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Anderson SR, Burg E, Suveg L, Litovsky RY. Review of Binaural Processing With Asymmetrical Hearing Outcomes in Patients With Bilateral Cochlear Implants. Trends Hear 2024; 28:23312165241229880. [PMID: 38545645 PMCID: PMC10976506 DOI: 10.1177/23312165241229880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 01/11/2024] [Accepted: 01/16/2024] [Indexed: 04/01/2024] Open
Abstract
Bilateral cochlear implants (BiCIs) result in several benefits, including improvements in speech understanding in noise and sound source localization. However, the benefit bilateral implants provide among recipients varies considerably across individuals. Here we consider one of the reasons for this variability: difference in hearing function between the two ears, that is, interaural asymmetry. Thus far, investigations of interaural asymmetry have been highly specialized within various research areas. The goal of this review is to integrate these studies in one place, motivating future research in the area of interaural asymmetry. We first consider bottom-up processing, where binaural cues are represented using excitation-inhibition of signals from the left ear and right ear, varying with the location of the sound in space, and represented by the lateral superior olive in the auditory brainstem. We then consider top-down processing via predictive coding, which assumes that perception stems from expectations based on context and prior sensory experience, represented by cascading series of cortical circuits. An internal, perceptual model is maintained and updated in light of incoming sensory input. Together, we hope that this amalgamation of physiological, behavioral, and modeling studies will help bridge gaps in the field of binaural hearing and promote a clearer understanding of the implications of interaural asymmetry for future research on optimal patient interventions.
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Affiliation(s)
- Sean R. Anderson
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical School, Aurora, CO, USA
| | - Emily Burg
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lukas Suveg
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Ruth Y. Litovsky
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, USA
- Department of Surgery, Division of Otolaryngology, University of Wisconsin-Madison, Madison, WI, USA
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2
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Li YH, Joris PX. Case reopened: A temporal basis for harmonic pitch templates in the early auditory system?a). THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 154:3986-4003. [PMID: 38149819 DOI: 10.1121/10.0023969] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 12/04/2023] [Indexed: 12/28/2023]
Abstract
A fundamental assumption of rate-place models of pitch is the existence of harmonic templates in the central nervous system (CNS). Shamma and Klein [(2000). J. Acoust. Soc. Am. 107, 2631-2644] hypothesized that these templates have a temporal basis. Coincidences in the temporal fine-structure of neural spike trains, even in response to nonharmonic, stochastic stimuli, would be sufficient for the development of harmonic templates. The physiological plausibility of this hypothesis is tested. Responses to pure tones, low-pass noise, and broadband noise from auditory nerve fibers and brainstem "high-sync" neurons are studied. Responses to tones simulate the output of fibers with infinitely sharp filters: for these responses, harmonic structure in a coincidence matrix comparing pairs of spike trains is indeed found. However, harmonic template structure is not observed in coincidences across responses to broadband noise, which are obtained from nerve fibers or neurons with enhanced synchronization. Using a computer model based on that of Shamma and Klein, it is shown that harmonic templates only emerge when consecutive processing steps (cochlear filtering, lateral inhibition, and temporal enhancement) are implemented in extreme, physiologically implausible form. It is concluded that current physiological knowledge does not support the hypothesis of Shamma and Klein (2000).
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Affiliation(s)
- Yi-Hsuan Li
- Laboratory of Auditory Neurophysiology, Medical School, Campus Gasthuisberg, University of Leuven, B-3000 Leuven, Belgium
| | - Philip X Joris
- Laboratory of Auditory Neurophysiology, Medical School, Campus Gasthuisberg, University of Leuven, B-3000 Leuven, Belgium
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3
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Wei L, Verschooten E, Joris PX. Enhancement of phase-locking in rodents. II. An axonal recording study in chinchilla. J Neurophysiol 2023; 130:751-767. [PMID: 37609701 DOI: 10.1152/jn.00474.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 08/07/2023] [Accepted: 08/15/2023] [Indexed: 08/24/2023] Open
Abstract
The trapezoid body (TB) contains axons of neurons residing in the anteroventral cochlear nucleus (AVCN) that provide excitatory and inhibitory inputs to the main monaural and binaural nuclei in the superior olivary complex (SOC). To understand the monaural and binaural response properties of neurons in the medial and lateral superior olive (MSO and LSO), it is important to characterize the temporal firing properties of these inputs. Because of its exceptional low-frequency hearing, the chinchilla (Chinchilla lanigera) is one of the widely used small animal models for studies of hearing. However, the characterization of the output of its ventral cochlear nucleus to the nuclei of the SOC is fragmentary. We obtained responses of TB axons to stimuli typically used in binaural studies and compared these responses to those of auditory nerve (AN) fibers, with a focus on temporal coding. We found enhancement of phase-locking and entrainment, i.e., the ability of a neuron to fire action potentials at a certain stimulus phase for nearly every stimulus period, in TB axons relative to AN fibers. Enhancement in phase-locking and entrainment are quantitatively more modest than in the cat but greater than in the gerbil. As in these species, these phenomena occur not only in low-frequency neurons stimulated at their characteristic frequency but also in neurons tuned to higher frequencies when stimulated with low-frequency tones, to which complex phase-locking behavior with multiple modes of firing per stimulus cycle is frequently observed.NEW & NOTEWORTHY The sensitivity of neurons to small time differences in sustained sounds to both ears is important for binaural hearing, and this sensitivity is critically dependent on phase-locking in the monaural pathways. Although studies in cat showed a marked improvement in phase-locking from the peripheral to the central auditory nervous system, the evidence in rodents is mixed. Here, we recorded from AN and TB of chinchilla and found temporal enhancement, though more limited than in cat.
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Affiliation(s)
- Liting Wei
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Eric Verschooten
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Philip X Joris
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
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4
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Mittring A, Moser T, Huet AT. Graded optogenetic activation of the auditory pathway for hearing restoration. Brain Stimul 2023; 16:466-483. [PMID: 36702442 PMCID: PMC10159867 DOI: 10.1016/j.brs.2023.01.1671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/24/2023] Open
Abstract
Optogenetic control of neural activity enables innovative approaches to improve functional restoration of diseased sensory and motor systems. For clinical translation to succeed, optogenetic stimulation needs to closely match the coding properties of the targeted neuronal population and employ optimally operating emitters. This requires the customization of channelrhodopsins, emitters and coding strategies. Here, we provide a framework to parametrize optogenetic neural control and apply it to the auditory pathway that requires high temporal fidelity of stimulation. We used a viral gene transfer of ultrafast targeting-optimized Chronos into spiral ganglion neurons (SGNs) of the cochlea of mice. We characterized the light-evoked response by in vivo recordings from individual SGNs and neurons of the anteroventral cochlear nucleus (AVCN) that detect coincident SGN inputs. Our recordings from single SGNs demonstrated that their spike probability can be graded by adjusting the duration of light pulses at constant intensity, which optimally serves efficient laser diode operation. We identified an effective pulse width of 1.6 ms to maximize encoding in SGNs at the maximal light intensity employed here (∼35 mW). Alternatively, SGNs were activated at lower energy thresholds using short light pulses (<1 ms). An upper boundary of optical stimulation rates was identified at 316 Hz, inducing a robust spike rate adaptation that required a few tens of milliseconds to recover. We developed a semi-stochastic stimulation paradigm to rapidly (within minutes) estimate the input/output function from light to SGN firing and approximate the time constant of neuronal integration in the AVCN. By that, our data pave the way to design the sound coding strategies of future optical cochlear implants.
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Affiliation(s)
- Artur Mittring
- Auditory Circuit Lab, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany; Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany; Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
| | - Antoine Tarquin Huet
- Auditory Circuit Lab, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany; Auditory Neuroscience and Optogenetics Laboratory, German Primate Center, Göttingen, Germany.
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5
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Mammalian octopus cells are direction selective to frequency sweeps by excitatory synaptic sequence detection. Proc Natl Acad Sci U S A 2022; 119:e2203748119. [PMID: 36279465 PMCID: PMC9636937 DOI: 10.1073/pnas.2203748119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Octopus cells are remarkable projection neurons of the mammalian cochlear nucleus, with extremely fast membranes and wide-frequency tuning. They are considered prime examples of coincidence detectors but are poorly characterized in vivo. We discover that octopus cells are selective to frequency sweep direction, a feature that is absent in their auditory nerve inputs. In vivo intracellular recordings reveal that direction selectivity does not derive from across-frequency coincidence detection but hinges on the amplitudes and activation sequence of auditory nerve inputs tuned to clusters of hot spot frequencies. A simple biophysical octopus cell model excited with real nerve spike trains recreates direction selectivity through interaction of intrinsic membrane conductances with the activation sequence of clustered excitatory inputs. We conclude that octopus cells are sequence detectors, sensitive to temporal patterns across cochlear frequency channels. The detection of sequences rather than coincidences is a much simpler but powerful operation to extract temporal information.
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6
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Märcher-Rørsted J, Encina-Llamas G, Dau T, Liberman MC, Wu PZ, Hjortkjær J. Age-related reduction in frequency-following responses as a potential marker of cochlear neural degeneration. Hear Res 2021; 414:108411. [PMID: 34929535 DOI: 10.1016/j.heares.2021.108411] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/28/2022]
Abstract
Healthy aging may be associated with neural degeneration in the cochlea even before clinical hearing loss emerges. Reduction in frequency-following responses (FFRs) to tonal carriers in older clinically normal-hearing listeners has previously been reported, and has been argued to reflect an age-dependent decline in temporal processing in the central auditory system. Alternatively, age-dependent loss of auditory nerve fibers (ANFs) may have little effect on audiometric sensitivity and yet compromise the precision of neural phase-locking relying on joint activity across populations of fibers. This peripheral loss may, in turn, contribute to reduced neural synchrony in the brainstem as reflected in the FFR. Here, we combined human electrophysiology and auditory nerve (AN) modeling to investigate whether age-related changes in the FFR would be consistent with peripheral neural degeneration. FFRs elicited by pure tones and frequency sweeps at carrier frequencies between 200 and 1200 Hz were obtained in older (ages 48-76) and younger (ages 20-30) listeners, both groups having clinically normal audiometric thresholds up to 6 kHz. The same stimuli were presented to a computational model of the AN in which age-related loss of hair cells or ANFs was modelled using human histopathological data. In the older human listeners, the measured FFRs to both sweeps and pure tones were found to be reduced across the carrier frequencies examined. These FFR reductions were consistent with model simulations of age-related ANF loss. In model simulations, the phase-locked response produced by the population of remaining fibers decreased proportionally with increasing loss of the ANFs. Basal-turn loss of inner hair cells also reduced synchronous activity at lower frequencies, albeit to a lesser degree. Model simulations of age-related threshold elevation further indicated that outer hair cell dysfunction had no negative effect on phase-locked AN responses. These results are consistent with a peripheral source of the FFR reductions observed in older normal-hearing listeners, and indicate that FFRs at lower carrier frequencies may potentially be a sensitive marker of peripheral neural degeneration.
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Affiliation(s)
- Jonatan Märcher-Rørsted
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - Gerard Encina-Llamas
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - Torsten Dau
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark
| | - M Charles Liberman
- Eaton-Peabody Laboratories and Department of Otolaryngology, Head and Neck Surgery, Massachusetts Eye and Ear, Boston, MA 02114 USA
| | - Pei-Zhe Wu
- Eaton-Peabody Laboratories and Department of Otolaryngology, Head and Neck Surgery, Massachusetts Eye and Ear, Boston, MA 02114 USA
| | - Jens Hjortkjær
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Ørsteds Plads, Building 352, DK-2800 Kgs. Lyngby, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Kettegård Allé 30, DK-2650 Hvidovre, Denmark.
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7
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Ming C, Haro S, Simmons AM, Simmons JA. A comprehensive computational model of animal biosonar signal processing. PLoS Comput Biol 2021; 17:e1008677. [PMID: 33596199 PMCID: PMC7888678 DOI: 10.1371/journal.pcbi.1008677] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 01/07/2021] [Indexed: 11/23/2022] Open
Abstract
Computational models of animal biosonar seek to identify critical aspects of echo processing responsible for the superior, real-time performance of echolocating bats and dolphins in target tracking and clutter rejection. The Spectrogram Correlation and Transformation (SCAT) model replicates aspects of biosonar imaging in both species by processing wideband biosonar sounds and echoes with auditory mechanisms identified from experiments with bats. The model acquires broadband biosonar broadcasts and echoes, represents them as time-frequency spectrograms using parallel bandpass filters, translates the filtered signals into ten parallel amplitude threshold levels, and then operates on the resulting time-of-occurrence values at each frequency to estimate overall echo range delay. It uses the structure of the echo spectrum by depicting it as a series of local frequency nulls arranged regularly along the frequency axis of the spectrograms after dechirping them relative to the broadcast. Computations take place entirely on the timing of threshold-crossing events for each echo relative to threshold-events for the broadcast. Threshold-crossing times take into account amplitude-latency trading, a physiological feature absent from conventional digital signal processing. Amplitude-latency trading transposes the profile of amplitudes across frequencies into a profile of time-registrations across frequencies. Target shape is extracted from the spacing of the object's individual acoustic reflecting points, or glints, using the mutual interference pattern of peaks and nulls in the echo spectrum. These are merged with the overall range-delay estimate to produce a delay-based reconstruction of the object's distance as well as its glints. Clutter echoes indiscriminately activate multiple parts in the null-detecting system, which then produces the equivalent glint-delay spacings in images, thus blurring the overall echo-delay estimates by adding spurious glint delays to the image. Blurring acts as an anticorrelation process that rejects clutter intrusion into perceptions.
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Affiliation(s)
- Chen Ming
- Department of Neuroscience and Carney Institute for Brain Science, Brown University Providence, United States of America
| | - Stephanie Haro
- Speech and Hearing Biosciences and Technology, Harvard University, Boston, United States of America
| | - Andrea Megela Simmons
- Department of Cognitive, Linguistic and Psychological Sciences and Carney Institute for Brain Science, Brown University Providence, United States of America
| | - James A. Simmons
- Department of Neuroscience and Carney Institute for Brain Science, Brown University Providence, United States of America
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8
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Anderson S, Bieber R, Schloss A. Peripheral deficits and phase-locking declines in aging adults. Hear Res 2021; 403:108188. [PMID: 33581668 DOI: 10.1016/j.heares.2021.108188] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 01/16/2021] [Accepted: 01/20/2021] [Indexed: 10/22/2022]
Abstract
Age-related difficulties in speech understanding may arise from a decrease in the neural representation of speech sounds. A loss of outer hair cells or decrease in auditory nerve fibers may lead to a loss of temporal precision that can affect speech clarity. This study's purpose was to evaluate the peripheral contributors to phase-locking strength, a measure of temporal precision, in recordings to a sustained vowel in 30 younger and 30 older listeners with normal to near normal audiometric thresholds. Thresholds were obtained for pure tones and distortion-product otoacoustic emissions (DPOAEs). Auditory brainstem responses (ABRs) were recorded in quiet and in three levels of continuous white noise (+30, +20, and +10 dB SNR). Absolute amplitudes and latencies of Wave I in quiet and of Wave V across presentation conditions, in addition to the slope of Wave V amplitude and latency changes in noise, were calculated from these recordings. Frequency-following responses (FFRs) were recorded to synthesized /ba/ syllables of two durations, 170 and 260 ms, to determine whether age-related phase-locking deficits are more pronounced for stimuli that are sustained for longer durations. Phase locking was calculated for the early and late regions of the steady-state vowel for both syllables. Group differences were found for nearly every measure except for the slopes of Wave V latency and amplitude changes in noise. We found that outer hair cell function (DPOAEs) contributed to the variance in phase locking. However, the ABR and FFR differences were present after covarying for DPOAEs, suggesting the existence of temporal processing deficits in older listeners that are somewhat independent of outer hair cell function.
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Affiliation(s)
- Samira Anderson
- Department of Hearing and Speech Sciences, University of Maryland, College Park, MD 20742, United States.
| | - Rebecca Bieber
- Department of Hearing and Speech Sciences, University of Maryland, College Park, MD 20742, United States.
| | - Alanna Schloss
- Department of Hearing and Speech Sciences, University of Maryland, College Park, MD 20742, United States.
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9
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Koert E, Kuenzel T. Small dendritic synapses enhance temporal coding in a model of cochlear nucleus bushy cells. J Neurophysiol 2021; 125:915-937. [PMID: 33471627 DOI: 10.1152/jn.00331.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spherical bushy cells (SBCs) in the anteroventral cochlear nucleus receive a single or very few powerful axosomatic inputs from the auditory nerve. However, SBCs are also contacted by small regular bouton synapses of the auditory nerve, located in their dendritic tree. The function of these small inputs is unknown. It was speculated that the interaction of axosomatic inputs with small dendritic inputs improved temporal precision, but direct evidence for this is missing. In a compartment model of spherical bushy cells with a stylized or realistic three-dimensional (3-D) representation of the bushy dendrite, we explored this hypothesis. Phase-locked dendritic inputs caused both tonic depolarization and a modulation of the model SBC membrane potential at the frequency of the stimulus. For plausible model parameters, dendritic inputs were subthreshold. Instead, the tonic depolarization increased the excitability of the SBC model and the modulation of the membrane potential caused a phase-dependent increase in the efficacy of the main axosomatic input. This improved response rate and entrainment for low-input frequencies and temporal precision of output at and above the characteristic frequency. A careful exploration of morphological and biophysical parameters of the bushy dendrite suggested a functional explanation for the peculiar shape of the bushy dendrite. Our model for the first time directly implied a role for the small excitatory dendritic inputs in auditory processing: they modulate the efficacy of the main input and are thus a plausible mechanism for the improvement of temporal precision and fidelity in these central auditory neurons.NEW & NOTEWORTHY We modeled dendritic inputs from the auditory nerve that spherical bushy cells of the cochlear nucleus receive. Dendritic inputs caused both tonic depolarization and modulation of the membrane potential at the input frequency. This improved the rate, entrainment, and temporal precision of output action potentials. Our simulations suggest a role for small dendritic inputs in auditory processing: they modulate the efficacy of the main input supporting temporal precision and fidelity in these central auditory neurons.
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Affiliation(s)
- Elisabeth Koert
- Auditory Neurophysiology Group, Department of Chemosensation, RWTH Aachen University, Aachen, Germany
| | - Thomas Kuenzel
- Auditory Neurophysiology Group, Department of Chemosensation, RWTH Aachen University, Aachen, Germany
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10
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Lucchetti F, Nonclercq A, Avan P, Giraudet F, Fan X, Deltenre P. Subcortical neural generators of the envelope-following response in sleeping children: A transfer function analysis. Hear Res 2020; 401:108157. [PMID: 33360182 DOI: 10.1016/j.heares.2020.108157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 12/10/2020] [Accepted: 12/14/2020] [Indexed: 01/23/2023]
Abstract
Multiple auditory structures, from cochlea to cortex, phase-lock to the envelope of complex stimuli. The relative contributions of these structures to the human surface-recorded envelope-following response (EFR) are still uncertain. Identification of the active contributor(s) is complicated by the fact that even the simplest two-tone (f1&f2) stimulus, targeting its (f2-f1) envelope, evokes additional linear (f1&f2) and non-linear (2f1-f2) phase-locked components as well as a transient auditory brainstem response (ABR). Here, we took advantage of the generalized primary tone phase variation method to isolate each predictable component in the time domain, allowing direct measurements of onset latency, duration and phase discontinuity values from which the involved generators were inferred. Targeting several envelope frequencies (0.22-1 kHz), we derived the EFR transfer functions along a vertical vertex-to-neck and a horizontal earlobe-to-earlobe recording channels, yielding respectively EFR-V and EFR-H waveforms. Subjects (N= 30) were sleeping children with normal electrophysiological thresholds and normal oto-acoustic emissions. Both EFR-H and EFR-V phase-locking values (PLV) transfer functions had a low-pass profile, EFR-V showing a lower cut-off frequency than EFR-H. We also computed the frequency-latency relationships of both EFRs onset latencies. EFR-H data fitted a power-law function incorporating a frequency-dependent traveling wave delay and a fixed one amounting to 1.2 ms. The fitted function nicely fell within five published estimations of the latency-frequency function of the ABR wave-I, thus pointing to a cochlear nerve origin. The absence of phase discontinuity and overall response durations that were equal to that of the stimulus indicated no contribution from a later generator. The recording of an entirely similar EFR-H response in a patient who had severe brainstem encephalitis with a normal, isolated, ABR wave-I but complete absence of later waves, further substantiated a cochlear nerve origin. Modeling of the EFR-V latency-frequency functions indicated a fixed transport time of 2 ms with respect to EFR-H onset, suggesting a cochlear nucleus (CN) origin, here also, without indication for multiple generators. Other features of the EFR-V response pointing to the CN were, at least for the EFR frequency below the cut-off values of the transfer functions, higher PLVs coupled with increased harmonic distortion. Such a behavior has been described in the so-called highly-synchronized neurons of the ventral cochlear nucleus (VCN). The present study compellingly demonstrated the advantage of isolating the EFR in the temporal domain so as to extract detailed spectro-temporal parameters that, combined with orthogonal recording channels, shed new light on the involved neural generators.
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Affiliation(s)
- Federico Lucchetti
- Bio-, Electro- and Mechanical Systems, CP165/56, Université Libre de Bruxelles, Avenue F. D. Roosevelt, 50, Brussels 1050, Belgium; Laboratoire de Neurophysiologie Sensorielle et Cognitive, CP403/22, Brugmann Hospital, Place Van Gehuchten 4, Brussels 1020, Belgium.
| | - Antoine Nonclercq
- Bio-, Electro- and Mechanical Systems, CP165/56, Université Libre de Bruxelles, Avenue F. D. Roosevelt, 50, Brussels 1050, Belgium; Laboratoire de Neurophysiologie Sensorielle et Cognitive, CP403/22, Brugmann Hospital, Place Van Gehuchten 4, Brussels 1020, Belgium; Laboratory of Neurosensory Biophysics Unité mixte de recherche, Institut national de la santé et de la recherche médicale, University Clermont Auvergne, 28 Place Henri Dunant, BP38, Clermont-Ferrand F63001, France.
| | - Paul Avan
- Laboratory of Neurosensory Biophysics Unité mixte de recherche, Institut national de la santé et de la recherche médicale, University Clermont Auvergne, 28 Place Henri Dunant, BP38, Clermont-Ferrand F63001, France.
| | - Fabrice Giraudet
- Laboratory of Neurosensory Biophysics Unité mixte de recherche, Institut national de la santé et de la recherche médicale, University Clermont Auvergne, 28 Place Henri Dunant, BP38, Clermont-Ferrand F63001, France.
| | - Xiaoya Fan
- Bio-, Electro- and Mechanical Systems, CP165/56, Université Libre de Bruxelles, Avenue F. D. Roosevelt, 50, Brussels 1050, Belgium.
| | - Paul Deltenre
- Laboratoire de Neurophysiologie Sensorielle et Cognitive, CP403/22, Brugmann Hospital, Place Van Gehuchten 4, Brussels 1020, Belgium.
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11
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Sinz FH, Sachgau C, Henninger J, Benda J, Grewe J. Simultaneous spike-time locking to multiple frequencies. J Neurophysiol 2020; 123:2355-2372. [PMID: 32374223 DOI: 10.1152/jn.00615.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Locking of neural firing is ubiquitously observed in the brain and occurs when neurons fire at a particular phase or in synchronization with an external signal. Here we study in detail the locking of single neurons to multiple distinct frequencies at the example of p-type electroreceptor afferents in the electrosensory system of the weakly electric fish Apteronotus leptorhynchus (brown ghost knifefish). We find that electrosensory afferents and pyramidal cells in the electrosensory lateral line lobe (ELL) lock to multiple frequencies, including the electric organ discharge (EOD) frequency, beat, and stimulus itself. We identify key elements necessary for locking to multiple frequencies, study its limits, and provide concise mathematical models reproducing our main findings. Our findings provide another example of how rate and temporal codes can coexist and complement each other in single neurons and demonstrate that sensory coding in p-type electroreceptor afferents provides a much richer representation of the sensory environment than commonly assumed. Since the underlying mechanisms are not specific to the electrosensory system, our results could provide the basis for studying multiple frequency locking in other systems.NEW & NOTEWORTHY Locking of neuronal spikes to external and internal signals is a ubiquitous neurophysiological mechanism that has been extensively studied in several brain areas and species. Using experimental data from the electrosensory system and concise mathematical models, we analyze how a single neuron can simultaneously lock to multiple frequencies. Our findings demonstrate how temporal and rate codes can complement each other and lead to rich neuronal representations of sensory signals.
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Affiliation(s)
- Fabian H Sinz
- Institute for Bioinformatics and Medical Informatics, University Tübingen, Tübingen, Germany.,Bernstein Center for Computational Neuroscience, Tübingen, Germany.,Center for Neuroscience and Artificial Intelligence, Baylor College of Medicine, Houston, Texas
| | - Carolin Sachgau
- Department of Neuroethology, Institute for Neuroscience, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Jörg Henninger
- Charité, Medical School of Humboldt University, Berlin, Germany
| | - Jan Benda
- Department of Neuroethology, Institute for Neuroscience, Eberhard Karls University Tübingen, Tübingen, Germany.,Bernstein Center for Computational Neuroscience, Tübingen, Germany
| | - Jan Grewe
- Department of Neuroethology, Institute for Neuroscience, Eberhard Karls University Tübingen, Tübingen, Germany
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Heeringa AN, Zhang L, Ashida G, Beutelmann R, Steenken F, Köppl C. Temporal Coding of Single Auditory Nerve Fibers Is Not Degraded in Aging Gerbils. J Neurosci 2020. [PMID: 31719164 DOI: 10.1101/2020.02.10.942011] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023] Open
Abstract
People suffering from age-related hearing loss typically present with deficits in temporal processing tasks. Temporal processing deficits have also been shown in single-unit studies at the level of the auditory brainstem, midbrain, and cortex of aged animals. In this study, we explored whether temporal coding is already affected at the level of the input to the central auditory system. Single-unit auditory nerve fiber recordings were obtained from 41 Mongolian gerbils of either sex, divided between young, middle-aged, and old gerbils. Temporal coding quality was evaluated as vector strength in response to tones at best frequency, and by constructing shuffled and cross-stimulus autocorrelograms, and reverse correlations, from responses to 1 s noise bursts at 10-30 dB sensation level (dB above threshold). At comparable sensation levels, all measures showed that temporal coding was not altered in auditory nerve fibers of aging gerbils. Furthermore, both temporal fine structure and envelope coding remained unaffected. However, spontaneous rates were decreased in aging gerbils. Importantly, despite elevated pure tone thresholds, the frequency tuning of auditory nerve fibers was not affected. These results suggest that age-related temporal coding deficits arise more centrally, possibly due to a loss of auditory nerve fibers (or their peripheral synapses) but not due to qualitative changes in the responses of remaining auditory nerve fibers. The reduced spontaneous rate and elevated thresholds, but normal frequency tuning, of aged auditory nerve fibers can be explained by the well known reduction of endocochlear potential due to strial dysfunction in aged gerbils.SIGNIFICANCE STATEMENT As our society ages, age-related hearing deficits become ever more prevalent. Apart from decreased hearing sensitivity, elderly people often suffer from a reduced ability to communicate in daily settings, which is thought to be caused by known age-related deficits in auditory temporal processing. The current study demonstrated, using several different stimuli and analysis techniques, that these putative temporal processing deficits are not apparent in responses of single-unit auditory nerve fibers of quiet-aged gerbils. This suggests that age-related temporal processing deficits may develop more central to the auditory nerve, possibly due to a reduced population of active auditory nerve fibers, which will be of importance for the development of treatments for age-related hearing disorders.
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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
| | - Lichun Zhang
- 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
| | - Go Ashida
- 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
| | - Rainer Beutelmann
- 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
| | - Friederike Steenken
- 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
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Neuronal population model of globular bushy cells covering unit-to-unit variability. PLoS Comput Biol 2019; 15:e1007563. [PMID: 31881018 PMCID: PMC6934273 DOI: 10.1371/journal.pcbi.1007563] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 11/25/2019] [Indexed: 01/02/2023] Open
Abstract
Computations of acoustic information along the central auditory pathways start in the cochlear nucleus. Bushy cells in the anteroventral cochlear nucleus, which innervate monaural and binaural stations in the superior olivary complex, process and transfer temporal cues relevant for sound localization. These cells are categorized into two groups: spherical and globular bushy cells (SBCs/GBCs). Spontaneous rates of GBCs innervated by multiple auditory nerve (AN) fibers are generally lower than those of SBCs that receive a small number of large AN synapses. In response to low-frequency tonal stimulation, both types of bushy cells show improved phase-locking and entrainment compared to AN fibers. When driven by high-frequency tones, GBCs show primary-like-with-notch or onset-L peristimulus time histograms and relatively irregular spiking. However, previous in vivo physiological studies of bushy cells also found considerable unit-to-unit variability in these response patterns. Here we present a population of models that can simulate the observed variation in GBCs. We used a simple coincidence detection model with an adaptive threshold and systematically varied its six parameters. Out of 567000 parameter combinations tested, 7520 primary-like-with-notch models and 4094 onset-L models were selected that satisfied a set of physiological criteria for a GBC unit. Analyses of the model parameters and output measures revealed that the parameters of the accepted model population are weakly correlated with each other to retain major GBC properties, and that the output spiking patterns of the model are affected by a combination of multiple parameters. Simulations of frequency-dependent temporal properties of the model GBCs showed a reasonable fit to empirical data, supporting the validity of our population modeling. The computational simplicity and efficiency of the model structure makes our approach suitable for future large-scale simulations of binaural information processing that may involve thousands of GBC units. In the auditory system, specialized neuronal circuits process various types of acoustic information. A group of neurons, called globular bushy cells (GBCs), faithfully transfer timing information of acoustic signals to their downstream neurons responsible for the perception of sound location. Previous physiological studies found representative activity patterns of GBCs, but with substantial individual variations among them. In this study, we present a population of models, instead of creating one best model, to account for the observed variations of GBCs. We varied all six parameters of a simple auditory neuron model and selected the combinations of parameters that led to acceptable activity patterns of GBCs. In total, we tested more than half a million combinations and accepted ~11600 GBC models. Temporal spiking patterns of real GBCs depend on the sound frequency, and our model population was able to replicate this trend. The model used here is computationally efficient and can thus serve as a building block for future large-scale simulations of auditory information processing.
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14
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Kuenzel T. Modulatory influences on time-coding neurons in the ventral cochlear nucleus. Hear Res 2019; 384:107824. [DOI: 10.1016/j.heares.2019.107824] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 09/10/2019] [Accepted: 10/14/2019] [Indexed: 02/07/2023]
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15
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Temporal Coding of Single Auditory Nerve Fibers Is Not Degraded in Aging Gerbils. J Neurosci 2019; 40:343-354. [PMID: 31719164 DOI: 10.1523/jneurosci.2784-18.2019] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 10/25/2019] [Accepted: 11/04/2019] [Indexed: 02/03/2023] Open
Abstract
People suffering from age-related hearing loss typically present with deficits in temporal processing tasks. Temporal processing deficits have also been shown in single-unit studies at the level of the auditory brainstem, midbrain, and cortex of aged animals. In this study, we explored whether temporal coding is already affected at the level of the input to the central auditory system. Single-unit auditory nerve fiber recordings were obtained from 41 Mongolian gerbils of either sex, divided between young, middle-aged, and old gerbils. Temporal coding quality was evaluated as vector strength in response to tones at best frequency, and by constructing shuffled and cross-stimulus autocorrelograms, and reverse correlations, from responses to 1 s noise bursts at 10-30 dB sensation level (dB above threshold). At comparable sensation levels, all measures showed that temporal coding was not altered in auditory nerve fibers of aging gerbils. Furthermore, both temporal fine structure and envelope coding remained unaffected. However, spontaneous rates were decreased in aging gerbils. Importantly, despite elevated pure tone thresholds, the frequency tuning of auditory nerve fibers was not affected. These results suggest that age-related temporal coding deficits arise more centrally, possibly due to a loss of auditory nerve fibers (or their peripheral synapses) but not due to qualitative changes in the responses of remaining auditory nerve fibers. The reduced spontaneous rate and elevated thresholds, but normal frequency tuning, of aged auditory nerve fibers can be explained by the well known reduction of endocochlear potential due to strial dysfunction in aged gerbils.SIGNIFICANCE STATEMENT As our society ages, age-related hearing deficits become ever more prevalent. Apart from decreased hearing sensitivity, elderly people often suffer from a reduced ability to communicate in daily settings, which is thought to be caused by known age-related deficits in auditory temporal processing. The current study demonstrated, using several different stimuli and analysis techniques, that these putative temporal processing deficits are not apparent in responses of single-unit auditory nerve fibers of quiet-aged gerbils. This suggests that age-related temporal processing deficits may develop more central to the auditory nerve, possibly due to a reduced population of active auditory nerve fibers, which will be of importance for the development of treatments for age-related hearing disorders.
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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]
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17
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Joris PX, van der Heijden M. Early Binaural Hearing: The Comparison of Temporal Differences at the Two Ears. Annu Rev Neurosci 2019; 42:433-457. [DOI: 10.1146/annurev-neuro-080317-061925] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many mammals, including humans, are exquisitely sensitive to tiny time differences between sounds at the two ears. These interaural time differences are an important source of information for sound detection, for sound localization in space, and for environmental awareness. Two brainstem circuits are involved in the initial temporal comparisons between the ears, centered on the medial and lateral superior olive. Cells in these nuclei, as well as their afferents, display a large number of striking physiological and anatomical specializations to enable submillisecond sensitivity. As such, they provide an important model system to study temporal processing in the central nervous system. We review the progress that has been made in characterizing these primary binaural circuits as well as the variety of mechanisms that have been proposed to underlie their function.
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Affiliation(s)
- Philip X. Joris
- Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium
| | - Marcel van der Heijden
- Department of Neuroscience, Erasmus University Medical Center, 3000 CA Rotterdam, Netherlands
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Higgins I, Stringer S, Schnupp J. A Computational Account of the Role of Cochlear Nucleus and Inferior Colliculus in Stabilizing Auditory Nerve Firing for Auditory Category Learning. Neural Comput 2018; 30:1801-1829. [PMID: 29652586 DOI: 10.1162/neco_a_01085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
It is well known that auditory nerve (AN) fibers overcome bandwidth limitations through the volley principle, a form of multiplexing. What is less well known is that the volley principle introduces a degree of unpredictability into AN neural firing patterns that may be affecting even simple stimulus categorization learning. We use a physiologically grounded, unsupervised spiking neural network model of the auditory brain with spike time dependent plasticity learning to demonstrate that plastic auditory cortex is unable to learn even simple auditory object categories when exposed to the raw AN firing input without subcortical preprocessing. We then demonstrate the importance of nonplastic subcortical preprocessing within the cochlear nucleus and the inferior colliculus for stabilizing and denoising AN responses. Such preprocessing enables the plastic auditory cortex to learn efficient robust representations of the auditory object categories. The biological realism of our model makes it suitable for generating neurophysiologically testable hypotheses.
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Affiliation(s)
- Irina Higgins
- Department of Experimental Psychology, University of Oxford, Oxford, OX2 6GG, U.K.
| | - Simon Stringer
- Department of Experimental Psychology, University of Oxford, Oxford, OX2 6GG, U.K.
| | - Jan Schnupp
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, U.K.
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Wei L, Karino S, Verschooten E, Joris PX. Enhancement of phase-locking in rodents. I. An axonal recording study in gerbil. J Neurophysiol 2017; 118:2009-2023. [PMID: 28701535 DOI: 10.1152/jn.00194.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 07/10/2017] [Accepted: 07/11/2017] [Indexed: 11/22/2022] Open
Abstract
The trapezoid body (TB) contains axons of neurons in the anteroventral cochlear nucleus projecting to monaural and binaural nuclei in the superior olivary complex (SOC). Characterization of these monaural inputs is important for the interpretation of response properties of SOC neurons. In particular, understanding of the sensitivity to interaural time differences (ITDs) in neurons of the medial and lateral superior olive requires knowledge of the temporal firing properties of the monaural excitatory and inhibitory inputs to these neurons. In recent years, studies of ITD sensitivity of SOC neurons have made increasing use of small animal models with good low-frequency hearing, particularly the gerbil. We presented stimuli as used in binaural studies to monaural neurons in the TB and studied their temporal coding. We found that general trends as have been described in the cat are present in gerbil, but with some important differences. Phase-locking to pure tones tends to be higher in TB axons and in neurons of the medial nucleus of the TB (MNTB) than in the auditory nerve for neurons with characteristic frequencies (CFs) below 1 kHz, but this enhancement is quantitatively more modest than in cat. Stronger enhancement is common when TB neurons are stimulated at low frequencies below CF. It is rare for TB neurons in gerbil to entrain to low-frequency stimuli, i.e., to discharge a well-timed spike on every stimulus cycle. Also, complex phase-locking behavior, with multiple modes of increased firing probability per stimulus cycle, is common in response to low frequencies below CF.NEW & NOTEWORTHY Phase-locking is an important property of neurons in the early auditory pathway: it is critical for the sensitivity to time differences between the two ears enabling spatial hearing. Studies in cat have shown an improvement in phase-locking from the peripheral to the central auditory nervous system. We recorded from axons in an output tract of the cochlear nucleus and show that a similar but more limited form of temporal enhancement is present in gerbil.
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Affiliation(s)
- Liting Wei
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Shotaro Karino
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Eric Verschooten
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Philip X Joris
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
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Input timing for spatial processing is precisely tuned via constant synaptic delays and myelination patterns in the auditory brainstem. Proc Natl Acad Sci U S A 2017; 114:E4851-E4858. [PMID: 28559325 DOI: 10.1073/pnas.1702290114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Precise timing of synaptic inputs is a fundamental principle of neural circuit processing. The temporal precision of postsynaptic input integration is known to vary with the computational requirements of a circuit, yet how the timing of action potentials is tuned presynaptically to match these processing demands is not well understood. In particular, action potential timing is shaped by the axonal conduction velocity and the duration of synaptic transmission delays within a pathway. However, it is not known to what extent these factors are adapted to the functional constraints of the respective circuit. Here, we report the finding of activity-invariant synaptic transmission delays as a functional adaptation for input timing adjustment in a brainstem sound localization circuit. We compared axonal and synaptic properties of the same pathway between two species with dissimilar timing requirements (gerbil and mouse): In gerbils (like humans), neuronal processing of sound source location requires exceptionally high input precision in the range of microseconds, but not in mice. Activity-invariant synaptic transmission and conduction delays were present exclusively in fast conducting axons of gerbils that also exhibited unusual structural adaptations in axon myelination for increased conduction velocity. In contrast, synaptic transmission delays in mice varied depending on activity levels, and axonal myelination and conduction velocity exhibited no adaptations. Thus, the specializations in gerbils and their absence in mice suggest an optimization of axonal and synaptic properties to the specific demands of sound localization. These findings significantly advance our understanding of structural and functional adaptations for circuit processing.
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Rudnicki M, Hemmert W. High Entrainment Constrains Synaptic Depression Levels of an In vivo Globular Bushy Cell Model. Front Comput Neurosci 2017; 11:16. [PMID: 28373839 PMCID: PMC5357671 DOI: 10.3389/fncom.2017.00016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 03/02/2017] [Indexed: 12/15/2022] Open
Abstract
Globular bushy cells (GBCs) located in the ventral cochlear nucleus are an essential part of the sound localization pathway in the mammalian auditory system. They receive inputs directly from the auditory nerve and are particularly sensitive to temporal cues due to their synaptic and membrane specializations. GBCs act as coincidence detectors for incoming spikes through large synapses-endbulbs of Held-which connect to their soma. Since endbulbs of Held are an integral part of the auditory information conveying and processing pathway, they were extensively studied. Virtually all in vitro studies showed large synaptic depression, but on the other hand a few in vivo studies showed relatively small depression. It is also still not well understood how synaptic properties functionally influence firing properties of GBCs. Here we show how different levels of synaptic depression shape firing properties of GBCs in in vivo-like conditions using computer simulations. We analyzed how an interplay of synaptic depression (0-70%) and the number of auditory nerve fiber inputs (10-70) contributes to the variability of the experimental data from previous studies. We predict that the majority of synapses of GBCs with high characteristic frequencies (CF > 500 Hz) have a rate dependent depression of less than 20%. GBCs with lower CF (<500 Hz) work also with strong depressing synapses (up to 50% or more). We also showed that synapses explicitly fitted to in vitro experiments with paired-pulse stimuli did not operate properly in in vivo-like conditions and required further extension to capture the differences between in vitro and in vivo experimental conditions. Overall, this study helps to understand how synaptic properties shape temporal processing in the auditory system. It also integrates, compares, and reconciles results of various experimental studies.
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Affiliation(s)
- Marek Rudnicki
- Bio-Inspired Information Processing, Technische Universität München München, Germany
| | - Werner Hemmert
- Bio-Inspired Information Processing, Technische Universität München München, Germany
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22
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Synchronous spikes are necessary but not sufficient for a synchrony code in populations of spiking neurons. Proc Natl Acad Sci U S A 2017; 114:E1977-E1985. [PMID: 28202729 DOI: 10.1073/pnas.1615561114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synchronous activity in populations of neurons potentially encodes special stimulus features. Selective readout of either synchronous or asynchronous activity allows formation of two streams of information processing. Theoretical work predicts that such a synchrony code is a fundamental feature of populations of spiking neurons if they operate in specific noise and stimulus regimes. Here we experimentally test the theoretical predictions by quantifying and comparing neuronal response properties in tuberous and ampullary electroreceptor afferents of the weakly electric fish Apteronotus leptorhynchus These related systems show similar levels of synchronous activity, but only in the more irregularly firing tuberous afferents a synchrony code is established, whereas in the more regularly firing ampullary afferents it is not. The mere existence of synchronous activity is thus not sufficient for a synchrony code. Single-cell features such as the irregularity of spiking and the frequency dependence of the neuron's transfer function determine whether synchronous spikes possess a distinct meaning for the encoding of time-dependent signals.
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Huguet G, Meng X, Rinzel J. Phasic Firing and Coincidence Detection by Subthreshold Negative Feedback: Divisive or Subtractive or, Better, Both. Front Comput Neurosci 2017; 11:3. [PMID: 28210218 PMCID: PMC5288357 DOI: 10.3389/fncom.2017.00003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 01/16/2017] [Indexed: 11/26/2022] Open
Abstract
Phasic neurons typically fire only for a fast-rising input, say at the onset of a step current, but not for steady or slow inputs, a property associated with type III excitability. Phasic neurons can show extraordinary temporal precision for phase locking and coincidence detection. Exemplars are found in the auditory brain stem where precise timing is used in sound localization. Phasicness at the cellular level arises from a dynamic, voltage-gated, negative feedback that can be recruited subthreshold, preventing the neuron from reaching spike threshold if the voltage does not rise fast enough. We consider two mechanisms for phasicness: a low threshold potassium current (subtractive mechanism) and a sodium current with subthreshold inactivation (divisive mechanism). We develop and analyze three reduced models with either divisive or subtractive mechanisms or both to gain insight into the dynamical mechanisms for the potentially high temporal precision of type III-excitable neurons. We compare their firing properties and performance for a range of stimuli. The models have characteristic non-monotonic input-output relations, firing rate vs. input intensity, for either stochastic current injection or Poisson-timed excitatory synaptic conductance trains. We assess performance according to precision of phase-locking and coincidence detection by the models' responses to repetitive packets of unitary excitatory synaptic inputs with more or less temporal coherence. We find that each mechanism contributes features but best performance is attained if both are present. The subtractive mechanism confers extraordinary precision for phase locking and coincidence detection but only within a restricted parameter range when the divisive mechanism of sodium inactivation is inoperative. The divisive mechanism guarantees robustness of phasic properties, without compromising excitability, although with somewhat less precision. Finally, we demonstrate that brief transient inhibition if properly timed can enhance the reliability of firing.
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Affiliation(s)
- Gemma Huguet
- Departament de Matemàtiques, Universitat Politècnica de Catalunya Barcelona, Spain
| | - Xiangying Meng
- Biology Department, University of Maryland College Park, MD, USA
| | - John Rinzel
- Center for Neural Science, New York UniversityNew York, NY, USA; Courant Institute of Mathematical Sciences, New York UniversityNew York, NY, USA
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Entracking as a Brain Stem Code for Pitch: The Butte Hypothesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016. [PMID: 27080675 DOI: 10.1007/978-3-319-25474-6_36] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2024]
Abstract
The basic nature of pitch is much debated. A robust code for pitch exists in the auditory nerve in the form of an across-fiber pooled interspike interval (ISI) distribution, which resembles the stimulus autocorrelation. An unsolved question is how this representation can be "read out" by the brain. A new view is proposed in which a known brain-stem property plays a key role in the coding of periodicity, which I refer to as "entracking", a contraction of "entrained phase-locking". It is proposed that a scalar rather than vector code of periodicity exists by virtue of coincidence detectors that code the dominant ISI directly into spike rate through entracking. Perfect entracking means that a neuron fires one spike per stimulus-waveform repetition period, so that firing rate equals the repetition frequency. Key properties are invariance with SPL and generalization across stimuli. The main limitation in this code is the upper limit of firing (~ 500 Hz). It is proposed that entracking provides a periodicity tag which is superimposed on a tonotopic analysis: at low SPLs and fundamental frequencies > 500 Hz, a spectral or place mechanism codes for pitch. With increasing SPL the place code degrades but entracking improves and first occurs in neurons with low thresholds for the spectral components present. The prediction is that populations of entracking neurons, extended across characteristic frequency, form plateaus ("buttes") of firing rate tied to periodicity.
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25
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Ito T, Bishop DC, Oliver DL. Functional organization of the local circuit in the inferior colliculus. Anat Sci Int 2015; 91:22-34. [PMID: 26497006 DOI: 10.1007/s12565-015-0308-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Accepted: 10/05/2015] [Indexed: 01/12/2023]
Abstract
The inferior colliculus (IC) is the first integration center of the auditory system. After the transformation of sound to neural signals in the cochlea, the signals are analyzed by brainstem auditory nuclei that, in turn, transmit this information to the IC. However, the neural circuitry that underlies this integration is unclear. This review consists of two parts: one is about the cell type which is likely to integrate sound information, and the other is about a technique which is useful for studying local circuitry. Large GABAergic (LG) neurons receive dense excitatory axosomatic terminals that originate from the lower brainstem auditory nuclei as well as local IC neurons. Dozens of axons coming from both local and lower brainstem neurons converge on a single LG soma. Excitatory neurons in IC can innervate many nearby LG somata in the same fibrodendritic lamina. The combination of local and ascending inputs is well suited for auditory integration. LG neurons are one of the main sources of inhibition in the medial geniculate body (MGB). LG neurons and the tectothalamic inhibitory system are present in a wide variety of mammalian species. This suggests that the circuitry of excitatory and inhibitory tectothalamic projections may have evolved earlier than GABAergic interneurons in the MGB, which are found in fewer species. Cellular-level functional imaging provides both morphological and functional information about local circuitry. In the last part of this review, we describe an in vivo calcium imaging study that sheds light on the functional organization of the IC.
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Affiliation(s)
- Tetsufumi Ito
- Department of Anatomy, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, 910-1193, Japan. .,Research and Education Program for Life Science, University of Fukui, Fukui, Fukui, 910-8507, Japan.
| | - Deborah C Bishop
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, 06030-3401, USA
| | - Douglas L Oliver
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, 06030-3401, USA
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26
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Rubio ME, Nagy JI. Connexin36 expression in major centers of the auditory system in the CNS of mouse and rat: Evidence for neurons forming purely electrical synapses and morphologically mixed synapses. Neuroscience 2015; 303:604-29. [PMID: 26188286 PMCID: PMC4576740 DOI: 10.1016/j.neuroscience.2015.07.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/08/2015] [Accepted: 07/09/2015] [Indexed: 10/23/2022]
Abstract
Electrical synapses formed by gap junctions composed of connexin36 (Cx36) are widely distributed in the mammalian central nervous system (CNS). Here, we used immunofluorescence methods to document the expression of Cx36 in the cochlear nucleus and in various structures of the auditory pathway of rat and mouse. Labeling of Cx36 visualized exclusively as Cx36-puncta was densely distributed primarily on the somata and initial dendrites of neuronal populations in the ventral cochlear nucleus, and was abundant in superficial layers of the dorsal cochlear nucleus. Other auditory centers displaying Cx36-puncta included the medial nucleus of the trapezoid body (MNTB), regions surrounding the lateral superior olivary nucleus, the dorsal nucleus of the medial lemniscus, the nucleus sagulum, all subnuclei of the inferior colliculus, and the auditory cerebral cortex. In EGFP-Cx36 transgenic mice, EGFP reporter was detected in neurons located in each of auditory centers that harbored Cx36-puncta. In the ventral cochlear nuclei and the MNTB, many neuronal somata were heavily innervated by nerve terminals containing vesicular glutamate transporter-1 (vglut1) and Cx36 was frequently localized at these terminals. Cochlear ablation caused a near total depletion of vglut1-positive terminals in the ventral cochlear nuclei, with a commensurate loss of labeling for Cx36 around most neuronal somata, but preserved Cx36-puncta at somatic neuronal appositions. The results suggest that electrical synapses formed by Cx36-containing gap junctions occur in most of the widely distributed centers of the auditory system. Further, it appears that morphologically mixed chemical/electrical synapses formed by nerve terminals are abundant in the ventral cochlear nucleus, including those at endbulbs of Held formed by cochlear primary afferent fibers, and those at calyx of Held synapses on MNTB neurons.
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Affiliation(s)
- M E Rubio
- Departments of Otolaryngology and Neurobiology, University of Pittsburgh Medical School, Pittsburgh, USA
| | - J I Nagy
- Department of Physiology and Pathophysiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
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Keine C, Rübsamen R. Inhibition shapes acoustic responsiveness in spherical bushy cells. J Neurosci 2015; 35:8579-92. [PMID: 26041924 PMCID: PMC6605330 DOI: 10.1523/jneurosci.0133-15.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 04/23/2015] [Accepted: 04/23/2015] [Indexed: 12/24/2022] Open
Abstract
Signal processing in the auditory brainstem is based on an interaction of neuronal excitation and inhibition. To date, we have incomplete knowledge of how the dynamic interplay of both contributes to the processing power and temporal characteristics of signal coding. The spherical bushy cells (SBCs) of the anteroventral cochlear nucleus (AVCN) receive their primary excitatory input through auditory nerve fibers via large, axosomatic synaptic terminals called the endbulbs of Held and by additional, acoustically driven inhibitory inputs. SBCs provide the input to downstream nuclei of the brainstem sound source localization circuitry, such as the medial and lateral superior olive, which rely on temporal precise inputs. In this study, we used juxtacellular recordings in anesthetized Mongolian gerbils to assess the effect of acoustically evoked inhibition on the SBCs input-output function and on temporal precision of SBC spiking. Acoustically evoked inhibition proved to be strong enough to suppress action potentials (APs) of SBCs in a stimulus-dependent manner. Inhibition shows slow onset and offset dynamics and increasing strength at higher sound intensities. In addition, inhibition decreases the rising slope of the EPSP and prolongs the EPSP-to-AP transition time. Both effects can be mimicked by iontophoretic application of glycine. Inhibition also improves phase locking of SBC APs to low-frequency tones by acting as a gain control to suppress poorly timed EPSPs from generating postsynaptic APs to maintain precise SBC spiking across sound intensities. The present data suggest that inhibition substantially contributes to the processing power of second-order neurons in the ascending auditory system.
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Affiliation(s)
- Christian Keine
- Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, D-04103 Leipzig, Germany
| | - Rudolf Rübsamen
- Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, D-04103 Leipzig, Germany
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28
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Ito T, Hioki H, Sohn J, Okamoto S, Kaneko T, Iino S, Oliver DL. Convergence of Lemniscal and Local Excitatory Inputs on Large GABAergic Tectothalamic Neurons. J Comp Neurol 2015; 523:2277-96. [PMID: 25879870 DOI: 10.1002/cne.23789] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 04/07/2015] [Accepted: 04/08/2015] [Indexed: 12/11/2022]
Abstract
Large GABAergic (LG) neurons form a distinct cell type in the inferior colliculus (IC), identified by the presence of dense VGLUT2-containing axosomatic terminals. Although some of the axosomatic terminals originate from local and commissural IC neurons, it has been unclear whether LG neurons also receive axosomatic inputs from the lower auditory brainstem nuclei, i.e., cochlear nuclei (CN), superior olivary complex (SOC), and nuclei of the lateral lemniscus (NLL). In this study we injected recombinant viral tracers that force infected cells to express GFP in a Golgi-like manner into the lower auditory brainstem nuclei to determine whether these nuclei directly innervate LG cell somata. Labeled axons from CN, SOC, and NLL terminated as excitatory axosomatic endings, identified by colabeling of GFP and VGLUT2, on single LG neurons in the IC. Each excitatory axon made only a few axosomatic contacts on each LG neuron. Inputs to a single LG cell are unlikely to be from a single brainstem nucleus, since lesions of individual nuclei failed to eliminate most VGLUT2-positive terminals on the LG neurons. The estimated number of inputs on a single LG cell body was almost proportional to the surface area of the cell body. Double injections of different viruses into IC and a brainstem nucleus showed that LG neurons received inputs from both. These results demonstrated that both ascending and intrinsic sources converge on the LG somata to control inhibitory tectothalamic projections.
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Affiliation(s)
- Tetsufumi Ito
- Department of Anatomy, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.,Research and Education Program for Life Science, University of Fukui, Fukui, 910-8507, Japan
| | - Hiroyuki Hioki
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Jaerin Sohn
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan.,Research Fellow of Japan Society for the Promotion of Science (JSPS), 5-3-1 Koujimachi, Tokyo, 102-8472, Japan
| | - Shinichiro Okamoto
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Takeshi Kaneko
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Satoshi Iino
- Department of Anatomy, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.,Research and Education Program for Life Science, University of Fukui, Fukui, 910-8507, Japan
| | - Douglas L Oliver
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, 06030-3401, USA
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29
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Dynamic fidelity control to the central auditory system: synergistic glycine/GABAergic inhibition in the cochlear nucleus. J Neurosci 2014; 34:11604-20. [PMID: 25164657 DOI: 10.1523/jneurosci.0719-14.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
GABA and glycine are the major inhibitory transmitters that attune neuronal activity in the CNS of mammals. The respective transmitters are mostly spatially separated, that is, synaptic inhibition in the forebrain areas is mediated by GABA, whereas glycine is predominantly used in the brainstem. Accordingly, inhibition in auditory brainstem circuits is largely mediated by glycine, but there are few auditory synapses using both transmitters in maturity. Little is known about physiological advantages of such a two-transmitter inhibitory mechanism. We explored the benefit of engaging both glycine and GABA with inhibition at the endbulb of Held-spherical bushy cell synapse in the auditory brainstem of juvenile Mongolian gerbils. This model synapse enables selective in vivo activation of excitatory and inhibitory neuronal inputs through systemic sound stimulation and precise analysis of the input (endbulb of Held) output (spherical bushy cell) function. The combination of in vivo and slice electrophysiology revealed that the dynamic AP inhibition in spherical bushy cells closely matches the inhibitory conductance profile determined by the glycine-R and GABAA-R. The slow and potent glycinergic component dominates the inhibitory conductance, thereby primarily accounting for its high-pass filter properties. GABAergic transmission enhances the inhibitory strength and shapes its duration in an activity-dependent manner, thus increasing the inhibitory potency to suppress the excitation through the endbulb of Held. Finally, in silico modeling provides a strong link between in vivo and slice data by simulating the interactions between the endbulb- and the synergistic glycine-GABA-conductances during in vivo-like spontaneous and sound evoked activities.
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30
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Franken TP, Bremen P, Joris PX. Coincidence detection in the medial superior olive: mechanistic implications of an analysis of input spiking patterns. Front Neural Circuits 2014; 8:42. [PMID: 24822037 PMCID: PMC4013490 DOI: 10.3389/fncir.2014.00042] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 04/07/2014] [Indexed: 11/24/2022] Open
Abstract
Coincidence detection by binaural neurons in the medial superior olive underlies sensitivity to interaural time difference (ITD) and interaural correlation (ρ). It is unclear whether this process is akin to a counting of individual coinciding spikes, or rather to a correlation of membrane potential waveforms resulting from converging inputs from each side. We analyzed spike trains of axons of the cat trapezoid body (TB) and auditory nerve (AN) in a binaural coincidence scheme. ITD was studied by delaying "ipsi-" vs. "contralateral" inputs; ρ was studied by using responses to different noises. We varied the number of inputs; the monaural and binaural threshold and the coincidence window duration. We examined physiological plausibility of output "spike trains" by comparing their rate and tuning to ITD and ρ to those of binaural cells. We found that multiple inputs are required to obtain a plausible output spike rate. In contrast to previous suggestions, monaural threshold almost invariably needed to exceed binaural threshold. Elevation of the binaural threshold to values larger than 2 spikes caused a drastic decrease in rate for a short coincidence window. Longer coincidence windows allowed a lower number of inputs and higher binaural thresholds, but decreased the depth of modulation. Compared to AN fibers, TB fibers allowed higher output spike rates for a low number of inputs, but also generated more monaural coincidences. We conclude that, within the parameter space explored, the temporal patterns of monaural fibers require convergence of multiple inputs to achieve physiological binaural spike rates; that monaural coincidences have to be suppressed relative to binaural ones; and that the neuron has to be sensitive to single binaural coincidences of spikes, for a number of excitatory inputs per side of 10 or less. These findings suggest that the fundamental operation in the mammalian binaural circuit is coincidence counting of single binaural input spikes.
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Affiliation(s)
| | | | - Philip X. Joris
- Laboratory of Auditory Neurophysiology, Department of Neurosciences, KU LeuvenLeuven, Belgium
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31
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McLaughlin M, Franken TP, van der Heijden M, Joris PX. The interaural time difference pathway: a comparison of spectral bandwidth and correlation sensitivity at three anatomical levels. J Assoc Res Otolaryngol 2014; 15:203-18. [PMID: 24402167 DOI: 10.1007/s10162-013-0436-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 12/20/2013] [Indexed: 11/25/2022] Open
Abstract
Temporal differences between the two ears are critical for spatial hearing. They can be described along axes of interaural time difference (ITD) and interaural correlation, and their processing starts in the brainstem with the convergence of monaural pathways which are tuned in frequency and which carry temporal information. In previous studies, we examined the bandwidth (BW) of frequency tuning at two stages: the auditory nerve (AN) and inferior colliculus (IC), and showed that BW depends on characteristic frequency (CF) but that there is no difference in the mean BW of these two structures when measured in a binaural, temporal framework. This suggested that there is little frequency convergence in the ITD pathway between AN and IC and that frequency selectivity determined by the cochlear filter is preserved up to the IC. Unexpectedly, we found that AN and IC neurons can be similar in CF and BW, yet responses to changes in interaural correlation in the IC were different than expected from coincidence patterns ("pseudo-binaural" responses) in the AN. To better understand this, we here examine the responses of bushy cells, which provide monaural inputs to binaural neurons. Using broadband noise, we measured BW and correlation sensitivity in the cat trapezoid body (TB), which contains the axons of bushy cells. This allowed us to compare these two metrics at three stages in the ITD pathway. We found that BWs in the TB are similar to those in the AN and IC. However, TB neurons were found to be more sensitive to changes in stimulus correlation than AN or IC neurons. This is consistent with findings that show that TB fibers are more temporally precise than AN fibers, but is surprising because it suggests that the temporal information available monaurally is not fully exploited binaurally.
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Affiliation(s)
- Myles McLaughlin
- Laboratory of Auditory Neurophysiology, Medical School, K.U. Leuven, Campus Gasthuisberg O&N 2, Herestraat 49 bus 1021, 3000, Leuven, Belgium,
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32
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Ashida G, Funabiki K, Carr CE. Theoretical foundations of the sound analog membrane potential that underlies coincidence detection in the barn owl. Front Comput Neurosci 2013; 7:151. [PMID: 24265616 PMCID: PMC3821005 DOI: 10.3389/fncom.2013.00151] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 10/11/2013] [Indexed: 11/15/2022] Open
Abstract
A wide variety of neurons encode temporal information via phase-locked spikes. In the avian auditory brainstem, neurons in the cochlear nucleus magnocellularis (NM) send phase-locked synaptic inputs to coincidence detector neurons in the nucleus laminaris (NL) that mediate sound localization. Previous modeling studies suggested that converging phase-locked synaptic inputs may give rise to a periodic oscillation in the membrane potential of their target neuron. Recent physiological recordings in vivo revealed that owl NL neurons changed their spike rates almost linearly with the amplitude of this oscillatory potential. The oscillatory potential was termed the sound analog potential, because of its resemblance to the waveform of the stimulus tone. The amplitude of the sound analog potential recorded in NL varied systematically with the interaural time difference (ITD), which is one of the most important cues for sound localization. In order to investigate the mechanisms underlying ITD computation in the NM-NL circuit, we provide detailed theoretical descriptions of how phase-locked inputs form oscillating membrane potentials. We derive analytical expressions that relate presynaptic, synaptic, and postsynaptic factors to the signal and noise components of the oscillation in both the synaptic conductance and the membrane potential. Numerical simulations demonstrate the validity of the theoretical formulations for the entire frequency ranges tested (1–8 kHz) and potential effects of higher harmonics on NL neurons with low best frequencies (<2 kHz).
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Affiliation(s)
- Go Ashida
- Department of Biology, University of Maryland College Park, MD, USA
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33
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Fontaine B, Benichoux V, Joris PX, Brette R. Predicting spike timing in highly synchronous auditory neurons at different sound levels. J Neurophysiol 2013; 110:1672-88. [PMID: 23864375 PMCID: PMC4042421 DOI: 10.1152/jn.00051.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 07/15/2013] [Indexed: 11/22/2022] Open
Abstract
A challenge for sensory systems is to encode natural signals that vary in amplitude by orders of magnitude. The spike trains of neurons in the auditory system must represent the fine temporal structure of sounds despite a tremendous variation in sound level in natural environments. It has been shown in vitro that the transformation from dynamic signals into precise spike trains can be accurately captured by simple integrate-and-fire models. In this work, we show that the in vivo responses of cochlear nucleus bushy cells to sounds across a wide range of levels can be precisely predicted by deterministic integrate-and-fire models with adaptive spike threshold. Our model can predict both the spike timings and the firing rate in response to novel sounds, across a large input level range. A noisy version of the model accounts for the statistical structure of spike trains, including the reliability and temporal precision of responses. Spike threshold adaptation was critical to ensure that predictions remain accurate at different levels. These results confirm that simple integrate-and-fire models provide an accurate phenomenological account of spike train statistics and emphasize the functional relevance of spike threshold adaptation.
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Affiliation(s)
- Bertrand Fontaine
- Laboratoire Psychologie de la Perception, CNRS, Université Paris Descartes, Paris, France
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34
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Directional hearing by linear summation of binaural inputs at the medial superior olive. Neuron 2013; 78:936-48. [PMID: 23764292 DOI: 10.1016/j.neuron.2013.04.028] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2013] [Indexed: 11/24/2022]
Abstract
Neurons in the medial superior olive (MSO) enable sound localization by their remarkable sensitivity to submillisecond interaural time differences (ITDs). Each MSO neuron has its own "best ITD" to which it responds optimally. A difference in physical path length of the excitatory inputs from both ears cannot fully account for the ITD tuning of MSO neurons. As a result, it is still debated how these inputs interact and whether the segregation of inputs to opposite dendrites, well-timed synaptic inhibition, or asymmetries in synaptic potentials or cellular morphology further optimize coincidence detection or ITD tuning. Using in vivo whole-cell and juxtacellular recordings, we show here that ITD tuning of MSO neurons is determined by the timing of their excitatory inputs. The inputs from both ears sum linearly, whereas spike probability depends nonlinearly on the size of synaptic inputs. This simple coincidence detection scheme thus makes accurate sound localization possible.
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35
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van Hemmen JL, Vollmayr AN. Resonating vector strength: what happens when we vary the "probing" frequency while keeping the spike times fixed. BIOLOGICAL CYBERNETICS 2013; 107:491-494. [PMID: 23982849 DOI: 10.1007/s00422-013-0560-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 06/17/2013] [Indexed: 06/02/2023]
Abstract
The synchrony vector, whose length stands for the vector strength (VS), is a means to quantify the amount of periodicity in a neuronal response to a given periodic signal, say, the stimulus. One usually chooses the input angular frequency and evaluates the synchrony vector as a weighted sum of exponentials taken at given experimental spike times of the neuronal response in combination with the driving input frequency. Given the experimental spike times, we replace the stimulus frequency by a variable probing frequency, study the synchrony vector in dependence upon this probing frequency, i.e., as a function of the frequency as a real variable, and exhibit both mathematically and experimentally a resonance behavior once the variable frequency is in the neighborhood of the stimulus frequency. Furthermore, a "resonating" VS is shown to be quite useful since one need not know the external frequency but can simply stick to the given spike times and analyze the ensuing resonance as the frequency varies, for example, to determine at the same time a "best" frequency and the corresponding VS. Finally, it is straightforward to determine the corresponding phase originating from, say, a delay as well.
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Affiliation(s)
- J Leo van Hemmen
- Physik Department T35 and BCCN-Munich, Technische Universität München, 85747, Garching bei München, Germany.
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36
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van Hemmen JL. Vector strength after Goldberg, Brown, and von Mises: biological and mathematical perspectives. BIOLOGICAL CYBERNETICS 2013; 107:385-396. [PMID: 23982848 DOI: 10.1007/s00422-013-0561-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 06/17/2013] [Indexed: 06/02/2023]
Abstract
The vector strength, a number between 0 and 1, is a classical notion in biology. It was first used in neurobiology by Goldberg and Brown (J Neurophys 31:639-656, 1969) but dates back at least to von Mises (Phys Z 19:490-500, 1918). It is widely used as a means to measure the periodicity or lack of periodicity of a neuronal response to an outside periodic signal. Here, we provide a self-contained and simple treatment of a closely related notion, the synchrony vector, a complex number with the vector strength as its absolute value and with a definite phase that one can directly relate to a biophysical delay. The present analysis is essentially geometrical and based on convexity. As such it does two things. First, it maps a sequence of points, events such as spike times on the time axis, onto the unit circle in the complex plane so that for a perfectly periodic repetition, a single point on the unit circle appears. Second, events hardly ever occur periodically, so that we need a criterion of how to extract periodicity out of a set of real numbers. It is here where convex geometry comes in, and a geometrically intuitive picture results. We also quantify how the events cluster around a period as the vector strength goes to 1. A typical example from the auditory system is used to illustrate the general considerations. Furthermore, von Mises' seminal contribution to the notion of vector strength is explained in detail. Finally, we generalize the synchrony vector to a function of angular frequency, not fixed on the input frequency at hand and indicate its potential as a "resonating" vector strength.
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Affiliation(s)
- J Leo van Hemmen
- Physik Department T35 & BCCN-Munich, Technische Universität München, 85747 , Garching bei München, Germany.
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37
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Avissar M, Wittig JH, Saunders JC, Parsons TD. Refractoriness enhances temporal coding by auditory nerve fibers. J Neurosci 2013; 33:7681-90. [PMID: 23637161 PMCID: PMC3865560 DOI: 10.1523/jneurosci.3405-12.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 02/17/2013] [Accepted: 03/19/2013] [Indexed: 11/21/2022] Open
Abstract
A universal property of spiking neurons is refractoriness, a transient decrease in discharge probability immediately following an action potential (spike). The refractory period lasts only one to a few milliseconds, but has the potential to affect temporal coding of acoustic stimuli by auditory neurons, which are capable of submillisecond spike-time precision. Here this possibility was investigated systematically by recording spike times from chicken auditory nerve fibers in vivo while stimulating with repeated pure tones at characteristic frequency. Refractory periods were tightly distributed, with a mean of 1.58 ms. A statistical model was developed to recapitulate each fiber's responses and then used to predict the effect of removing the refractory period on a cell-by-cell basis for two largely independent facets of temporal coding: faithful entrainment of interspike intervals to the stimulus frequency and precise synchronization of spike times to the stimulus phase. The ratio of the refractory period to the stimulus period predicted the impact of refractoriness on entrainment and synchronization. For ratios less than ∼0.9, refractoriness enhanced entrainment and this enhancement was often accompanied by an increase in spike-time precision. At higher ratios, little or no change in entrainment or synchronization was observed. Given the tight distribution of refractory periods, the ability of refractoriness to improve temporal coding is restricted to neurons responding to low-frequency stimuli. Enhanced encoding of low frequencies likely affects sound localization and pitch perception in the auditory system, as well as perception in nonauditory sensory modalities, because all spiking neurons exhibit refractoriness.
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Affiliation(s)
- Michael Avissar
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine
| | - John H. Wittig
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine
- Department of Bioengineering, School of Engineering and Applied Science, and
| | - James C. Saunders
- Department of Otorhinolaryngology: Head and Neck Surgery, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Thomas D. Parsons
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine
- Department of Otorhinolaryngology: Head and Neck Surgery, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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38
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Wittig JH, Boahen K. Potassium conductance dynamics confer robust spike-time precision in a neuromorphic model of the auditory brain stem. J Neurophysiol 2013; 110:307-21. [PMID: 23554436 DOI: 10.1152/jn.00433.2012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A fundamental question in neuroscience is how neurons perform precise operations despite inherent variability. This question also applies to neuromorphic engineering, where low-power microchips emulate the brain using large populations of diverse silicon neurons. Biological neurons in the auditory pathway display precise spike timing, critical for sound localization and interpretation of complex waveforms such as speech, even though they are a heterogeneous population. Silicon neurons are also heterogeneous, due to a key design constraint in neuromorphic engineering: smaller transistors offer lower power consumption and more neurons per unit area of silicon, but also more variability between transistors and thus between silicon neurons. Utilizing this variability in a neuromorphic model of the auditory brain stem with 1,080 silicon neurons, we found that a low-voltage-activated potassium conductance (g(KL)) enables precise spike timing via two mechanisms: statically reducing the resting membrane time constant and dynamically suppressing late synaptic inputs. The relative contribution of these two mechanisms is unknown because blocking g(KL) in vitro eliminates dynamic adaptation but also lengthens the membrane time constant. We replaced g(KL) with a static leak in silico to recover the short membrane time constant and found that silicon neurons could mimic the spike-time precision of their biological counterparts, but only over a narrow range of stimulus intensities and biophysical parameters. The dynamics of g(KL) were required for precise spike timing robust to stimulus variation across a heterogeneous population of silicon neurons, thus explaining how neural and neuromorphic systems may perform precise operations despite inherent variability.
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Affiliation(s)
- John H Wittig
- Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, MD 20892, USA.
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39
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Joris PX, Verschooten E. On the limit of neural phase locking to fine structure in humans. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 787:101-8. [PMID: 23716214 DOI: 10.1007/978-1-4614-1590-9_12] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The frequency extent over which temporal fine structure is available in the human auditory system has recently become a topic of much discussion. It is common, in both the physiological and psychophysical literature, to encounter the assumption that fine structure is available to humans up to about 5 kHz or even higher. We argue from existing physiological, anatomical, and behavioral data in animals, combined with behavioral and anatomical data in humans, that it is unlikely that the human central nervous system has access to fine structure above a few kHz.
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Affiliation(s)
- Philip X Joris
- Laboratory of Auditory Neurophysiology, University of Leuven, Leuven, Belgium.
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40
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Discrimination of low-frequency tones employs temporal fine structure. PLoS One 2012; 7:e45579. [PMID: 23029113 PMCID: PMC3446936 DOI: 10.1371/journal.pone.0045579] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 08/22/2012] [Indexed: 12/02/2022] Open
Abstract
An auditory neuron can preserve the temporal fine structure of a low-frequency tone by phase-locking its response to the stimulus. Apart from sound localization, however, much about the role of this temporal information for signal processing in the brain remains unknown. Through psychoacoustic studies we provide direct evidence that humans employ temporal fine structure to discriminate between frequencies. To this end we construct tones that are based on a single frequency but in which, through the concatenation of wavelets, the phase changes randomly every few cycles. We then test the frequency discrimination of these phase-changing tones, of control tones without phase changes, and of short tones that consist of a single wavelet. For carrier frequencies below a few kilohertz we find that phase changes systematically worsen frequency discrimination. No such effect appears for higher carrier frequencies at which temporal information is not available in the central auditory system.
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41
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Recio-Spinoso A. Enhancement and distortion in the temporal representation of sounds in the ventral cochlear nucleus of chinchillas and cats. PLoS One 2012; 7:e44286. [PMID: 23028514 PMCID: PMC3445608 DOI: 10.1371/journal.pone.0044286] [Citation(s) in RCA: 18] [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: 03/26/2012] [Accepted: 08/01/2012] [Indexed: 11/18/2022] Open
Abstract
A subset of neurons in the cochlear nucleus (CN) of the auditory brainstem has the ability to enhance the auditory nerve's temporal representation of stimulating sounds. These neurons reside in the ventral region of the CN (VCN) and are usually known as highly synchronized, or high-sync, neurons. Most published reports about the existence and properties of high-sync neurons are based on recordings performed on a VCN output tract--not the VCN itself--of cats. In other species, comprehensive studies detailing the properties of high-sync neurons, or even acknowledging their existence, are missing.Examination of the responses of a population of VCN neurons in chinchillas revealed that a subset of those neurons have temporal properties similar to high-sync neurons in the cat. Phase locking and entrainment--the ability of a neuron to fire action potentials at a certain stimulus phase and at almost every stimulus period, respectively--have similar maximum values in cats and chinchillas. Ranges of characteristic frequencies for high-sync neurons in chinchillas and cats extend up to 600 and 1000 Hz, respectively. Enhancement of temporal processing relative to auditory nerve fibers (ANFs), which has been shown previously in cats using tonal and white-noise stimuli, is also demonstrated here in the responses of VCN neurons to synthetic and spoken vowel sounds.Along with the large amount of phase locking displayed by some VCN neurons there occurs a deterioration in the spectral representation of the stimuli (tones or vowels). High-sync neurons exhibit a greater distortion in their responses to tones or vowels than do other types of VCN neurons and auditory nerve fibers.Standard deviations of first-spike latency measured in responses of high-sync neurons are lower than similar values measured in ANFs' responses. This might indicate a role of high-sync neurons in other tasks beyond sound localization.
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Affiliation(s)
- Alberto Recio-Spinoso
- Laboratory for Auditory Neuroengineering, IDINE, Universidad de Castilla-La Mancha, Albacete, Spain.
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42
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Wang GI, Delgutte B. Sensitivity of cochlear nucleus neurons to spatio-temporal changes in auditory nerve activity. J Neurophysiol 2012; 108:3172-95. [PMID: 22972956 DOI: 10.1152/jn.00160.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The spatio-temporal pattern of auditory nerve (AN) activity, representing the relative timing of spikes across the tonotopic axis, contains cues to perceptual features of sounds such as pitch, loudness, timbre, and spatial location. These spatio-temporal cues may be extracted by neurons in the cochlear nucleus (CN) that are sensitive to relative timing of inputs from AN fibers innervating different cochlear regions. One possible mechanism for this extraction is "cross-frequency" coincidence detection (CD), in which a central neuron converts the degree of coincidence across the tonotopic axis into a rate code by preferentially firing when its AN inputs discharge in synchrony. We used Huffman stimuli (Carney LH. J Neurophysiol 64: 437-456, 1990), which have a flat power spectrum but differ in their phase spectra, to systematically manipulate relative timing of spikes across tonotopically neighboring AN fibers without changing overall firing rates. We compared responses of CN units to Huffman stimuli with responses of model CD cells operating on spatio-temporal patterns of AN activity derived from measured responses of AN fibers with the principle of cochlear scaling invariance. We used the maximum likelihood method to determine the CD model cell parameters most likely to produce the measured CN unit responses, and thereby could distinguish units behaving like cross-frequency CD cells from those consistent with same-frequency CD (in which all inputs would originate from the same tonotopic location). We find that certain CN unit types, especially those associated with globular bushy cells, have responses consistent with cross-frequency CD cells. A possible functional role of a cross-frequency CD mechanism in these CN units is to increase the dynamic range of binaural neurons that process cues for sound localization.
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Affiliation(s)
- Grace I Wang
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
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van Hemmen JL, Longtin A, Vollmayr AN. Testing resonating vector strength: auditory system, electric fish, and noise. CHAOS (WOODBURY, N.Y.) 2011; 21:047508. [PMID: 22225382 DOI: 10.1063/1.3670512] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Quite often a response to some input with a specific frequency ν(○) can be described through a sequence of discrete events. Here, we study the synchrony vector, whose length stands for the vector strength, and in doing so focus on neuronal response in terms of spike times. The latter are supposed to be given by experiment. Instead of singling out the stimulus frequency ν(○) we study the synchrony vector as a function of the real frequency variable ν. Its length turns out to be a resonating vector strength in that it shows clear maxima in the neighborhood of ν(○) and multiples thereof, hence, allowing an easy way of determining response frequencies. We study this "resonating" vector strength for two concrete but rather different cases, viz., a specific midbrain neuron in the auditory system of cat and a primary detector neuron belonging to the electric sense of the wave-type electric fish Apteronotus leptorhynchus. We show that the resonating vector strength always performs a clear resonance correlated with the phase locking that it quantifies. We analyze the influence of noise and demonstrate how well the resonance associated with maximal vector strength indicates the dominant stimulus frequency. Furthermore, we exhibit how one can obtain a specific phase associated with, for instance, a delay in auditory analysis.
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Affiliation(s)
- J Leo van Hemmen
- Physik Department T35 & BCCN - Munich, Technische Universität München, 85747 Garching bei München, Germany
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Abstract
The calyx of Held is an axosomatic terminal in the auditory brainstem that has attracted anatomists because of its giant size and physiologists because of its accessibility to patch-clamp recordings. The calyx allows the principal neurons in the medial nucleus of the trapezoid body (MNTB) to provide inhibition that is both well timed and sustained to many other auditory nuclei. The special adaptations that allow the calyx to drive its principal neuron even when frequencies are high include a large number of release sites with low release probability, a large readily releasable pool, fast presynaptic calcium clearance and little delayed release, a large quantal size, and fast AMPA-type glutamate receptors. The transformation from a synapse that is unremarkable except for its giant size into a fast and reliable auditory relay happens in just a few days. In rodents this transformation is essentially ready when hearing starts.
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Affiliation(s)
- J Gerard G Borst
- Department of Neuroscience, Erasmus MC, University Medical Center, 3015 GE Rotterdam, The Netherlands.
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Responses of auditory nerve and anteroventral cochlear nucleus fibers to broadband and narrowband noise: implications for the sensitivity to interaural delays. J Assoc Res Otolaryngol 2011; 12:485-502. [PMID: 21567250 PMCID: PMC3123442 DOI: 10.1007/s10162-011-0268-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 04/11/2011] [Indexed: 11/30/2022] Open
Abstract
The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived from AVCN neurons were lower than those derived from AN fibers, showing that the enhanced temporal coding in the AVCN improves binaural sensitivity to ITDs. AVCN processing also increased the dynamic range of ITD sensitivity and changed the shape of the frequency dependence of ITD sensitivity. Bandwidth dependence of ITD jnds from AN as well as AVCN fibers agreed with psychophysical data. These findings demonstrate that monaural preprocessing in the AVCN improves the temporal code in a way that is beneficial for binaural processing and may be crucial in achieving the exquisite sensitivity to ITDs observed in binaural pathways.
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Lauer AM, May BJ. The medial olivocochlear system attenuates the developmental impact of early noise exposure. J Assoc Res Otolaryngol 2011; 12:329-43. [PMID: 21347798 DOI: 10.1007/s10162-011-0262-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 02/07/2011] [Indexed: 10/18/2022] Open
Abstract
The early onset of peripheral deafness profoundly alters the functional maturation of the central auditory system. A prolonged exposure to an artificial acoustic environment has a similar disruptive influence. These observations establish the importance of normal patterns of sound-driven activity during the initial stages of auditory development. The present study was designed to address the role of cochlear gain control during these activity-dependent developmental processes. It was hypothesized that the regulation of auditory nerve activity by the medial olivocochlear system (MOCS) would preserve normal development when the immature auditory system was challenged by continuous background noise. To test this hypothesis, knock-out mice lacking MOCS feedback were reared in noisy or quiet environments and then evaluated with behavioral paradigms for auditory processing deficits. Relative to wild-type controls, noise-reared knock-out mice showed a decreased ability to process rapid acoustic events. Additional anatomical and physiological assessments linked these perceptual deficits to synaptic defects in the auditory brainstem that shared important features with human auditory neuropathy. Our findings offer a new perspective on the potentially damaging effects of environmental noise and how these risks are ameliorated by the protective role of MOCS feedback.
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Affiliation(s)
- Amanda M Lauer
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, MD 21205, USA.
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Spatial selective auditory attention in the presence of reverberant energy: individual differences in normal-hearing listeners. J Assoc Res Otolaryngol 2010; 12:395-405. [PMID: 21128091 DOI: 10.1007/s10162-010-0254-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 11/16/2010] [Indexed: 10/18/2022] Open
Abstract
Listeners can selectively attend to a desired target by directing attention to known target source features, such as location or pitch. Reverberation, however, reduces the reliability of the cues that allow a target source to be segregated and selected from a sound mixture. Given this, it is likely that reverberant energy interferes with selective auditory attention. Anecdotal reports suggest that the ability to focus spatial auditory attention degrades even with early aging, yet there is little evidence that middle-aged listeners have behavioral deficits on tasks requiring selective auditory attention. The current study was designed to look for individual differences in selective attention ability and to see if any such differences correlate with age. Normal-hearing adults, ranging in age from 18 to 55 years, were asked to report a stream of digits located directly ahead in a simulated rectangular room. Simultaneous, competing masker digit streams were simulated at locations 15° left and right of center. The level of reverberation was varied to alter task difficulty by interfering with localization cues (increasing localization blur). Overall, performance was best in the anechoic condition and worst in the high-reverberation condition. Listeners nearly always reported a digit from one of the three competing streams, showing that reverberation did not render the digits unintelligible. Importantly, inter-subject differences were extremely large. These differences, however, were not significantly correlated with age, memory span, or hearing status. These results show that listeners with audiometrically normal pure tone thresholds differ in their ability to selectively attend to a desired source, a task important in everyday communication. Further work is necessary to determine if these differences arise from differences in peripheral auditory function or in more central function.
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Ashida G, Carr CE. Effect of sampling frequency on the measurement of phase-locked action potentials. Front Neurosci 2010; 4. [PMID: 20953249 PMCID: PMC2955492 DOI: 10.3389/fnins.2010.00172] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 08/31/2010] [Indexed: 12/02/2022] Open
Abstract
Phase-locked spikes in various types of neurons encode temporal information. To quantify the degree of phase-locking, the metric called vector strength (VS) has been most widely used. Since VS is derived from spike timing information, error in measurement of spike occurrence should result in errors in VS calculation. In electrophysiological experiments, the timing of an action potential is detected with finite temporal precision, which is determined by the sampling frequency. In order to evaluate the effects of the sampling frequency on the measurement of VS, we derive theoretical upper and lower bounds of VS from spikes collected with finite sampling rates. We next estimate errors in VS assuming random sampling effects, and show that our theoretical calculation agrees with data from electrophysiological recordings in vivo. Our results provide a practical guide for choosing the appropriate sampling frequency in measuring VS.
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Affiliation(s)
- Go Ashida
- Department of Biology, University of Maryland, College Park MD, USA
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Dehmel S, Kopp-Scheinpflug C, Weick M, Dörrscheidt GJ, Rübsamen R. Transmission of phase-coupling accuracy from the auditory nerve to spherical bushy cells in the Mongolian gerbil. Hear Res 2010; 268:234-49. [PMID: 20561574 DOI: 10.1016/j.heares.2010.06.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 06/06/2010] [Accepted: 06/08/2010] [Indexed: 10/19/2022]
Abstract
The phase of low-frequency sinusoids is encoded in phase-coupled discharges of spherical bushy cells (SBCs) of the anteroventral cochlear nucleus and transmitted to the medial superior olive, where binaural input-coincidence is used for processing of sound source localization. SBCs are innervated by auditory nerve fibers through large, excitatory synapses (endbulbs of Held) and by inhibitory inputs, which effectively reduce SBC discharge rates. Here we monitor presynaptic potentials of endbulb-terminals and postsynaptic spikes of SBCs in extracellular single unit recordings in vivo. We compare postsynaptic phase-coupling of SBCs and their presynaptic immediate auditory nerve input. In all but one SBC discharge rates at the characteristic frequency were reduced pre-to-postsynaptically and phase-coupling accuracy was increased in one-third of them. We investigated the contribution of systemic inhibition on spike timing in SBCs by iontophoretic application of glycine- and GABA-receptor antagonists (strychnine, bicuculline). Discharge rate increased in one-third of the units during antagonist application, which was accompanied by a deterioration of phase-coupling accuracy in half of those units. These results suggest that the phase-coupling accuracy is improved in a subpopulation of SBCs during transmission from the auditory nerve to the SBCs by reduction of spike rates.
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Affiliation(s)
- Susanne Dehmel
- Faculty of Biosciences, University of Leipzig, Talstrasse 33, 04103 Leipzig, Germany
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Borst JGG. The low synaptic release probability in vivo. Trends Neurosci 2010; 33:259-66. [DOI: 10.1016/j.tins.2010.03.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 03/09/2010] [Accepted: 03/16/2010] [Indexed: 01/20/2023]
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