DOCSLIB.ORG

Organization of the Inferior Colliculus

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Neurobiology of Hearing… Introduction UCHC-INCYL-USAL 2019 David Pérez González Hearing . Far-range sense: like vision . Omnidirectional Essential for communication of animal and men Sound: quick variations of pressure Compressed air Rarefied air pressure Air One Distance cycle Sound and Sound propagation Wavelength Sound Amplitude pressure Wavelength λ C = λ * ν (~ 330m/s) ν = Frequency = number of cycles/s (Hz) Properties of a sine wave • Frequency: Cycles per second, or Hertz (Hz). • Phase: angle (degrees). • Amplitude: decibels (dB) Sound frequency and intensity Low frequency High frequency Air Air pressure Low intensity High intensity Air Air pressure Distance Distance Sound pressure level 200,000,000 • The difference in amplitudes between the quietest and loudest sounds we can hear is massive • Normal air pressure: 100k Pascals. • We can hear a .000000001% change in pressure. 20 Sound pressure level 140 • The decibel scale: the logarithm of a ratio (relative to 20µPa): 20log 10(p/ 20µPa) 20µPa 0dB SPL 200µPa 20dB SPL 2000 µPa 40dB SPL etc. 0 Decibel Scale • Relative • Logarithmic I p dB SPL = 10 log 10 = 20 log 10 I0 p0 -5 • Reference pressure p0 = 2x10 Pa (hearing threshold 1kHz) Auditory thresholds in humans (dB) Threshold of pain Speech Sound intensity Absolute threshold Sound frequency (kHz) Mammalian audiograms Pure tones and complex sounds aaa Zeit The auditory information arriving at the ears is a mixture of all the sounds in the environment. The individual sound waves are combined into a single, complex sound wave. The peripheral auditory system Function of the Middle Ear Transformation: Pressure p Area: Al : As = 17 : 1 Lever deflexion d : lm : li = 1,3 : 1 combined: d / p = 22 : 1 p / d = z * ω = Impedance * Frequency The Inner Ear (Bony Labyrinth) Vestibular Nerve Cochlea Sacculus Travelling wave in the Cochlea Travelling wave in the Cochlea Low Frequency Travelling wave in the Cochlea High Frequency Frequency Analysis in the Cochlea Pelicula cochlea The cochlea Organ of Corti 30 Detail of the organ of Corti: IHC OHC Hair cells: transduction QUIETSOUND Hair cell depolarization Hair cell depolarization • The movement of the cilia produces changes on the membrane potential Inner and outer hair cells Inner hair cell Outer hair cells Stimulus propagation Amplification Effect of sound on a outer hair cell ¿What is the role of outer hair cells? Hearing loss Hair cell innervation The human auditory brain Kiang and Peake (1988) The cochlear nucleus is the first step into the central auditory system Cochlear nuclei Auditory nerve Cochlea Cytoarchitecture of the cochlear nuclei. Golgi staining Cytoarchitecture of the cochlear nuclei. Golgi staining The cochlear nuclei: parallel processing pathways Superior olivary complex Mechanisms for sound localization in the horizontal plane (azimuth) Time and intensity differences for localizing a sound source Interaural time differences (ITDs) Interaural level differences (ILDs) Mechanisms for sound localization in the vertical plane (elevation) Structure of DC the inferior colliculus CN • Central nucleus (CN) LC • Dorsal cortex (DC) • Lateral cortex (LC) FUNCTIONAL PROPERTIES OF THE INFERIOR COLLICULUS FUNCTIONAL PROPERTIES OF THE INFERIOR COLLICULUS Inputs to the Inferior Colliculus Inputs from Cochlear Nucleus INFERIOR IC COLLICULUS DLL DLL VLL VLL Monaural inputs to IC DCN DCN Monaural inputs to SOC and IC VCN VCN LSO MSO MSO LSO CONTRA IPSI Inputs from SOC INFERIOR IC COLLICULUS DLL DLL VLL VLL ITDONLY DCN ILD DCN - ITD VCN ILD-ITD VCN LSO MSO MSO LSO CONTRA IPSI Inputs from Lateral Lemniscus INFERIOR IC COLLICULUS DLL ILD-ITD DLL VLL VLL Monaural DCN DCN VCN VCN LSO MSO MSO LSO CONTRA IPSI CONTRA Frequency Band Lamina IPSI INFERIOR COLLICULUS DLL VLL Monaural DCN VCN LSO MSO Binaural MSO LSO Inputs Create Functional From Loftus et al (2010) J Neurosci • Zones in the IC 30(40):13396 –13408 The organisation and function of the auditory thalamus From Bear Connors and Paradiso: Neuroscience, Exploring the brain The human auditory system Auditory cortex Medial geniculate body (Thalamus) Inferior Dorsal cochlear colliculus nucleus Ventral cochlear nucleus Lateral lemniscus (Adapted from Bear et al) Cochlea Superior olive Spiral ganglion Medial geniculate body D Auditory cortex Thalamic reticular nucleus M L V MGD IC (dorsal cortex) IC (external cortex) MGM Superior Colliculus VNLL MGV Po DNLL Cochlear nucleus Spinal cord IC (central) Circuits for auditory fear conditioning Auditory cortex Amygdala Central MGM MGV Lateral Defence responses Behaviour Hypothalamus / pituitary Autonomic nervous Conditioned stimulus -tone system The auditory cortex Location of auditory cortex in human brain Planum Temporale Primary auditory cortex: Heschl’s gyrus Neurons and layers of rat auditory cortex Neurons and layers of rat auditory cortex The auditory cortex in mouse and cat Multiple tonotopic maps in the cortex Rostral Caudal Petkov et al 2006 Plasticity in the auditory cortex Plasticity in auditory cortex following stimulation of nucleus basalis in rat Reorganisation of the frequency map in rat A1 following nucleus basalis stimulation Kilgard et al 1997 Science 279 1715 .
Recommended publications
  • Fibroblast Growth Factor (Fgf) Implication in the Neonatal Development of the Cochlear Innervation G

    Fibroblast Growth Factor (Fgf) Implication in the Neonatal Development of the Cochlear Innervation G

    FIBROBLAST GROWTH FACTOR (FGF) IMPLICATION IN THE NEONATAL DEVELOPMENT OF THE COCHLEAR INNERVATION G. Després, I. Jalenques, R. Romand To cite this version: G. Després, I. Jalenques, R. Romand. FIBROBLAST GROWTH FACTOR (FGF) IMPLICATION IN THE NEONATAL DEVELOPMENT OF THE COCHLEAR INNERVATION. Journal de Physique IV Proceedings, EDP Sciences, 1992, 02 (C1), pp.C1-173-C1-176. 10.1051/jp4:1992134. jpa-00251205 HAL Id: jpa-00251205 https://hal.archives-ouvertes.fr/jpa-00251205 Submitted on 1 Jan 1992 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNAL DE PHYSIQUE IV Colloque C1, suppICment au Journal de Physique 111, Volume 2, avril 1992 FIBROBLAST GROWMI FACTOR (FGF) IMPLICATION IN TIlE NEONATAL DEVELOPMENT OF THE COCIiLEAR INNERVATION G. DESPR~S,I. JALENQUES and R. ROMAND Laboratoire de Neurobiolc@e et Physwlogie du Dkeloppement, Universite'BIaise Pascal, F-63177Aubi2re ceder, France The presence of fibroblast growth factor-like protein has been investigated on cryostat sections from Sprague Dawley rat cochleae and auditory brainstem nuclei of various neonatal stages by indirect immunofluorescence and immunoperoxydase techniques with an antibody directed against the 1-24 amino-acid sequence of brain derived basic FGF.
  • The Superior and Inferior Colliculi of the Mole (Scalopus Aquaticus Machxinus)

    The Superior and Inferior Colliculi of the Mole (Scalopus Aquaticus Machxinus)

    THE SUPERIOR AND INFERIOR COLLICULI OF THE MOLE (SCALOPUS AQUATICUS MACHXINUS) THOMAS N. JOHNSON' Laboratory of Comparative Neurology, Departmmt of Amtomy, Un&versity of hfiehigan, Ann Arbor INTRODUCTION This investigation is a study of the afferent and efferent connections of the tectum of the midbrain in the mole (Scalo- pus aquaticus machrinus). An attempt is made to correlate these findings with the known habits of the animal. A subterranean animal of the middle western portion of the United States, Scalopus aquaticus machrinus is the largest of the genus Scalopus and its habits have been more thor- oughly studied than those of others of this genus according to Jackson ('15) and Hamilton ('43). This animal prefers a well-drained, loose soil. It usually frequents open fields and pastures but also is found in thin woods and meadows. Following a rain, new superficial burrows just below the surface of the ground are pushed in all directions to facili- tate the capture of worms and other soil life. Ten inches or more below the surface the regular permanent highway is constructed; the mole retreats here during long periods of dry weather or when frost is in the ground. The principal food is earthworms although, under some circumstances, larvae and adult insects are the more usual fare. It has been demonstrated conclusively that, under normal conditions, moles will eat vegetable matter. It seems not improbable that they may take considerable quantities of it at times. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the University of Michigan.
  • 5.1. Structure of the Spiral Ganglion

    5.1. Structure of the Spiral Ganglion

    CHAPTER 5. INNERVATION OF THE ORGAN OF CORTI The investigation of nerve components of the acoustic system’s periph- eral part is so difficult methodologically that a whole series of questions which were solved long ago during the investigation of the other sensory system have not yet been clarified. The basic difficulty for the morphologists lies in the fact that the organ of Corti, together with its nerve elements, is located within the osseous tissue. In addition, it is in the shape of a spirally involut- ed geometrical figure. These structural peculiarities create considerable dif- ficulties during the determination of the connections between the types of peripheral and central neuron’s processes and bodies of the spiral ganglion of the cochlea. Therefore, most of the work on the cochlea’s innervation and the computation of the different element’s quantity demands an application of special methods, including graphical reconstruction of the serial sections. The Golgi method was and still remains the basic histological method of the organ of Corti’s innervation study, which has been supplemented by the cochlea’s electron-microscope investigations in the normal conditions and during the experimentally induced degenerations. 5.1. Structure of the spiral ganglion The neurons which innervate the auditory receptor cells form a spiral ganglion: a nerve-knot of the VIII pair’s acoustic part of the craniocerebral nerves. The ganglion fills the Rosental’s canal in the cochlea’s axis and re- peats the number of its spiral turns. The ganglionic neuron has, as a rule, a widened body with two processes: peripheral and central (Diagram 7).
  • Auditory Neuropathy After Damage to Cochlear Spiral Ganglion Neurons

    Auditory Neuropathy After Damage to Cochlear Spiral Ganglion Neurons

    www.nature.com/scientificreports OPEN Auditory Neuropathy after Damage to Cochlear Spiral Ganglion Neurons in Mice Resulting from Conditional Received: 27 July 2016 Accepted: 15 June 2017 Expression of Diphtheria Toxin Published online: 25 July 2017 Receptors Haolai Pan1, Qiang Song1, Yanyan Huang1, Jiping Wang1, Renjie Chai2, Shankai Yin1 & Jian Wang 1,3 Auditory neuropathy (AN) is a hearing disorder characterized by normal cochlear amplifcation to sound but poor temporal processing and auditory perception in noisy backgrounds. These defcits likely result from impairments in auditory neural synchrony; such dyssynchrony of the neural responses has been linked to demyelination of auditory nerve fbers. However, no appropriate animal models are currently available that mimic this pathology. In this study, Cre-inducible diphtheria toxin receptor (iDTR+/+) mice were cross-mated with mice containing Cre (Bhlhb5-Cre+/−) specifc to spiral ganglion neurons (SGNs). In double-positive ofspring mice, the injection of diphtheria toxin (DT) led to a 30–40% rate of death for SGNs, but no hair cell damage. Demyelination types of pathologies were observed around the surviving SGNs and their fbers, many of which were distorted in shape. Correspondingly, a signifcant reduction in response synchrony to amplitude modulation was observed in this group of animals compared to the controls, which had a Cre− genotype. Taken together, our results suggest that SGN damage following the injection of DT in mice with Bhlhb5-Cre+/− and iDTR+/− is likely to be a good AN model of demyelination. Auditory neuropathy (AN) is a hearing disorder characterized as having normal cochlear microphonic (CM) potentials and otoacoustic emissions (OAEs), but largely reduced or missing auditory brainstem responses (ABRs).
  • Neuronal Organization in the Inferior Colliculus Revisited with Cell-Type- Dependent Monosynaptic Tracing

    Neuronal Organization in the Inferior Colliculus Revisited with Cell-Type- Dependent Monosynaptic Tracing

    This Accepted Manuscript has not been copyedited and formatted. The final version may differ from this version. Research Articles: Systems/Circuits Neuronal organization in the inferior colliculus revisited with cell-type- dependent monosynaptic tracing Chenggang Chen1, Mingxiu Cheng1,2, Tetsufumi Ito3 and Sen Song1 1Tsinghua Laboratory of Brain and Intelligence (THBI) and Department of Biomedical Engineering, Beijing Innovation Center for Future Chip, Center for Brain-Inspired Computing Research, McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China 2National Institute of Biological Sciences, Beijing, 102206, China 3Anatomy II, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, 920-0293, Japan DOI: 10.1523/JNEUROSCI.2173-17.2018 Received: 31 July 2017 Revised: 2 February 2018 Accepted: 7 February 2018 Published: 24 February 2018 Author contributions: C.C., T.I., and S.S. designed research; C.C. and M.C. performed research; C.C. and T.I. analyzed data; C.C. wrote the first draft of the paper; C.C., T.I., and S.S. edited the paper; C.C., T.I., and S.S. wrote the paper. Conflict of Interest: The authors declare no competing financial interests. This work was supported by funding from the National Natural Science Foundation of China (31571095, 91332122, for S.S.), Special Fund of Suzhou-Tsinghua Innovation Leading Action (for S.S.), Beijing Program on the Study of Brain-Inspired Computing System and Related Core Technologies (for S.S.), Beijing Innovation Center for Future Chip (for S.S.), and Chinese Academy of Sciences Institute of Psychology Key Laboratory of Mental Health Open Research Grant (KLMH2012K02, for S.S.), grants from Ministry of Education, Science, and Culture of Japan (KAKENHI grant, Grant numbers 16K07026 and 16H01501; for T.I.), and Takahashi Industrial and Economic Research Foundation (for T.I.).
  • MR Imaging of Primary Trochlear Nerve Neoplasms

    MR Imaging of Primary Trochlear Nerve Neoplasms

    707 MR Imaging of Primary Trochlear Nerve Neoplasms Lindell R. Gentry 1 We present the clinical, anatomic, and MR imaging findings in six patients with seven Rahul C. Mehta 1 primary trochlear nerve neoplasms, as well as the MR and clinical criteria that serve to Richard E. Appen2 establish the diagnosis of these rare cranial nerve neoplasms. Three patients had a Joel M. Weinstein2 history of neurofibromatosis and five patients had clinical evidence of a trochlear nerve palsy. Six of seven neoplasms produced localized, fusiform enlargement of the proximal cisternal segments of the trochlear nerves. The lesions that were visible on noncontrast MR scans (T1-, T2-, and proton density-weighted) had signal intensities that were virtually identical to normal brain parenchyma. All lesions showed intense, homogeneous enhancement on contrast-enhanced scans. Contrast-enhanced imaging was necessary for the detection of five of seven lesions and greatly increased the value of the MR study in all six patients. AJNR 12:707-713, July/August 1991; AJR 157: September 1991 Primary neoplasms arising from pure motor cranial nerves such as the trochlear nerve are rare. To our knowledge just nine primary trochlear nerve neoplasms have been reported in the literature [1-7), only one of which was imaged with MR [1). Over the last 6 years, since we began to use MR as the primary imaging method for evaluating patients with cranial nerve palsies , we have noticed a striking increase in the number of primary trochlear nerve neoplasms over those encountered during the CT era. We believe this is due to a much greater sensitivity of MR in detecting these typically small lesions.
  • Auditory and Vestibular Systems Objective • to Learn the Functional

    Auditory and Vestibular Systems Objective • to Learn the Functional

    Auditory and Vestibular Systems Objective • To learn the functional organization of the auditory and vestibular systems • To understand how one can use changes in auditory function following injury to localize the site of a lesion • To begin to learn the vestibular pathways, as a prelude to studying motor pathways controlling balance in a later lab. Ch 7 Key Figs: 7-1; 7-2; 7-4; 7-5 Clinical Case #2 Hearing loss and dizziness; CC4-1 Self evaluation • Be able to identify all structures listed in key terms and describe briefly their principal functions • Use neuroanatomy on the web to test your understanding ************************************************************************************** List of media F-5 Vestibular efferent connections The first order neurons of the vestibular system are bipolar cells whose cell bodies are located in the vestibular ganglion in the internal ear (NTA Fig. 7-3). The distal processes of these cells contact the receptor hair cells located within the ampulae of the semicircular canals and the utricle and saccule. The central processes of the bipolar cells constitute the vestibular portion of the vestibulocochlear (VIIIth cranial) nerve. Most of these primary vestibular afferents enter the ipsilateral brain stem inferior to the inferior cerebellar peduncle to terminate in the vestibular nuclear complex, which is located in the medulla and caudal pons. The vestibular nuclear complex (NTA Figs, 7-2, 7-3), which lies in the floor of the fourth ventricle, contains four nuclei: 1) the superior vestibular nucleus; 2) the inferior vestibular nucleus; 3) the lateral vestibular nucleus; and 4) the medial vestibular nucleus. Vestibular nuclei give rise to secondary fibers that project to the cerebellum, certain motor cranial nerve nuclei, the reticular formation, all spinal levels, and the thalamus.
  • Projections of Physiologically Defined Subdivisions of the Inferior Colliculus in the Mustached Bat: Targets in the Medial Geniculate Body and Extrathalamic Nuclei

    Projections of Physiologically Defined Subdivisions of the Inferior Colliculus in the Mustached Bat: Targets in the Medial Geniculate Body and Extrathalamic Nuclei

    THE JOURNAL OF COMPARATIVE NEUROLOGY 346207-236 (1994) Projections of Physiologically Defined Subdivisions of the Inferior Colliculus in the Mustached Bat: Targets in the Medial Geniculate Body and Extrathalamic Nuclei JEFFREY J. WENSTRUP, DAVID T. LARUE, AND JEFFERY A. WINER Department of Neurobiology, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio 44272-0095 (J.J.W.) and Division of Neurobiology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720-3200 (J.J.W.,D.T.L., J.A.W.) ABSTRACT This study examined the output of the central nucleus of the inferior colliculus to the medial geniculate body and other parts of the nervous system in the mustached bat (Pteronotus parnellii). Small deposits of anterograde tracers (horseradish peroxidase, [3Hlleucine, Phaseo- lus uulgaris leucoagglutinin, wheat germ agglutinin conjugated to horseradish peroxidase, or biocytin) were made at physiologically defined sites in the central nucleus representing major components of the bat’s echolocation signal. The topography, frequency specificity, and axonal morphology of these outputs were studied. The medial geniculate body was a major target of inferior collicular neurons, with three distinct input patterns. The projection to the ventral division was tonotopically organized, but had a relatively sparse contribution from neurons representing frequency modulated compo- nents of the biosonar pulse. The second input was to the rostral medial geniculate body, in which projections from inferior collicular neurons representing constant frequency sonar components were separated from those representing frequency modulated components. A third input was to the suprageniculate nucleus, which received strong, topographically arranged projections. Inputs to the dorsal nucleus and medial division were also observed.
  • Cranial Nerve VIII

    Cranial Nerve VIII

    Cranial Nerve VIII Color Code Important (The Vestibulo-Cochlear Nerve) Doctors Notes Notes/Extra explanation Please view our Editing File before studying this lecture to check for any changes. Objectives At the end of the lecture, the students should be able to: ✓ List the nuclei related to vestibular and cochlear nerves in the brain stem. ✓ Describe the type and site of each nucleus. ✓ Describe the vestibular pathways and its main connections. ✓ Describe the auditory pathway and its main connections. Due to the difference of arrangement of the lecture between the girls and boys slides we will stick to the girls slides then summarize the pathway according to the boys slides. Ponto-medullary Sulcus (cerebello- pontine angle) Recall: both cranial nerves 8 and 7 emerge from the ventral surface of the brainstem at the ponto- medullary sulcus (cerebello-pontine angle) Brain – Ventral Surface Vestibulo-Cochlear (VIII) 8th Cranial Nerve o Type: Special sensory (SSA) o Conveys impulses from inner ear to nervous system. o Components: • Vestibular part: conveys impulses associated with body posture ,balance and coordination of head & eye movements. • Cochlear part: conveys impulses associated with hearing. o Vestibular & cochlear parts leave the ventral surface* of brain stem through the pontomedullary sulcus ‘at cerebellopontine angle*’ (lateral to facial nerve), run laterally in posterior cranial fossa and enter the internal acoustic meatus along with 7th (facial) nerve. *see the previous slide Auditory Pathway Only on the girls’ slides 04:14 Characteristics: o It is a multisynaptic pathway o There are several locations between medulla and the thalamus where axons may synapse and not all the fibers behave in the same manner.
  • Auditory Nerve.Pdf

    Auditory Nerve.Pdf

    1 Sound waves from the auditory environment all combine in the ear canal to form a complex waveform. This waveform is deconstructed by the cochlea with respect to time, loudness, and frequency and neural signals representing these features are carried into the brain by the auditory nerve. It is thought that features of the sounds are processed centrally along parallel and hierarchical pathways where eventually percepts of the sounds are organized. 2 In mammals, the neural representation of acoustic information enters the brain by way of the auditory nerve. The auditory nerve terminates in the cochlear nucleus, and the cochlear nucleus in turn gives rise to multiple output projections that form separate but parallel limbs of the ascending auditory pathways. How the brain normally processes acoustic information will be heavily dependent upon the organization of auditory nerve input to the cochlear nucleus and on the nature of the different neural circuits that are established at this early stage. 3 This histology slide of a cat cochlea (right) illustrates the sensory receptors, the auditory nerve, and its target the cochlear nucleus. The orientation of the cut is illustrated by the pink line in the drawing of the cat head (left). We learned about the relationship between these structures by inserting a dye-filled micropipette into the auditory nerve and making small injections of the dye. After histological processing, stained single fibers were reconstruct back to their origin, and traced centrally to determine how they terminated in the brain. We will review the components of the nerve with respect to composition, innervation of the receptors, cell body morphology, myelination, and central terminations.
  • THE CEREBELLAR VERMIS ROBUSTLY MODULATES NEURAL ACTIVITY in the INFERIOR COLLICULUS by Richard Jiang Sima

    THE CEREBELLAR VERMIS ROBUSTLY MODULATES NEURAL ACTIVITY in the INFERIOR COLLICULUS by Richard Jiang Sima

    THE CEREBELLAR VERMIS ROBUSTLY MODULATES NEURAL ACTIVITY IN THE INFERIOR COLLICULUS by Richard Jiang Sima A dissertation submitted to Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland May 2019 © 2019 Richard Jiang Sima All Rights Reserved. Abstract of the Dissertation To survive in an ever-changing world, animals need to rapidly detect and appropriately respond to external stimuli. In the auditory system, the inferior colliculus (IC) is well-positioned as an obligatory auditory hub involved with making acousticomotor responses to initiate these behavioral responses to auditory stimuli. However, it is not well understood how the relevant contextual information needed to detect and respond appropriately to stimuli is conveyed. In this thesis, I investigate the cerebellar vermis as one possible source of this contextual information. My experiments revealed that optogenetic stimulation of the cerebellar vermis robustly modulates the majority of neurons throughout IC in awake mice head-fixed on a treadmill. Because I was to monitor the movement of the treadmill, I also found that vermis stimulation produces a similar behavioral response as auditory stimuli, and that vermis evoked activity in the IC is in part related to this motor response. Furthermore, my results show that animal running modulates IC activity by reducing auditory and vermis responses, while increasing spontaneous activity. Thesis Committee: Professor Sascha du Lac, Thesis Advisor Professor David J. Linden, Chair Professor Jeremiah Y. Cohen, Thesis Reader Professor Amanda M. Lauer Professor Elisabeth B. Glowatzki ii This thesis is dedicated to my mom and dad, Drs. Qing Jiang and Hong Sima, and to my sister, Renee Sima.
  • Lack of Neurotrophin 3 Causes Losses of Both Classes of Spiral Ganglion Neurons in the Cochlea in a Region-Specific Fashion

    Lack of Neurotrophin 3 Causes Losses of Both Classes of Spiral Ganglion Neurons in the Cochlea in a Region-Specific Fashion

    The Journal of Neuroscience, August 15, 1997, 17(16):6213–6225 Lack of Neurotrophin 3 Causes Losses of Both Classes of Spiral Ganglion Neurons in the Cochlea in a Region-Specific Fashion Bernd Fritzsch,1 Isabel Farin˜ as,2 and Louis F. Reichardt2 1Department of Biomedical Sciences, Creighton University, Omaha, Nebraska 68178, and 2Program in Neuroscience, Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, California 94143-0724 Essential functions of neurotrophin 3 (NT-3) in regulating affer- The presence of fibers extending to both inner and outer hair ent and efferent innervation of the cochlea have been charac- cells suggests that subsets of types I and II sensory neurons terized by comparison of normal and NT-3 mutant mice. NT-3 survive in the absence of NT-3. Likewise, projections of the deficiency has striking, region-specific effects, with complete cochlea to auditory nuclei of the brainstem were attenuated but loss of sensory neurons in the basal turn and dramatic but otherwise present. Equally striking changes in efferent innerva- incomplete neuronal loss in the middle and apical turns. The tion were observed in mutant animals that closely mimicked the sensory innervation of inner and outer hair cells was reorga- abnormal sensory innervation pattern. Despite these impres- nized in mutant animals. Instead of a strictly radial pattern of sive innervation deficiencies, the morphology of the organ of innervation, the axons of remaining sensory neurons projected Corti and the development of inner and outer hair cells ap- spirally along the row of inner hair cells to innervate even the peared comparatively normal.