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Meng X, Mukherjee D, Kao JPY, Kanold PO. Early peripheral activity alters nascent subplate circuits in the auditory cortex. SCIENCE ADVANCES 2021; 7:eabc9155. [PMID: 33579707 PMCID: PMC7880598 DOI: 10.1126/sciadv.abc9155] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 12/28/2020] [Indexed: 05/10/2023]
Abstract
Cortical function can be shaped by sensory experience during a critical period. The onset of the critical period is thought to coincide with the onset of thalamocortical transmission to the thalamo-recipient layer 4 (L4). In early development, subplate neurons (SPNs), and not L4 neurons, are the first targets of thalamic afferents. SPNs are transiently involved in early development and are largely eliminated during development. Activation of L4 by thalamic afferents coincides with the opening of ear canal (~P11 in mice) and precedes the later critical period. Here, we show in mice that abolishing peripheral function or presenting sound stimuli even before P11 leads to bidirectionally altered functional connectivity of SPNs in auditory cortex. Thus, early sensory experience can sculpt subplate circuits before thalamocortical circuits to L4 are mature. Our results show that peripheral activity shapes cortical circuits in a sequential manner and from earlier ages than has been appreciated.
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Affiliation(s)
- Xiangying Meng
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Didhiti Mukherjee
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Patrick O Kanold
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.
- Department of Biology, University of Maryland, College Park, MD 20742, USA
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21205, USA
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Wang X, Liu J, Zhang J. Chronic Unilateral Hearing Loss Disrupts Neural Tuning to Sound-Source Azimuth in the Rat Primary Auditory Cortex. Front Neurosci 2019; 13:477. [PMID: 31133797 PMCID: PMC6524417 DOI: 10.3389/fnins.2019.00477] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 04/26/2019] [Indexed: 02/05/2023] Open
Abstract
Accurate sound localization requires normal binaural input and precise auditory neuronal representation of sound spatial locations. Previous studies showed that unilateral hearing loss profoundly impaired the sound localization abilities. However, the underlying neural mechanism is not fully understood. Here, we investigated how chronic unilateral conductive hearing loss (UCHL) affected the neural tuning to sound source azimuth in the primary auditory cortex (AI). The UCHL was manipulated by the removal of tympanic membrane and malleus in the right ear of young (P14) rats and adult (P57) rats. We recorded the azimuth tuning of neurons in the left AI contralateral to the operated ear in the two groups of rats that experienced 2 months of UCHL, and in the left AI of age-matched control rats. We found that AI neurons in control rats showed predominant preference to sound from contralateral azimuths. However, UCHL weakened the cortical neuronal representation of contralateral azimuths on the operated ear side and strengthened the cortical neuronal representation of ipsilateral azimuths on the intact ear side. This effect was stronger in rats with UCHL at young age than in rats with UCHL in adulthood. Moreover, UCHL degraded the azimuth selectivity and azimuth sensitivity of AI neurons, and this effect was stronger in rats with UCHL in adulthood than in rats with UCHL at young age. These findings highlight a remarkable age-related experience-dependent plasticity of neural tuning to sound source azimuth in AI, and imply a neural mechanism for the impacts of chronic UCHL on sound localization abilities.
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Affiliation(s)
- Xiuwen Wang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jing Liu
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jiping Zhang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
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Kim S, Kwon HJ, Kang EJ, Kim DW. Diffusion-Tensor Tractography of the Auditory Neural Pathway : Clinical Usefulness in Patients with Unilateral Sensorineural Hearing Loss. Clin Neuroradiol 2018; 30:115-122. [PMID: 30374668 DOI: 10.1007/s00062-018-0733-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 10/10/2018] [Indexed: 11/28/2022]
Abstract
PURPOSE The purpose of this study was to evaluate the structural integrity of the auditory neural pathway in patients with unilateral sensorineural hearing loss using quantitative diffusion-tensor tractography. METHODS Diffusion-tensor tractography imaging was performed using a 3T magnetic resonance imaging system to evaluate structural alterations in the auditory neural pathway of patients with unilateral sensorineural hearing loss. The two diffusion-tensor tractography parameters, fractional anisotropy and the apparent diffusion coefficient were compared between the ipsilateral side and the contralateral side in patients and controls. Additionally, correlations between the parameter values and the hearing loss level in patients were evaluated. RESULTS A total of 24 sensorineural hearing loss patients (14 males; age range, 17-65 years; average age, 45.3 years) and 24 age and sex-matched control subjects were enrolled. Fractional anisotropy values on the ipsilateral and contralateral sides were significantly lower in patients than in the control group (p = 0.004 and 0.001, respectively). The differences in the apparent diffusion coefficient values for the ipsilateral and contralateral sides between the two groups were not significant (p = 0.279 and 0.248, respectively). There was an inverse relationship between fractional anisotropy and the severity of hearing impairment on the ipsilateral and contralateral sides (r = -0.519, p = 0.005 and r = -0.454, p = 0.015, respectively). No significant correlation was found between the apparent diffusion coefficient and hearing loss level on the ipsilateral and contralateral sides (r = 0.172, p = 0.380 and r = 0.131, p = 0.508, respectively). CONCLUSION Quantitative diffusion-tensor tractography can be used to detect microstructural alterations in the auditory neural pathway in sensorineural hearing loss patients with normal results in standard imaging studies.
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Affiliation(s)
- Sanghyeon Kim
- Department of Radiology, College of Medicine, Dong-A University, 1,3-ga, Dongdaeshin-dong, Seogu, Busan, Korea (Republic of).
| | - Hee Jin Kwon
- Department of Radiology, College of Medicine, Dong-A University, 1,3-ga, Dongdaeshin-dong, Seogu, Busan, Korea (Republic of)
| | - Eun-Ju Kang
- Department of Radiology, College of Medicine, Dong-A University, 1,3-ga, Dongdaeshin-dong, Seogu, Busan, Korea (Republic of)
| | - Dong Won Kim
- Department of Radiology, College of Medicine, Dong-A University, 1,3-ga, Dongdaeshin-dong, Seogu, Busan, Korea (Republic of)
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Lee JK, Kim MJ. The distribution of calbindin-D28k, parvalbumin, and calretinin immunoreactivity in the inferior colliculus of circling mouse. Anat Cell Biol 2017; 50:230-238. [PMID: 29043102 PMCID: PMC5639178 DOI: 10.5115/acb.2017.50.3.230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 07/24/2017] [Accepted: 07/26/2017] [Indexed: 11/27/2022] Open
Abstract
The circling mice with tmie gene mutation are known as an animal deafness model, which showed hyperactive circling movement. Recently, the reinvestigation of circling mouse was performed to check the inner ear pathology as a main lesion of early hearing loss. In this trial, the inner ear organs were not so damaged to cause the hearing deficit of circling (cir/cir) mouse at 18 postnatal day (P18) though auditory brainstem response data indicated hearing loss of cir/cir mice at P18. Thus, another mechanism may be correlated with the early hearing loss of cir/cir mice at P18. Hearing loss in the early life can disrupt the ascending and descending information to inferior colliculus (IC) as integration site. There were many reports that hearing loss could result in the changes in Ca2+ concentration by either cochlear ablation or genetic defect. However, little was known to be reported about the correlation between the pathology of IC and Ca2+ changes in circling mice. Therefore, the present study investigated the distribution of calcium-binding proteins (CaBPs), calbindin-D28k, parvalbumin, and calretinin immunoreactivity (IR) in the IC to compare among wild-type (+/+), heterozygous (+/cir), and homozygous (cir/cir) mice by immunohistochemistry. The decreases of CaBPs IR in cir/cir were statistically significant in the neurons as well as neuropil of IC. Thus, this study proposed overall distributional alteration of CaBPs IR in the IC caused by early hearing defect and might be helpful to elucidate the pathology of central auditory disorder related with Ca2+ metabolism.
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Affiliation(s)
- Jin-Koo Lee
- Department of Pharmacology, Dankook University College of Medicine, Cheonan, Korea
| | - Myeung Ju Kim
- Department of Anatomy, Dankook University College of Medicine, Cheonan, Korea
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Neural Hyperactivity of the Central Auditory System in Response to Peripheral Damage. Neural Plast 2016; 2016:2162105. [PMID: 26881094 PMCID: PMC4736999 DOI: 10.1155/2016/2162105] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/12/2015] [Accepted: 11/15/2015] [Indexed: 11/19/2022] Open
Abstract
It is increasingly appreciated that cochlear pathology is accompanied by adaptive responses in the central auditory system. The cause of cochlear pathology varies widely, and it seems that few commonalities can be drawn. In fact, despite intricate internal neuroplasticity and diverse external symptoms, several classical injury models provide a feasible path to locate responses to different peripheral cochlear lesions. In these cases, hair cell damage may lead to considerable hyperactivity in the central auditory pathways, mediated by a reduction in inhibition, which may underlie some clinical symptoms associated with hearing loss, such as tinnitus. Homeostatic plasticity, the most discussed and acknowledged mechanism in recent years, is most likely responsible for excited central activity following cochlear damage.
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Wang HC, Bergles DE. Spontaneous activity in the developing auditory system. Cell Tissue Res 2015; 361:65-75. [PMID: 25296716 PMCID: PMC7046314 DOI: 10.1007/s00441-014-2007-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022]
Abstract
Spontaneous electrical activity is a common feature of sensory systems during early development. This sensory-independent neuronal activity has been implicated in promoting their survival and maturation, as well as growth and refinement of their projections to yield circuits that can rapidly extract information about the external world. Periodic bursts of action potentials occur in auditory neurons of mammals before hearing onset. This activity is induced by inner hair cells (IHCs) within the developing cochlea, which establish functional connections with spiral ganglion neurons (SGNs) several weeks before they are capable of detecting external sounds. During this pre-hearing period, IHCs fire periodic bursts of Ca(2+) action potentials that excite SGNs, triggering brief but intense periods of activity that pass through auditory centers of the brain. Although spontaneous activity requires input from IHCs, there is ongoing debate about whether IHCs are intrinsically active and their firing periodically interrupted by external inhibitory input (IHC-inhibition model), or are intrinsically silent and their firing periodically promoted by an external excitatory stimulus (IHC-excitation model). There is accumulating evidence that inner supporting cells in Kölliker's organ spontaneously release ATP during this time, which can induce bursts of Ca(2+) spikes in IHCs that recapitulate many features of auditory neuron activity observed in vivo. Nevertheless, the role of supporting cells in this process remains to be established in vivo. A greater understanding of the molecular mechanisms responsible for generating IHC activity in the developing cochlea will help reveal how these events contribute to the maturation of nascent auditory circuits.
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Affiliation(s)
- Han Chin Wang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Auditory neuroplasticity, hearing loss and cochlear implants. Cell Tissue Res 2014; 361:251-69. [DOI: 10.1007/s00441-014-2004-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/04/2014] [Indexed: 10/24/2022]
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Maskey D, Kim HG, Suh MW, Roh GS, Kim MJ. Alteration of glycine receptor immunoreactivity in the auditory brainstem of mice following three months of exposure to radiofrequency radiation at SAR 4.0 W/kg. Int J Mol Med 2014; 34:409-19. [PMID: 24866721 PMCID: PMC4094587 DOI: 10.3892/ijmm.2014.1784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 04/11/2014] [Indexed: 11/24/2022] Open
Abstract
The increasing use of mobile communication has triggered an interest in its possible effects on the regulation of neurotransmitter signals. Due to the close proximity of mobile phones to hearing-related brain regions during usage, its use may lead to a decrease in the ability to segregate sounds, leading to serious auditory dysfunction caused by the prolonged exposure to radiofrequency (RF) radiation. The interplay among auditory processing, excitation and inhibitory molecule interactions plays a major role in auditory function. In particular, inhibitory molecules, such a glycine, are predominantly localized in the auditory brainstem. However, the effects of exposure to RF radiation on auditory function have not been reported to date. Thus, the aim of the present study was to investigate the effects of exposure to RF radiation on glycine receptor (GlyR) immunoreactivity (IR) in the auditory brainstem region at 835 MHz with a specific absorption rate of 4.0 W/kg for three months using free-floating immunohistochemistry. Compared with the sham control (SC) group, a significant loss of staining intensity of neuropils and cells in the different subdivisions of the auditory brainstem regions was observed in the mice exposed to RF radiation (E4 group). A decrease in the number of GlyR immunoreactive cells was also noted in the cochlear nuclear complex [anteroventral cochlear nucleus (AVCN), 31.09%; dorsal cochlear nucleus (DCN), 14.08%; posteroventral cochlear nucleus (PVCN), 32.79%] and the superior olivary complex (SOC) [lateral superior olivary nucleus (LSO), 36.85%; superior paraolivary nucleus (SPN), 24.33%, medial superior olivary nucleus (MSO), 23.23%; medial nucleus of the trapezoid body (MNTB), 10.15%] of the mice in the E4 group. Auditory brainstem response (ABR) analysis also revealed a significant threshold elevation of in the exposed (E4) group, which may be associated with auditory dysfunction. The present study suggests that the auditory brainstem region is susceptible to chronic exposure to RF radiation, which may affect the function of the central auditory system.
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Affiliation(s)
- Dhiraj Maskey
- Department of Anatomy, Dankook University College of Medicine, Cheonan-si, Chungnam, Republic of Korea
| | - Hyung Gun Kim
- Department of Pharmacology, Dankook University College of Medicine, Cheonan-si, Chungnam, Republic of Korea
| | - Myung-Whan Suh
- Department of Otorhinolaryngology, Seoul National University Hospital, Jongno-gu, Seoul, Republic of Korea
| | - Gu Seob Roh
- Department of Anatomy, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, Gyeongsang, Republic of Korea
| | - Myeung Ju Kim
- Department of Anatomy, Dankook University College of Medicine, Cheonan-si, Chungnam, Republic of Korea
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Grande G, Negandhi J, Harrison RV, Wang LY. Remodelling at the calyx of Held-MNTB synapse in mice developing with unilateral conductive hearing loss. J Physiol 2014; 592:1581-600. [PMID: 24469075 DOI: 10.1113/jphysiol.2013.268839] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Structure and function of central synapses are profoundly influenced by experience during developmental sensitive periods. Sensory synapses, which are the indispensable interface for the developing brain to interact with its environment, are particularly plastic. In the auditory system, moderate forms of unilateral hearing loss during development are prevalent but the pre- and postsynaptic modifications that occur when hearing symmetry is perturbed are not well understood. We investigated this issue by performing experiments at the large calyx of Held synapse. Principal neurons of the medial nucleus of the trapezoid body (MNTB) are innervated by calyx of Held terminals that originate from the axons of globular bushy cells located in the contralateral ventral cochlear nucleus. We compared populations of synapses in the same animal that were either sound deprived (SD) or sound experienced (SE) after unilateral conductive hearing loss (CHL). Middle ear ossicles were removed 1 week prior to hearing onset (approx. postnatal day (P) 12) and morphological and electrophysiological approaches were applied to auditory brainstem slices taken from these mice at P17-19. Calyces in the SD and SE MNTB acquired their mature digitated morphology but these were structurally more complex than those in normal hearing mice. This was accompanied by bilateral decreases in initial EPSC amplitude and synaptic conductance despite the CHL being unilateral. During high-frequency stimulation, some SD synapses displayed short-term depression whereas others displayed short-term facilitation followed by slow depression similar to the heterogeneities observed in normal hearing mice. However SE synapses predominantly displayed short-term facilitation followed by slow depression which could be explained in part by the decrease in release probability. Furthermore, the excitability of principal cells in the SD MNTB had increased significantly. Despite these unilateral changes in short-term plasticity and excitability, heterogeneities in the spiking fidelity among the population of both SD and SE synapses showed similar continuums to those in normal hearing mice. Our study suggests that preservations in the heterogeneity in spiking fidelity via synaptic remodelling ensures symmetric functional stability which is probably important for retaining the capability to maximally code sound localization cues despite moderate asymmetries in hearing experience.
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Affiliation(s)
- Giovanbattista Grande
- Corresponding Author L.-Y. Wang, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario, Canada M5G 1X8.
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Wallace MM, Kavianpour SM, Gabriele ML. Ephrin-B2 reverse signaling is required for topography but not pattern formation of lateral superior olivary inputs to the inferior colliculus. J Comp Neurol 2013; 521:1585-97. [PMID: 23042409 DOI: 10.1002/cne.23243] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 09/05/2012] [Accepted: 10/03/2012] [Indexed: 12/19/2022]
Abstract
Graded and modular expressions of Eph-ephrins are known to provide positional information for the formation of topographic maps and patterning in the developing nervous system. Previously we have shown that ephrin-B2 is expressed in a continuous gradient across the tonotopic axis of the central nucleus of the inferior colliculus (CNIC), whereas patterns are discontinuous and modular in the lateral cortex of the IC (LCIC). The present study explores the involvement of ephrin-B2 signaling in the development of projections to the CNIC and LCIC arising from the lateral superior olivary nuclei (LSO) prior to hearing onset. Anterograde and retrograde fluorescent tracing methods in neonatal fixed tissue preparations were used to compare topographic mapping and the establishment of LSO layers/modules in wild-type and ephrin-B2(lacZ/+) mice (severely compromised reverse signaling). At birth, pioneer LSO axons occupy the ipsilateral IC in both groups but are delayed contralaterally in ephrin-B2(lacZ/+) mutants. By the onset of hearing, both wild-type and mutant projections form discernible layers bilaterally in the CNIC and modular arrangements within the ipsilateral LCIC. In contrast, ephrin-B2(lacZ/+) mice lack a reliable topography in LSO-IC projections, suggesting that fully functional ephrin-B2 reverse signaling is required for normal projection mapping. Taken together, these ephrin-B2 findings paired with known coexpression of EphA4 suggest the importance of these signaling proteins in establishing functional auditory circuits prior to experience.
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Affiliation(s)
- Matthew M Wallace
- Department of Biology, MSC 7801, James Madison University, Harrisonburg, Virginia 22807, USA
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Hatano M, Ito M, Yoshizaki T, Kelly JB. Changes in projections to the inferior colliculus following early hearing loss in rats. Hear Res 2012; 287:57-66. [DOI: 10.1016/j.heares.2012.03.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 03/06/2012] [Accepted: 03/26/2012] [Indexed: 11/16/2022]
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Gabriele ML, Brubaker DQ, Chamberlain KA, Kross KM, Simpson NS, Kavianpour SM. EphA4 and ephrin-B2 expression patterns during inferior colliculus projection shaping prior to experience. Dev Neurobiol 2011; 71:182-99. [PMID: 20886601 DOI: 10.1002/dneu.20842] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Central processing of complex auditory tasks requires elaborate circuitry. The auditory midbrain, or inferior colliculus (IC), epitomizes such precise organization, where converging inputs form discrete, tonotopically-arranged axonal layers. Previously in rat, we established that shaping of multiple afferent patterns in the IC central nucleus (CNIC) occurs prior to experience. This study implicates an Eph receptor tyrosine kinase and a corresponding ephrin ligand in signaling this early topographic registry. We report that EphA4 and ephrin-B2 expression patterns in the neonatal rat and mouse IC correlate temporally and spatially with that of developing axonal layers. DiI-labeling confirms projections arising from the lateral superior olive (LSO) form frequency-specific layers within the ipsilateral and contralateral mouse CNIC, as has been described in other species. Immunohistochemistry (EphA4 and ephrin-B2) and ephrin-B2 lacZ histochemistry reveal clear gradients in expression across the tonotopic axis, with most concentrated labeling observed in high-frequency, ventromedial aspects of the CNIC. Discrete patches of labeling were also discernible in the external cortex of the IC (ECIC; EphA4 patches in rat, ephrin-B2 patches in mouse). Observed gradients in the CNIC and compartmentalized ECIC expression persisted through the first postnatal week, before becoming less intense and more homogeneously distributed by the functional onset of hearing. EphA4 and ephrin-B2-positive neurons were evident in several auditory brainstem nuclei known to send patterened inputs to the IC. These findings suggest the involvement of cell-cell EphA4 and ephrin-B2 signaling in establishing order in the developing IC.
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Affiliation(s)
- Mark L Gabriele
- Department of Biology, James Madison University, MSC 7801, 820 Madison Drive, Harrisonburg, Virginia 22807, USA.
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Razak KA, Fuzessery ZM. Development of parallel auditory thalamocortical pathways for two different behaviors. Front Neuroanat 2010; 4. [PMID: 20941327 PMCID: PMC2952463 DOI: 10.3389/fnana.2010.00134] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 08/29/2010] [Indexed: 11/13/2022] Open
Abstract
Auditory thalamocortical connections are organized as parallel pathways that originate in different divisions of the medial geniculate body (MGB). These pathways may be involved in different functions. Surprisingly little is known about the development of these connections. Here we review studies of the organization and development of auditory thalamocortical pathways in the pallid bat. The pallid bat depends primarily on passive hearing of prey-generated noise for localizing prey, while reserving echolocation for general orientation and obstacle avoidance. In the inferior colliculus (IC) and the auditory cortex, physiological studies show that noise and echolocation calls are processed in segregated regions. Injection of retrograde tracers in physiologically characterized cortical sites show that the ventral division of the MGB (MGBv) projects to the cortical region selective for noise. The cortical region selective for echolocation calls receives input from the suprageniculate (SG) nucleus in the dorsal MGB, but not from the MGBv. Taken together, these studies reveal parallel IC-MGB-cortex pathways involved in echolocation and passive listening. There is overlap of thalamocortical pathways during development. At 2-weeks postnatal, when the bat begins to exhibit adult-like hearing thresholds, the SG projects to both noise- and echolocation call-selective regions. The MGBv, as in adults, projects only to the noise-selective region. The connections become adult-like only after 2-months postnatal. These data suggest that parallel auditory thalamocortical pathways may segregate in an experience-dependent fashion, a hypothesis that remains to be tested in any species.
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Affiliation(s)
- Khaleel A Razak
- Department of Psychology, University of California Riverside, CA, USA
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O'Neil JN, Limb CJ, Baker CA, Ryugo DK. Bilateral effects of unilateral cochlear implantation in congenitally deaf cats. J Comp Neurol 2010; 518:2382-404. [PMID: 20437534 DOI: 10.1002/cne.22339] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Congenital deafness results in synaptic abnormalities in auditory nerve endings. These abnormalities are most prominent in terminals called endbulbs of Held, which are large, axosomatic synaptic endings whose size and evolutionary conservation emphasize their importance. Transmission jitter, delay, or failures, which would corrupt the processing of timing information, are possible consequences of the perturbations at this synaptic junction. We sought to determine whether electrical stimulation of the congenitally deaf auditory system via cochlear implants would restore the endbulb synapses to their normal morphology. Three and 6-month-old congenitally deaf cats received unilateral cochlear implants and were stimulated for a period of 10-19 weeks by using human speech processors. Implanted cats exhibited acoustic startle responses and were trained to approach their food dish in response to a specific acoustic stimulus. Endbulb synapses were examined by using serial section electron microscopy from cohorts of cats with normal hearing, congenital deafness, or congenital deafness with a cochlear implant. Synapse restoration was evident in endbulb synapses on the stimulated side of cats implanted at 3 months of age but not at 6 months. In the young implanted cats, postsynaptic densities exhibited normal size, shape, and distribution, and synaptic vesicles had density values typical of hearing cats. Synapses of the contralateral auditory nerve in early implanted cats also exhibited synapses with more normal structural features. These results demonstrate that electrical stimulation with a cochlear implant can help preserve central auditory synapses through direct and indirect pathways in an age-dependent fashion.
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Affiliation(s)
- Jahn N O'Neil
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Bureš Z, Grécová J, Popelář J, Syka J. Noise exposure during early development impairs the processing of sound intensity in adult rats. Eur J Neurosci 2010; 32:155-64. [DOI: 10.1111/j.1460-9568.2010.07280.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Razak KA, Zumsteg T, Fuzessery ZM. Development of auditory thalamocortical connections in the pallid bat, Antrozous pallidus. J Comp Neurol 2009; 515:231-42. [PMID: 19412955 DOI: 10.1002/cne.22050] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Auditory thalamocortical connections are organized as parallel pathways originating in various nuclei of the medial geniculate body (MGB). The development of these pathways has not been studied. Therefore it remains unclear whether thalamocortical connections segregate before the onset of hearing or whether refinement of exuberant thalamocortical connections occurs following hearing onset. We studied this issue in the pallid bat. In adult pallid bats, parallel thalamocortical pathways represent two different sounds used in two different behaviors. The suprageniculate (SG) nucleus of the dorsal division of the MGB (MGBd) projects to a high-frequency cortical region selective for the echolocation calls, but not to a low-frequency cortical region sensitive to noise transients used in the localization of prey. Conversely, the ventral division (MGBv) projects to the low-frequency, but not the high-frequency, cortical region. Here we studied the development of these parallel pathways. Based on retrograde tracer injections in electrophysiologically characterized cortical loci, we show that there is an asymmetrical overlap in projection patterns from postnatal (P) day 15-60. The low-frequency region receives extensive input from both the SG and the MGBv. In contrast, the high-frequency region receives the great majority of its input from the SG, as in adults, whereas projections from the MGBv appear to make only a minor contribution, if any. By P150, these pathways are segregated and adult-like. These data suggest that these anatomically segregated pathways arise through postnatal refinement of initially overlapping connections.
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Affiliation(s)
- Khaleel A Razak
- Department of Psychology, University of California, Riverside, California 92521, USA
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Wu CM, Ng SH, Wang JJ, Liu TC. Diffusion tensor imaging of the subcortical auditory tract in subjects with congenital cochlear nerve deficiency. AJNR Am J Neuroradiol 2009; 30:1773-7. [PMID: 19574496 DOI: 10.3174/ajnr.a1681] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Cochlear nerve deficiency (CND), including aplasia and hypoplasia, is a rare cause of congenital hearing loss. The purpose of this study was to evaluate the neuronal integrity of the subcortical auditory pathway in subjects with CND by diffusion tensor MR imaging (DTI). MATERIALS AND METHODS Twelve subjects with unilateral congenital CND were included in this prospective study. Twelve normal-hearing subjects served as controls. DTIs were acquired from these subjects on a 3T MR imaging scanner. Several indices including axial diffusivity (lambda( ||)), radial diffusivity (lambda( perpendicular)), mean diffusivity (MD), and fractional anisotropy (FA) along the auditory pathway were extracted. Two regions of interest were selected bilaterally for evaluation: the lateral lemniscus (LL) and inferior colliculus (IC). The mean values of lambda( ||), lambda( perpendicular), MD, and FA at both regions of interest were compared between the ipsilateral and contralateral sides of subjects with CND with those in the control group. RESULTS Significant decrease of FA and increase of MD on both the ipsilateral and contralateral sides of patients with CND as compared with normal subjects in both LL and IC were found. The decrease of FA was due to the increase of lambda( perpendicular), whereas lambda( ||) remained unchanged. CONCLUSIONS The maintained axial diffusion implied that the orientation of neural fibers along the subcortical auditory pathway in subjects with unilateral CND is intact. However, the reduction in FA and increase in lambda( perpendicular) on both the ipsilateral and contralateral sides might be attributed to axonal loss and/or demyelination of the subcortical auditory tract in these subjects.
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Affiliation(s)
- C-M Wu
- Department of Otolaryngology, College of Medicine, Chang-Gung University, Linkou, Taiwan
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18
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Fathke RL, Gabriele ML. Patterning of multiple layered projections to the auditory midbrain prior to experience. Hear Res 2009; 249:36-43. [PMID: 19271271 DOI: 10.1016/j.heares.2009.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The precise arrangement of patterned inputs into discrete functional domains is a common organizational feature of primary sensory structures. While the specific organization of patterned connections has been well documented in the visual and somatosensory systems, comparatively little is known about the arrangement of neighboring afferent patterns in the emerging auditory system. Here we report early projection specificity for multiple converging inputs to the rat central nucleus of the inferior colliculus (ICC). Afferents arising from the dorsal cochlear nucleus (DCN), the dorsal nucleus of the lateral lemniscus (DNLL), and the lateral superior olive (LSO) establish discernible axonal layers a week prior to experience. By hearing onset, contralateral DCN and contralateral LSO layers are clearly defined and segregated from contralateral DNLL terminal zones. Layering of the ipsilateral LSO projection, on the other hand, exhibits considerable spatial overlap with the contralateral DNLL pattern. This fine laminar structure of interdigitating and overlapping inputs likely underlies the complex signal processing performed in the auditory midbrain and may serve as a model system for examining competitive interactions between neighboring excitatory and inhibitory projections early in development.
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Affiliation(s)
- Robert L Fathke
- James Madison University, Department of Biology, MSC 7801, Harrisonburg, VA 22807, USA
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19
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Franklin SR, Brunso-Bechtold JK, Henkel CK. Bilateral cochlear ablation in postnatal rat disrupts development of banded pattern of projections from the dorsal nucleus of the lateral lemniscus to the inferior colliculus. Neuroscience 2008; 154:346-54. [PMID: 18372115 DOI: 10.1016/j.neuroscience.2008.02.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Revised: 01/25/2008] [Accepted: 02/13/2008] [Indexed: 11/16/2022]
Abstract
Axonal projections from the dorsal nucleus of the lateral lemniscus (DNLL) distribute contralaterally in a pattern of banded layers in the central nucleus of the inferior colliculus (IC). The banded pattern of DNLL projections is already in the IC by onset of hearing in postnatal rat pups. Previously, it was shown that unilateral cochlear ablation in neonatal rat pups disrupted the banded pattern in IC for the projections of the DNLL contralateral to the ablation but not those of the DNLL ipsilateral to the ablation. In the present study, bilateral cochlear ablation or sham surgery was performed at postnatal day 9 (P9) after which rat pups were killed at P12 and the brains removed to study axonal projections of the DNLL. A lipophilic carbocyanine dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), was placed in the dorsal tegmental commissure of Probst to label decussating DNLL axons that end in the central nucleus of the contralateral IC. The distribution of labeled fibers across the central nucleus of the IC was analyzed in digital images by comparing the pattern of labeling with a sine model of periodic distribution of banded layers. In the control group, labeled axons formed a regular pattern of dense banded layers in IC. In the bilateral cochlear ablation group, labeled axons in the IC were distributed diffusely and there was little or no regular pattern of dense bands of axonal labeling. The influence of the cochlea on developing auditory circuits possibly mediated by activity-dependent mechanisms is discussed.
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Affiliation(s)
- S R Franklin
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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20
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Henkel CK, Keiger CJ, Franklin SR, Brunso-Bechtold JK. Development of banded afferent compartments in the inferior colliculus before onset of hearing in ferrets. Neuroscience 2007; 146:225-35. [PMID: 17324524 PMCID: PMC1973092 DOI: 10.1016/j.neuroscience.2007.01.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 01/05/2007] [Accepted: 01/12/2007] [Indexed: 11/28/2022]
Abstract
Axonal projections from the lateral superior olivary nuclei (LSO), as well as from the dorsal cochlear nucleus (DCN) and dorsal nucleus of the lateral lemniscus (DNLL), converge in frequency-ordered layers in the central nucleus of the inferior colliculus (IC) where they distribute among different synaptic compartments. A carbocyanine dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), was used as a tracer to study the postnatal development of axonal projections in the ferret IC. The results indicated that projections from all three nuclei are present at birth, but are not segregated into bands. During the postnatal week between approximately postnatal days 4 and 12 (P4-P12), axons from LSO proliferate in IC, become more branched, and segregate into a series of bands composed of densely packed fibers and endings. LSO projections in these afferent bands course parallel to IC layers and are separated by intervening regions with few endings. A modest fit of a sine curve (R2>0.15) to the pattern of spacing of LSO projections in IC indicated that regularly spaced bands are forming by P7. Similarly, banded patterns of DCN and DNLL projections to IC have developed by the end of the first postnatal week. Thus, well before hearing onset in ferret (P28-30), three different afferent projections have segregated into banded compartments along layers in the central nucleus of the ferret IC. Possible mechanisms in circuit development are discussed.
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Affiliation(s)
- C K Henkel
- Wake Forest University Health Sciences, Neuroscience Program and Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
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