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Mitchell PW, Carney LH. A Computational Model of Auditory Chirp-Velocity Sensitivity and Amplitude-Modulation Tuning in Inferior Colliculus Neurons. RESEARCH SQUARE 2024:rs.3.rs-4450943. [PMID: 38883707 PMCID: PMC11177976 DOI: 10.21203/rs.3.rs-4450943/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
We demonstrate a model of chirp-velocity sensitivity in the inferior colliculus (IC) that retains the tuning to amplitude modulation (AM) that was established in earlier models. The mechanism of velocity sensitivity is sequence detection by octopus cells of the posteroventral cochlear nucleus, which have been proposed in physiological studies to respond preferentially to the order of arrival of cross-frequency inputs of different amplitudes. Model architecture is based on coincidence detection of a combination of excitatory and inhibitory inputs. Chirp-sensitivity of the IC output is largely controlled by the strength and timing of the chirp-sensitive octopus-cell inhibitory input. AM tuning is controlled by inhibition and excitation that are tuned to the same frequency. We present several example neurons that demonstrate the feasibility of the model in simulating realistic chirp-sensitivity and AM tuning for a wide range of characteristic frequencies. Additionally, we explore the systematic impact of varying parameters on model responses. The proposed model can be used to assess the contribution of IC chirp-velocity sensitivity to responses to complex sounds, such as speech.
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Affiliation(s)
- Paul W. Mitchell
- Department of Biomedical Engineering, University of Rochester, 601 Elmwood Ave, Rochester, NY, 14642, USA
| | - Laurel H. Carney
- Department of Biomedical Engineering, University of Rochester, 601 Elmwood Ave, Rochester, NY, 14642, USA
- Department of Neuroscience, University of Rochester, 601 Elmwood Ave, Rochester, NY, 14642, USA
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2
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Stoll TJ, Maddox RK. Enhanced Place Specificity of the Parallel Auditory Brainstem Response: An Electrophysiological Study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.10.584313. [PMID: 38559254 PMCID: PMC10979863 DOI: 10.1101/2024.03.10.584313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Purpose This study investigates the effect of parallel stimulus presentation on the place specificity of the auditory brainstem response (ABR) in human listeners. Frequency-specific stimuli do not guarantee a response from the place on the cochlea corresponding only to that characteristic frequency - especially for brief and high-level stimuli. Adding masking noise yields responses that are more place specific, and a prior modeling study has suggested similar effects when multiple frequency-specific stimuli are presented in parallel. We tested this hypothesis experimentally here, comparing the place specificity of responses to serial and parallel stimuli at two stimulus frequencies and three stimulus rates. Methods Parallel ABR (pABR) stimuli were presented alongside high-pass filtered noise with a varied cutoff frequency. Serial presentation was also tested by isolating and presenting single-frequency stimulus trains from the pABR ensemble. Latencies of the ABRs were examined to assess place specificity of responses. Response bands were derived by subtracting responses from different high pass noise conditions. The response amplitude from each derived response band was then used to determine how much individual frequency regions of the auditory system were contributing to the overall response. Results We found that parallel presentation improves place specificity of ABRs for the lower stimulus frequency and at higher stimulus rates. At a higher stimulus frequency, serial and parallel presentation were equally place specific. Conclusion Parallel presentation can provide more place specific responses than serial for lower stimulus frequencies. The improvement increases with higher stimulus rates and is in addition to the pABR's primary benefit of faster test times.
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Affiliation(s)
- Thomas J Stoll
- University of Rochester, Department of Biomedical Engineering and
- University of Rochester, Department of Neuroscience
- University of Michigan, Kresge Hearing Research Institute
| | - Ross K Maddox
- University of Rochester, Department of Biomedical Engineering and
- University of Rochester, Department of Neuroscience
- University of Michigan, Kresge Hearing Research Institute
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Kreeger LJ, Honnuraiah S, Maeker S, Shea S, Fishell G, Goodrich LV. An Anatomical and Physiological Basis for Coincidence Detection Across Time Scales in the Auditory System. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.29.582808. [PMID: 38464181 PMCID: PMC10925315 DOI: 10.1101/2024.02.29.582808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Coincidence detection is a common neural computation that identifies co-occurring stimuli by integration of inputs. In the auditory system, octopus cells act as coincidence detectors for complex sounds that include both synchronous and sequenced combinations of frequencies. Octopus cells must detect coincidence on both the millisecond and submillisecond time scale, unlike the average neuron, which integrates inputs over time on the order of tens of milliseconds. Here, we show that octopus cell computations in the cell body are shaped by inhibition in the dendrites, which adjusts the strength and timing of incoming signals to achieve submillisecond acuity. This mechanism is crucial for the fundamental process of integrating the synchronized frequencies of natural auditory signals over time.
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Affiliation(s)
- Lauren J Kreeger
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
| | - Suraj Honnuraiah
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Sydney Maeker
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
| | - Siobhan Shea
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
| | - Gord Fishell
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Lisa V Goodrich
- Harvard Medical School, Department of Neurobiology, Boston, MA 02115, USA
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Jing J, Hu M, Ngodup T, Ma Q, Lau SNN, Ljungberg C, McGinley MJ, Trussell LO, Jiang X. Comprehensive analysis of cellular specializations that initiate parallel auditory processing pathways in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.15.539065. [PMID: 37293040 PMCID: PMC10245571 DOI: 10.1101/2023.05.15.539065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The cochlear nuclear complex (CN) is the starting point for all central auditory processing and comprises a suite of neuronal cell types that are highly specialized for neural coding of acoustic signals. To examine how their striking functional specializations are determined at the molecular level, we performed single-nucleus RNA sequencing of the mouse CN to molecularly define all constituent cell types and related them to morphologically- and electrophysiologically-defined neurons using Patch-seq. We reveal an expanded set of molecular cell types encompassing all previously described major types and discover new subtypes both in terms of topographic and cell-physiologic properties. Our results define a complete cell-type taxonomy in CN that reconciles anatomical position, morphological, physiological, and molecular criteria. This high-resolution account of cellular heterogeneity and specializations from the molecular to the circuit level illustrates molecular underpinnings of functional specializations and enables genetic dissection of auditory processing and hearing disorders with unprecedented specificity.
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Affiliation(s)
- Junzhan Jing
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Ming Hu
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Tenzin Ngodup
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Qianqian Ma
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Shu-Ning Natalie Lau
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Cecilia Ljungberg
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Matthew J. McGinley
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Laurence O. Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Xiaolong Jiang
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
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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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Scarpa GB, Starrett JR, Li GL, Brooks C, Morohashi Y, Yazaki-Sugiyama Y, Remage-Healey L. Estrogens rapidly shape synaptic and intrinsic properties to regulate the temporal precision of songbird auditory neurons. Cereb Cortex 2022; 33:3401-3420. [PMID: 35849820 PMCID: PMC10068288 DOI: 10.1093/cercor/bhac280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 01/14/2023] Open
Abstract
Sensory neurons parse millisecond-variant sound streams like birdsong and speech with exquisite precision. The auditory pallial cortex of vocal learners like humans and songbirds contains an unconventional neuromodulatory system: neuronal expression of the estrogen synthesis enzyme aromatase. Local forebrain neuroestrogens fluctuate when songbirds hear a song, and subsequently modulate bursting, gain, and temporal coding properties of auditory neurons. However, the way neuroestrogens shape intrinsic and synaptic properties of sensory neurons remains unknown. Here, using a combination of whole-cell patch clamp electrophysiology and calcium imaging, we investigate estrogenic neuromodulation of auditory neurons in a region resembling mammalian auditory association cortex. We found that estradiol rapidly enhances the temporal precision of neuronal firing via a membrane-bound G-protein coupled receptor and that estradiol rapidly suppresses inhibitory synaptic currents while sparing excitation. Notably, the rapid suppression of intrinsic excitability by estradiol was predicted by membrane input resistance and was observed in both males and females. These findings were corroborated by analysis of in vivo electrophysiology recordings, in which local estrogen synthesis blockade caused acute disruption of the temporal correlation of song-evoked firing patterns. Therefore, on a modulatory timescale, neuroestrogens alter intrinsic cellular properties and inhibitory neurotransmitter release to regulate the temporal precision of higher-order sensory neurons.
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Affiliation(s)
- Garrett B Scarpa
- Neuroscience and Behavior, Center for Neuroendocrine Studies, University of Massachusetts, 639 N. Pleasant St., Amherst, MA 01003, United States
| | - Joseph R Starrett
- Neuroscience and Behavior, Center for Neuroendocrine Studies, University of Massachusetts, 639 N. Pleasant St., Amherst, MA 01003, United States
| | - Geng-Lin Li
- Department of Otorhinolaryngology, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd, Xuhui District, Shanghai 200031, China
| | - Colin Brooks
- Neuroscience and Behavior, Center for Neuroendocrine Studies, University of Massachusetts, 639 N. Pleasant St., Amherst, MA 01003, United States
| | - Yuichi Morohashi
- Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa, Japan
| | - Yoko Yazaki-Sugiyama
- Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa, Japan
| | - Luke Remage-Healey
- Neuroscience and Behavior, Center for Neuroendocrine Studies, University of Massachusetts, 639 N. Pleasant St., Amherst, MA 01003, United States
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Rebhan M, Leibold C. A phenomenological spiking model for octopus cells in the posterior-ventral cochlear nucleus. BIOLOGICAL CYBERNETICS 2021; 115:331-341. [PMID: 34109476 PMCID: PMC8382648 DOI: 10.1007/s00422-021-00881-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 05/29/2021] [Indexed: 06/12/2023]
Abstract
Octopus cells in the posteroventral cochlear nucleus exhibit characteristic onset responses to broad band transients but are little investigated in response to more complex sound stimuli. In this paper, we propose a phenomenological, but biophysically motivated, modeling approach that allows to simulate responses of large populations of octopus cells to arbitrary sound pressure waves. The model depends on only few parameters and reproduces basic physiological characteristics like onset firing and phase locking to amplitude modulations. Simulated responses to speech stimuli suggest that octopus cells are particularly sensitive to high-frequency transients in natural sounds and their sustained firing to phonemes provides a population code for sound level.
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Affiliation(s)
- Michael Rebhan
- Department Biology II, Ludwig-Maximilians Universität München, 82152, Martinsried, Germany
| | - Christian Leibold
- Department Biology II, Bernstein Center for Computational Neuroscience Munich, Ludwig-Maximilians Universität München, 82152, Martinsried, Germany.
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8
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Romero GE, Trussell LO. Distinct forms of synaptic plasticity during ascending vs descending control of medial olivocochlear efferent neurons. eLife 2021; 10:66396. [PMID: 34250904 PMCID: PMC8321555 DOI: 10.7554/elife.66396] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 07/09/2021] [Indexed: 12/14/2022] Open
Abstract
Activity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine the neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN) and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with the VCN input showing depression and the IC input showing marked facilitation. By using a conductance-clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.
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Affiliation(s)
- Gabriel E Romero
- Physiology & Pharmacology Graduate Program, Oregon Health & Science University, Portland, United States
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, United States
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9
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Bal R, Ozturk G, Etem EO, Eraslan E, Ozaydin S. Modulation of the excitability of stellate neurons in the ventral cochlear nucleus of mice by TRPM2 channels. Eur J Pharmacol 2020; 882:173163. [PMID: 32485244 DOI: 10.1016/j.ejphar.2020.173163] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 03/14/2020] [Accepted: 04/29/2020] [Indexed: 10/24/2022]
Abstract
Oxidative stress-induced Ca2+ permeable transient receptor potential melastatin 2 (TRPM2) channels are expressed at high levels in the brain, appear to link neuronal excitability to cellular metabolism, and are involved in the pathogenesis of neurodegenerative disorders. We aimed to study the electrophysiological properties of TRPM2 channels in stellate cells of the mouse ventral cochlear nucleus (VCN) using molecular, immunohistochemical and electrophysiological approaches. In the present study, the real time PCR analysis revealed the presence of the TRPM2 mRNA in the mouse VCN tissue. Cell bodies of stellate cells were moderately labeled with TRPM2 antibodies using immunohistochemical staining. Stellate cells were sensitive to intracellular ADP-ribose (ADPR), a TRPM2 agonist. Upon the application of ADPR, the resting membrane potential of the stellate cells was significantly depolarized, shifting from -61.2 ± 0.9 mV to -57.0 ± 0.8 mV (P < 0.001; n = 21), and the firing rate significantly increased (P < 0.001, n = 6). When the pipette solution contained ADPR (300 μM) and the TRPM2 antagonists flufenamic acid (FFA) (100 μM), N-(p-amylcinnamoyl) anthranilic acid (ACA) (50 μM) and 8-bromo-cADP-Ribose (8-Br-cADPR) (50 μM), the membrane potential shifted in a hyperpolarizing direction. ADPR did not significantly change the resting membrane potential and action potential firing rate of stellate cells from TRPM2-/- mice. In conclusion, the results obtained using these molecular, immunohistochemical and electrophysiological approaches reveal the expression of functional TRPM2 channels in stellate neurons of the mouse VCN. TRPM2 might exert a significant modulatory effect on setting the level of resting excitability.
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Affiliation(s)
- Ramazan Bal
- Dept. of Physiology, Faculty of Medicine, Gaziantep University, 27310, Gaziantep, Turkey.
| | - Gurkan Ozturk
- Department of Physiology, Faculty of Medicine, Medipol University, Istanbul, Turkey
| | - Ebru Onalan Etem
- Dept. of Medical Biology, Faculty of Medicine, Firat University, 23119, Elazig, Turkey
| | - Ersen Eraslan
- Dept. of Physiology, Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Seda Ozaydin
- Dept. of Medical Biology, Faculty of Medicine, Firat University, 23119, Elazig, Turkey
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10
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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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11
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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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12
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In-vivo optogenetics and pharmacology in deep intracellular recordings. J Neurosci Methods 2019; 325:108324. [DOI: 10.1016/j.jneumeth.2019.108324] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 06/18/2019] [Accepted: 06/24/2019] [Indexed: 12/17/2022]
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13
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Cakir Z, Yildirim C, Buran I, Önalan EE, Bal R. Acid-sensing ion channels (ASICs) influence excitability of stellate neurons in the mouse cochlear nucleus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:769-781. [PMID: 31451914 DOI: 10.1007/s00359-019-01365-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 08/08/2019] [Accepted: 08/13/2019] [Indexed: 02/06/2023]
Abstract
Acid-sensing ion channels (ASICs) are voltage-independent and proton-gated channels. In this study, we aimed to test the hypothesis whether ASICs might be involved in modifying the excitability of stellate cells in the cochlear nucleus (CN). We determined gene expressions of ASIC1, ASIC2 and ASIC3 in the CN of BALB/mice. ASIC currents in stellate cells were characterized by using whole-cell patch-clamp technique. In the voltage-clamp experiments, inward currents were recorded upon application of 2-[N-Morpholino ethanesulfonic acid]-normal artificial cerebrospinal fluid (MES-aCSF), whose pH 50 was 5.84. Amiloride inhibited the acid-induced currents in a dose-dependent manner. Inhibition of the ASIC currents by extracellular Ca2+ and Pb2+ (10 μM) was significant evidence for the existence of homomeric ASIC1a subunits. ASIC currents were increased by 20% upon extracellular application of Zn2+ (300 μM) (p < 0.05, n = 13). In current-clamp experiments, application of MES-aCSF resulted in the depolarization of stellate cells. The results show that the ASIC currents in stellate cells of the cochlear nucleus are carried largely by the ASIC1a and ASIC2a channels. ASIC channels affect the excitability of the stellate cells and therefore they appear to have a role in the processing of auditory information.
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Affiliation(s)
- Ziya Cakir
- Department of Physiology, Faculty of Medicine, Tokat Gaziosmanpasa University, 60250, Tokat, Turkey
| | - Caner Yildirim
- Department of Physiology, Faculty of Medicine, Kafkas University, 36100, Kars, Turkey
| | - Ilay Buran
- Department of Medical Biology, Faculty of Medicine, Firat University, 23100, Elazig, Turkey
| | - Ebru Etem Önalan
- Department of Medical Biology, Faculty of Medicine, Firat University, 23100, Elazig, Turkey
| | - Ramazan Bal
- Department of Physiology, Faculty of Medicine, Gaziantep University, 27310, Gaziantep, Turkey.
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14
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Cost of auditory sharpness: Model-Based estimate of energy use by auditory brainstem "octopus" neurons. J Theor Biol 2019; 469:137-147. [PMID: 30831173 DOI: 10.1016/j.jtbi.2019.01.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/07/2019] [Accepted: 01/21/2019] [Indexed: 11/21/2022]
Abstract
Octopus cells (OCs) of the mammalian auditory brainstem precisely encode timing of fast transient sounds and tone onsets. Sharp temporal fidelity of OCs relies on low resting membrane resistance, which suggests high energy expenditure on maintaining ion gradients across plasma membrane. We provide a model-based estimate of energy consumption in resting and spiking OCs. Our results predict that a resting OC consumes up to 2.6 × 109 ATP molecules (ATPs) per second which remarkably exceeds energy consumption of other CNS neurons. Glucose usage by all OCs in the rat is nevertheless low due to their low number. Major part of the OCs energy use results from the ion mechanisms providing for the low membrane resistance: hyperpolarization-activated mixed cation conductance and low-voltage activated K+-conductance. Spatially ordered synapses-a feature of the OCs allowing them to compensate for asynchrony of the synaptic input-brings only a 12% energy saving to OCs excitability cost. Only 13% of total OC energy used for an AP generation (1.5 × 107 ATPs) is associated with the AP generation in the axon initial segment, 64%-with synaptic currents processing and 23%-with keeping resting potential.
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15
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Brown DH, Hyson RL. Intrinsic physiological properties underlie auditory response diversity in the avian cochlear nucleus. J Neurophysiol 2019; 121:908-927. [PMID: 30649984 DOI: 10.1152/jn.00459.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sensory systems exploit parallel processing of stimulus features to enable rapid, simultaneous extraction of information. Mechanisms that facilitate this differential extraction of stimulus features can be intrinsic or synaptic in origin. A subdivision of the avian cochlear nucleus, nucleus angularis (NA), extracts sound intensity information from the auditory nerve and contains neurons that exhibit diverse responses to sound and current injection. NA neurons project to multiple regions ascending the auditory brain stem including the superior olivary nucleus, lateral lemniscus, and avian inferior colliculus, with functional implications for inhibitory gain control and sound localization. Here we investigated whether the diversity of auditory response patterns in NA can be accounted for by variation in intrinsic physiological features. Modeled sound-evoked auditory nerve input was applied to NA neurons with dynamic clamp during in vitro whole cell recording at room temperature. Temporal responses to auditory nerve input depended on variation in intrinsic properties, and the low-threshold K+ current was implicated as a major contributor to temporal response diversity and neuronal input-output functions. An auditory nerve model of acoustic amplitude modulation produced synchrony coding of modulation frequency that depended on the intrinsic physiology of the individual neuron. In Primary-Like neurons, varying low-threshold K+ conductance with dynamic clamp altered temporal modulation tuning bidirectionally. Taken together, these data suggest that intrinsic physiological properties play a key role in shaping auditory response diversity to both simple and more naturalistic auditory stimuli in the avian cochlear nucleus. NEW & NOTEWORTHY This article addresses the question of how the nervous system extracts different information in sounds. Neurons in the cochlear nucleus show diverse responses to acoustic stimuli that may allow for parallel processing of acoustic features. The present studies suggest that diversity in intrinsic physiological features of individual neurons, including levels of a low voltage-activated K+ current, play a major role in regulating the diversity of auditory responses.
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Affiliation(s)
- David H Brown
- Program in Neuroscience, Department of Psychology, Florida State University , Tallahassee, Florida
| | - Richard L Hyson
- Program in Neuroscience, Department of Psychology, Florida State University , Tallahassee, Florida
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16
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The ion channels and synapses responsible for the physiological diversity of mammalian lower brainstem auditory neurons. Hear Res 2018; 376:33-46. [PMID: 30606624 DOI: 10.1016/j.heares.2018.12.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/12/2018] [Accepted: 12/22/2018] [Indexed: 11/20/2022]
Abstract
The auditory part of the brainstem is composed of several nuclei specialized in the computation of the different spectral and temporal features of the sound before it reaches the higher auditory regions. There are a high diversity of neuronal types in these nuclei, many with remarkable electrophysiological and synaptic properties unique to these structures. This diversity reflects specializations necessary to process the different auditory signals in order to extract precisely the acoustic information necessary for the auditory perception by the animal. Low threshold Kv1 channels and HCN channels are expressed in neurons that use timing clues for auditory processing, like bushy and octopus cells, in order to restrict action potential firing and reduce input resistance and membrane time constant. Kv3 channels allow principal neurons of the MNTB and pyramidal DCN neurons to fire fast trains of action potentials. Calcium channels on cartwheel DCN neurons produce complex spikes characteristic of these neurons. Calyceal synapses compensate the low input resistance of bushy and principal neurons of the MNTB by releasing hundreds of glutamate vesicles resulting in large EPSCs acting in fast ionotropic glutamate receptors, in order to reduce temporal summation of synaptic potentials, allowing more precise correspondence of pre- and post-synaptic potentials, and phase-locking. Pre-synaptic calyceal sodium channels have fast recovery from inactivation allowing extremely fast trains of action potential firing, and persistent sodium channels produce spontaneous activity of fusiform neurons at rest, which expands the dynamic range of these neurons. The unique combinations of different ion channels, ionotropic receptors and synaptic structures create a unique functional diversity of neurons extremely adapted to their complex functions in the auditory processing.
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17
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Gómez-Álvarez M, Gourévitch B, Felix RA, Nyberg T, Hernández-Montiel HL, Magnusson AK. Temporal information in tones, broadband noise, and natural vocalizations is conveyed by differential spiking responses in the superior paraolivary nucleus. Eur J Neurosci 2018; 48:2030-2049. [PMID: 30019495 DOI: 10.1111/ejn.14073] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/12/2018] [Accepted: 06/26/2018] [Indexed: 12/31/2022]
Abstract
Communication sounds across all mammals consist of multiple frequencies repeated in sequence. The onset and offset of vocalizations are potentially important cues for recognizing distinct units, such as phonemes and syllables, which are needed to perceive meaningful communication. The superior paraolivary nucleus (SPON) in the auditory brainstem has been implicated in the processing of rhythmic sounds. Here, we compared how best frequency tones (BFTs), broadband noise (BBN), and natural mouse calls elicit onset and offset spiking in the mouse SPON. The results demonstrate that onset spiking typically occurs in response to BBN, but not BFT stimulation, while spiking at the sound offset occurs for both stimulus types. This effect of stimulus bandwidth on spiking is consistent with two of the established inputs to the SPON from the octopus cells (onset spiking) and medial nucleus of the trapezoid body (offset spiking). Natural mouse calls elicit two main spiking peaks. The first spiking peak, which is weak or absent with BFT stimulation, occurs most consistently during the call envelope, while the second spiking peak occurs at the call offset. This suggests that the combined spiking activity in the SPON elicited by vocalizations reflects the entire envelope, that is, the coarse amplitude waveform. Since the output from the SPON is purely inhibitory, it is speculated that, at the level of the inferior colliculus, the broadly tuned first peak may improve the signal-to-noise ratio of the subsequent, more call frequency-specific peak. Thus, the SPON may provide a dual inhibition mechanism for tracking phonetic boundaries in social-vocal communication.
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Affiliation(s)
- Marcelo Gómez-Álvarez
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Boris Gourévitch
- Unité de Génétique et Physiologie de l'Audition, INSERM, Institut Pasteur, Sorbonne Université Paris, Paris, France.,CNRS, Paris, France
| | | | - Tobias Nyberg
- Division of Neuronic Engineering, Department of Biomedical Engineering and Health Systems, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Hebert L Hernández-Montiel
- Laboratorio de Neurobiología y Bioingeniería Celular, Clínica del Sistema Nervioso, Universidad Autónoma de Querétaro, Santiago de Querétaro, México
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
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18
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Spencer MJ, Meffin H, Burkitt AN, Grayden DB. Compensation for Traveling Wave Delay Through Selection of Dendritic Delays Using Spike-Timing-Dependent Plasticity in a Model of the Auditory Brainstem. Front Comput Neurosci 2018; 12:36. [PMID: 29922141 PMCID: PMC5996126 DOI: 10.3389/fncom.2018.00036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/14/2018] [Indexed: 12/03/2022] Open
Abstract
Asynchrony among synaptic inputs may prevent a neuron from responding to behaviorally relevant sensory stimuli. For example, “octopus cells” are monaural neurons in the auditory brainstem of mammals that receive input from auditory nerve fibers (ANFs) representing a broad band of sound frequencies. Octopus cells are known to respond with finely timed action potentials at the onset of sounds despite the fact that due to the traveling wave delay in the cochlea, synaptic input from the auditory nerve is temporally diffuse. This paper provides a proof of principle that the octopus cells' dendritic delay may provide compensation for this input asynchrony, and that synaptic weights may be adjusted by a spike-timing dependent plasticity (STDP) learning rule. This paper used a leaky integrate and fire model of an octopus cell modified to include a “rate threshold,” a property that is known to create the appropriate onset response in octopus cells. Repeated audio click stimuli were passed to a realistic auditory nerve model which provided the synaptic input to the octopus cell model. A genetic algorithm was used to find the parameters of the STDP learning rule that reproduced the microscopically observed synaptic connectivity. With these selected parameter values it was shown that the STDP learning rule was capable of adjusting the values of a large number of input synaptic weights, creating a configuration that compensated the traveling wave delay of the cochlea.
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Affiliation(s)
- Martin J Spencer
- NeuroEngineering Laboratory, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia.,Centre for Neural Engineering, University of Melbourne, Melbourne, VIC, Australia
| | - Hamish Meffin
- NeuroEngineering Laboratory, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia.,Centre for Neural Engineering, University of Melbourne, Melbourne, VIC, Australia.,Victorian Research Laboratory, National ICT Australia, Sydney, NSW, Australia.,National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia.,Department of Optometry and Vision Sciences, ARC Centre of Excellence for Integrative Brain Function, University of Melbourne, Melbourne, VIC, Australia
| | - Anthony N Burkitt
- NeuroEngineering Laboratory, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia.,Centre for Neural Engineering, University of Melbourne, Melbourne, VIC, Australia
| | - David B Grayden
- NeuroEngineering Laboratory, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia.,Centre for Neural Engineering, University of Melbourne, Melbourne, VIC, Australia
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19
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Modulation of Excitability of Stellate Neurons in the Ventral Cochlear Nucleus of Mice by ATP-Sensitive Potassium Channels. J Membr Biol 2018; 251:163-178. [PMID: 29379989 DOI: 10.1007/s00232-017-0011-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Accepted: 12/19/2017] [Indexed: 12/21/2022]
Abstract
Major voltage-activated ionic channels of stellate cells in the ventral part of cochlear nucleus (CN) were largely characterized previously. However, it is not known if these cells are equipped with other ion channels apart from the voltage-sensitive ones. In the current study, it was aimed to study subunit composition and function of ATP-sensitive potassium channels (KATP) in stellate cells of the ventral cochlear nucleus. Subunits of KATP channels, Kir6.1, Kir6.2, SUR1, and SUR2, were expressed at the mRNA level and at the protein level in the mouse VCN tissue. The specific and clearly visible bands for all subunits but that for Kir6.1 were seen in Western blot. Using immunohistochemical staining technique, stellate cells were strongly labeled with SUR1 and Kir6.2 antibodies and moderately labeled with SUR2 antibody, whereas the labeling signals for Kir6.1 were too weak. In patch clamp recordings, KATP agonists including cromakalim (50 µM), diazoxide (0.2 mM), 3-Amino-1,2,4-triazole (ATZ) (1 mM), 2,2-Dithiobis (5-nitro pyridine) (DTNP) (330 µM), 6-Chloro-3-isopropylamino- 4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NNC 55-0118) (1 µM), 6-chloro-3-(methylcyclopropyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NN414) (1 µM), and H2O2 (0.88 mM) induced marked responses in stellate cells, characterized by membrane hyperpolarization which were blocked by KATP antagonists. Blockers of KATP channels, glibenclamide (0.2 mM), tolbutamide (0.1 mM) as well as 5-hydroxydecanoic acid (1 mM), and catalase (500 IU/ml) caused depolarization of stellate cells, increasing spontaneous action potential firing. In conclusion, KATP channels seemed to be composed dominantly of Kir 6.2 subunit and SUR1 and SUR2 and activation or inhibition of KATP channels regulates firing properties of stellate cells by means of influencing resting membrane potential and input resistance.
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20
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Manis PB, Campagnola L. A biophysical modelling platform of the cochlear nucleus and other auditory circuits: From channels to networks. Hear Res 2017; 360:76-91. [PMID: 29331233 DOI: 10.1016/j.heares.2017.12.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 11/27/2017] [Accepted: 12/23/2017] [Indexed: 12/12/2022]
Abstract
Models of the auditory brainstem have been an invaluable tool for testing hypotheses about auditory information processing and for highlighting the most important gaps in the experimental literature. Due to the complexity of the auditory brainstem, and indeed most brain circuits, the dynamic behavior of the system may be difficult to predict without a detailed, biologically realistic computational model. Despite the sensitivity of models to their exact construction and parameters, most prior models of the cochlear nucleus have incorporated only a small subset of the known biological properties. This confounds the interpretation of modelling results and also limits the potential future uses of these models, which require a large effort to develop. To address these issues, we have developed a general purpose, biophysically detailed model of the cochlear nucleus for use both in testing hypotheses about cochlear nucleus function and also as an input to models of downstream auditory nuclei. The model implements conductance-based Hodgkin-Huxley representations of cells using a Python-based interface to the NEURON simulator. Our model incorporates most of the quantitatively characterized intrinsic cell properties, synaptic properties, and connectivity available in the literature, and also aims to reproduce the known response properties of the canonical cochlear nucleus cell types. Although we currently lack the empirical data to completely constrain this model, our intent is for the model to continue to incorporate new experimental results as they become available.
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Affiliation(s)
- Paul B Manis
- Dept. of Otolaryngology/Head and Neck Surgery, B027 Marsico Hall, 125 Mason Farm Road, UNC Chapel Hill, Chapel Hill, NC 27599-7070, USA.
| | - Luke Campagnola
- Dept. of Otolaryngology/Head and Neck Surgery, B027 Marsico Hall, 125 Mason Farm Road, UNC Chapel Hill, Chapel Hill, NC 27599-7070, USA
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21
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Dagostin AA, Lovell PV, Hilscher MM, Mello CV, Leão RM. Control of Phasic Firing by a Background Leak Current in Avian Forebrain Auditory Neurons. Front Cell Neurosci 2015; 9:471. [PMID: 26696830 PMCID: PMC4674572 DOI: 10.3389/fncel.2015.00471] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 11/19/2015] [Indexed: 12/02/2022] Open
Abstract
Central neurons express a variety of neuronal types and ion channels that promote firing heterogeneity among their distinct neuronal populations. Action potential (AP) phasic firing, produced by low-threshold voltage-activated potassium currents (VAKCs), is commonly observed in mammalian brainstem neurons involved in the processing of temporal properties of the acoustic information. The avian caudomedial nidopallium (NCM) is an auditory area analogous to portions of the mammalian auditory cortex that is involved in the perceptual discrimination and memorization of birdsong and shows complex responses to auditory stimuli We performed in vitro whole-cell patch-clamp recordings in brain slices from adult zebra finches (Taeniopygia guttata) and observed that half of NCM neurons fire APs phasically in response to membrane depolarizations, while the rest fire transiently or tonically. Phasic neurons fired APs faster and with more temporal precision than tonic and transient neurons. These neurons had similar membrane resting potentials, but phasic neurons had lower membrane input resistance and time constant. Surprisingly phasic neurons did not express low-threshold VAKCs, which curtailed firing in phasic mammalian brainstem neurons, having similar VAKCs to other NCM neurons. The phasic firing was determined not by VAKCs, but by the potassium background leak conductances, which was more prominently expressed in phasic neurons, a result corroborated by pharmacological, dynamic-clamp, and modeling experiments. These results reveal a new role for leak currents in generating firing diversity in central neurons.
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Affiliation(s)
- André A Dagostin
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo Ribeirão Preto, Brazil
| | - Peter V Lovell
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland OR, USA
| | - Markus M Hilscher
- Brain Institute, Federal University of Rio Grande do Norte Natal, Brazil ; Institute for Analysis and Scientific Computing, Vienna University of Technology Vienna, Austria
| | - Claudio V Mello
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland OR, USA
| | - Ricardo M Leão
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo Ribeirão Preto, Brazil
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22
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O'Connell MN, Barczak A, Ross D, McGinnis T, Schroeder CE, Lakatos P. Multi-Scale Entrainment of Coupled Neuronal Oscillations in Primary Auditory Cortex. Front Hum Neurosci 2015; 9:655. [PMID: 26696866 PMCID: PMC4673342 DOI: 10.3389/fnhum.2015.00655] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/17/2015] [Indexed: 12/02/2022] Open
Abstract
Earlier studies demonstrate that when the frequency of rhythmic tone sequences or streams is task relevant, ongoing excitability fluctuations (oscillations) of neuronal ensembles in primary auditory cortex (A1) entrain to stimulation in a frequency dependent way that sharpens frequency tuning. The phase distribution across A1 neuronal ensembles at time points when attended stimuli are predicted to occur reflects the focus of attention along the spectral attribute of auditory stimuli. This study examined how neuronal activity is modulated if only the temporal features of rhythmic stimulus streams are relevant. We presented macaques with auditory clicks arranged in 33 Hz (gamma timescale) quintets, repeated at a 1.6 Hz (delta timescale) rate. Such multi-scale, hierarchically organized temporal structure is characteristic of vocalizations and other natural stimuli. Monkeys were required to detect and respond to deviations in the temporal pattern of gamma quintets. As expected, engagement in the auditory task resulted in the multi-scale entrainment of delta- and gamma-band neuronal oscillations across all of A1. Surprisingly, however, the phase-alignment, and thus, the physiological impact of entrainment differed across the tonotopic map in A1. In the region of 11–16 kHz representation, entrainment most often aligned high excitability oscillatory phases with task-relevant events in the input stream and thus resulted in response enhancement. In the remainder of the A1 sites, entrainment generally resulted in response suppression. Our data indicate that the suppressive effects were due to low excitability phase delta oscillatory entrainment and the phase amplitude coupling of delta and gamma oscillations. Regardless of the phase or frequency, entrainment appeared stronger in left A1, indicative of the hemispheric lateralization of auditory function.
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Affiliation(s)
- M N O'Connell
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA
| | - A Barczak
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA
| | - D Ross
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA
| | - T McGinnis
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA
| | - C E Schroeder
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA ; Department of Psychiatry, Columbia College of Physicians and Surgeons New York, NY, USA
| | - P Lakatos
- Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute Orangeburg, NY, USA ; Department of Psychiatry, NYU School of Medicine New York, NY, USA
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23
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Decreased temporal precision of neuronal signaling as a candidate mechanism of auditory processing disorder. Hear Res 2015; 330:213-20. [PMID: 26119177 DOI: 10.1016/j.heares.2015.06.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 06/09/2015] [Accepted: 06/23/2015] [Indexed: 11/22/2022]
Abstract
The sense of hearing is the fastest of our senses and provides the first all-or-none action potential in the auditory nerve in less than four milliseconds. Short stimulus evoked latencies and their minimal variability are hallmarks of auditory processing from spiral ganglia to cortex. Here, we review how even small changes in first spike latencies (FSL) and their variability (jitter) impact auditory temporal processing. We discuss a number of mouse models with degraded FSL/jitter whose mutations occur exclusively in the central auditory system and therefore might serve as candidates to investigate the cellular mechanisms underlying auditory processing disorders (APD).
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24
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Spencer MJ, Nayagam DAX, Clarey JC, Paolini AG, Meffin H, Burkitt AN, Grayden DB. Broadband onset inhibition can suppress spectral splatter in the auditory brainstem. PLoS One 2015; 10:e0126500. [PMID: 25978772 PMCID: PMC4433210 DOI: 10.1371/journal.pone.0126500] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 04/02/2015] [Indexed: 12/02/2022] Open
Abstract
In vivo intracellular responses to auditory stimuli revealed that, in a particular population of cells of the ventral nucleus of the lateral lemniscus (VNLL) of rats, fast inhibition occurred before the first action potential. These experimental data were used to constrain a leaky integrate-and-fire (LIF) model of the neurons in this circuit. The post-synaptic potentials of the VNLL cell population were characterized using a method of triggered averaging. Analysis suggested that these inhibited VNLL cells produce action potentials in response to a particular magnitude of the rate of change of their membrane potential. The LIF model was modified to incorporate the VNLL cells’ distinctive action potential production mechanism. The model was used to explore the response of the population of VNLL cells to simple speech-like sounds. These sounds consisted of a simple tone modulated by a saw tooth with exponential decays, similar to glottal pulses that are the repeated impulses seen in vocalizations. It was found that the harmonic component of the sound was enhanced in the VNLL cell population when compared to a population of auditory nerve fibers. This was because the broadband onset noise, also termed spectral splatter, was suppressed by the fast onset inhibition. This mechanism has the potential to greatly improve the clarity of the representation of the harmonic content of certain kinds of natural sounds.
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Affiliation(s)
- Martin J. Spencer
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- National ICT Australia, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- Centre for Neural Engineering, University of Melbourne, Melbourne, Australia
- * E-mail:
| | - David A. X. Nayagam
- Bionics Institute, Melbourne, Australia
- Department of Pathology, University of Melbourne, Melbourne, Australia
| | | | - Antonio G. Paolini
- Health Innovations Research Institute, RMIT University, Melbourne, Australia
| | - Hamish Meffin
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- National ICT Australia, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- Centre for Neural Engineering, University of Melbourne, Melbourne, Australia
| | - Anthony N. Burkitt
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- National ICT Australia, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- Centre for Neural Engineering, University of Melbourne, Melbourne, Australia
- Bionics Institute, Melbourne, Australia
| | - David B. Grayden
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- National ICT Australia, Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Australia
- Centre for Neural Engineering, University of Melbourne, Melbourne, Australia
- Bionics Institute, Melbourne, Australia
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25
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Kopp-Scheinpflug C, Pigott BM, Forsythe ID. Nitric oxide selectively suppresses IH currents mediated by HCN1-containing channels. J Physiol 2015; 593:1685-700. [PMID: 25605440 PMCID: PMC4386966 DOI: 10.1113/jphysiol.2014.282194] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 01/16/2015] [Indexed: 12/12/2022] Open
Abstract
Hyperpolarization-activated non-specific cation-permeable channels (HCN) mediate I(H) currents, which are modulated by cGMP and cAMP and by nitric oxide (NO) signalling. Channel properties depend upon subunit composition (HCN1-4 and accessory subunits) as demonstrated in expression systems, but physiological relevance requires investigation in native neurons with intact intracellular signalling. Here we use the superior olivary complex (SOC), which exhibits a distinctive pattern of HCN1 and HCN2 expression, to investigate NO modulation of the respective I(H) currents, and compare properties in wild-type and HCN1 knockout mice. The medial nucleus of the trapezoid body (MNTB) expresses HCN2 subunits exclusively, and sends inhibitory projections to the medial and lateral superior olives (MSO, LSO) and the superior paraolivary nucleus (SPN). In contrast to the MNTB, these target nuclei possess an I(H) with fast kinetics, and they express HCN1 subunits. NO is generated in the SOC following synaptic activity and here we show that NO selectively suppresses HCN1, while enhancing IH mediated by HCN2 subunits. NO hyperpolarizes the half-activation of HCN1-mediated currents and slows the kinetics of native IH currents in the MSO, LSO and SPN. This modulation was independent of cGMP and absent in transgenic mice lacking HCN1. Independently, NO signalling depolarizes the half-activation of HCN2-mediated I(H) currents in a cGMP-dependent manner. Thus, NO selectively suppresses fast HCN1-mediated I(H) and facilitates a slow HCN2-mediated I(H) , so generating a spectrum of modulation, dependent on the local expression of HCN1 and/or HCN2.
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Affiliation(s)
- Cornelia Kopp-Scheinpflug
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University Munich, Großhadernerstr. 282152, Planegg-Martinsried, Germany
| | - Beatrice M Pigott
- Department of Cell Physiology and Pharmacology, University of LeicesterLeicester, LE1 9HN, UK
| | - Ian D Forsythe
- Department of Cell Physiology and Pharmacology, University of LeicesterLeicester, LE1 9HN, UK
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26
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Franken TP, Roberts MT, Wei L, Golding NL, Joris PX. In vivo coincidence detection in mammalian sound localization generates phase delays. Nat Neurosci 2015; 18:444-52. [PMID: 25664914 PMCID: PMC4410695 DOI: 10.1038/nn.3948] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 01/14/2015] [Indexed: 11/09/2022]
Abstract
Sound localization critically depends on detection of differences in arrival time of sounds at the two ears (acoustic delay). The fundamental mechanisms are debated, but all proposals include a process of coincidence detection and a separate source of internal delay which offsets the acoustic delay and determines neural tuning. We obtained in vivo patch clamp recordings of binaural neurons in the Mongolian gerbil, combined with pharmacological manipulations, to directly compare neuronal input to output and to separate excitation from inhibition. The results cannot be accounted for by existing models and reveal that coincidence detection is not an instantaneous process but is shaped by the interaction of intrinsic conductances with preceding synaptic activity. This interaction generates an internal delay as an intrinsic part of the process of coincidence detection. The multiplication and time-shifting stages thought to extract synchronous activity in many brain areas can thus be combined in a single operation.
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Affiliation(s)
- Tom P Franken
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Michael T Roberts
- Department of Neuroscience and Center for Learning and Memory, University of Texas at Austin, Austin, Texas, USA
| | - Liting Wei
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
| | - Nace L Golding
- Department of Neuroscience and Center for Learning and Memory, University of Texas at Austin, Austin, Texas, USA
| | - Philip X Joris
- Laboratory of Auditory Neurophysiology, KU Leuven, Leuven, Belgium
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27
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Negm MH, Bruce IC. The Effects of HCN and KLT Ion Channels on Adaptation and Refractoriness in a Stochastic Auditory Nerve Model. IEEE Trans Biomed Eng 2014; 61:2749-59. [DOI: 10.1109/tbme.2014.2327055] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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28
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Laudanski J, Torben-Nielsen B, Segev I, Shamma S. Spatially distributed dendritic resonance selectively filters synaptic input. PLoS Comput Biol 2014; 10:e1003775. [PMID: 25144440 PMCID: PMC4140644 DOI: 10.1371/journal.pcbi.1003775] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 06/30/2014] [Indexed: 11/25/2022] Open
Abstract
An important task performed by a neuron is the selection of relevant inputs from among thousands of synapses impinging on the dendritic tree. Synaptic plasticity enables this by strenghtening a subset of synapses that are, presumably, functionally relevant to the neuron. A different selection mechanism exploits the resonance of the dendritic membranes to preferentially filter synaptic inputs based on their temporal rates. A widely held view is that a neuron has one resonant frequency and thus can pass through one rate. Here we demonstrate through mathematical analyses and numerical simulations that dendritic resonance is inevitably a spatially distributed property; and therefore the resonance frequency varies along the dendrites, and thus endows neurons with a powerful spatiotemporal selection mechanism that is sensitive both to the dendritic location and the temporal structure of the incoming synaptic inputs.
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Affiliation(s)
- Jonathan Laudanski
- Scientific and Clinical Research Department, Neurelec, Vallauris, France
- Equipe Audition, Département d'études cognitives, Ecole Normale Supérieure, Paris, France
| | - Benjamin Torben-Nielsen
- Computational Neuroscience Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
- Department of Neurobiology and the Edmond and Lily Safra Center for Brain Science, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Idan Segev
- Department of Neurobiology and the Edmond and Lily Safra Center for Brain Science, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Shihab Shamma
- Equipe Audition, Département d'études cognitives, Ecole Normale Supérieure, Paris, France
- Institute for Systems Research and Department of Electrical & Computer Engineering, University of Maryland, College Park, Maryland, United States of America
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29
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Hamlet WR, Liu YW, Tang ZQ, Lu Y. Interplay between low threshold voltage-gated K(+) channels and synaptic inhibition in neurons of the chicken nucleus laminaris along its frequency axis. Front Neural Circuits 2014; 8:51. [PMID: 24904297 PMCID: PMC4033047 DOI: 10.3389/fncir.2014.00051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 04/24/2014] [Indexed: 11/16/2022] Open
Abstract
Central auditory neurons that localize sound in horizontal space have specialized intrinsic and synaptic cellular mechanisms to tightly control the threshold and timing for action potential generation. However, the critical interplay between intrinsic voltage-gated conductances and extrinsic synaptic conductances in determining neuronal output are not well understood. In chicken, neurons in the nucleus laminaris (NL) encode sound location using interaural time difference (ITD) as a cue. Along the tonotopic axis of NL, there exist robust differences among low, middle, and high frequency (LF, MF, and HF, respectively) neurons in a variety of neuronal properties such as low threshold voltage-gated K+ (LTK) channels and depolarizing inhibition. This establishes NL as an ideal model to examine the interactions between LTK currents and synaptic inhibition across the tonotopic axis. Using whole-cell patch clamp recordings prepared from chicken embryos (E17–E18), we found that LTK currents were larger in MF and HF neurons than in LF neurons. Kinetic analysis revealed that LTK currents in MF neurons activated at lower voltages than in LF and HF neurons, whereas the inactivation of the currents was similar across the tonotopic axis. Surprisingly, blockade of LTK currents using dendrotoxin-I (DTX) tended to broaden the duration and increase the amplitude of the depolarizing inhibitory postsynaptic potentials (IPSPs) in NL neurons without dependence on coding frequency regions. Analyses of the effects of DTX on inhibitory postsynaptic currents led us to interpret this unexpected observation as a result of primarily postsynaptic effects of LTK currents on MF and HF neurons, and combined presynaptic and postsynaptic effects in LF neurons. Furthermore, DTX transferred subthreshold IPSPs to spikes. Taken together, the results suggest a critical role for LTK currents in regulating inhibitory synaptic strength in ITD-coding neurons at various frequencies.
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Affiliation(s)
- William R Hamlet
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
| | - Yu-Wei Liu
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University Rootstown, OH, USA
| | - Zheng-Quan Tang
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University Rootstown, OH, USA
| | - Yong Lu
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University Rootstown, OH, USA ; School of Biomedical Sciences, Kent State University Kent, OH, USA
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Nogueira J, Caputi AA. From the intrinsic properties to the functional role of a neuron phenotype: an example from electric fish during signal trade-off. ACTA ACUST UNITED AC 2014; 216:2380-92. [PMID: 23761463 DOI: 10.1242/jeb.082651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This review deals with the question: what is the relationship between the properties of a neuron and the role that the neuron plays within a given neural circuit? Answering this kind of question requires collecting evidence from multiple neuron phenotypes and comparing the role of each type in circuits that perform well-defined computational tasks. The focus here is on the spherical neurons in the electrosensory lobe of the electric fish Gymnotus omarorum. They belong to the one-spike-onset phenotype expressed at the early stages of signal processing in various sensory modalities and diverse taxa. First, we refer to the one-spike neuron intrinsic properties, their foundation on a low-threshold K(+) conductance, and the potential roles of this phenotype in different circuits within a comparative framework. Second, we present a brief description of the active electric sense of weakly electric fish and the particularities of spherical one-spike-onset neurons in the electrosensory lobe of G. omarorum. Third, we introduce one of the specific tasks in which these neurons are involved: the trade-off between self- and allo-generated signals. Fourth, we discuss recent evidence indicating a still-undescribed role for the one-spike phenotype. This role deals with the blockage of the pathway after being activated by the self-generated electric organ discharge and how this blockage favors self-generated electrosensory information in the context of allo-generated interference. Based on comparative analysis we conclude that one-spike-onset neurons may play several functional roles in animal sensory behavior. There are specific adaptations of the neuron's 'response function' to the circuit and task. Conversely, the way in which a task is accomplished depends on the intrinsic properties of the neurons involved. In short, the role of a neuron within a circuit depends on the neuron and its functional context.
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Affiliation(s)
- Javier Nogueira
- Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Avenida General Flores, 2125 Montevideo, Uruguay
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Nogueira J, Caputi AA. Pharmacological study of the one spike spherical neuron phenotype in Gymnotus omarorum. Neuroscience 2013; 258:347-54. [PMID: 24269939 DOI: 10.1016/j.neuroscience.2013.11.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 11/03/2013] [Accepted: 11/09/2013] [Indexed: 10/26/2022]
Abstract
The intrinsic properties of spherical neurons play a fundamental role in the sensory processing of self-generated signals along a fast electrosensory pathway in electric fish. Previous results indicate that the spherical neuron's intrinsic properties depend mainly on the presence of two resonant currents that tend to clamp the voltage near the resting potential. Here we show that these are: a low-threshold potassium current blocked by 4-aminopyridine and a mixed cationic current blocked by cesium chloride. We also show that the low-threshold potassium current also causes the long refractory period, explaining the necessary properties that implement the dynamic filtering of the self-generated signals previously described. Comparative data from other fish and from the auditory system indicate that other single spiking onset neurons might differ in the channel repertoire observed in the spherical neurons of Gymnotus omarorum.
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Affiliation(s)
- J Nogueira
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Avenue Italia 3318, Montevideo, Uruguay; Department of Histology and Embriology, Facultad de Medicina, Universidad de la República, Gral. Flores 2515, Montevideo, Uruguay
| | - A A Caputi
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Avenue Italia 3318, Montevideo, Uruguay.
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Rattay F, Potrusil T, Wenger C, Wise AK, Glueckert R, Schrott-Fischer A. Impact of morphometry, myelinization and synaptic current strength on spike conduction in human and cat spiral ganglion neurons. PLoS One 2013; 8:e79256. [PMID: 24260179 PMCID: PMC3832640 DOI: 10.1371/journal.pone.0079256] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 09/20/2013] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Our knowledge about the neural code in the auditory nerve is based to a large extent on experiments on cats. Several anatomical differences between auditory neurons in human and cat are expected to lead to functional differences in speed and safety of spike conduction. METHODOLOGY/PRINCIPAL FINDINGS Confocal microscopy was used to systematically evaluate peripheral and central process diameters, commonness of myelination and morphology of spiral ganglion neurons (SGNs) along the cochlea of three human and three cats. Based on these morphometric data, model analysis reveales that spike conduction in SGNs is characterized by four phases: a postsynaptic delay, constant velocity in the peripheral process, a presomatic delay and constant velocity in the central process. The majority of SGNs are type I, connecting the inner hair cells with the brainstem. In contrast to those of humans, type I neurons of the cat are entirely myelinated. Biophysical model evaluation showed delayed and weak spikes in the human soma region as a consequence of a lack of myelin. The simulated spike conduction times are in accordance with normal interwave latencies from auditory brainstem response recordings from man and cat. Simulated 400 pA postsynaptic currents from inner hair cell ribbon synapses were 15 times above threshold. They enforced quick and synchronous spiking. Both of these properties were not present in type II cells as they receive fewer and much weaker (∼26 pA) synaptic stimuli. CONCLUSIONS/SIGNIFICANCE Wasting synaptic energy boosts spike initiation, which guarantees the rapid transmission of temporal fine structure of auditory signals. However, a lack of myelin in the soma regions of human type I neurons causes a large delay in spike conduction in comparison with cat neurons. The absent myelin, in combination with a longer peripheral process, causes quantitative differences of temporal parameters in the electrically stimulated human cochlea compared to the cat cochlea.
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Affiliation(s)
- Frank Rattay
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Thomas Potrusil
- Department of Otorhinolaryngology, Innsbruck Medical University, Innsbruck, Austria
- Faculty of Informatics, Vienna University of Technology, Vienna, Austria
| | - Cornelia Wenger
- Institute of Biophysics and Biomedical Engeneering, Faculty of Science, University of Lisbon, Lisbon, Portugal
| | | | - Rudolf Glueckert
- Department of Otorhinolaryngology, Innsbruck Medical University, Innsbruck, Austria
- University Clinics Innsbruck, Tiroler Landeskrankenanstalten, Innsbruck, Austria
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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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Rusznák Z, Pál B, Kőszeghy A, Fu Y, Szücs G, Paxinos G. The hyperpolarization-activated non-specific cation current (In ) adjusts the membrane properties, excitability, and activity pattern of the giant cells in the rat dorsal cochlear nucleus. Eur J Neurosci 2013; 37:876-90. [PMID: 23301797 DOI: 10.1111/ejn.12116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 11/19/2012] [Accepted: 11/30/2012] [Indexed: 12/16/2022]
Abstract
Giant cells of the cochlear nucleus are thought to integrate multimodal sensory inputs and participate in monaural sound source localization. Our aim was to explore the significance of a hyperpolarization-activated current in determining the activity of giant neurones in slices prepared from 10 to 14-day-old rats. When subjected to hyperpolarizing stimuli, giant cells produced a 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyridinium chloride (ZD7288)-sensitive inward current with a reversal potential and half-activation voltage of -36 and -88 mV, respectively. Consequently, the current was identified as the hyperpolarization-activated non-specific cationic current (Ih ). At the resting membrane potential, 3.5% of the maximum Ih conductance was available. Immunohistochemistry experiments suggested that hyperpolarization-activated, cyclic nucleotide-gated, cation non-selective (HCN)1, HCN2, and HCN4 subunits contribute to the assembly of the functional channels. Inhibition of Ih hyperpolarized the membrane by 6 mV and impeded spontaneous firing. The frequencies of spontaneous inhibitory and excitatory postsynaptic currents reaching the giant cell bodies were reduced but no significant change was observed when evoked postsynaptic currents were recorded. Giant cells are affected by biphasic postsynaptic currents consisting of an excitatory and a subsequent inhibitory component. Inhibition of Ih reduced the frequency of these biphasic events by 65% and increased the decay time constants of the inhibitory component. We conclude that Ih adjusts the resting membrane potential, contributes to spontaneous action potential firing, and may participate in the dendritic integration of the synaptic inputs of the giant neurones. Because its amplitude was higher in young than in adult rats, Ih of the giant cells may be especially important during the postnatal maturation of the auditory system.
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Affiliation(s)
- Zoltán Rusznák
- Neuroscience Research Australia, Sydney, NSW 2031, Australia.
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Deficits in responding to brief noise offsets in Kcna1 -/- mice reveal a contribution of this gene to precise temporal processing seen previously only for stimulus onsets. J Assoc Res Otolaryngol 2012; 13:351-8. [PMID: 22302114 DOI: 10.1007/s10162-011-0312-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 12/25/2011] [Indexed: 10/14/2022] Open
Abstract
The voltage-gated potassium channel subunit Kv1.1 encoded by the Kcna1 gene is expressed in many brainstem nuclei, and electrophysiological studies of Kcna1-null mutant (-/-) single neurons suggest that channels containing this subunit are critical for precise processing of rapid acoustic perturbations. We tested the hypothesis that brief offsets of a background noise are behaviorally less salient for Kcna1 -/- mice, measured by changes in noise offset inhibition of acoustic startle reflexes (ASR). In experiment 1, noise offset was followed by ASR-eliciting sound bursts either after 1-10 ms quiet intervals or after the return of noise for 10-290 ms following 10-ms quiet gaps. ASR inhibition to offset and gaps was initially higher in +/+ mice but persisted longer in -/- mice. Experiment 2 contrasted brief abrupt offsets with ramped offsets of the same duration up to 10 ms, the ramps intended to simulate progressively slower internal decays of afferent processing. Both groups had greater inhibition for abrupt offsets at asymptote, and this difference was evident at the 1-ms interval in +/+ but not -/- mice. Further, the asymptotic effect of ramped offsets in +/+ mice was equal to that produced by abrupt offsets in null mutants, suggesting more perseveration of internal afferent activity following noise offset in -/- mice. Overall, these data are consistent with prior electrophysiological studies showing that the neural mechanisms for processing acoustic transients are less effective in Kcna1 -/- mice and support previous proposals that Kv1.1 contributes to the perception of animal vocalizations and human speech.
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Ashida G, Funabiki K, Kuokkanen PT, Kempter R, Carr CE. Signal-to-noise ratio in the membrane potential of the owl's auditory coincidence detectors. J Neurophysiol 2012; 108:2837-45. [PMID: 22933726 DOI: 10.1152/jn.00366.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Owls use interaural time differences (ITDs) to locate a sound source. They compute ITD in a specialized neural circuit that consists of axonal delay lines from the cochlear nucleus magnocellularis (NM) and coincidence detectors in the nucleus laminaris (NL). Recent physiological recordings have shown that tonal stimuli induce oscillatory membrane potentials in NL neurons (Funabiki K, Ashida G, Konishi M. J Neurosci 31: 15245-15256, 2011). The amplitude of these oscillations varies with ITD and is strongly correlated to the firing rate. The oscillation, termed the sound analog potential, has the same frequency as the stimulus tone and is presumed to originate from phase-locked synaptic inputs from NM fibers. To investigate how these oscillatory membrane potentials are generated, we applied recently developed signal-to-noise ratio (SNR) analysis techniques (Kuokkanen PT, Wagner H, Ashida G, Carr CE, Kempter R. J Neurophysiol 104: 2274-2290, 2010) to the intracellular waveforms obtained in vivo. Our theoretical prediction of the band-limited SNRs agreed with experimental data for mid- to high-frequency (>2 kHz) NL neurons. For low-frequency (≤2 kHz) NL neurons, however, measured SNRs were lower than theoretical predictions. These results suggest that the number of independent NM fibers converging onto each NL neuron and/or the population-averaged degree of phase-locking of the NM fibers could be significantly smaller in the low-frequency NL region than estimated for higher best-frequency NL.
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Affiliation(s)
- Go Ashida
- Department of Biology, University of Maryland, College Park, Maryland 20742, USA.
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Abstract
Some neurons in the mammalian auditory system are able to detect and report the coincident firing of inputs with remarkable temporal precision. A strong, low-voltage-activated potassium conductance (g(KL)) at the cell body and dendrites gives these neurons sensitivity to the rate of depolarization by EPSPs, allowing neurons to assess the coincidence of the rising slopes of unitary EPSPs. Two groups of neurons in the brain stem, octopus cells in the posteroventral cochlear nucleus and principal cells of the medial superior olive (MSO), extract acoustic information by assessing coincident firing of their inputs over a submillisecond timescale and convey that information at rates of up to 1000 spikes s(-1). Octopus cells detect the coincident activation of groups of auditory nerve fibres by broadband transient sounds, compensating for the travelling wave delay by dendritic filtering, while MSO neurons detect coincident activation of similarly tuned neurons from each of the two ears through separate dendritic tufts. Each makes use of filtering that is introduced by the spatial distribution of inputs on dendrites.
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Affiliation(s)
- Nace L Golding
- Section of Neurobiology and Center for Learning and Memory, University of Texas at Austin, Austin, TX, USA
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Felix RA, Kadner A, Berrebi AS. Effects of ketamine on response properties of neurons in the superior paraolivary nucleus of the mouse. Neuroscience 2011; 201:307-19. [PMID: 22123167 DOI: 10.1016/j.neuroscience.2011.11.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 11/09/2011] [Accepted: 11/10/2011] [Indexed: 11/19/2022]
Abstract
The superior paraolivary nucleus (SPON; alternative abbreviation: SPN for the same nucleus in certain species) is a prominent brainstem structure that provides strong inhibitory input to the auditory midbrain. Previous studies established that SPON neurons encode temporal sound features with high precision. These earlier characterizations of SPON responses were recorded under the influence of ketamine, a dissociative anesthetic agent and known antagonist of N-methyl-d-aspartate glutamate (NMDA) receptors. Because NMDA alters neural responses from the auditory brainstem, single unit extracellular recordings of SPON neurons were performed in the presence and absence of ketamine. In doing so, this study represents the first in vivo examination of the SPON of the mouse. Herein, independent data sets of SPON neurons are characterized that did or did not receive ketamine, as well as neurons that were recorded both prior to and following ketamine administration. In all conditions, SPON neurons exhibited contralaterally driven spikes triggered by the offset of pure tone stimuli. Ketamine lowered both evoked and spontaneous spiking, decreased the sharpness of frequency tuning, and increased auditory thresholds and first-spike latencies. In addition, ketamine limited the range of modulation frequencies to which neurons phase-locked to sinusoidally amplitude-modulated tones.
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Affiliation(s)
- R A Felix
- Department of Otolaryngology-Head and Neck Surgery, and the Sensory Neuroscience Research Center, PO Box 9303 Health Sciences Center, West Virginia University School of Medicine, Morgantown, WV 26506, USA
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Cao XJ, Oertel D. The magnitudes of hyperpolarization-activated and low-voltage-activated potassium currents co-vary in neurons of the ventral cochlear nucleus. J Neurophysiol 2011; 106:630-40. [PMID: 21562186 DOI: 10.1152/jn.00015.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the ventral cochlear nucleus (VCN), neurons have hyperpolarization-activated conductances, which in some cells are enormous, that contribute to the ability of neurons to convey acoustic information in the timing of their firing by decreasing the input resistance and speeding-up voltage changes. Comparisons of the electrophysiological properties of neurons in the VCN of mutant mice that lack the hyperpolarization-activated cyclic nucleotide-gated channel α subunit 1 (HCN1(-/-)) (Nolan et al. 2003) with wild-type controls (HCN1(+/+)) and with outbred ICR mice reveal that octopus, T stellate, and bushy cells maintain their electrophysiological distinctions in all strains. Hyperpolarization-activated (I(h)) currents were smaller and slower, input resistances were higher, and membrane time constants were longer in HCN1(-/-) than in HCN1(+/+) in octopus, bushy, and T stellate cells. There were significant differences in the average magnitudes of I(h), input resistances, and time constants between HCN1(+/+) and ICR mice, but the resting potentials did not differ between strains. I(h) is opposed by a low-voltage-activated potassium (I(KL)) current in bushy and octopus cells, whose magnitudes varied widely between neuronal types and between strains. The magnitudes of I(h) and I(KL) were correlated across neuronal types and across mouse strains. Furthermore, these currents balanced one another at the resting potential in individual cells. The magnitude of I(h) and I(KL) is linked in bushy and octopus cells and varies not only between HCN1(-/-) and HCN1(+/+) but also between "wild-type" strains of mice, raising the question to what extent the wild-type strains reflect normal mice.
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Affiliation(s)
- Xiao-Jie Cao
- Department of Neuroscience, School of Neuroscience Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA
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Cao XJ, Oertel D. Auditory nerve fibers excite targets through synapses that vary in convergence, strength, and short-term plasticity. J Neurophysiol 2010; 104:2308-20. [PMID: 20739600 PMCID: PMC3350034 DOI: 10.1152/jn.00451.2010] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 08/20/2010] [Indexed: 12/19/2022] Open
Abstract
Auditory nerve fibers are the major source of excitation to the three groups of principal cells of the ventral cochlear nucleus (VCN), bushy, T stellate, and octopus cells. Shock-evoked excitatory postsynaptic currents (eEPSCs) in slices from mice showed systematic differences between groups of principal cells, indicating that target cells contribute to determining pre- and postsynaptic properties of synapses from spiral ganglion cells. Bushy cells likely to be small spherical bushy cells receive no more than three, most often two, excitatory inputs; those likely to be globular bushy cells receive at least four, most likely five, inputs. T stellate cells receive 6.5 inputs. Octopus cells receive >60 inputs. The N-methyl-d-aspartate (NMDA) components of eEPSCs were largest in T stellate, smaller in bushy, and smallest in octopus cells, and they were larger in neurons from younger than older mice. The average AMPA conductance of a unitary input is 22 ± 15 nS in both groups of bushy cells, <1.5 nS in octopus cells, and 4.6 ± 3 nS in T stellate cells. Sensitivity to philanthotoxin (PhTX) and rectification in the intracellular presence of spermine indicate that AMPA receptors that mediate eEPSCs in T stellate cells contain more GluR2 subunits than those in bushy and octopus cells. The AMPA components of eEPSCs were briefer in bushy (0.5 ms half-width) than in T stellate and octopus cells (0.8-0.9 ms half-width). Widening of eEPSCs in the presence of cyclothiazide (CTZ) indicates that desensitization shortens eEPSCs. CTZ-insensitive synaptic depression of the AMPA components was greater in bushy and octopus than in T stellate cells.
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Affiliation(s)
- Xiao-Jie Cao
- Department of Physiology, School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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Inhibitory projections from the ventral nucleus of the lateral lemniscus and superior paraolivary nucleus create directional selectivity of frequency modulations in the inferior colliculus: a comparison of bats with other mammals. Hear Res 2010; 273:134-44. [PMID: 20451594 DOI: 10.1016/j.heares.2010.03.083] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 03/02/2010] [Accepted: 03/02/2010] [Indexed: 11/21/2022]
Abstract
This review considers four auditory brainstem nuclear groups and shows how studies of both bats and other mammals have provided insights into their response properties and the impact of their convergence in the inferior colliculus (IC). The four groups are octopus cells in the cochlear nucleus, their connections with the ventral nucleus of the lateral lemniscus (VNLL) and the superior paraolivary nucleus (SPON), and the connections of the VNLL and SPON with the IC. The theme is that the response properties of neurons in the SPON and VNLL map closely onto the synaptic response features of a unique subpopulation of cells in the IC of bats whose inputs are dominated by inhibition. We propose that the convergence of VNLL and SPON inputs generates the tuning of these IC cells, their unique temporal responses to tones, and their directional selectivities for frequency modulated (FM) sweeps. Other IC neurons form directional properties in other ways, showing that selective response properties are formed in multiple ways. In the final section we discuss why multiple formations of common response properties could amplify differences in population activity patterns evoked by signals that have similar spectrotemporal features.
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Yi E, Roux I, Glowatzki E. Dendritic HCN channels shape excitatory postsynaptic potentials at the inner hair cell afferent synapse in the mammalian cochlea. J Neurophysiol 2010; 103:2532-43. [PMID: 20220080 DOI: 10.1152/jn.00506.2009] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synaptic transmission at the inner hair cell (IHC) afferent synapse, the first synapse in the auditory pathway, is specialized for rapid and reliable signaling. Here we investigated the properties of a hyperpolarization-activated current (I(h)), expressed in the afferent dendrite of auditory nerve fibers, and its role in shaping postsynaptic activity. We used whole cell patch-clamp recordings from afferent dendrites directly where they contact the IHC in excised postnatal rat cochlear turns. Excitatory postsynaptic potentials (EPSPs) of variable amplitude (1-35 mV) were found with 10-90% rise times of about 1 ms and time constants of decay of about 5 ms at room temperature. Current-voltage relations recorded in afferent dendrites revealed I(h). The pharmacological profile and reversal potential (-45 mV) indicated that I(h) is mediated by hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels. The HCN channel subunits HCN1, HCN2, and HCN4 were found to be expressed in afferent dendrites using immunolabeling. Raising intracellular cAMP levels sped up the activation kinetics, increased the magnitude of I(h) and shifted the half activation voltage (V(half)) to more positive values (-104 +/- 3 to -91 +/- 2 mV). Blocking I(h) with 50 microM ZD7288 resulted in hyperpolarization of the resting membrane potential (approximately 4 mV) and slowing the decay of the EPSP by 47%, suggesting that I(h) is active at rest and shortens EPSPs, thereby potentially improving rapid and reliable signaling at this first synapse in the auditory pathway.
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Affiliation(s)
- Eunyoung Yi
- The Johns Hopkins School of Medicine, Department of Otolaryngology-Head and Neck Surgery, Baltimore, MD 21205, USA
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43
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Bahmer A, Langner G. Parameters for a model of an oscillating neuronal network in the cochlear nucleus defined by genetic algorithms. BIOLOGICAL CYBERNETICS 2010; 102:81-93. [PMID: 20012082 DOI: 10.1007/s00422-009-0353-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 11/17/2009] [Indexed: 05/28/2023]
Abstract
Chopper neurons in the cochlear nucleus are characterized by intrinsic oscillations with short average interspike intervals (ISIs) and relative level independence of their response (Pfeiffer, Exp Brain Res 1:220-235, 1966; Blackburn and Sachs, J Neurophysiol 62:1303-1329, 1989), properties which are unattained by models of single chopper neurons (e.g., Rothman and Manis, J Neurophysiol 89:3070-3082, 2003a). In order to achieve short ISIs, we optimized the time constants of Rothman and Manis single neuron model with genetic algorithms. Some parameters in the optimization, such as the temperature and the capacity of the cell, turned out to be crucial for the required acceleration of their response. In order to achieve the relative level independence, we have simulated an interconnected network consisting of Rothman and Manis neurons. The results indicate that by stabilization of intrinsic oscillations, it is possible to simulate the physiologically observed level independence of ISIs. As previously reviewed and demonstrated (Bahmer and Langner, Biol Cybern 95:371-379, 2006a), chopper neurons show a preference for ISIs which are multiples of 0.4 ms. It was also demonstrated that the network consisting of two optimized Rothman and Manis neurons which activate each other with synaptic delays of 0.4 ms shows a preference for ISIs of 0.8 ms. Oscillations with various multiples of 0.4 ms as ISIs may be derived from neurons in a more complex network that is activated by simultaneous input of an onset neuron and several auditory nerve fibers.
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Affiliation(s)
- Andreas Bahmer
- Clinic for Otolaryngology, Audiological Acoustics, University of Frankfurt Main, 60590, Frankfurt, Germany.
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44
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Bal R, Baydas G, Naziroglu M. Electrophysiological properties of ventral cochlear nucleus neurons of the dog. Hear Res 2009; 256:93-103. [DOI: 10.1016/j.heares.2009.07.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 06/22/2009] [Accepted: 07/12/2009] [Indexed: 11/24/2022]
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Hassfurth B, Magnusson AK, Grothe B, Koch U. Sensory deprivation regulates the development of the hyperpolarization-activated current in auditory brainstem neurons. Eur J Neurosci 2009; 30:1227-38. [PMID: 19788576 DOI: 10.1111/j.1460-9568.2009.06925.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are highly expressed in the superior olivary complex, the primary locus for binaural information processing. This hyperpolarization-activated current (I(h)) regulates the excitability of neurons and enhances the temporally precise analysis of the binaural acoustic cues. By using the whole-cell patch-clamp technique, we examined the properties of I(h) current in neurons of the lateral superior olive (LSO) and the medial nucleus of the trapezoid body (MNTB) before and after hearing onset. Moreover, we tested the hypothesis that I(h) currents are actively regulated by sensory input activity by performing bilateral and unilateral cochlear ablations before hearing onset, resulting in a chronic auditory deprivation. The results show that after hearing onset, I(h) currents are rapidly upregulated in LSO neurons, but change only marginally in neurons of the MNTB. We also found a striking difference in maximal current density, voltage dependence and activation time constant between the LSO and the MNTB in mature-like animals. Following bilateral cochlear ablations before hearing onset, the I(h) currents were scaled up in the LSO and scaled down in the MNTB. Consequently, in the LSO this resulted in a depolarized resting membrane potential and a lower input resistance of these neurons. This type of activity-dependent homeostatic change could thus result in an augmented response to the remaining inputs.
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Affiliation(s)
- Benjamin Hassfurth
- Department Biologie II, Division of Neurobiology, Ludwig-Maximilans University München, 82152 Martinsried, Germany
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Blackmer T, Kuo SP, Bender KJ, Apostolides PF, Trussell LO. Dendritic calcium channels and their activation by synaptic signals in auditory coincidence detector neurons. J Neurophysiol 2009; 102:1218-26. [PMID: 19553482 DOI: 10.1152/jn.90513.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The avian nucleus laminaris (NL) encodes the azimuthal location of low-frequency sound sources by detecting the coincidence of binaural signals. Accurate coincidence detection requires precise developmental regulation of the lengths of the fine, bitufted dendrites that characterize neurons in NL. Such regulation has been suggested to be driven by local, synaptically mediated, dendritic signals such as Ca(2+). We examined Ca(2+) signaling through patch clamp and ion imaging experiments in slices containing nucleus laminaris from embryonic chicks. Voltage-clamp recordings of neurons located in the NL showed the presence of large Ca(2+) currents of two types, a low voltage-activated, fast inactivating Ni(2+) sensitive channel resembling mammalian T-type channels, and a high voltage-activated, slowly inactivating Cd(2+) sensitive channel. Two-photon Ca(2+) imaging showed that both channel types were concentrated on dendrites, even at their distal tips. Single action potentials triggered synaptically or by somatic current injection immediately elevated Ca(2+) throughout the entire cell. Ca(2+) signals triggered by subthreshold synaptic activity were highly localized. Thus when electrical activity is suprathreshold, Ca(2+) channels ensure that Ca(2+) rises in all dendrites, even those that are synaptically inactive.
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Affiliation(s)
- Trillium Blackmer
- Vollum Institute and Oregon Hearing Research Center, Oregon Health and Science University, Portland, Oregon 97239, USA
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Electrophysiological properties of octopus neurons of the cat cochlear nucleus: an in vitro study. J Assoc Res Otolaryngol 2009; 10:281-93. [PMID: 19277784 DOI: 10.1007/s10162-009-0159-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 02/05/2009] [Indexed: 12/25/2022] Open
Abstract
Electrophysiological studies from mice in vitro have suggested that octopus cells of the mammalian ventral cochlear nucleus (VCN) are anatomically and biophysically specialized for detecting the coincident firing of a population of auditory nerve fibers. Recordings from cats in vivo have shown that octopus cells fire rapidly and with exceptional temporal precision as they convey the timing of that coincidence to higher auditory centers. The current study addresses the question whether the biophysical properties of octopus cells that have until now been examined only in mice, are shared by octopus cells in cats. Whole-cell patch-clamp recordings confirm that octopus cells in brain slices from kittens share the anatomical and biophysical features of octopus cells in mice. As in mice, octopus cells in kittens have large cell bodies and thick dendrites that extend in one direction. Voltage changes produced by depolarizing and hyperpolarizing current injection were small and rapid. Input resistances and membrane time constants in octopus cells of 16-day-old kittens were 15.8 +/- 1.5 MOmega (n = 16) and 1.28 +/- 0.3 ms (n = 16), respectively. Octopus cells fired only a single action potential at the onset of a depolarizing current pulse; suprathreshold stimuli were greater than 1.8 nA. A tetrodotoxin (TTX)-sensitive sodium conductance (gNa) was responsible for the generation of the action potentials. Octopus cells displayed outward rectification that lasted for the duration of the depolarizing pulses. Hyperpolarizations produced by the injection of current exhibited a depolarizing sag of the membrane potential toward the resting value. A 4-aminopyridine (4-AP) and alpha-dendrotoxin (alpha-DTX)-sensitive, low-voltage-activated potassium conductance (gKL) and a ZD7288-sensitive, mixed-cation conductance (gh) were partially activated at rest, giving the octopus cells low input resistances and, as a consequence, brief time constants. In 7-day-old kittens, action potentials were taller and broader, input resistances higher, and both inward and outward rectification was weaker than in 16-day-old kittens. Also as in mice, stellate cells of the VCN fired trains of action potentials with constant interspike intervals when they were depolarized (n = 10) and bushy cells of the VCN fired only a single action potential at the onset of depolarizations (n = 6). In conclusion, the similarity of octopus cells in mice and kittens suggests that the anatomical and biophysical specializations that allow octopus cells to detect and convey synchronous firing among auditory nerve fibers are common to all mammals.
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Bahmer A, Langner G. A simulation of chopper neurons in the cochlear nucleus with wideband input from onset neurons. BIOLOGICAL CYBERNETICS 2009; 100:21-33. [PMID: 19015873 DOI: 10.1007/s00422-008-0276-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Accepted: 10/14/2008] [Indexed: 05/27/2023]
Abstract
The unique temporal and spectral properties of chopper neurons in the cochlear nucleus cannot be fully explained by current popular models. A new model of sustained chopper neurons was therefore suggested based on the assumption that chopper neurons receive input both from onset neurons and the auditory nerve (Bahmer and Langner in Biol Cybern 95:4, 2006). As a result of the interaction of broadband input from onset neurons and narrowband input from the auditory nerve, the chopper neurons in our model are characterized by a remarkable combination of sharp frequency tuning to pure tones and faithful periodicity coding. Our simulations show that the width of the spectral integration of the onset neuron is crucial for both the precision of periodicity coding and their resolution of single components of sinusoidally amplitude-modulated sine waves. One may hypothesize, therefore, that it would be an advantage if the hearing system were able to adapt the spectral integration of onset neurons to varying stimulus conditions.
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Affiliation(s)
- Andreas Bahmer
- University of Frankfurt Main, Clinic for Otolaryngology, Audiological Acoustics, 60590, Frankfurt, Germany.
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Kuba H, Ohmori H. Roles of axonal sodium channels in precise auditory time coding at nucleus magnocellularis of the chick. J Physiol 2008; 587:87-100. [PMID: 19001045 DOI: 10.1113/jphysiol.2008.162651] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
How the axonal distribution of Na(+) channels affects the precision of spike timing is not well understood. We addressed this question in auditory relay neurons of the avian nucleus magnocellularis. These neurons encode and convey information about the fine structure of sounds to which they are tuned by generating precisely timed action potentials in response to synaptic inputs. Patterns of synaptic inputs differ as a function of tuning. A small number of large inputs innervate high- and middle-frequency neurons, while a large number of small inputs innervate low-frequency neurons. We found that the distribution and density of Na(+) channels in the axon initial segments varied with the synaptic inputs, and were distinct in the low-frequency neurons. Low-frequency neurons had a higher density of Na(+) channels within a longer axonal stretch, and showed a larger spike amplitude and whole-cell Na(+) current than high/middle-frequency neurons. Computer simulations revealed that for low-frequency neurons, a large number of Na(+) channels were crucial for preserving spike timing because it overcame Na(+) current inactivation and K(+) current activation during compound EPSPs evoked by converging small inputs. In contrast, fewer channels were sufficient to generate a spike with high precision in response to an EPSP induced by a single massive input in the high/middle-frequency neurons. Thus the axonal Na(+) channel distribution is effectively coupled with synaptic inputs, allowing these neurons to convey auditory information in the timing of firing.
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Affiliation(s)
- Hiroshi Kuba
- Career-Path Promotion Unit for Young Life Scientists, Kyoto University Graduate School of Medicine, Kyoto, 606-8501 Japan.
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Castelló ME, Nogueira J, Trujillo-Cenóz O, Caputi AA. Sensory processing in the fast electrosensory pathway of pulse gymnotids studied at multiple integrative levels. Comp Biochem Physiol A Mol Integr Physiol 2008; 151:370-380. [PMID: 17513149 DOI: 10.1016/j.cbpa.2007.04.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 03/01/2007] [Accepted: 04/07/2007] [Indexed: 11/22/2022]
Abstract
Pulse gymnotids extract information about the environment using the pulsed discharge of an electric organ. Cutaneous electroreceptor organs transduce and encode the changes that objects imprint on the self-generated transcutaneous electric field. This review deals with the role of a neural circuit, the fast electrosensory path of pulse gymnotids, in the streaming of self generated electrosensory signals. The activation of this path triggers a low-responsiveness window slightly shorter than the interval between electric organ discharges. This phenomenon occurs at the electrosensory lateral line lobe where primary afferent terminals project on the somata of spherical neurons. The main subservient mechanism of the low-responsiveness window rely on the intrinsic properties of spherical neurons (dominated by a voltage dependent, low-threshold, non-inactivating and slowly-deactivating K(+) conductance) determining the cell to respond with a single spike followed by a long refractory period. Externally generated signals that randomly occur within the interval between self-generated discharges are likely blocked by the low responsiveness window. Repetitive signals, as those emitted by conspecifics with a slightly lower rate, occur progressively at longer delays beyond the duration of the low responsiveness window. Transient increases of the discharge rate relocate the interference within the low-responsiveness window. We propose that this combination of sensory filtering and electromotor control favors the self-generated signals in detriment of other, securing the continuity of the electrolocation stream.
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Affiliation(s)
- María E Castelló
- Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de la Facultad de Ciencias, Universidad de la República. Montevideo, Av Italia 3318, 11600, Uruguay; Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República. Montevideo, Uruguay
| | - Javier Nogueira
- Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de la Facultad de Ciencias, Universidad de la República. Montevideo, Av Italia 3318, 11600, Uruguay; Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República. Montevideo, Uruguay
| | - Omar Trujillo-Cenóz
- Departamento de Neuroanatomía Comparada, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de la Facultad de Ciencias, Universidad de la República. Montevideo, Uruguay
| | - Angel A Caputi
- Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Asociada de la Facultad de Ciencias, Universidad de la República. Montevideo, Av Italia 3318, 11600, Uruguay.
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