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Low-Intensity Ultrasound Causes Direct Excitation of Auditory Cortical Neurons. Neural Plast 2021; 2021:8855055. [PMID: 33883994 PMCID: PMC8041518 DOI: 10.1155/2021/8855055] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/02/2020] [Accepted: 03/19/2021] [Indexed: 02/06/2023] Open
Abstract
Cochlear implantation is the first-line treatment for severe and profound hearing loss in children and adults. However, deaf patients with cochlear malformations or with cochlear nerve deficiencies are ineligible for cochlear implants. Meanwhile, the limited spatial selectivity and high risk of invasive craniotomy restrict the wide application of auditory brainstem implants. A noninvasive alternative strategy for safe and effective neuronal stimulation is urgently needed to address this issue. Because of its advantage in neural modulation over electrical stimulation, low-intensity ultrasound (US) is considered a safe modality for eliciting neural activity in the central auditory system. Although the neural modulation ability of low-intensity US has been demonstrated in the human primary somatosensory cortex and primary visual cortex, whether low-intensity US can directly activate auditory cortical neurons is still a topic of debate. To clarify the direct effects on auditory neurons, in the present study, we employed low-intensity US to stimulate auditory cortical neurons in vitro. Our data show that both low-frequency (0.8 MHz) and high-frequency (>27 MHz) US stimulation can elicit the inward current and action potentials in cultured neurons. c-Fos staining results indicate that low-intensity US is efficient for stimulating most neurons. Our study suggests that low-intensity US can excite auditory cortical neurons directly, implying that US-induced neural modulation can be a potential approach for activating the auditory cortex of deaf patients.
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Carson RG. Inter‐hemispheric inhibition sculpts the output of neural circuits by co‐opting the two cerebral hemispheres. J Physiol 2020; 598:4781-4802. [DOI: 10.1113/jp279793] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/04/2020] [Indexed: 01/11/2023] Open
Affiliation(s)
- Richard G. Carson
- Trinity College Institute of Neuroscience and School of Psychology Trinity College Dublin Dublin 2 Ireland
- School of Psychology Queen's University Belfast Belfast BT7 1NN UK
- School of Human Movement and Nutrition Sciences University of Queensland St Lucia QLD 4072 Australia
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Suga N. Plasticity of the adult auditory system based on corticocortical and corticofugal modulations. Neurosci Biobehav Rev 2020; 113:461-478. [DOI: 10.1016/j.neubiorev.2020.03.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 03/05/2020] [Accepted: 03/17/2020] [Indexed: 10/24/2022]
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Kermen F, Lal P, Faturos NG, Yaksi E. Interhemispheric connections between olfactory bulbs improve odor detection. PLoS Biol 2020; 18:e3000701. [PMID: 32310946 PMCID: PMC7192517 DOI: 10.1371/journal.pbio.3000701] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 04/30/2020] [Accepted: 04/02/2020] [Indexed: 01/06/2023] Open
Abstract
Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. However, the cellular and spatial organization of interhemispheric networks and the computational properties they mediate in vertebrates are still poorly understood. Thus, it remains unclear to what extent the connectivity between left and right brain hemispheres participates in sensory processing. Here, we show that the zebrafish olfactory bulbs (OBs) receive direct interhemispheric projections from their contralateral counterparts in addition to top-down inputs from the contralateral zebrafish homolog of olfactory cortex. The direct interhemispheric projections between the OBs reach peripheral layers of the contralateral OB and retain a precise topographic organization, which directly connects similarly tuned olfactory glomeruli across hemispheres. In contrast, interhemispheric top-down inputs consist of diffuse projections that broadly innervate the inhibitory granule cell layer. Jointly, these interhemispheric connections elicit a balance of topographically organized excitation and nontopographic inhibition on the contralateral OB and modulate odor responses. We show that the interhemispheric connections in the olfactory system enable the modulation of odor response and contribute to a small but significant improvement in the detection of a reproductive pheromone when presented together with complex olfactory cues by potentiating the response of the pheromone selective neurons. Taken together, our data show a previously unknown function for an interhemispheric connection between chemosensory maps of the olfactory system. Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. This study shows that interhemispheric olfactory connections in the zebrafish brain improve the detection of a reproductive pheromone within a noisy odor background.
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Affiliation(s)
- Florence Kermen
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway
- Neuro-Electronics Research Flanders, Leuven, Belgium
- Department of Biology, Faculty of Natural Sciences, Norwegian University of Science and Technology, Trondheim, Norway
- * E-mail: (FK); (EY)
| | - Pradeep Lal
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway
| | - Nicholas G. Faturos
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway
| | - Emre Yaksi
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway
- Neuro-Electronics Research Flanders, Leuven, Belgium
- * E-mail: (FK); (EY)
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Butman JA, Suga N. Inhibitory mechanisms shaping delay-tuned combination-sensitivity in the auditory cortex and thalamus of the mustached bat. Hear Res 2019; 373:71-84. [PMID: 30612026 DOI: 10.1016/j.heares.2018.12.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/11/2018] [Accepted: 12/21/2018] [Indexed: 10/27/2022]
Abstract
Delay-tuned auditory neurons of the mustached bat show facilitative responses to a combination of signal elements of a biosonar pulse-echo pair with a specific echo delay. The subcollicular nuclei produce latency-constant phasic on-responding neurons, and the inferior colliculus produces delay-tuned combination-sensitive neurons, designated "FM-FM" neurons. The combination-sensitivity is a facilitated response to the coincidence of the excitatory rebound following glycinergic inhibition to the pulse (1st harmonic) and the short-latency response to the echo (2nd-4th harmonics). The facilitative response of thalamic FM-FM neurons is mediated by glutamate receptors (NMDA and non-NMDA receptors). Different from collicular FM-FM neurons, thalamic ones respond more selectively to pulse-echo pairs than individual signal elements. A number of differences in response properties between collicular and thalamic or cortical FM-FM neurons have been reported. However, differences between thalamic and cortical FM-FM neurons have remained to be studied. Here, we report that GABAergic inhibition controls the duration of burst of spikes of facilitative responses of thalamic FM-FM neurons and sharpens the delay tuning of cortical ones. That is, intra-cortical inhibition sharpens the delay tuning of cortical FM-FM neurons that is potentially broad because of divergent/convergent thalamo-cortical projections. Compared with thalamic neurons, cortical ones tend to show sharper delay tuning, longer response duration, and larger facilitation index. However, those differences are statistically insignificant.
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Affiliation(s)
- John A Butman
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63130, USA.
| | - Nobuo Suga
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63130, USA.
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Synaptic mechanisms shaping delay-tuned combination-sensitivity in the auditory thalamus of mustached bats. Hear Res 2016; 331:69-82. [DOI: 10.1016/j.heares.2015.10.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 09/24/2015] [Accepted: 10/20/2015] [Indexed: 11/21/2022]
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Kössl M, Hechavarria J, Voss C, Schaefer M, Vater M. Bat auditory cortex – model for general mammalian auditory computation or special design solution for active time perception? Eur J Neurosci 2015; 41:518-32. [PMID: 25728173 DOI: 10.1111/ejn.12801] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 11/03/2014] [Accepted: 11/06/2014] [Indexed: 01/28/2023]
Abstract
Audition in bats serves passive orientation, alerting functions and communication as it does in other vertebrates. In addition, bats have evolved echolocation for orientation and prey detection and capture. This put a selective pressure on the auditory system in regard to echolocation-relevant temporal computation and frequency analysis. The present review attempts to evaluate in which respect the processing modules of bat auditory cortex (AC) are a model for typical mammalian AC function or are designed for echolocation-unique purposes. We conclude that, while cortical area arrangement and cortical frequency processing does not deviate greatly from that of other mammals, the echo delay time-sensitive dorsal cortex regions contain special designs for very powerful time perception. Different bat species have either a unique chronotopic cortex topography or a distributed salt-and-pepper representation of echo delay. The two designs seem to enable similar behavioural performance.
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Affiliation(s)
- Manfred Kössl
- Institute for Cell Biology and Neuroscience, University of Frankfurt, Max-von-Laue-Str.13, 60438, Frankfurt, Germany
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Suga N. Neural processing of auditory signals in the time domain: Delay-tuned coincidence detectors in the mustached bat. Hear Res 2015; 324:19-36. [DOI: 10.1016/j.heares.2015.02.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 02/15/2015] [Accepted: 02/24/2015] [Indexed: 11/25/2022]
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Hechavarría JC, Kössl M. Footprints of inhibition in the response of cortical delay-tuned neurons of bats. J Neurophysiol 2014; 111:1703-16. [PMID: 24478161 DOI: 10.1152/jn.00777.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Responses of echo-delay-tuned neurons that encode target distance were investigated in the dorsal auditory cortex of anesthetized short-tailed fruit bats (Carollia perspicillata). This species echolocates using short downward frequency-modulated (FM) biosonar signals. In response to FM sweeps of increasing level, 60 out of 131 studied neurons (47%) displayed a "paradoxical latency shift," i.e., longer response latency to loud sounds and shorter latency to faint sounds. In addition, a disproportionately large number of neurons (80%) displayed nonmonotonic responses, i.e., weaker responses to loud sounds and stronger responses to faint sounds. We speculate that the observed paradoxical latency shift and nonmonotonic responses are extracellular footprints of inhibitory processes evoked by loud sounds and that they could represent a specialization for the processing of the emitted loud biosonar pulse. Supporting this idea is the fact that all studied neurons displayed strong response suppression when an artificial loud pulse and a faint echo were presented together at a nonoptimal delay. In 24 neurons, iontophoresis of bicuculline (an antagonist of A-type γ-aminobutyric acid receptors) did not remove inhibitory footprints but did increase the overall spike output, and in some cases it also modified the response bandwidth and shifted the neuron's "best delay." We suggest that inhibition could play a dual role in shaping delay tuning in different auditory stations. Below the cortex it participates in delay-tuning implementation and leaves a footprint that is measurable in cortical responses, while in the cortex it provides a substrate for an in situ control of neuronal selectivity.
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Affiliation(s)
- Julio C Hechavarría
- Institut für Zellbiologie und Neurowissenschaft, Goethe-Universität, Frankfurt, Germany
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Kössl M, Hechavarria JC, Voss C, Macias S, Mora EC, Vater M. Neural maps for target range in the auditory cortex of echolocating bats. Curr Opin Neurobiol 2013; 24:68-75. [PMID: 24492081 DOI: 10.1016/j.conb.2013.08.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 08/16/2013] [Accepted: 08/18/2013] [Indexed: 11/25/2022]
Abstract
Computational brain maps as opposed to maps of receptor surfaces strongly reflect functional neuronal design principles. In echolocating bats, computational maps are established that topographically represent the distance of objects. These target range maps are derived from the temporal delay between emitted call and returning echo and constitute a regular representation of time (chronotopy). Basic features of these maps are innate, and in different bat species the map size and precision varies. An inherent advantage of target range maps is the implementation of mechanisms for lateral inhibition and excitatory feedback. Both can help to focus target ranging depending on the actual echolocation situation. However, these maps are not absolutely necessary for bat echolocation since there are bat species without cortical target-distance maps, which use alternative ensemble computation mechanisms.
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Affiliation(s)
- M Kössl
- Institute for Cell Biology and Neuroscience, Goethe University, Frankfurt, Max-von-Laue-Str. 13, 60439 Frankfurt, Germany.
| | - J C Hechavarria
- Institute for Cell Biology and Neuroscience, Goethe University, Frankfurt, Max-von-Laue-Str. 13, 60439 Frankfurt, Germany
| | - C Voss
- Institute for Cell Biology and Neuroscience, Goethe University, Frankfurt, Max-von-Laue-Str. 13, 60439 Frankfurt, Germany
| | - S Macias
- Department of Animal and Human Biology, Faculty of Biology, Havana University, calle 25 No. 455 entre J e I, Vedado, CP 10400, Ciudad de La Habana, Cuba
| | - E C Mora
- Department of Animal and Human Biology, Faculty of Biology, Havana University, calle 25 No. 455 entre J e I, Vedado, CP 10400, Ciudad de La Habana, Cuba
| | - M Vater
- Institute for Biochemistry and Biology, University of Potsdam, Karl Liebknecht Str. 26, 14476 Golm, Germany
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Carrasco A, Kok MA, Lomber SG. Effects of core auditory cortex deactivation on neuronal response to simple and complex acoustic signals in the contralateral anterior auditory field. Cereb Cortex 2013; 25:84-96. [PMID: 23960202 DOI: 10.1093/cercor/bht205] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Interhemispheric communication has been implicated in various functions of sensory signal processing and perception. Despite ample evidence demonstrating this phenomenon in the visual and somatosensory systems, to date, limited functional assessment of transcallosal transmission during periods of acoustic signal exposure has hindered our understanding of the role of interhemispheric connections between auditory cortical fields. Consequently, the present investigation examines the impact of core auditory cortical field deactivation on response properties of contralateral anterior auditory field (AAF) neurons in the felis catus. Single-unit responses to simple and complex acoustic signals were measured across AAF before, during, and after individual and combined cooling deactivation of contralateral primary auditory cortex (A1) and AAF neurons. Data analyses revealed that on average: 1) interhemispheric projections from core auditory areas to contralateral AAF neurons are predominantly excitatory, 2) changes in response strength vary based on acoustic features, 3) A1 and AAF projections can modulate AAF activity differently, 4) decreases in response strength are not specific to particular cortical laminae, and 5) contralateral inputs modulate AAF neuronal response thresholds. Collectively, these observations demonstrate that A1 and AAF neurons predominantly modulate AAF response properties via excitatory projections.
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Affiliation(s)
- Andres Carrasco
- Brain and Mind Institute, Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada N6A 5C1 Cerebral Systems Laboratory, Department of Psychology, University of Western Ontario, London, ON, Canada N6A 5C2
| | - Melanie A Kok
- Brain and Mind Institute, Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada N6A 5C1 Cerebral Systems Laboratory, Department of Psychology, University of Western Ontario, London, ON, Canada N6A 5C2
| | - Stephen G Lomber
- Brain and Mind Institute, Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada N6A 5C1 Cerebral Systems Laboratory, Department of Psychology, University of Western Ontario, London, ON, Canada N6A 5C2
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Diesch E, Schummer V, Kramer M, Rupp A. Structural changes of the corpus callosum in tinnitus. Front Syst Neurosci 2012; 6:17. [PMID: 22470322 PMCID: PMC3312098 DOI: 10.3389/fnsys.2012.00017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 03/05/2012] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES In tinnitus, several brain regions seem to be structurally altered, including the medial partition of Heschl's gyrus (mHG), the site of the primary auditory cortex. The mHG is smaller in tinnitus patients than in healthy controls. The corpus callosum (CC) is the main interhemispheric commissure of the brain connecting the auditory areas of the left and the right hemisphere. Here, we investigate whether tinnitus status is associated with CC volume. METHODS The midsagittal cross-sectional area of the CC was examined in tinnitus patients and healthy controls in which an examination of the mHG had been carried out earlier. The CC was extracted and segmented into subregions which were defined according to the most common CC morphometry schemes introduced by Witelson (1989) and Hofer and Frahm (2006). RESULTS For both CC segmentation schemes, the CC posterior midbody was smaller in male patients than in male healthy controls and the isthmus, the anterior midbody, and the genou were larger in female patients than in female controls. With CC size normalized relative to mHG volume, the normalized CC splenium was larger in male patients than male controls and the normalized CC splenium, the isthmus and the genou were larger in female patients than female controls. Normalized CC segment size expresses callosal interconnectivity relative to auditory cortex volume. CONCLUSION It may be argued that the predominant function of the CC is excitatory. The stronger callosal interconnectivity in tinnitus patients, compared to healthy controls, may facilitate the emergence and maintenance of a positive feedback loop between tinnitus generators located in the two hemispheres.
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Affiliation(s)
- Eugen Diesch
- Department of Clinical and Cognitive Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
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Suga N. Tuning shifts of the auditory system by corticocortical and corticofugal projections and conditioning. Neurosci Biobehav Rev 2012; 36:969-88. [PMID: 22155273 PMCID: PMC3265669 DOI: 10.1016/j.neubiorev.2011.11.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 10/19/2011] [Accepted: 11/21/2011] [Indexed: 11/21/2022]
Abstract
The central auditory system consists of the lemniscal and nonlemniscal systems. The thalamic lemniscal and nonlemniscal auditory nuclei are different from each other in response properties and neural connectivities. The cortical auditory areas receiving the projections from these thalamic nuclei interact with each other through corticocortical projections and project down to the subcortical auditory nuclei. This corticofugal (descending) system forms multiple feedback loops with the ascending system. The corticocortical and corticofugal projections modulate auditory signal processing and play an essential role in the plasticity of the auditory system. Focal electric stimulation - comparable to repetitive tonal stimulation - of the lemniscal system evokes three major types of changes in the physiological properties, such as the tuning to specific values of acoustic parameters of cortical and subcortical auditory neurons through different combinations of facilitation and inhibition. For such changes, a neuromodulator, acetylcholine, plays an essential role. Electric stimulation of the nonlemniscal system evokes changes in the lemniscal system that is different from those evoked by the lemniscal stimulation. Auditory signals ascending from the lemniscal and nonlemniscal thalamic nuclei to the cortical auditory areas appear to be selected or adjusted by a "differential" gating mechanism. Conditioning for associative learning and pseudo-conditioning for nonassociative learning respectively elicit tone-specific and nonspecific plastic changes. The lemniscal, corticofugal and cholinergic systems are involved in eliciting the former, but not the latter. The current article reviews the recent progress in the research of corticocortical and corticofugal modulations of the auditory system and its plasticity elicited by conditioning and pseudo-conditioning.
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Affiliation(s)
- Nobuo Suga
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO 63130, USA.
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Corticofugal modulation of initial neural processing of sound information from the ipsilateral ear in the mouse. PLoS One 2010; 5:e14038. [PMID: 21124980 PMCID: PMC2987806 DOI: 10.1371/journal.pone.0014038] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2010] [Accepted: 10/30/2010] [Indexed: 12/04/2022] Open
Abstract
Background Cortical neurons implement a high frequency-specific modulation of subcortical nuclei that includes the cochlear nucleus. Anatomical studies show that corticofugal fibers terminating in the auditory thalamus and midbrain are mostly ipsilateral. Differently, corticofugal fibers terminating in the cochlear nucleus are bilateral, which fits to the needs of binaural hearing that improves hearing quality. This leads to our hypothesis that corticofugal modulation of initial neural processing of sound information from the contralateral and ipsilateral ears could be equivalent or coordinated at the first sound processing level. Methodology/Principal Findings With the focal electrical stimulation of the auditory cortex and single unit recording, this study examined corticofugal modulation of the ipsilateral cochlear nucleus. The same methods and procedures as described in our previous study of corticofugal modulation of contralateral cochlear nucleus were employed simply for comparison. We found that focal electrical stimulation of cortical neurons induced substantial changes in the response magnitude, response latency and receptive field of ipsilateral cochlear nucleus neurons. Cortical stimulation facilitated auditory response and shortened the response latency of physiologically matched neurons whereas it inhibited auditory response and lengthened the response latency of unmatched neurons. Finally, cortical stimulation shifted the best frequencies of cochlear neurons towards those of stimulated cortical neurons. Conclusion Our data suggest that cortical neurons enable a high frequency-specific remodelling of sound information processing in the ipsilateral cochlear nucleus in the same manner as that in the contralateral cochlear nucleus.
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Nonlinear spectrotemporal interactions underlying selectivity for complex sounds in auditory cortex. J Neurosci 2009; 29:11192-202. [PMID: 19741126 DOI: 10.1523/jneurosci.1286-09.2009] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the auditory cortex of awake animals, a substantial number of neurons do not respond to pure tones. These neurons have historically been classified as "unresponsive" and even been speculated as being nonauditory. We discovered, however, that many of these neurons in the primary auditory cortex (A1) of awake marmoset monkeys were in fact highly selective for complex sound features. We then investigated how such selectivity might arise from the tone-tuned inputs that these neurons likely receive. We found that these non-tone responsive neurons exhibited nonlinear combination-sensitive responses that require precise spectral and temporal combinations of two tone pips. The nonlinear spectrotemporal maps derived from these neurons were correlated with their selectivity for complex acoustic features. These non-tone responsive and nonlinear neurons were commonly encountered at superficial cortical depths in A1. Our findings demonstrate how temporally and spectrally specific nonlinear integration of putative tone-tuned inputs might underlie a diverse range of high selectivity of A1 neurons in awake animals. We propose that describing A1 neurons with complex response properties in terms of tone-tuned input channels can conceptually unify a wide variety of observed neural selectivity to complex sounds into a lower dimensional description.
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Corticocortical interactions between and within three cortical auditory areas specialized for time-domain signal processing. J Neurosci 2009; 29:7230-7. [PMID: 19494145 DOI: 10.1523/jneurosci.0373-09.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In auditory cortex of the mustached bat, the FF (F means frequency modulation), dorsal fringe (DF), and ventral fringe (VF) areas consist of "combination-sensitive" neurons tuned to the pair of an emitted biosonar pulse and its echo with a specific delay (best delay: BD). The DF and VF areas are hierarchically at a higher level than the FF area. Focal electric stimulation of the FF area evokes "centrifugal" BD shifts of DF neurons, i.e., shifts away from the BD of the stimulated FF neurons, whereas stimulation of the DF neurons evokes "centripetal" BD shifts of FF neurons, i.e., shifts toward the BD of the stimulated DF neurons. In our current studies, we found that the feedforward projection from FF neurons evokes centrifugal BD shifts of VF neurons, that the feedback projection from VF neurons evokes centripetal BD shifts of FF neurons, that the contralateral projection from DF neurons evokes centripetal BD shifts of DF neurons, and that the centripetal BD shifts evoked by the DF and VF neurons are 2.5 times larger than the centrifugal BD shifts evoked by the FF neurons. The centrifugal BD shifts shape the selective neural representation of a specific target distance, whereas the centripetal BD shifts expand the representation of the selected specific target distance to focus on the processing of the target information at a specific distance. The centrifugal and centripetal BD shifts evoked by the feedforward and feedback projections promote finer analysis of a target at shorter distances.
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Schneider P, Andermann M, Wengenroth M, Goebel R, Flor H, Rupp A, Diesch E. Reduced volume of Heschl's gyrus in tinnitus. Neuroimage 2009; 45:927-39. [PMID: 19168138 DOI: 10.1016/j.neuroimage.2008.12.045] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 12/15/2008] [Accepted: 12/17/2008] [Indexed: 12/01/2022] Open
Abstract
The neural basis of tinnitus is unknown. Recent neuroimaging studies point towards involvement of several cortical and subcortical regions. Here we demonstrate that tinnitus may be associated with structural changes in the auditory cortex. Using individual morphological segmentation, the medial partition of Heschl's gyrus (mHG) was studied in individuals with and without chronic tinnitus using magnetic resonance imaging. Both the tinnitus and the non-tinnitus group included musicians and non-musicians. Patients exhibited significantly smaller mHG gray matter volumes than controls. In unilateral tinnitus, this effect was almost exclusively seen in the hemisphere ipsilateral to the affected ear. In bilateral tinnitus, mHG volume was substantially reduced in both hemispheres. The tinnitus-related volume reduction was found across the full extent of mHG, not only in the high-frequency part usually most affected by hearing loss-induced deafferentation. However, there was also evidence for a relationship between volume reduction and hearing loss. Correlations between volume and hearing level depended on the subject group as well as the asymmetry of the hearing loss. The volume changes observed may represent antecedents or consequences of tinnitus and tinnitus-associated hearing loss and also raise the possibility that small cortical volume constitutes a vulnerability factor.
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Affiliation(s)
- Peter Schneider
- Department of Clinical and Cognitive Neuroscience, Central Institute of Mental Health, University of Heidelberg, Mannheim, Germany.
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18
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Current World Literature. Curr Opin Otolaryngol Head Neck Surg 2008; 16:490-5. [DOI: 10.1097/moo.0b013e3283130f63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Modulation of auditory processing by cortico-cortical feed-forward and feedback projections. Proc Natl Acad Sci U S A 2008; 105:7600-5. [PMID: 18495931 DOI: 10.1073/pnas.0802961105] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The auditory center in the cerebrum, the auditory cortex, consists of multiple interconnected areas. The functional role of these interconnections is poorly understood. The auditory cortex of the mustached bat consists of at least nine areas, including the frequency modulation-frequency modulation (FF) and dorsal fringe (DF) areas. The FF and DF areas consist of neurons tuned to specific echo delays carrying target-distance information. The DF area is hierarchically at a higher level than the FF area. Here, we show that the feedback projection from the DF area to the FF area shifts the delay-tuning of FF neurons toward that of the stimulated DF neurons. In contrast, the feed-forward projection from the FF area to the DF area shifts the delay-tuning of DF neurons away from that of the stimulated FF neurons. The lateral projection within the DF area shifts the delay-tuning of DF neurons toward that of the stimulated DF neurons. In contrast, the lateral projection within the FF area shifts the delay-tuning of FF neurons away from that of the stimulated FF neurons. The delay-tuning shift evoked by the DF stimulation was 2.5 times larger than that evoked by the FF stimulation. Our data indicate that the FF-DF feed-forward and FF-FF lateral projections shape the highly selective neural representation of the tuning of the excited DF neurons, whereas the DF-FF feedback and DF-DF lateral projections enhance the representation of the selected tuning, perhaps, for focal processing of information carried by the excited FF neurons.
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