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Cederroth CR, Park JS, Basinou V, Weger BD, Tserga E, Sarlus H, Magnusson AK, Kadri N, Gachon F, Canlon B. Circadian Regulation of Cochlear Sensitivity to Noise by Circulating Glucocorticoids. Curr Biol 2019; 29:2477-2487.e6. [PMID: 31353184 PMCID: PMC6904421 DOI: 10.1016/j.cub.2019.06.057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 05/21/2019] [Accepted: 06/20/2019] [Indexed: 01/27/2023]
Abstract
The cochlea possesses a robust circadian clock machinery that regulates auditory function. How the cochlear clock is influenced by the circadian system remains unknown. Here, we show that cochlear rhythms are system driven and require local Bmal1 as well as central input from the suprachiasmatic nuclei (SCN). SCN ablations disrupted the circadian expression of the core clock genes in the cochlea. Because the circadian secretion of glucocorticoids (GCs) is controlled by the SCN and GCs are known to modulate auditory function, we assessed their influence on circadian gene expression. Removal of circulating GCs by adrenalectomy (ADX) did not have a major impact on core clock gene expression in the cochlea. Rather it abolished the transcription of clock-controlled genes involved in inflammation. ADX abolished the known differential auditory sensitivity to day and night noise trauma and prevented the induction of GABA-ergic and glutamate receptors mRNA transcripts. However, these improvements were unrelated to changes at the synaptic level, suggesting other cochlear functions may be involved. Due to this circadian regulation of noise sensitivity by GCs, we evaluated the actions of the synthetic glucocorticoid dexamethasone (DEX) at different times of the day. DEX was effective in protecting from acute noise trauma only when administered during daytime, when circulating glucocorticoids are low, indicating that chronopharmacological approaches are important for obtaining optimal treatment strategies for hearing loss. GCs appear as a major regulator of the differential sensitivity to day or night noise trauma, a mechanism likely involving the circadian control of inflammatory responses.
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Affiliation(s)
| | - Jung-Sub Park
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm 17177, Sweden; Department of Otolaryngology, Ajou University School of Medicine, 164, Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea
| | - Vasiliki Basinou
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm 17177, Sweden
| | - Benjamin D Weger
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland
| | - Evangelia Tserga
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm 17177, Sweden
| | - Heela Sarlus
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm 17177, Sweden
| | - Anna K Magnusson
- Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm 17177, Sweden
| | - Nadir Kadri
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm 17177, Sweden
| | - Frédéric Gachon
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland; School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Barbara Canlon
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm 17177, Sweden
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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3
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Felix Ii RA, Gourévitch B, Gómez-Álvarez M, Leijon SCM, Saldaña E, Magnusson AK. Octopus Cells in the Posteroventral Cochlear Nucleus Provide the Main Excitatory Input to the Superior Paraolivary Nucleus. Front Neural Circuits 2017; 11:37. [PMID: 28620283 PMCID: PMC5449481 DOI: 10.3389/fncir.2017.00037] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 05/19/2017] [Indexed: 12/26/2022] Open
Abstract
Auditory streaming enables perception and interpretation of complex acoustic environments that contain competing sound sources. At early stages of central processing, sounds are segregated into separate streams representing attributes that later merge into acoustic objects. Streaming of temporal cues is critical for perceiving vocal communication, such as human speech, but our understanding of circuits that underlie this process is lacking, particularly at subcortical levels. The superior paraolivary nucleus (SPON), a prominent group of inhibitory neurons in the mammalian brainstem, has been implicated in processing temporal information needed for the segmentation of ongoing complex sounds into discrete events. The SPON requires temporally precise and robust excitatory input(s) to convey information about the steep rise in sound amplitude that marks the onset of voiced sound elements. Unfortunately, the sources of excitation to the SPON and the impact of these inputs on the behavior of SPON neurons have yet to be resolved. Using anatomical tract tracing and immunohistochemistry, we identified octopus cells in the contralateral cochlear nucleus (CN) as the primary source of excitatory input to the SPON. Cluster analysis of miniature excitatory events also indicated that the majority of SPON neurons receive one type of excitatory input. Precise octopus cell-driven onset spiking coupled with transient offset spiking make SPON responses well-suited to signal transitions in sound energy contained in vocalizations. Targets of octopus cell projections, including the SPON, are strongly implicated in the processing of temporal sound features, which suggests a common pathway that conveys information critical for perception of complex natural sounds.
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Affiliation(s)
- Richard A Felix Ii
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
| | - Boris Gourévitch
- Institut Pasteur, Unité de Génétique et Physiologie de l'AuditionParis, France.,Institut National de la Santé et de la Recherche Médicale, UMRS 1120Paris, France.,Université Pierre et Marie CurieParis, France
| | - Marcelo Gómez-Álvarez
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden.,Neuroscience Institute of Castilla y León (INCyL), Universidad de SalamancaSalamanca, Spain.,Institute of Biomedical Research of Salamanca (IBSAL)Salamanca, Spain
| | - Sara C M Leijon
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
| | - Enrique Saldaña
- Neuroscience Institute of Castilla y León (INCyL), Universidad de SalamancaSalamanca, Spain.,Institute of Biomedical Research of Salamanca (IBSAL)Salamanca, Spain
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden
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Leijon SC, Peyda S, Magnusson AK. Temporal processing capacity in auditory-deprived superior paraolivary neurons is rescued by sequential plasticity during early development. Neuroscience 2016; 337:315-330. [DOI: 10.1016/j.neuroscience.2016.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 09/01/2016] [Accepted: 09/09/2016] [Indexed: 01/04/2023]
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Felix RA, Magnusson AK. Development of excitatory synaptic transmission to the superior paraolivary and lateral superior olivary nuclei optimizes differential decoding strategies. Neuroscience 2016; 334:1-12. [PMID: 27476438 DOI: 10.1016/j.neuroscience.2016.07.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 07/08/2016] [Accepted: 07/23/2016] [Indexed: 11/17/2022]
Abstract
The superior paraolivary nucleus (SPON) is a prominent structure in the mammalian auditory brainstem with a proposed role in encoding transient broadband sounds such as vocalized utterances. Currently, the source of excitatory pathways that project to the SPON and how these inputs contribute to SPON function are poorly understood. To shed light on the nature of these inputs, we measured evoked excitatory postsynaptic currents (EPSCs) in the SPON originating from the intermediate acoustic stria and compared them with the properties of EPSCs in the lateral superior olive (LSO) originating from the ventral acoustic stria during auditory development from postnatal day 5 to 22 in mice. Before hearing onset, EPSCs in the SPON and LSO are very similar in size and kinetics. After the onset of hearing, SPON excitation is refined to extremely few (2:1) fibers, with each strengthened by an increase in release probability, yielding fast and strong EPSCs. LSO excitation is recruited from more fibers (5:1), resulting in strong EPSCs with a comparatively broader stimulus-response range after hearing onset. Evoked SPON excitation is comparatively weaker than evoked LSO excitation, likely due to a larger fraction of postsynaptic GluR2-containing Ca2+-impermeable AMPA receptors after hearing onset. Taken together, SPON excitation develops synaptic properties that are suited for transmitting single events with high temporal reliability and the strong, dynamic LSO excitation is compatible with high rate-level sensitivity. Thus, the excitatory input pathways to the SPON and LSO mature to support different decoding strategies of respective coarse temporal and sound intensity information at the brainstem level.
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Affiliation(s)
- Richard A Felix
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.
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6
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Felix RA, Magnusson AK, Berrebi AS. The superior paraolivary nucleus shapes temporal response properties of neurons in the inferior colliculus. Brain Struct Funct 2015; 220:2639-52. [PMID: 24973970 PMCID: PMC4278952 DOI: 10.1007/s00429-014-0815-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 06/04/2014] [Indexed: 10/25/2022]
Abstract
The mammalian superior paraolivary nucleus (SPON) is a major source of GABAergic inhibition to neurons in the inferior colliculus (IC), a well-studied midbrain nucleus that is the site of convergence and integration for the majority ascending auditory pathways en route to the cortex. Neurons in the SPON and IC exhibit highly precise responses to temporal sound features, which are important perceptual cues for naturally occurring sounds. To determine how inhibitory input from the SPON contributes to the encoding of temporal information in the IC, a reversible inactivation procedure was conducted to silence SPON neurons, while recording responses to amplitude-modulated tones and silent gaps between tones in the IC. The results show that SPON-derived inhibition shapes responses of onset and sustained units in the IC via different mechanisms. Onset neurons appear to be driven primarily by excitatory inputs and their responses are shaped indirectly by SPON-derived inhibition, whereas sustained neurons are heavily influenced directly by transient offset inhibition from the SPON. The findings also demonstrate that a more complete dissection of temporal processing pathways is critical for understanding how biologically important sounds are encoded by the brain.
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Affiliation(s)
- Richard A. Felix
- Department of Otolaryngology–Head and Neck Surgery and the Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, West Virginia 26506 USA
| | - Anna K. Magnusson
- Center for Hearing and Communication Research, Karolinska Institutet and Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, 17176 Stockholm, Sweden
| | - Albert S. Berrebi
- Department of Otolaryngology–Head and Neck Surgery and the Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, West Virginia 26506 USA
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Leijon S, Magnusson AK. Physiological characterization of vestibular efferent brainstem neurons using a transgenic mouse model. PLoS One 2014; 9:e98277. [PMID: 24867596 PMCID: PMC4035287 DOI: 10.1371/journal.pone.0098277] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 04/30/2014] [Indexed: 01/31/2023] Open
Abstract
The functional role of efferent innervation of the vestibular end-organs in the inner ear remains elusive. This study provides the first physiological characterization of the cholinergic vestibular efferent (VE) neurons in the brainstem by utilizing a transgenic mouse model, expressing eGFP under a choline-acetyltransferase (ChAT)-locus spanning promoter in combination with targeted patch clamp recordings. The intrinsic electrical properties of the eGFP-positive VE neurons were compared to the properties of the lateral olivocochlear (LOC) brainstem neurons, which gives rise to efferent innervation of the cochlea. Both VE and the LOC neurons were marked by their negative resting membrane potential <-75 mV and their passive responses in the hyperpolarizing range. In contrast, the response properties of VE and LOC neurons differed significantly in the depolarizing range. When injected with positive currents, VE neurons fired action potentials faithfully to the onset of depolarization followed by sparse firing with long inter-spike intervals. This response gave rise to a low response gain. The LOC neurons, conversely, responded with a characteristic delayed tonic firing upon depolarizing stimuli, giving rise to higher response gain than the VE neurons. Depolarization triggered large TEA insensitive outward currents with fast inactivation kinetics, indicating A-type potassium currents, in both the inner ear-projecting neuronal types. Immunohistochemistry confirmed expression of Kv4.3 and 4.2 ion channel subunits in both the VE and LOC neurons. The difference in spiking responses to depolarization is related to a two-fold impact of these transient outward currents on somatic integration in the LOC neurons compared to in VE neurons. It is speculated that the physiological properties of the VE neurons might be compatible with a wide-spread control over motion and gravity sensation in the inner ear, providing likewise feed-back amplification of abrupt and strong phasic signals from the semi-circular canals and of tonic signals from the gravito-sensitive macular organs.
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Affiliation(s)
- Sara Leijon
- Center for Hearing and Communication Research, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Science, Intervention and Technology, Unit of Audiology, Karolinska University Hospital, Stockholm, Sweden
| | - Anna K. Magnusson
- Center for Hearing and Communication Research, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Science, Intervention and Technology, Unit of Audiology, Karolinska University Hospital, Stockholm, Sweden
- * E-mail:
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Felix RA, Vonderschen K, Berrebi AS, Magnusson AK. Development of on-off spiking in superior paraolivary nucleus neurons of the mouse. J Neurophysiol 2013; 109:2691-704. [PMID: 23515791 DOI: 10.1152/jn.01041.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The superior paraolivary nucleus (SPON) is a prominent cell group in the auditory brain stem that has been increasingly implicated in representing temporal sound structure. Although SPON neurons selectively respond to acoustic signals important for sound periodicity, the underlying physiological specializations enabling these responses are poorly understood. We used in vitro and in vivo recordings to investigate how SPON neurons develop intrinsic cellular properties that make them well suited for encoding temporal sound features. In addition to their hallmark rebound spiking at the stimulus offset, SPON neurons were characterized by spiking patterns termed onset, adapting, and burst in response to depolarizing stimuli in vitro. Cells with burst spiking had some morphological differences compared with other SPON neurons and were localized to the dorsolateral region of the nucleus. Both membrane and spiking properties underwent strong developmental regulation, becoming more temporally precise with age for both onset and offset spiking. Single-unit recordings obtained in young mice demonstrated that SPON neurons respond with temporally precise onset spiking upon tone stimulation in vivo, in addition to the typical offset spiking. Taken together, the results of the present study demonstrate that SPON neurons develop sharp on-off spiking, which may confer sensitivity to sound amplitude modulations or abrupt sound transients. These findings are consistent with the proposed involvement of the SPON in the processing of temporal sound structure, relevant for encoding communication cues.
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Affiliation(s)
- Richard A Felix
- Center for Hearing and Communication Research, Karolinska Institutet and Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Stockholm, Sweden
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9
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Abstract
In a single-electrode current-clamp recording, the measured potential includes both the response of the membrane and that of the measuring electrode. The electrode response is traditionally removed using bridge balance, where the response of an ideal resistor representing the electrode is subtracted from the measurement. Because the electrode is not an ideal resistor, this procedure produces capacitive transients in response to fast or discontinuous currents. More sophisticated methods exist, but they all require a preliminary calibration phase, to estimate the properties of the electrode. If these properties change after calibration, the measurements are corrupted. We propose a compensation method that does not require preliminary calibration. Measurements are compensated offline by fitting a model of the neuron and electrode to the trace and subtracting the predicted electrode response. The error criterion is designed to avoid the distortion of compensated traces by spikes. The technique allows electrode properties to be tracked over time and can be extended to arbitrary models of electrode and neuron. We demonstrate the method using biophysical models and whole cell recordings in cortical and brain-stem neurons.
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Affiliation(s)
- Cyrille Rossant
- Laboratoire Psychologie de la Perception, Centre National de la Recherche Scientifique, Université Paris Descartes, Paris, France
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Abstract
Computational modeling is increasingly used to understand the function of neural circuits in systems neuroscience. These studies require models of individual neurons with realistic input-output properties. Recently, it was found that spiking models can accurately predict the precisely timed spike trains produced by cortical neurons in response to somatically injected currents, if properly fitted. This requires fitting techniques that are efficient and flexible enough to easily test different candidate models. We present a generic solution, based on the Brian simulator (a neural network simulator in Python), which allows the user to define and fit arbitrary neuron models to electrophysiological recordings. It relies on vectorization and parallel computing techniques to achieve efficiency. We demonstrate its use on neural recordings in the barrel cortex and in the auditory brainstem, and confirm that simple adaptive spiking models can accurately predict the response of cortical neurons. Finally, we show how a complex multicompartmental model can be reduced to a simple effective spiking model.
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Affiliation(s)
- Cyrille Rossant
- Laboratoire Psychologie de la Perception, CNRS, Université Paris DescartesParis, France
- Equipe Audition, Département d'Etudes Cognitives, Ecole Normale SupérieureParis, France
| | - Dan F. M. Goodman
- Laboratoire Psychologie de la Perception, CNRS, Université Paris DescartesParis, France
- Equipe Audition, Département d'Etudes Cognitives, Ecole Normale SupérieureParis, France
| | - Bertrand Fontaine
- Laboratoire Psychologie de la Perception, CNRS, Université Paris DescartesParis, France
- Equipe Audition, Département d'Etudes Cognitives, Ecole Normale SupérieureParis, France
| | - Jonathan Platkiewicz
- Institut des Systèmes Intelligents et de Robotique, Université Pierre et Marie Curie-Paris 06Paris, France
| | - Anna K. Magnusson
- Center for Hearing and Communication Research, Karolinska InstitutetStockholm, Sweden
- Department of Clinical Neuroscience, Karolinska University HospitalStockholm, Sweden
| | - Romain Brette
- Laboratoire Psychologie de la Perception, CNRS, Université Paris DescartesParis, France
- Equipe Audition, Département d'Etudes Cognitives, Ecole Normale SupérieureParis, France
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Koch U, Magnusson AK. Unconventional GABA release: mechanisms and function. Curr Opin Neurobiol 2009; 19:305-10. [DOI: 10.1016/j.conb.2009.03.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Revised: 03/13/2009] [Accepted: 03/17/2009] [Indexed: 10/20/2022]
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Magnusson AK, Linderholm P, Vieider C, Ulfendahl M, Erlandsson A. Surface protein patterns govern morphology, proliferation, and expression of cellular markers but have no effect on physiological properties of cortical precursor cells. J Neurosci Res 2008; 86:2363-75. [PMID: 18381765 DOI: 10.1002/jnr.21688] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ability to differentiate and give rise to neurons, astrocytes, and oligodendrocytes is an inherent feature of neural stem cells, which raises hopes for cell-based therapies of neurodegenerative diseases. However, there are many hurdles to cross before such regimens can be applied clinically. A considerable challenge is to elucidate the factors that contribute to neural differentiation. In this study, we evaluated the possibility of steering neuronal maturation by growing cortical precursor cells on microscale surface patterns of extracellular matrix (ECM) proteins. When the cells were encouraged to extend processes along lines of ECM proteins, they displayed a much more mature morphology, less proliferation capacity, and greater expression of a neuronal marker in comparison with cells grown in clusters on ECM dots. This implied that the growth pattern alone could play a crucial role for neural differentiation. However, in spite of the strikingly different morphology, when performing whole-cell patch-clamp experiments, we never observed any differences in the functional properties between cells grown on the two patterns. These results clearly demonstrate that morphological appearances are not representative measures of the functional phenotype or grade of neuronal maturation, stressing the importance of complementary electrophysiological evidence. To develop successful transplantation therapies, increased cell survival is critical. Because process-bearing neurons are sensitive and break easily, it would be of clinical interest to explore further the differentiating capacity of the cells cultured on the ECM dot pattern, described in this article, which are devoid of processes but display the same functional properties as neurons with mature morphology.
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Affiliation(s)
- Anna K Magnusson
- Center for Hearing and Communication Research, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Magnusson AK, Park TJ, Pecka M, Grothe B, Koch U. Retrograde GABA signaling adjusts sound localization by balancing excitation and inhibition in the brainstem. Neuron 2008; 59:125-37. [PMID: 18614034 DOI: 10.1016/j.neuron.2008.05.011] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 03/26/2008] [Accepted: 05/07/2008] [Indexed: 10/21/2022]
Abstract
Central processing of acoustic cues is critically dependent on the balance between excitation and inhibition. This balance is particularly important for auditory neurons in the lateral superior olive, because these compare excitatory inputs from one ear and inhibitory inputs from the other ear to compute sound source location. By applying GABA(B) receptor antagonists during sound stimulation in vivo, it was revealed that these neurons adjust their binaural sensitivity through GABA(B) receptors. Using an in vitro approach, we then demonstrate that these neurons release GABA during spiking activity. Consequently, GABA differentially regulates transmitter release from the excitatory and inhibitory terminals via feedback to presynaptic GABA(B) receptors. Modulation of the synaptic input strength, by putative retrograde release of neurotransmitter, may enable these auditory neurons to rapidly adjust the balance between excitation and inhibition, and thus their binaural sensitivity, which could play an important role as an adaptation to various listening situations.
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Affiliation(s)
- Anna K Magnusson
- Department Biologie II, Division of Neurobiology, LMU Munich, Grosshadernerstrasse 2, 82152 Martinsried, Germany.
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Magnusson AK, Tham R. Reversible and controlled peripheral vestibular loss by continuous infusion of ropivacaine (Narop) into the round window niche of rats. Neurosci Lett 2006; 400:16-20. [PMID: 16503375 DOI: 10.1016/j.neulet.2006.02.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 01/10/2006] [Accepted: 02/06/2006] [Indexed: 11/19/2022]
Abstract
This paper describes a method for achieving a peripheral vestibular blockade in rats by instillation of local anaesthetics over the round window membrane through a permanently implanted cannula. Being rapidly reversible, the effect of the anaesthetic drug is easily controlled by a single continuous infusion, which can be repeated at any time. The method offers a unique opportunity to study the consequence of single or repeated transient vestibular loss without any use of general anaesthetics, which may be a severe confounding factor. Such studies might shed light on balance disorders related to permanent vestibular loss or episodic vestibular dysfunction. To evaluate the method, spontaneous horizontal eye movements were recorded during the first 4 h of continuous infusion. Unilateral infusion of ropivacaine gave rise to a high-frequency spontaneous nystagmus, reaching levels that have not been documented after a surgical labyrinthectomy under general anaesthesia. This vestibulo-oculomotor behaviour is consistent with a previous report using a single intratympanic instillation of lidocaine to achieve a short-lasting vestibular blockade. In the present study, it was demonstrated that the initial high-frequency nystagmus decreased during the first 100 min of infusion before stabilizing at the same level as recorded when the effect of general anaesthesia has worn off after a surgical ablation. When the transient vestibular blockade was repeated by a second infusion during the following day, the nystagmus frequency saturated on a significantly lower level than during the first blockade. Also, serial single infusions, with recovery between each functional vestibular loss, gave rise to a less severe nystagmus. It is suggested that this phenomenon is an expression of the behavioural concept of 'vestibular habituation', the neural substrate of which is rather unknown.
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Affiliation(s)
- Anna K Magnusson
- Department of Neuroscience and Locomotion, Faculty of Health Sciences, SE-581 85 Linköping, Sweden.
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Abstract
The neurones of the medial superior olive (MSO) are the most temporally sensitive neurones in the brain. They respond to the arrival time difference of sound at the two ears with a microsecond resolution; these interaural time differences are used to localize low-frequency sounds. In addition to the excitatory inputs from each ear, the MSO neurones also receive binaural glycinergic projections, which have a critical role in sound localization processing. Recently, it was shown that the glycinergic input to the MSO undergoes an experience-dependent structural reorganization after hearing onset. To explore the maturation of inhibition during the development of sound localization on a cellular level, glycinergic currents and potentials were measured in gerbil MSO principal cells from postnatal (P) day P12-P25 by whole-cell patch-clamp recordings. The synaptic glycinergic currents accelerated to rapid decay kinetics (approximately 2 ms) and rise times (approximately 0.4 ms) after hearing onset, reaching maturity around P17. Since the kinetics of miniature glycinergic currents did not change with age, it is likely that a higher degree of transmitter release synchrony is the underlying mechanism influencing the acceleration of the kinetics. During the same period, the synaptic glycinergic potentials accelerated four-fold, largely as a result of a prominent decrease in input resistance. In accordance with a reorganization of the glycinergic inputs, the evoked peak conductances decreased more than two-fold, together with a three-fold reduction in the frequency of miniature events after hearing onset. These age-dependent changes were absent in animals that had been reared in omni-directional noise, indicating that an experience-dependent pruning of synaptic inputs is important for the maturation of functional inhibition in the MSO. Taken together, these striking developmental adjustments of the glycinergic inhibition in the MSO most probably reflect an adaptation to improve the encoding of auditory cues with great temporal precision and fidelity during the maturation of sound localization behaviour.
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Affiliation(s)
- Anna K Magnusson
- Division of Neurobiology, Department Biologie II, Ludwig-Maximilians-University, Martinsried, Germany.
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Magnusson AK, Tham R. [Built-in emergency brake in the balance system. Animal experiment research shows that a hierarchy of mechanisms compensate after acute peripheral vestibular decline]. Lakartidningen 2005; 102:1524-6, 1529. [PMID: 15973878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A sudden unilateral loss of peripheral vestibular input results in the onset of acute dizziness and imbalance associated with spontaneous nystagmus, postural instability and nausea. Fortunately, these symptoms ameliorate rapidly, even without treatment, due to central nervous plastic changes which are collectively termed "vestibular compensation". This concept has become a widely accepted research model for studying lesion-induced plasticity. Recent research has dealt in particular with the plasticity of the medial vestibular nuclei that mediate the horizontal vestibulo-ocular reflex. Studies range from a cellular level in vitro to a functional level in vivo. Taken together, results from such studies have contributed greatly to what is known of vestibular compensation today. This article summarises evidence for several plasticity mechanisms that drive the recovery of spontaneous nystagmus, one of which is dependent on an endocrine stress-response. In the long run, such knowledge might influence the management and treatment of patients with balance disorders.
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Affiliation(s)
- Anna K Magnusson
- Abteilung Neurobiologie, Ludwig-Maximilians Universität, München
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Abstract
The effects of a transient vestibular nerve blockade, achieved by intra-tympanic instillation of lidocaine, were studied in rats by recording horizontal eye movements in darkness. Evaluation of the dose-response relationship showed that a maximal effect was attained with a concentration of 4% lidocaine. Within 15 min of lidocaine instillation, a vigorous spontaneous nystagmus was observed which reached maximal frequency and velocity of the slow phase after about 20 min. Subsequently, the nystagmus failed for approximately half an hour before it reappeared. This could be avoided by providing visual feedback in between the recordings in darkness or by a contralateral instillation of 2.5% lidocaine. It is suggested that the failure reflects an overload of the vestibulo-oculomotor circuits. After recovery from the nerve blockade, when the gaze was stable, dynamic vestibular tests were performed. They revealed that a decrease of the slow phase velocity gain and the dominant time constant during, respectively, sinusoidal- and step stimulation toward the unanaesthetised side, had developed with the nerve blockade. These modulations were impaired by a nodulo-uvulectomy but not by bilateral flocculectomy, which is consistent with the concept of vestibular habituation. A GABA(B) receptor antagonist, CGP 56433A, given systemically during the nerve blockade, aggravated the vestibular asymmetry. The same effect has previously been demonstrated in both short- (days) and long-term (months) compensated rats, by antagonising the GABA(B) receptor. In summary, this study provides the first observations of vestibulo-oculomotor disturbances during the first hour after a rapid and transient unilateral vestibular loss in the rat. By using this method, it is possible to study immediate behavioural consequences and possible neural changes that might outlast the nerve blockade.
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MESH Headings
- Adaptation, Physiological
- Anesthetics, Local/pharmacology
- Animals
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Benzoates/pharmacology
- Denervation
- Dose-Response Relationship, Drug
- Eye Movements/drug effects
- Eye Movements/physiology
- Functional Laterality
- GABA Antagonists/pharmacology
- Lidocaine/pharmacology
- Male
- Nystagmus, Physiologic
- Phosphinic Acids/pharmacology
- Posture
- Rats
- Rats, Inbred Strains
- Reflex, Vestibulo-Ocular/drug effects
- Reflex, Vestibulo-Ocular/physiology
- Saccades/drug effects
- Saccades/physiology
- Time Factors
- Vestibule, Labyrinth/drug effects
- Vestibule, Labyrinth/physiology
- Vestibule, Labyrinth/surgery
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Affiliation(s)
- A K Magnusson
- Department of Biomedicine and Surgery, Faculty of Health Sciences, SE-581 85, Linköping, Sweden.
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Magnusson AK, Ulfendahl M, Tham R. Early compensation of vestibulo-oculomotor symptoms after unilateral vestibular loss in rats is related to GABA(B) receptor function. Neuroscience 2002; 111:625-34. [PMID: 12031349 DOI: 10.1016/s0306-4522(01)00618-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The horizontal vestibulo-oculomotor reflex was studied in pigmented rats during the first 5 days after a unilateral chemical or surgical vestibular deafferentation. Spontaneous eye movements in darkness and slow phase velocity gain of compensatory eye movements during horizontal sinusoidal rotation were evaluated. The most evident vestibulo-oculomotor symptom immediately after a unilateral vestibular loss was a spontaneous nystagmus, which gradually abated during the following days. Further, an asymmetry between ipsi- and contra-lesional gains was evident during sinusoidal vestibular stimulation. Single systemic doses of the GABA(B) receptor antagonist [3-[1-(S)-[[3-(cyclohexylmethyl)-hydroxyphosphinoyl]-2-(S)-hydroxypropyl]amino]ethyl]-benzoic acid (CGP 56433A), the agonist baclofen, or the GABA(A) receptor agonist (4,5,6,7-tetrahydroisoxazolo-[5,4-c]-pyridin-3-ol (THIP) were given at different intervals after unilateral vestibular deafferentation. CGP 56433A highly aggravated the vestibulo-oculomotor symptoms, observed as an increase in spontaneous nystagmus and slow phase velocity gain asymmetry. This effect was most pronounced during the first 2 days after unilateral vestibular loss, when CGP 56433A even decompensated the vestibular system to the extent that all vestibular responses were abolished. Baclofen caused no effect during the first days after unilateral vestibular loss, but in parallel with the abatement of spontaneous nystagmus, the drug equilibrated or even reversed the remaining spontaneous nystagmus with corresponding effects on the slow-phase velocity gain asymmetry. The effects of baclofen were very similar after both chemical and surgical deafferentation. THIP caused a slight depression of all vestibular responses. All single dose effects of the drugs were transient. Altogether these results reveal that endogenous stimulation of GABA(B) receptors in GABA-ergic vestibulo-oculomotor circuits are important for reducing the vestibular asymmetry during the early period after unilateral vestibular deafferentation. A possible role for GABA(B) receptors in the reciprocal inhibitory commissural pathways in the vestibular nuclei is suggested.
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MESH Headings
- Adaptation, Physiological/drug effects
- Adaptation, Physiological/physiology
- Animals
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Denervation
- Eye Movements/drug effects
- Eye Movements/physiology
- GABA Agonists/pharmacology
- GABA Antagonists/pharmacology
- GABA-A Receptor Agonists
- GABA-B Receptor Agonists
- GABA-B Receptor Antagonists
- Male
- Posture
- Rats
- Receptors, GABA-B/physiology
- Reflex, Vestibulo-Ocular/drug effects
- Reflex, Vestibulo-Ocular/physiology
- Rotation
- Saccades/drug effects
- Saccades/physiology
- Vestibular Nerve/physiology
- Vestibule, Labyrinth/drug effects
- Vestibule, Labyrinth/innervation
- Vestibule, Labyrinth/physiology
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Affiliation(s)
- A K Magnusson
- Department of Biomedicine and Surgery, Division of Cell Biology, Faculty of Health Sciences, SE-581 85 Linköping, Sweden.
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Abstract
The horizontal vestibulo-ocular reflex was studied in pigmented rats, which had been unilaterally, chemically labyrinthectomised 6-144 days previously. During this partially compensated stage after unilateral labyrinthectomy (UL), both static and dynamic deficits remain. The former was evaluated by recording of spontaneous eye movements in darkness, and the latter by estimating the slow-phase velocity (SPV) gain of compensatory eye movements during horizontal vestibular stimulation. The GABA(B) agonist baclofen caused a reversal of the remaining ipsilesional drift of the eyes in darkness into a nystagmus with a contralesional slow phase. The GABA(B) antagonist CGP 36742 caused a decompensation by exaggerating the remaining ipsilesional eye drift. Further, baclofen equilibrated or reversed the asymmetry between ipsi- and contralesional SPV gains during horizontal sinusoidal rotations at 0.2 Hz and 0.8 Hz. This was achieved by an increase in the ipsilesional gain and a decrease in the contralesional gain. The phase lead during sinusoidal rotation (0.2 Hz) was larger following rotation to the lesioned side than to the intact side in UL rats. This asymmetry was reversed by baclofen. CGP 36742 inhibited the effects of baclofen, while the antagonist per se aggravated SPV gain and phase lead asymmetries in UL rats during vestibular stimulation. Per- and post-rotatory nystagmus induced by velocity step stimulation revealed an imperfect velocity-storage function in UL animals, which was modulated by baclofen. An investigation of the baclofen effect on SPV gain asymmetry during different time intervals after chemical UL showed a completely developed effect on the 6th day. Bilateral flocculectomy did not alter the effects of baclofen on UL animals. It is concluded that physiological stimulation of GABA(B) receptors contributes to minimise the vestibulo-oculomotor asymmetry during the partially compensated period after UL. Administration of an agonist or an antagonist changes the asymmetry towards the ipsi- or contralesional side, possibly by altering the spontaneous neuronal activity in the bilateral medial vestibular nuclei. The results are compatible with a hypothesis, supported by in vitro slice experiments, that the efficacy of GABA(B) receptors is up-regulated on the ipsilesional side and down-regulated on the contralesional side.
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Affiliation(s)
- A K Magnusson
- Department of Biomedicine and Surgery, Faculty of Health Sciences, University of Linköping, Sweden.
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Abstract
Horizontal eye movements, elicited by sinusoidal rotation in darkness, were recorded with a magnetic search coil technique in pigmented rats, hemilabyrinthectomised 8-12 weeks before the investigation. Separate gains during rotation towards the lesioned side (LS) and the intact side (IS) were calculated by a computer program, demonstrating an asymmetry. Systemic single administration of the GABAB agonist baclofen caused a dose-related temporary rebalancing of the compensatory eye movements to the LS and the IS. At an optimal dose of 14 micromol/kg b.wt symmetry was achieved by excitation of eye movements during rotation to the LS and depression during rotation to the IS. Administration of the GABAA agonist THIP did not obviously reduce the asymmetry. It is suggested that stimulation of GABAB receptors modifies the tonic imbalance between the bilateral vestibular nuclei and/or the central processing of the input from the peripheral sensory organs.
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Affiliation(s)
- A K Magnusson
- Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, University of Linköping, S-581 85 Linköping, Sweden.
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Abstract
The effects of toluene on discharge rate and membrane properties of tonically active medial vestibular nucleus (MVN) neurones were investigated in an in vitro slice preparation of the dorsal brainstem of the rat. The majority of the cells (50/56) were inhibited in a dose-dependent manner by toluene. The inhibitory effects of toluene persisted after blockade of synaptic transmission. Complementary patch-clamp recordings showed that toluene caused a hyperpolarisation of 2-5 mV associated with an increase in membrane conductance. These findings indicate that toluene might interfere with specific ion channels or the receptors regulating them along the cell membrane. The effective toluene concentrations used in this experiment are comparable to the concentrations producing vestibulo-ocular disturbances in vivo.
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Affiliation(s)
- A K Magnusson
- Department of Biomedicine and Surgery, Faculty of Health Sciences, University of Linköping, Sweden.
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