through later phases of development, and potential interactions between Pou3f4 and SGNs during this period had not been explored. To address this, we documented Pou3f4 protein expression in the early postnatal mouse cochlea and compared SGNs in Pou3f4 knockout mice and littermate controls. In Pou3f4y/- mice, SGN density begins to decline by the end of the first postnatal week, with approximately 25% of SGNs ultimately lost. This period of SGN loss in Pou3f4y/- cochleae coincides with significant elevations in SGN apoptosis. Interestingly, this period also coincides with the presence of a transient population of Pou3f4-expressing cells around and within the spiral ganglion. To determine if Pou3f4 is normally required for SGN peripheral axon extension into the sensory domain, we used a genetic sparse labeling approach to track SGNs and found no differences compared with controls. We also found that Pou3f4 loss did not lead to changes in the proportions of Type I SGN subtypes. Overall, these data suggest that otic mesenchyme cells may play a role in maintaining SGN populations during the early postnatal period.
Collapse
Affiliation(s)
- Paige M Brooks
- Department of Biology, Georgetown University, Washington, District of Columbia
| | - Kevin P Rose
- Department of Otorhinolaryngology Head and Neck Surgery, University of Maryland School of Medicine, University of Maryland, Baltimore, Maryland
| | - Meaghan L MacRae
- Department of Biology, Georgetown University, Washington, District of Columbia
| | | | - Mansa Gurjar
- Department of Biology, Georgetown University, Washington, District of Columbia
| | - Ronna Hertzano
- Department of Otorhinolaryngology Head and Neck Surgery, University of Maryland School of Medicine, University of Maryland, Baltimore, Maryland.,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, University of Maryland, Baltimore, Maryland.,Institute for Genome Sciences, University of Maryland School of Medicine, University of Maryland, Baltimore, Maryland
| | - Thomas M Coate
- Department of Biology, Georgetown University, Washington, District of Columbia
| |
Collapse
|
23
|
Bachmaier R, Encke J, Obando-Leitón M, Hemmert W, Bai S. Comparison of Multi-Compartment Cable Models of Human Auditory Nerve Fibers. Front Neurosci 2019; 13:1173. [PMID: 31749676 PMCID: PMC6848226 DOI: 10.3389/fnins.2019.01173] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/16/2019] [Indexed: 11/13/2022] Open
Abstract
Background: Multi-compartment cable models of auditory nerve fibers have been developed to assist in the improvement of cochlear implants. With the advancement of computational technology and the results obtained from in vivo and in vitro experiments, these models have evolved to incorporate a considerable degree of morphological and physiological details. They have also been combined with three-dimensional volume conduction models of the cochlea to simulate neural responses to electrical stimulation. However, no specific rules have been provided on choosing the appropriate cable model, and most models adopted in recent studies were chosen without a specific reason or by inheritance. Methods: Three of the most cited biophysical multi-compartment cable models of the human auditory nerve, i.e., Rattay et al. (2001b), Briaire and Frijns (2005), and Smit et al. (2010), were implemented in this study. Several properties of single fibers were compared among the three models, including threshold, conduction velocity, action potential shape, latency, refractory properties, as well as stochastic and temporal behaviors. Experimental results regarding these properties were also included as a reference for comparison. Results: For monophasic single-pulse stimulation, the ratio of anodic vs. cathodic thresholds in all models was within the experimental range despite a much larger ratio in the model by Briaire and Frijns. For biphasic pulse-train stimulation, thresholds as a function of both pulse rate and pulse duration differed between the models, but none matched the experimental observations even coarsely. Similarly, for all other properties including the conduction velocity, action potential shape, and latency, the models presented different outcomes and not all of them fell within the range observed in experiments. Conclusions: While all three models presented similar values in certain single fiber properties to those obtained in experiments, none matched all experimental observations satisfactorily. In particular, the adaptation and temporal integration behaviors were completely missing in all models. Further extensions and analyses are required to explain and simulate realistic auditory nerve fiber responses to electrical stimulation.
Collapse
Affiliation(s)
- Richard Bachmaier
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany
| | - Jörg Encke
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich School of Bioengineering, Technical University of Munich, Garching, Germany.,Medizinische Physik and Cluster of Excellence Hearing4all, Universität Oldenburg, Oldenburg, Germany
| | - Miguel Obando-Leitón
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich School of Bioengineering, Technical University of Munich, Garching, Germany.,Graduate School of Systemic Neurosciences, Ludwig Maximilian University of Munich, Planegg, Germany
| | - Werner Hemmert
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich School of Bioengineering, Technical University of Munich, Garching, Germany.,Graduate School of Systemic Neurosciences, Ludwig Maximilian University of Munich, Planegg, Germany
| | - Siwei Bai
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich School of Bioengineering, Technical University of Munich, Garching, Germany.,Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
| |
Collapse
|
24
|
Yin TC, Smith PH, Joris PX. Neural Mechanisms of Binaural Processing in the Auditory Brainstem. Compr Physiol 2019; 9:1503-1575. [DOI: 10.1002/cphy.c180036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
25
|
Review: Using diffusion-weighted magnetic resonance imaging techniques to explore the microstructure and connectivity of subcortical white matter tracts in the human auditory system. Hear Res 2019; 377:1-11. [DOI: 10.1016/j.heares.2019.02.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 02/16/2019] [Accepted: 02/26/2019] [Indexed: 12/13/2022]
|
26
|
Coate TM, Scott MK, Gurjar MC. Current concepts in cochlear ribbon synapse formation. Synapse 2019; 73:e22087. [PMID: 30592086 PMCID: PMC6573016 DOI: 10.1002/syn.22087] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 12/20/2018] [Accepted: 12/21/2018] [Indexed: 12/11/2022]
Abstract
In mammals, hair cells and spiral ganglion neurons (SGNs) in the cochlea together are sophisticated "sensorineural" structures that transduce auditory information from the outside world into the brain. Hair cells and SGNs are joined by glutamatergic ribbon-type synapses composed of a molecular machinery rivaling in complexity the mechanoelectric transduction components found at the apical side of the hair cell. The cochlear hair cell ribbon synapse has received much attention lately because of recent and important findings related to its damage (sometimes termed "synaptopathy") as a result of noise overexposure. During development, ribbon synapses between type I SGNs and inner hair cells form in the time window between birth and hearing onset and is a process coordinated with type I SGN myelination, spontaneous activity, synaptic pruning, and innervation by efferents. In this review, we highlight new findings regarding the diversity of type I SGNs and inner hair cell synapses, and the molecular mechanisms of selective hair cell targeting. Also discussed are cell adhesion molecules and protein constituents of the ribbon synapse, and how these factors participate in ribbon synapse formation. We also note interesting new insights into the morphological development of type II SGNs, and the potential for cochlear macrophages as important players in protecting SGNs. We also address recent studies demonstrating that the structural and physiological profiles of the type I SGNs do not reach full maturity until weeks after hearing onset, suggesting a protracted development that is likely modulated by activity.
Collapse
Affiliation(s)
- Thomas M. Coate
- Georgetown University, Department of Biology, 37th and O St. NW. Washington, DC. 20007. USA
| | - M. Katie Scott
- Department of Biological Sciences and Purdue Institute of Integrative Neuroscience, Purdue University, West Lafayette, Indiana 47907. USA
| | - Mansa C. Gurjar
- Georgetown University, Department of Biology, 37th and O St. NW. Washington, DC. 20007. USA
| |
Collapse
|
27
|
van Gendt MJ, Briaire JJ, Frijns JHM. Effect of neural adaptation and degeneration on pulse-train ECAPs: A model study. Hear Res 2019; 377:167-178. [PMID: 30947041 DOI: 10.1016/j.heares.2019.03.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 01/13/2019] [Accepted: 03/13/2019] [Indexed: 01/17/2023]
Abstract
Electrically evoked compound action potentials (eCAPs) are measurements of the auditory nerve's response to electrical stimulation. ECAP amplitudes during pulse trains can exhibit temporal alternations. The magnitude of this alternation tends to diminish over time during the stimulus. How this pattern relates to the temporal behavior of nerve fibers is not known. We hypothesized that the stochasticity, refractoriness, adaptation of the threshold and spike-times influence pulse-train eCAP responses. Thirty thousand auditory nerve fibers were modeled in a three-dimensional cochlear model incorporating pulse-shape effects, pulse-history effects, and stochasticity in the individual neural responses. ECAPs in response to pulse trains of different rates and amplitudes were modeled for fibers with different stochastic properties (by variation of the relative spread) and different temporal properties (by variation of the refractory periods, adaptation and latency). The model predicts alternation of peak amplitudes similar to available human data. In addition, the peak alternation was affected by changing the refractoriness, adaptation, and relative spread of auditory nerve fibers. As these parameters are related to factors such as the duration of deafness and neural survival, this study suggests that the eCAP pattern in response to pulse trains could be used to assess the underlying temporal and stochastic behavior of the auditory nerve. As these properties affect the nerve's response to pulse trains, they are of uttermost importance to sound perception with cochlear implants.
Collapse
Affiliation(s)
- M J van Gendt
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands.
| | - J J Briaire
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands
| | - J H M Frijns
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands; Leiden Institute for Brain and Cognition, PO Box 9600, 2300, RC Leiden, the Netherlands
| |
Collapse
|
28
|
Heeringa AN, Köppl C. The aging cochlea: Towards unraveling the functional contributions of strial dysfunction and synaptopathy. Hear Res 2019; 376:111-124. [PMID: 30862414 DOI: 10.1016/j.heares.2019.02.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/01/2019] [Accepted: 02/26/2019] [Indexed: 10/27/2022]
Abstract
Strial dysfunction is commonly observed as a key consequence of aging in the cochlea. A large body of animal research, especially in the quiet-aged Mongolian gerbil, shows specific histopathological changes in the cochlear stria vascularis and the putatively corresponding effects on endocochlear potential and auditory nerve responses. However, recent work suggests that synaptopathy, or the loss of inner hair cell-auditory nerve fiber synapses, also presents as a consequence of aging. It is now believed that the loss of synapses is the earliest age-related degenerative event. The present review aims to integrate classic and novel research on age-related pathologies of the inner ear. First, we summarize current knowledge on age-related strial dysfunction and synaptopathy. We describe how these cochlear pathologies fit into the categories for presbyacusis, as first defined by Schuknecht in the '70s. Further, we discuss how strial dysfunction and synaptopathy affect sound coding by the auditory nerve and how they can be experimentally induced to study their specific contributions to age-related hearing deficits. As such, we aim to give an overview of the current literature on age-related cochlear pathologies and hope to inspire further research on the role of cochlear aging in age-related hearing deficits.
Collapse
Affiliation(s)
- Amarins N Heeringa
- Cluster of Excellence 'Hearing4all' and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Christine Köppl
- Cluster of Excellence 'Hearing4all' and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany.
| |
Collapse
|
29
|
Guérit F, Marozeau J, Deeks JM, Epp B, Carlyon RP. Effects of the relative timing of opposite-polarity pulses on loudness for cochlear implant listeners. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 144:2751. [PMID: 30522299 DOI: 10.1121/1.5070150] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 10/19/2018] [Indexed: 06/09/2023]
Abstract
The symmetric biphasic pulses used in contemporary cochlear implants (CIs) consist of both cathodic and anodic currents, which may stimulate different sites on spiral ganglion neurons and, potentially, interact with each other. The effect on the order of anodic and cathodic stimulation on loudness at short inter-pulse intervals (IPIs; 0-800 μs) is investigated. Pairs of opposite-polarity pseudomonophasic (PS) pulses were used and the amplitude of each pulse was manipulated independently. In experiment 1 the two PS pulses differed in their current level in order to elicit the same loudness when presented separately. Six users of the Advanced Bionics CI (Valencia, CA) loudness-ranked trains of the pulse pairs using a midpoint-comparison procedure. Stimuli with anodic-leading polarity were louder than those with cathodic-leading polarity for IPIs shorter than 400 μs. This effect was small-about 0.3 dB-but consistent across listeners. When the same procedure was repeated with both PS pulses having the same current level (experiment 2), anodic-leading stimuli were still louder than cathodic-leading stimuli at very short intervals. However, when using symmetric biphasic pulses (experiment 3) the effect disappeared at short intervals and reversed at long intervals. Possible peripheral sources of such polarity interactions are discussed.
Collapse
Affiliation(s)
- François Guérit
- Hearing Systems Group, Department of Electrical Engineering, Technical University of Denmark, 352 Ørsteds Plads, Kongens Lyngby, 2800, Denmark
| | - Jeremy Marozeau
- Hearing Systems Group, Department of Electrical Engineering, Technical University of Denmark, 352 Ørsteds Plads, Kongens Lyngby, 2800, Denmark
| | - John M Deeks
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, United Kingdom
| | - Bastian Epp
- Hearing Systems Group, Department of Electrical Engineering, Technical University of Denmark, 352 Ørsteds Plads, Kongens Lyngby, 2800, Denmark
| | - Robert P Carlyon
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, United Kingdom
| |
Collapse
|
30
|
Spike-Conducting Integrate-and-Fire Model. eNeuro 2018; 5:eN-TNC-0112-18. [PMID: 30225348 PMCID: PMC6140110 DOI: 10.1523/eneuro.0112-18.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 11/29/2022] Open
Abstract
Modeling is a useful tool for investigating various biophysical characteristics of neurons. Recent simulation studies of propagating action potentials (spike conduction) along axons include the investigation of neuronal activity evoked by electrical stimulation from implantable prosthetic devices. In contrast to point-neuron simulations, where a large variety of models are readily available, Hodgkin–Huxley-type conductance-based models have been almost the only option for simulating axonal spike conduction, as simpler models cannot faithfully replicate the waveforms of propagating spikes. Since the amount of available physiological data, especially in humans, is usually limited, calibration, and justification of the large number of parameters of a complex model is generally difficult. In addition, not all simulation studies of axons require detailed descriptions of nonlinear ionic dynamics. In this study, we construct a simple model of spike generation and conduction based on the exponential integrate-and-fire model, which can simulate the rapid growth of the membrane potential at spike initiation. In terms of the number of parameters and equations, this model is much more compact than conventional models, but can still reliably simulate spike conduction along myelinated and unmyelinated axons that are stimulated intracellularly or extracellularly. Our simulations of auditory nerve fibers with this new model suggest that, because of the difference in intrinsic membrane properties, the axonal spike conduction of high-frequency nerve fibers is faster than that of low-frequency fibers. The simple model developed in this study can serve as a computationally efficient alternative to more complex models for future studies, including simulations of neuroprosthetic devices.
Collapse
|
31
|
Peterson AJ, Heil P. A simple model of the inner-hair-cell ribbon synapse accounts for mammalian auditory-nerve-fiber spontaneous spike times. Hear Res 2018; 363:1-27. [DOI: 10.1016/j.heares.2017.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 08/21/2017] [Accepted: 09/08/2017] [Indexed: 12/17/2022]
|
32
|
Carricondo F, Romero-Gómez B. The Cochlear Spiral Ganglion Neurons: The Auditory Portion of the VIII Nerve. Anat Rec (Hoboken) 2018; 302:463-471. [DOI: 10.1002/ar.23815] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 06/08/2017] [Accepted: 10/08/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Francisco Carricondo
- Laboratory of Neurobiology of Hearing, Dept. of Immunology, Ophthalmology and Otorhinolaryngology, Faculty of Medicine; Complutense University of Madrid (Spain)
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos" (IdISSC); Madrid Spain
| | - Bárbara Romero-Gómez
- Laboratory of Neurobiology of Hearing, Dept. of Immunology, Ophthalmology and Otorhinolaryngology, Faculty of Medicine; Complutense University of Madrid (Spain)
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos" (IdISSC); Madrid Spain
| |
Collapse
|
33
|
Orcioni S, Paffi A, Camera F, Apollonio F, Liberti M. Automatic decoding of input sinusoidal signal in a neuron model: High pass homomorphic filtering. Neurocomputing 2018. [DOI: 10.1016/j.neucom.2018.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
34
|
Resnick JM, O'Brien GE, Rubinstein JT. Simulated auditory nerve axon demyelination alters sensitivity and response timing to extracellular stimulation. Hear Res 2018; 361:121-137. [PMID: 29496363 DOI: 10.1016/j.heares.2018.01.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/06/2018] [Accepted: 01/23/2018] [Indexed: 11/18/2022]
Abstract
Since cochlear implant function involves direct depolarization of spiral ganglion neurons (SGNs) by applied current, SGN physiological health must be an important factor in cochlear implant (CI) outcomes. This expected relationship has, however, been difficult to confirm in implant recipients. Suggestively, animal studies have demonstrated both acute and progressive SGN ultrastructural changes (notably axon demyelination), even in the absence of soma death, and corresponding altered physiology following sensorineural deafening. Whether such demyelination occurs in humans and how such changes might impact CI function remains unknown. To approach this problem, we incorporated SGN demyelination into a biophysical model of extracellular stimulation of SGN fibers. Our approach enabled exploration of the entire parameter space corresponding to simulated myelin diameter and extent of fiber affected. All simulated fibers were stimulated distally with anodic monophasic, cathodic monophasic, anode-phase-first (AF) biphasic, and cathode-phase-first (CF) biphasic pulses from an extracellular disc electrode and monitored for spikes centrally. Not surprisingly, axon sensitivity generally decreased with demyelination, resulting in elevated thresholds, however, this effect was strongly non-uniform. Fibers with severe demyelination affecting only the most peripheral nodes responded nearly identically to normally myelinated fibers. Additionally, partial demyelination (<50%) yielded only minimal increases in threshold even when the entire fiber was impacted. The temporal effects of demyelination were more unexpected. Both latency and jitter of responses demonstrated resilience to modest changes but exhibited strongly non-monotonic and stimulus-dependent relationships to more profound demyelination. Normal, and modestly demyelinated fibers, were more sensitive to cathodic than anodic monophasic pulses and to CF than AF biphasic pulses, however, when demyelination was more severe these relative sensitivities were reversed. Comparison of threshold crossing between nodal segments demonstrated stimulus-dependent shifts in action potential initiation with different fiber demyelination states. For some demyelination scenarios, both phases of biphasic pulses could initiate action potentials at threshold resulting in bimodal latency and initiation site distributions and dramatically increased jitter. In summary, simulated demyelination leads to complex changes in fiber sensitivity and spike timing, mediated by alterations in action potential initiation site and slowed action potential conduction due to non-uniformities in the electrical properties of axons. Such demyelination-induced changes, if present in implantees, would have profound implications for the detection of fine temporal cues but not disrupt cues on the time scale of speech envelopes. These simulation results highlight the importance of exploring the SGN ultrastructural changes caused by a given etiology of hearing loss to more accurately predict cochlear implantation outcomes.
Collapse
Affiliation(s)
- Jesse M Resnick
- Virginia Merrill Bloedel Hearing Research Center, CHDD Clinic Bldg, University of Washington, NE Columbia Rd., Seattle, WA 98195, USA.
| | - Gabrielle E O'Brien
- Department of Speech & Hearing Sciences, University of Washington, 1417 NE 42nd Street, Box 354875, Seattle, WA 98105-6246, USA.
| | - Jay T Rubinstein
- Virginia Merrill Bloedel Hearing Research Center, CHDD Clinic Bldg, University of Washington, NE Columbia Rd., Seattle, WA 98195, USA.
| |
Collapse
|
35
|
Orcioni S, Paffi A, Camera F, Apollonio F, Liberti M. Automatic decoding of input sinusoidal signal in a neuron model: Improved SNR spectrum by low-pass homomorphic filtering. Neurocomputing 2017. [DOI: 10.1016/j.neucom.2017.06.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
36
|
van Gendt M, Briaire J, Kalkman R, Frijns J. A fast, stochastic, and adaptive model of auditory nerve responses to cochlear implant stimulation. Hear Res 2016; 341:130-143. [DOI: 10.1016/j.heares.2016.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 08/18/2016] [Accepted: 08/21/2016] [Indexed: 11/15/2022]
|
37
|
Zhang KD, Coate TM. Recent advances in the development and function of type II spiral ganglion neurons in the mammalian inner ear. Semin Cell Dev Biol 2016; 65:80-87. [PMID: 27760385 DOI: 10.1016/j.semcdb.2016.09.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 08/12/2016] [Accepted: 09/25/2016] [Indexed: 01/17/2023]
Abstract
In hearing, mechanically sensitive hair cells (HCs) in the cochlea release glutamate onto spiral ganglion neurons (SGNs) to relay auditory information to the central nervous system (CNS). There are two main SGN subtypes, which differ in morphology, number, synaptic targets, innervation patterns and firing properties. About 90-95% of SGNs are the type I SGNs, which make a single bouton connection with inner hair cells (IHCs) and have been well described in the canonical auditory pathway for sound detection. However, less attention has been given to the type II SGNs, which exclusively innervate outer hair cells (OHCs). In this review, we emphasize recent advances in the molecular mechanisms that control how type II SGNs develop and form connections with OHCs, and exciting new insights into the function of type II SGNs.
Collapse
Affiliation(s)
- Kaidi D Zhang
- Department of Biology, Georgetown University, Washington, DC, USA.
| | - Thomas M Coate
- Department of Biology, Georgetown University, Washington, DC, USA
| |
Collapse
|
38
|
Bender DA, Ni R, Barbour DL. Spontaneous activity is correlated with coding density in primary auditory cortex. J Neurophysiol 2016; 116:2789-2798. [PMID: 27707812 DOI: 10.1152/jn.00474.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/30/2016] [Indexed: 11/22/2022] Open
Abstract
Sensory neurons across sensory modalities and specific processing areas have diverse levels of spontaneous firing rates (SFRs) in the absence of sensory stimuli. However, the functional significance of this spontaneous activity is not well-understood. Previous studies in the auditory system have demonstrated that different levels of spontaneous activity are correlated with a variety of physiological and anatomic properties, suggesting that neurons with differing SFRs make unique contributions to the encoding of auditory stimuli. Additionally, altered SFRs are a correlate of tinnitus, arising in several auditory areas after exposure to ototoxic substances and noise trauma. In this study, we recorded single-unit activity from primary auditory cortex of awake marmoset monkeys while delivering wide-band random-spectrum stimuli and white Gaussian noise (WGN) to examine any divergences in stimulus encoding properties across SFR classes. We found that higher levels of spontaneous activity were associated with both higher levels of activation relative to suppression across a variety of wide-band stimuli and higher driven rates in response to WGN. Moreover, response latencies to WGN were negatively correlated with the level of activation in response to both stimulus types. These findings are consistent with a novel view of the role spontaneous spiking may play during normal stimulus processing in primary auditory cortex and how it may malfunction in cases of tinnitus.
Collapse
Affiliation(s)
- David A Bender
- Laboratory of Sensory Neuroscience and Neuroengineering, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri; and.,Department of Biology, Washington University in St. Louis, St. Louis, Missouri
| | - Ruiye Ni
- Laboratory of Sensory Neuroscience and Neuroengineering, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri; and
| | - Dennis L Barbour
- Laboratory of Sensory Neuroscience and Neuroengineering, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri; and
| |
Collapse
|
39
|
Heil P, Peterson AJ. Spike timing in auditory-nerve fibers during spontaneous activity and phase locking. Synapse 2016; 71:5-36. [DOI: 10.1002/syn.21925] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 07/20/2016] [Accepted: 07/24/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Peter Heil
- Department of Systems Physiology of Learning; Leibniz Institute for Neurobiology; Magdeburg 39118 Germany
- Center for Behavioral Brain Sciences; Magdeburg Germany
| | - Adam J. Peterson
- Department of Systems Physiology of Learning; Leibniz Institute for Neurobiology; Magdeburg 39118 Germany
| |
Collapse
|
40
|
Smith FL, Davis RL. Organ of Corti explants direct tonotopically graded morphology of spiral ganglion neurons in vitro. J Comp Neurol 2016; 524:2182-207. [PMID: 26663318 DOI: 10.1002/cne.23940] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 11/12/2015] [Accepted: 11/30/2015] [Indexed: 01/25/2023]
Abstract
The spiral ganglion is a compelling model system to examine how morphological form contributes to sensory function. While the ganglion is composed mainly of a single class of type I neurons that make simple one-to-one connections with inner hair cell sensory receptors, it has an elaborate overall morphological design. Specific features, such as soma size and axon outgrowth, are graded along the spiral contour of the cochlea. To begin to understand the interplay between different regulators of neuronal morphology, we cocultured neuron explants with peripheral target tissues removed from distinct cochlear locations. Interestingly, these "hair cell microisolates" were capable of both increasing and decreasing neuronal somata size, without adversely affecting survival. Moreover, axon characteristics elaborated de novo by the primary afferents in culture were systematically regulated by the sensory endorgan. Apparent peripheral nervous system (PNS)-like and central nervous system (CNS)-like axonal profiles were established in our cocultures allowing an analysis of putative PNS/CNS axon length ratios. As predicted from the in vivo organization, PNS-like axon bundles elaborated by apical cocultures were longer than their basal counterparts and this phenotype was methodically altered when neuron explants were cocultured with microisolates from disparate cochlear regions. Thus, location-dependent signals within the organ of Corti may set the "address" of neurons within the spiral ganglion, allowing them to elaborate the appropriate tonotopically associated morphological features in order to carry out their signaling function. J. Comp. Neurol. 524:2182-2207, 2016. © 2015 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Felicia L Smith
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
| | - Robin L Davis
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
| |
Collapse
|
41
|
Abstract
The mammalian cochlea is exquisitely designed to decompose complex sounds into their component frequencies, accounting in part for the superb auditory discrimination displayed by many species. To perform this task, numerous mechanical and electrical specializations are graded along the length of the cochlea that create a tonotopic map in which sounds of different frequencies produce maximal responses at different cochlear locations. Graded mechanical features include structural changes in the vibratory basilar membrane, on which the hair cell sensory receptors sit, to systematic changes in receptor cell size and stereociliary length. Furthermore, there is growing evidence that frequency specificity does not stop at mechanical and morphological elements in the cochlea, but also extends to the intrinsic electrical profile of the hair cell sensory receptors and the first neural element in the auditory system—the spiral ganglion neurons.
Collapse
Affiliation(s)
- Robin L Davis
- Department of Cell Biology & Neuroscience, Rutgers University, Nelson Laboratories, Piscataway, New Jersey 08854-8082, USA.
| |
Collapse
|
42
|
Gilles A, Schlee W, Rabau S, Wouters K, Fransen E, Van de Heyning P. Decreased Speech-In-Noise Understanding in Young Adults with Tinnitus. Front Neurosci 2016; 10:288. [PMID: 27445661 PMCID: PMC4923253 DOI: 10.3389/fnins.2016.00288] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/09/2016] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Young people are often exposed to high music levels which make them more at risk to develop noise-induced symptoms such as hearing loss, hyperacusis, and tinnitus of which the latter is the symptom perceived the most by young adults. Although, subclinical neural damage was demonstrated in animal experiments, the human correlate remains under debate. Controversy exists on the underlying condition of young adults with normal hearing thresholds and noise-induced tinnitus (NIT) due to leisure noise. The present study aimed to assess differences in audiological characteristics between noise-exposed adolescents with and without NIT. METHODS A group of 87 young adults with a history of recreational noise exposure was investigated by use of the following tests: otoscopy, impedance measurements, pure-tone audiometry including high-frequencies, transient and distortion product otoacoustic emissions, speech-in-noise testing with continuous and modulated noise (amplitude-modulated by 15 Hz), auditory brainstem responses (ABR) and questionnaires.Nineteen students reported NIT due to recreational noise exposure, and their measures were compared to the non-tinnitus subjects. RESULTS No significant differences between tinnitus and non-tinnitus subjects could be found for hearing thresholds, otoacoustic emissions, and ABR results.Tinnitus subjects had significantly worse speech reception in noise compared to non-tinnitus subjects for sentences embedded in steady-state noise (mean speech reception threshold (SRT) scores, respectively -5.77 and -6.90 dB SNR; p = 0.025) as well as for sentences embedded in 15 Hz AM-noise (mean SRT scores, respectively -13.04 and -15.17 dB SNR; p = 0.013). In both groups speech reception was significantly improved during AM-15 Hz noise compared to the steady-state noise condition (p < 0.001). However, the modulation masking release was not affected by the presence of NIT. CONCLUSIONS Young adults with and without NIT did not differ regarding audiometry, OAE, and ABR.However, tinnitus patients showed decreased speech-in-noise reception. The results are discussed in the light of previous findings suggestion NIT may occur in the absence of measurable peripheral damage as reflected in speech-in-noise deficits in tinnitus subjects.
Collapse
Affiliation(s)
- Annick Gilles
- University Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University HospitalEdegem, Belgium; Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of AntwerpWilrijk, Belgium; Department of Human and Social Welfare, University College GhentGhent, Belgium
| | - Winny Schlee
- University Department of Psychology, University of Konstanz Konstanz, Germany
| | - Sarah Rabau
- University Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University HospitalEdegem, Belgium; Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of AntwerpWilrijk, Belgium
| | - Kristien Wouters
- Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of AntwerpWilrijk, Belgium; University Department of Scientific Coordination and Biostatistics, Antwerp University HospitalEdegem, Belgium
| | - Erik Fransen
- Department of Medical Genetics, Faculty of Medicine and Health Sciences, University of Antwerp Wilrijk, Belgium
| | - Paul Van de Heyning
- University Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University HospitalEdegem, Belgium; Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of AntwerpWilrijk, Belgium
| |
Collapse
|
43
|
O'Brien GE, Imennov NS, Rubinstein JT. Simulating electrical modulation detection thresholds using a biophysical model of the auditory nerve. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2016; 139:2448. [PMID: 27250141 DOI: 10.1121/1.4947430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Modulation detection thresholds (MDTs) assess listeners' sensitivity to changes in the temporal envelope of a signal and have been shown to strongly correlate with speech perception in cochlear implant users. MDTs are simulated with a stochastic model of a population of auditory nerve fibers that has been verified to accurately simulate a number of physiologically important temporal response properties. The procedure to estimate detection thresholds has previously been applied to stimulus discrimination tasks. The population model simulates the MDT-stimulus intensity relationship measured in cochlear implant users. The model also recreates the shape of the modulation transfer function and the relationship between MDTs and carrier rate. Discrimination based on fluctuations in synchronous firing activity predicts better performance at low carrier rates, but quantitative measures of modulation coding predict better neural representation of high carrier rate stimuli. Manipulating the number of fibers and a temporal integration parameter, the width of a sliding temporal integration window, varies properties of the MDTs, such as cutoff frequency and peak threshold. These results demonstrate the importance of using a multi-diameter fiber population in modeling the MDTs and demonstrate a wider applicability of this model to simulating behavioral performance in cochlear implant listeners.
Collapse
Affiliation(s)
- Gabrielle E O'Brien
- Department of Otolaryngology, V. M. Bloedel Hearing Research Center, University of Washington, Box 3657923, CHDD building, CD 176, Seattle, Washington 98196, USA
| | - Nikita S Imennov
- Department of Otolaryngology, V. M. Bloedel Hearing Research Center, University of Washington, Box 3657923, CHDD building, CD 176, Seattle, Washington 98196, USA
| | - Jay T Rubinstein
- Department of Otolaryngology, V. M. Bloedel Hearing Research Center, University of Washington, Box 3657923, CHDD building, CD 176, Seattle, Washington 98196, USA
| |
Collapse
|
44
|
O'Brien GE, Rubinstein JT. The development of biophysical models of the electrically stimulated auditory nerve: Single-node and cable models. NETWORK (BRISTOL, ENGLAND) 2016; 27:135-156. [PMID: 27070730 DOI: 10.3109/0954898x.2016.1162338] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In the last few decades, biophysical models have emerged as a prominent tool in the study and improvement of cochlear implants, a neural prosthetic that restores a degree of sound perception to the profoundly deaf. Owing to the spatial phenomena associated with extracellular stimulation, these models have evolved to a relatively high degree of morphological and physiological detail: single-node models in the tradition of Hodgkin-Huxley are paired with cable descriptions of the auditory nerve fiber. No singular model has emerged as a frontrunner to the field; rather, parameter sets deriving from the channel kinetics and morphologies of numerous organisms (mammalian and otherwise) are combined and tuned to foster strong agreement with response properties observed in vivo, such as refractoriness, summation, and strength-duration relationships. Recently, biophysical models of the electrically stimulated auditory nerve have begun to incorporate adaptation and stochastic mechanisms, in order to better realize the goal of predicting realistic neural responses to a wide array of stimuli.
Collapse
Affiliation(s)
- Gabrielle E O'Brien
- a Department of Otolaryngology, V.M. Bloedel Hearing Research Center , University of Washington , Seattle , Washington , USA
| | - Jay T Rubinstein
- a Department of Otolaryngology, V.M. Bloedel Hearing Research Center , University of Washington , Seattle , Washington , USA
| |
Collapse
|
45
|
Barclay M, Constable R, James NR, Thorne PR, Montgomery JM. Reduced sensory stimulation alters the molecular make-up of glutamatergic hair cell synapses in the developing cochlea. Neuroscience 2016; 325:50-62. [PMID: 27012610 DOI: 10.1016/j.neuroscience.2016.03.043] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 02/26/2016] [Accepted: 03/16/2016] [Indexed: 12/20/2022]
Abstract
Neural activity during early development is known to alter innervation pathways in the central and peripheral nervous systems. We sought to examine how reduced sound-induced sensory activity in the cochlea affected the consolidation of glutamatergic synapses between inner hair cells (IHC) and the primary auditory neurons as these synapses play a primary role in transmitting sound information to the brain. A unilateral conductive hearing loss was induced prior to the onset of sound-mediated stimulation of the sensory hair cells, by rupturing the tympanic membrane and dislocating the auditory ossicles in the left ear of P11 mice. Auditory brainstem responses at P15 and P21 showed a 40-50-dB increase in thresholds for frequencies 8-32kHz in the dislocated ear relative to the control ear. Immunohistochemistry and confocal microscopy were subsequently used to examine the effect of this attenuation of sound stimulation on the expression of RIBEYE, which comprises the presynaptic ribbons, Shank-1, a postsynaptic scaffolding protein, and the GluA2/3 and 4 subunits of postsynaptic AMPA receptors. Our results show that dislocation did not alter the number of pre- or postsynaptic protein puncta. However, dislocation did increase the size of RIBEYE, GluA4, GluA2/3 and Shank-1 puncta, with postsynaptic changes preceding presynaptic changes. Our data suggest that a reduction in sound stimulation during auditory development induces plasticity in the molecular make-up of IHC glutamatergic synapses, but does not affect the number of these synapses. Up-regulation of synaptic proteins with sound attenuation may facilitate a compensatory increase in synaptic transmission due to the reduced sensory stimulation of the IHC.
Collapse
Affiliation(s)
- M Barclay
- Department of Physiology and Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - R Constable
- Department of Physiology and Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - N R James
- Department of Physiology and Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - P R Thorne
- Department of Physiology and Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; Section of Audiology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - J M Montgomery
- Department of Physiology and Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
| |
Collapse
|
46
|
Ford MC, Alexandrova O, Cossell L, Stange-Marten A, Sinclair J, Kopp-Scheinpflug C, Pecka M, Attwell D, Grothe B. Tuning of Ranvier node and internode properties in myelinated axons to adjust action potential timing. Nat Commun 2015; 6:8073. [PMID: 26305015 PMCID: PMC4560803 DOI: 10.1038/ncomms9073] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 07/15/2015] [Indexed: 12/04/2022] Open
Abstract
Action potential timing is fundamental to information processing; however, its determinants are not fully understood. Here we report unexpected structural specializations in the Ranvier nodes and internodes of auditory brainstem axons involved in sound localization. Myelination properties deviated significantly from the traditionally assumed structure. Axons responding best to low-frequency sounds had a larger diameter than high-frequency axons but, surprisingly, shorter internodes. Simulations predicted that this geometry helps to adjust the conduction velocity and timing of action potentials within the circuit. Electrophysiological recordings in vitro and in vivo confirmed higher conduction velocities in low-frequency axons. Moreover, internode length decreased and Ranvier node diameter increased progressively along the distal axon segments, which simulations show was essential to ensure precisely timed depolarization of the giant calyx of Held presynaptic terminal. Thus, individual anatomical parameters of myelinated axons can be tuned to optimize pathways involved in temporal processing. Action potential timing is fundamental to information processing, but its determinants are not fully understood. Here the authors demonstrate unexpected structural specializations of myelinated axons in the auditory brainstem that help to adjust action potential arrival time for sound localization.
Collapse
Affiliation(s)
- Marc C Ford
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany.,Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Olga Alexandrova
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| | - Lee Cossell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Annette Stange-Marten
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| | - James Sinclair
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| | - Conny Kopp-Scheinpflug
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| | - Michael Pecka
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| | - David Attwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Benedikt Grothe
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität Munich, Munich D-82152, Germany
| |
Collapse
|
47
|
Paffi A, Camera F, Apollonio F, d'Inzeo G, Liberti M. Restoring the encoding properties of a stochastic neuron model by an exogenous noise. Front Comput Neurosci 2015; 9:42. [PMID: 25999845 PMCID: PMC4422033 DOI: 10.3389/fncom.2015.00042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 03/19/2015] [Indexed: 11/13/2022] Open
Abstract
Here we evaluate the possibility of improving the encoding properties of an impaired neuronal system by superimposing an exogenous noise to an external electric stimulation signal. The approach is based on the use of mathematical neuron models consisting of stochastic HH-like circuit, where the impairment of the endogenous presynaptic inputs is described as a subthreshold injected current and the exogenous stimulation signal is a sinusoidal voltage perturbation across the membrane. Our results indicate that a correlated Gaussian noise, added to the sinusoidal signal can significantly increase the encoding properties of the impaired system, through the Stochastic Resonance (SR) phenomenon. These results suggest that an exogenous noise, suitably tailored, could improve the efficacy of those stimulation techniques used in neuronal systems, where the presynaptic sensory neurons are impaired and have to be artificially bypassed.
Collapse
Affiliation(s)
- Alessandra Paffi
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Francesca Camera
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Francesca Apollonio
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Guglielmo d'Inzeo
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Micaela Liberti
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| |
Collapse
|
48
|
Eggermont JJ. Animal models of spontaneous activity in the healthy and impaired auditory system. Front Neural Circuits 2015; 9:19. [PMID: 25983679 PMCID: PMC4415415 DOI: 10.3389/fncir.2015.00019] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 04/10/2015] [Indexed: 11/30/2022] Open
Abstract
Spontaneous neural activity in the auditory nerve fibers and in auditory cortex in healthy animals is discussed with respect to the question: Is spontaneous activity noise or information carrier? The studies reviewed suggest strongly that spontaneous activity is a carrier of information. Subsequently, I review the numerous findings in the impaired auditory system, particularly with reference to noise trauma and tinnitus. Here the common assumption is that tinnitus reflects increased noise in the auditory system that among others affects temporal processing and interferes with the gap-startle reflex, which is frequently used as a behavioral assay for tinnitus. It is, however, more likely that the increased spontaneous activity in tinnitus, firing rate as well as neural synchrony, carries information that shapes the activity of downstream structures, including non-auditory ones, and leading to the tinnitus percept. The main drivers of that process are bursting and synchronous firing, which facilitates transfer of activity across synapses, and allows formation of auditory objects, such as tinnitus.
Collapse
Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, Department of Psychology, University of Calgary Calgary, AB, Canada
| |
Collapse
|
49
|
Heil P, Peterson AJ. Basic response properties of auditory nerve fibers: a review. Cell Tissue Res 2015; 361:129-58. [PMID: 25920587 DOI: 10.1007/s00441-015-2177-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 03/19/2015] [Indexed: 01/26/2023]
Abstract
All acoustic information from the periphery is encoded in the timing and rates of spikes in the population of spiral ganglion neurons projecting to the central auditory system. Considerable progress has been made in characterizing the physiological properties of type-I and type-II primary auditory afferents and understanding the basic properties of type-I afferents in response to sounds. Here, we review some of these properties, with emphasis placed on issues such as the stochastic nature of spike timing during spontaneous and driven activity, frequency tuning curves, spike-rate-versus-level functions, dynamic-range and spike-rate adaptation, and phase locking to stimulus fine structure and temporal envelope. We also review effects of acoustic trauma on some of these response properties.
Collapse
Affiliation(s)
- Peter Heil
- Leibniz Institute for Neurobiology, Brenneckestrasse 6, 39118, Magdeburg, Germany,
| | | |
Collapse
|
50
|
Effects of electrode position on spatiotemporal auditory nerve fiber responses: a 3D computational model study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2015; 2015:934382. [PMID: 25755675 PMCID: PMC4338381 DOI: 10.1155/2015/934382] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/11/2015] [Accepted: 01/13/2015] [Indexed: 11/17/2022]
Abstract
A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance.
Collapse
|