DOCSLIB.ORG

Descending Projections to the Dorsal and Ventral Divisions of the Cochlear Nucleus in Guinea Pig

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Descending Projections to the Dorsal and Ventral Divisions of the Cochlear Nucleus in Guinea Pig Hearing Research, 52 (1991) 255-268 2% 0 1991 Elsevier Science publishers B.V. 0378-5955/91/$03.50 HEARES 01529 Descending projections to the dorsal and ventral divisions of the cochlear nucleus in guinea pig Susan E. Shore I, Robert H. Helfert 2, Sanford C. Bledsoe, Jr. 2, Richard A. Altschuler 2 and Donald A. Godfrey ’ ’ Department of Otolaryngologv, Medical College of Ohio, Toledo, Ohio, and ’ Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigutz, U.S.A. (Received 6 August 1990; accepted 17 October 1990) The origins of extrinsic projections to the guinea pig dorsal and ventral cochlear nuclei were identified by examining the retrograde transport of horseradish peroxidase conjugated to wheatgerm agglutinin following its injection into each of these divisions. Major projections originated in periolivary regions of the superior olivary complex, the contralateral cocblear nucleus and the inferior colliculus. There was no contribution from the nuclei of the lateral lemniscus to these pathways. The heaviest projection from the periolivary regions to both divisions of the co&ear nucleus arose bilaterally in the ventral nucleus of the trapezoid body. The ipsilateral lateral nucleus of the trapexoid body also projected heavily to dorsal and ventral cc&ear nucleus. In addition, the ventral co&ear nucleus received a substantial projection from the dorsal aspect of the ipsilateral dorsomedial periolivary nucleus. Projections originating bilaterally in the central nucleus of the inferior colliculus terminated in the deep layers of dorsal cochlear nucleus. These projections appear to be more strongly ipsilateral and specific than those reported in the cat. Horseradish peroxidase; Ventral cochlear nucleus; Dorsal cochlear nucleus; Superior olivary nuclei; Inferior colliculus Inaction Rasmussen, 1960, 1967; Osen et al., 1984; Van Noort, 1969; Adams, 1983; Elverland, 1977). Many Previous studies have shown that in addition to of the non-cochlear synaptic endings in the synaptic endings from the VIIIth nerve (for re- cochlear nucleus originate in neurons of the super- views see Cant and Morest, 1984; Caspary, 1986), ior olivary complex, nuclei of the lateral lemnis- most neurons in the co&ear nucleus receive in- cus, the inferior colliculus, and the contralateral nervation from non-co&ear sources (Cant, 1981; co&ear nucleus (Van Noort, 1969; Adams and Kane and Firm, 1977; Kane and Conlee, 1979; Wan, 1976; Kane, 1977; Elverland, 1977; Cant and Gaston, 1982; Adams, 1983; Spangler et al., 1987; Covey et al., 1984; Winter et al., 1989; Abbreviations: AVCN = Anteroventral cochlear nucleus; CN = Benson and Potashner, 1990). Cochlear nucleus; CPO = Caudal periolivary region; DCN = The manner in which periolivary cell groups Dorsal cochlear nucleus; DMPO = Dorsomedial periolivary and other auditory areas project to specific nucleus; DPO = Dorsal periolivary nucleus; IC = Inferior col- cochlear nucleus neuronal targets is critical to the liculus; LNTB = Lateral nucleus of the trapezoid body; LSO = Lateral superior olivary nucleus; MNTB = Medial nucleus of ability of these neurons to process complex signals the trapezoid body; MS0 = Medial superior olivary nucleus; and operate over a wide dynamic range. This OCB = Olivocochlear bundle; PVCN = Posteroventral co&ear study addresses the question of interspecies dif- nucleus; SOC = Superior olivary complex; VCN = Ventral ferences in the organization of olivary projections cochlear nucleus; VNTB-Ventral nucleus of the trapezoid to specific regions of the cochlear nucleus. The body. Correspondence to: S.E. Shore, Medical College of Ohio, De- methodology differs from other studies in the partment of Otolaryngology, Toledo, OH 43699, U.S.A. guinea pig by examining and quantifying the ret- 256 rograde transport of horseradish peroxidase con- set; 80 mg/kg) and xylazine (Rompun; 4 mg/kg) jugated to wheatgerm agglutinin from different administered intramuscularly. Periodic supple- regions of the cochlear nucleus to other brainstem mentation was used to maintain anesthetic levels nuclei. In the cat, these projections terminate in all t~ou~out the procedure. The left co&ear regions of the cochlear nucleus, with some nucleus was visualized, after a posterior fossa nucleotopic organization: The rostra1 periolivary surgical approach, by aspirating a small part of regions project more heavily to rostra1 cochlear the overlying cerebellum. A glass micropipette nucleus while the caudal periolivary groups pro- filled with 2% wheat germ agglutinin conjugated ject more heavily to caudal co&ear nucleus (Van to horseradish peroxidase (WGA-HRP), in phos- Noort, 1969; Adams, 1983; Spangler et al., 1987). phate buffered saline (pH 7.4), was placed under The tree shrew, on the other hand, shows a more visual control on the surface of the dorsal or specific dist~bution pattern, with the dorsomedial ventral co&ear nucleus. After the electrode place- periolivary region and dorsal periolivary region ment, the brain was covered with warm mineral projecting only to the anteroventral cochlear oil to prevent tissue desiccation and reduce brain nucleus, whereas the ventral nucleus of the pulsation. Evoked potentials in response to click trapezoid body and the caudal portion of the stimulation were recorded as the electrode was lateral nucleus of the trapezoid body project only advanced ventrally (see Shore and Nuttall, 1985). to dorsal cochlear nucleus and posteroventral At a depth corresponding to the maximum-ampli- cochlear nucleus (Covey et al., 1984). In contrast tude evoked potential, a continuous, positive cur- to the tree shrew, a recent study of the superior rent (3-5 PA) was passed through the silver re- olivary projections to cochlear nucleus in the cording wire for 2-15 min. After the electrode was guinea pig showed similar results to those found removed, some neck muscle was applied to replace in the cat (Winter et al., 1989). This was surprising the volume of aspirated brain, dental cement was in view of findings that brainstem projections to used to seal the opening, and the animal was the cochlea in guinea pig and cat differ in their sutured and allowed to recover. After a 24-h organization (Robertson, 1985; Robertson et al., survival period, the animal was deeply anesthe- 1987). tized with pe~tobarbital and perfused transcar- This study has confirmed reports that major dially with 50 ml of 0.05% sodium nitrite in nor- projections to the cochlear nucleus originate in mal saline, followed by 750 ml of mixed aldehyde periolivary regions of the superior olivary com- fixative (1.25% glutaraldehyde and 1.0% for- plex, the contralateral cochlear nucleus (see Shore maldehyde in phosphate buffer, pH 7.4). Follow- et al., 1991), and the inferior colliculus. The results ing their removal from the skull and postfixation here indicate that some periolivary nuclei in the for 2-4 h in the same fixative, the brainstems were guinea pig have more specific target areas in the immersed overnight in 20% sucrose in 0.12 M co&ear nucleus than previously indicated. In par- phosphate buffer, pH 7,4. After frozen sectioning, ticular, the projections from the dorsomedial peri- the 40 pm-thick transverse sections containing the olivary regions in the guinea pig terminate prim- cochlear nucleus (CN), superior olivary complex arily in the ventral division of the co&ear nucleus. (XX), nuclei of the lateral lemniscus (NLL) and The guinea pig also receives more strongly ipsi- IC were reacted with 3.3’-5,5’ -tetramethylben- lateral projections from periolivary nuclei to the zidine (TMB) to visualize the peroxidase (Mesu- cochlear nucleus, than the cat (e.g. Adams, 1983). lam, 1978). The reacted sections were then These findings imply that information processing mounted, counterst~ned with neutral red (Mesu- in the auditory brainstem may vary si~fic~tly lam, 1978) and studied using a Leitz Dialux mi- among species. croscope equipped with a drawing tube. An esti- mate of the total number of labeled cells in the M&hods SOC was obtained by counting those in every 5th section. Labeled cell types were described in terms Fifteen pigmented guinea pigs (250-400 g) were of soma shape and size, and the location of the anesthetized with ketamine hydrochloride (Keta- nucleus when possible. Soma size was measured 257 using a calibrated eyepiece micrometer. The mea- 1991). There was a different distribution of labeled surements presented are not corrected for tissue cells in each of these major regions, depending on shrinkage which occurs during processing. whether the injection was centered in dorsal cochlear nucleus (DCN) or ventral cochlear nucleus. Injections in the cochlear nucleus produced ret- Descending projections from the superior olivaty rograde labeling in the ipsilateral and con- complex tralateral cochlear nucleus, superior olivary com- plex (SOC) and inferior colliculus. Only the pro- jections from the SOC and inferior colliculus are Definition of periolivaly regions discussed in this paper; the cochlear nucleus pro- Periolivary nuclei are defined in terms of their jections are presented elsewhere (Shore et al., positions with respect to the lateral and medial 50, 50 D 45 A 45 6888 (PVCN) 53190 (DcN) 40 40 N-201 0 N-1338 35 35 i 30 / 30 25 25 20 20 15 15 10 10 5 5 n 0 LNTB VNTB MNTB DMPO DPO CPO LSO LNTB VNTB MNTB DMPO DPO CPO LSO 50 45 3288 (PVCN) 62988 (DCN) 1 E 40 N-=1380 N-1 155 35 30 25. 20. 15. 10- 5- o- LNTB VNTB MNTB DMPO DPO CPO LSO LNTB VNTB MNTB DMPO DPO CPO LSO I IPSUATERAL 817138 (DCN+WCN) m coNTRAlATERM N-1265 40 35 32489 (PVCN+AVCN) 30 N-3370 25 25 20 20 15 15 10 10 5 5 0 0 INlB VNTB MNTB DUPO DPO CPO Lso LNlB VNTB LlNlB DMW DPO CPO LSO SUPERIOR OLIVARY REGION SUPERIOR OLIVARY REGION Fig. 1. Percentages of labeled cells in different SGC nuclei following WGA-HRP injections centered on different cochlear nucleus regions, as indicated in parentheses. (A) Animal 53190; injection centered on medial DCN.
Load more

Recommended publications
  • Multisensory Integration in the Dorsal Cochlear Nucleus: Unit Responses to Acoustic and Trigeminal Ganglion Stimulation
    European Journal of Neuroscience, Vol. 21, pp. 3334–3348, 2005 ª Federation of European Neuroscience Societies Multisensory integration in the dorsal cochlear nucleus: unit responses to acoustic and trigeminal ganglion stimulation S. E. Shore Kresge Hearing Research Institute and Department of Otolaryngology, University of Michigan, 1301 East Ann Street, Ann Arbor, MI 48109, USA Keywords: auditory, guinea pig, multisensory, neural pathways, somatosensory, trigeminal Abstract A necessary requirement for multisensory integration is the convergence of pathways from different senses. The dorsal cochlear nucleus (DCN) receives auditory input directly via the VIIIth nerve and somatosensory input indirectly from the Vth nerve via granule cells. Multisensory integration may occur in DCN cells that receive both trigeminal and auditory nerve input, such as the fusiform cell. We investigated trigeminal system influences on guinea pig DCN cells by stimulating the trigeminal ganglion while recording spontaneous and sound-driven activity from DCN neurons. A bipolar stimulating electrode was placed into the trigeminal ganglion of anesthetized guinea pigs using stereotaxic co-ordinates. Electrical stimuli were applied as bipolar pulses (100 ls per phase) with amplitudes ranging from 10 to 100 lA. Responses from DCN units were obtained using a 16-channel, four-shank electrode. Current pulses were presented alone or preceding 100- or 200-ms broadband noise (BBN) bursts. Thirty percent of DCN units showed either excitatory, inhibitory or excitatory–inhibitory responses to trigeminal ganglion stimulation. When paired with BBN stimulation, trigeminal stimulation suppressed or facilitated the firing rate in response to BBN in 78% of units, reflecting multisensory integration. Pulses preceding the acoustic stimuli by as much as 95 ms were able to alter responses to BBN.
    [Show full text]
  • Direct Projections from Cochlear Nuclear Complex to Auditory Thalamus in the Rat
    The Journal of Neuroscience, December 15, 2002, 22(24):10891–10897 Direct Projections from Cochlear Nuclear Complex to Auditory Thalamus in the Rat Manuel S. Malmierca,1 Miguel A. Mercha´n,1 Craig K. Henkel,2 and Douglas L. Oliver3 1Laboratory for the Neurobiology of Hearing, Institute for Neuroscience of Castilla y Leo´ n and Faculty of Medicine, University of Salamanca, 37007 Salamanca, Spain, 2Wake Forest University School of Medicine, Department of Neurobiology and Anatomy, Winston-Salem, North Carolina 27157-1010, and 3University of Connecticut Health Center, Department of Neuroscience, Farmington, Connecticut 06030-3401 It is known that the dorsal cochlear nucleus and medial genic- inferior colliculus and are widely distributed within the medial ulate body in the auditory system receive significant inputs from division of the medial geniculate, suggesting that the projection somatosensory and visual–motor sources, but the purpose of is not topographic. As a nonlemniscal auditory pathway that such inputs is not totally understood. Moreover, a direct con- parallels the conventional auditory lemniscal pathway, its func- nection of these structures has not been demonstrated, be- tions may be distinct from the perception of sound. Because cause it is generally accepted that the inferior colliculus is an this pathway links the parts of the auditory system with prom- obligatory relay for all ascending input. In the present study, we inent nonauditory, multimodal inputs, it may form a neural have used auditory neurophysiology, double labeling with an- network through which nonauditory sensory and visual–motor terograde tracers, and retrograde tracers to investigate the systems may modulate auditory information processing.
    [Show full text]
  • 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.
    [Show full text]
  • Anatomy of the Superior Olivary Complex.Pdf
    Douglas Oliver University of Connecticut Health Center SUPERIOR OLIVE Auditory Pathways Auditory CORTEX GLUT Cortex GABA GLY Medial Geniculate MGB Body Inferior IC Colliculus DLL DLL COCHLEA VLL VLL DCN VCN SOC Auditory Pathways IC Organization of Superior Olivary Complex . Subdivisions and Cytoarchitecture . Neuron types . Inputs . Outputs . Synapses . Basic Circuit Cytoarchitecture of Superior Olivary Complex LSO LSO MSO MSO MNTB D MNTB M (somata & dendrites) (axons & endings) Tsuchitani, 1978, Fig. 10 Comparative anatomy of SOC Tetsufumi Ito & Shig Kuwada Binaural Basic Circuits 8 ‐ 9 Brodal Fig MSO: medial superior olive; LSO: lateral superior olive NTB: nucleus of trapezoid body; IC: inferior colliculus MSO Principle glutamate Cells . Fusiform . Bipolar . Disc‐shaped . Each dendrite innervated by a different side MSO‐In situ hybridization RPO MSO MNTB SPO LSO VGLUT1 VGLUT2 VIAAT NISSL MSO Inputs and Synapses H=high frequency EI - ILD L=low frequency EE - ITD LSO MSO L L B H B B H G LNTB TO LSO MNTB E=Excitation (glutamate) ‐‐‐ I=Inhibition (glycine) ITD CODING Unlike retinal targets, the cochlear nuclei contain maps of frequency, not location. So how does the auditory system know ‘where’ a sound is coming from? T + ITD T By comparing the interaural time differences (ITD) between the ears How is this accomplished?... LSO MSO Right Input A Right Input B C Time Code Time Code E E A A B B C C D D E E Output Output abcde Place Code abcde Place Code Excitation MSO creates a response to Left Input Left Input Inhibition interaural time differences I Time Code E Time Code DEMSO "peak" unit LSO "trough" unit ITD ITD Figure 14.2 Binaural Responses in MSO MSO Summary .
    [Show full text]
  • The Superior Olivary Complex +
    Excitatory and inhibitory transmission in the superior olivary complex. Ian D. Forsythe, Matt Barker, Margaret Barnes-Davies, Brian Billups, Paul Dodson, Fatima Osmani, Steven Owens and Adrian Wong. Department of Cell Physiology and Pharmacology, University of Leicester, Leicester LE1 9HN. UK. The timing and pattern of action potentials propagating into the brainstem from both cochleae contain information about the azimuth location of that sound in auditory space. This binaural information is integrated in the superior olivary complex. This part of the auditory pathway is adapted for fast conduction speeds and the preservation of timing information with several complimentary mechanisms (see Oertel, 1999; Trussell, 1999). There are large diameter axons terminating in giant somatic synapses that activate receptor ion channels with fast kinetics. The resultant postsynaptic potentials generated in the receiving neuron are integrated with a suite of voltage-gated ion channels that determine the action potential threshold, duration and repetitive firing properties. We have studied presynaptic and postsynaptic mechanisms that regulate efficacy, timing and integration of synaptic responses in the medial nucleus of the trapezoid body and the medial and lateral superior olives. Presynaptic calcium currents in the calyx of Held. The calyx of Held is a giant synaptic terminal that forms around the soma of principal cells in the Medial Nucleus of the Trapezoid Body (MNTB) (Forsythe, 1994). Each MNTB neuron receives a single calyx. Action potentials propagating into the synaptic terminal trigger the opening of P-type calcium channels (Forsythe et al. 1998) which in turn trigger the release of glutamate into the synaptic cleft (Borst et al., 1995).
    [Show full text]
  • Selective Degeneration of Synapses in the Dorsal Cochlear Nucleus of Chinchilla Following Acoustic Trauma and Effects of Antioxidant Treatment
    Hearing Research 283 (2012) 1e13 Contents lists available at SciVerse ScienceDirect Hearing Research journal homepage: www.elsevier.com/locate/heares Research paper Selective degeneration of synapses in the dorsal cochlear nucleus of chinchilla following acoustic trauma and effects of antioxidant treatment Xiaoping Du a, Kejian Chen a,1, Chul-Hee Choi a,2, Wei Li a, Weihua Cheng a, Charles Stewart a,b, Ning Hu a, Robert A. Floyd b, Richard D. Kopke a,c,d,* a Hough Ear Institute, Oklahoma, OK 73112, USA b Experimental Therapeutic Research Program, Oklahoma Medical Research Foundation, Oklahoma, OK 73104, USA c Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma, OK 73104, USA d Department of Otolaryngology, University of Oklahoma Health Sciences Center, Oklahoma, OK 73104, USA article info abstract Article history: The purpose of this study was to reveal synaptic plasticity within the dorsal cochlear nucleus (DCN) as Received 31 May 2011 a result of noise trauma and to determine whether effective antioxidant protection to the cochlea can Received in revised form also impact plasticity changes in the DCN. Expression of synapse activity markers (synaptophysin and 18 November 2011 precerebellin) and ultrastructure of synapses were examined in the DCN of chinchilla 10 days after Accepted 30 November 2011 a 105 dB SPL octave-band noise (centered at 4 kHz, 6 h) exposure. One group of chinchilla was treated Available online 9 December 2011 with a combination of antioxidants (4-hydroxy phenyl N-tert-butylnitrone, N-acetyl-L-cysteine and acetyl-L-carnitine) beginning 4 h after noise exposure. Down-regulated synaptophysin and precerebellin expression, as well as selective degeneration of nerve terminals surrounding cartwheel cells and their primary dendrites were found in the fusiform soma layer in the middle region of the DCN of the noise exposure group.
    [Show full text]
  • ON-LINE FIG 1. Selected Images of the Caudal Midbrain (Upper Row
    ON-LINE FIG 1. Selected images of the caudal midbrain (upper row) and middle pons (lower row) from 4 of 13 total postmortem brains illustrate excellent anatomic contrast reproducibility across individual datasets. Subtle variations are present. Note differences in the shape of cerebral peduncles (24), decussation of superior cerebellar peduncles (25), and spinothalamic tract (12) in the midbrain of subject D (top right). These can be attributed to individual anatomic variation, some mild distortion of the brain stem during procurement at postmortem examination, and/or differences in the axial imaging plane not easily discernable during its prescription parallel to the anterior/posterior commissure plane. The numbers in parentheses in the on-line legends refer to structures in the On-line Table. AJNR Am J Neuroradiol ●:●●2019 www.ajnr.org E1 ON-LINE FIG 3. Demonstration of the dentatorubrothalamic tract within the superior cerebellar peduncle (asterisk) and rostral brain stem. A, Axial caudal midbrain image angled 10° anterosuperior to posteroinferior relative to the ACPC plane demonstrates the tract traveling the midbrain to reach the decussation (25). B, Coronal oblique image that is perpendicular to the long axis of the hippocam- pus (structure not shown) at the level of the ventral superior cerebel- lar decussation shows a component of the dentatorubrothalamic tract arising from the cerebellar dentate nucleus (63), ascending via the superior cerebellar peduncle to the decussation (25), and then enveloping the contralateral red nucleus (3). C, Parasagittal image shows the relatively long anteroposterior dimension of this tract, which becomes less compact and distinct as it ascends toward the thalamus. ON-LINE FIG 2.
    [Show full text]
  • Auditory Pathway of the Epileptic Waltzing Mouse I
    Auditory Pathway of the Epileptic Waltzing Mouse I. A COMPARISON OF THE ACOUSTIC PATHWAYS OF THE NORMAL MOUSE WITH THOSE OF THE TOTALLY DEAF EPILEPTIC WALTZER MURIEL D. ROSS Department of Anatomy, Medical Center, University of Michigan, Ann Arbor, Michigan Waltzing and epilepsy are hereditary cisms of this paper, and to Dr. Edward traits which appear independently or to- Lauer for his suggestions and his assist- gether in various stocks of mice of the ance in matters of technique. She is also genus Peromyscus. They are inherited in grateful to Dr. Lee R. Dice and the Labo- general as Mendelian recessives (Dice, '35; ratory of Vertebrate Biology for making Watson, '39 j. Young members of the par- the mice and the testing equipment avail- ticular stock of Peromyscus rnnniculatus able to her for this study, and to Dr. Eliza- artemisiae to be described in this study ex- beth Barto, who tested the mice for range hibit both waltzing and epilepsy when of hearing. Assistance was obtained from stimulated by sounds of various kinds. a grant from the Alfonso Morton Clover At the sound of jingling keys, or of certain Scholarship and Research Fund to the pure tones, the young epileptic waltzer Laboratory of Comparative Neurology for whirls in circles and then dashes wildly the preparation of the material for micro- about the enclosure. After a few seconds, scopic examination. Aid in testing the he falls upon his side in an epileptic responses of the experimental animals seizure. His body becomes rigid, his fore- used in this study was supplied through legs are flexed and his hind legs are ex- a grant (MH 375 j to Dr.
    [Show full text]
  • Evolution of Mammalian Sound Localization Circuits: a Developmental Perspective
    Progress in Neurobiology 141 (2016) 1–24 Contents lists available at ScienceDirect Progress in Neurobiology journal homepage: www.elsevier.com/locate/pneurobio Review article Evolution of mammalian sound localization circuits: A developmental perspective a,b, Hans Gerd Nothwang * a Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany b Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany A R T I C L E I N F O A B S T R A C T Article history: Localization of sound sources is a central aspect of auditory processing. A unique feature of mammals is Received 29 May 2015 the smooth, tonotopically organized extension of the hearing range to high frequencies (HF) above Received in revised form 27 February 2016 10 kHz, which likely induced positive selection for novel mechanisms of sound localization. How this Accepted 27 February 2016 change in the auditory periphery is accompanied by changes in the central auditory system is unresolved. Available online 28 March 2016 + I will argue that the major VGlut2 excitatory projection neurons of sound localization circuits (dorsal cochlear nucleus (DCN), lateral and medial superior olive (LSO and MSO)) represent serial homologs with Keywords: modifications, thus being paramorphs. This assumption is based on common embryonic origin from an Brainstem + + Atoh1 /Wnt1 cell lineage in the rhombic lip of r5, same cell birth, a fusiform cell morphology, shared Evolution Homology genetic components such as Lhx2 and Lhx9 transcription factors, and similar projection patterns. Such a Innovation parsimonious evolutionary mechanism likely accelerated the emergence of neurons for sound Rhombomere localization in all three dimensions.
    [Show full text]
  • Acoustically Responsive Fibers in the Vestibular Nerve of the Cat
    The Journal of Neuroscience, October 1994, 74(10): 6056-6070 Acoustically Responsive Fibers in the Vestibular Nerve of the Cat Michael P. McCue1v2*a and John J. Guinan, Jr.r.2.3-4 ‘Eaton-Peabody Laboratory of Auditory Physiology, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, 2Harvard-MIT Division of Health Science and Technology and Research Laboratory of Electronics, and 3Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and 4Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02115 Recordings were made from single afferent fibers in the and levels within the normal range of human hearing. We inferior vestibular nerve, which innervates the saccule and suggest a number of auditory roles that these fibers may posterior semicircular canal. A substantial portion of the fi- play in the everyday life of mammals. bers with irregular background activity increased their firing [Key words: saccule, otoliths, auditory system, mamma- in response to moderately intense clicks and tones. lian sound reception, middle-ear muscles, cochlear nucleus] In responsive fibers, acoustic clicks evoked action poten- tials with minimum latencies of I 1 .O msec. Fibers fell into The vertebrate inner ear contains several senseorgans involved two classes, with the shortest latency either to condensation in the maintenance of equilibrium and the detection of vibra- clicks (PUSH fibers) or to rarefaction clicks (PULL fibers). tion. The precise sensory role assumedby homologous organs Low-frequency (800 Hz) tone bursts at moderately high sound varies among species.For example, the sacculeis thought to act levels (>80 dB SPL) caused synchronization of spikes to asa linear accelerometerin mammals(Fernindez and Goldberg, preferred phases of the tone cycle.
    [Show full text]
  • Processing in the Cochlear Nucleus
    Processing in The Cochlear Nucleus Alan R. Palmer Medical Research Council Institute of Hearing Research University Park Nottingham NG7 2RD, UK The Auditory Nervous System Cortex Cortex MGB Medial Geniculate Body Excitatory GABAergic IC Inferior Colliculus Glycinergic DNLL Nuclei of the Lateral Lemniscus Lateral Lemniscus Cochlear Nucleus DCN PVCN MSO Lateral Superior Olive AVCN Medial Superior Olive Cochlea MNTB Medial Nucleus of the Trapezoid Body Superior Olive The cochlear nucleus is the site of termination of fibres of the auditory nerve Cochlear Nucleus Auditory Nerve Cochlea 1 Frequency Tonotopicity Basilar membrane Inner hair cell Auditory nerve Fibre To the brain Each auditory-nerve fibre responds only to a narrow range of frequencies Tuning curve Action potential Evans 1975 2 Palmer and Evans 1975 There are many overlapping single-fibre tuning curves in the auditory nerve Audiogram Palmer and Evans 1975 Tonotopic Organisation Lorente - 1933 3 Tonotopic Organisation Base Anterior Cochlea Characteristic Basilar Membrane Frequency Hair Cells Auditory Nerve Apex Cochlear Nucleus Spiral Ganglion Posterior Tonotopic projection of auditory-nerve fibers into the cochlear nucleus Ryugo and Parks, 2003 The cochlear nucleus: the first auditory nucleus in the CNS Best frequency Position along electrode track (mm) Evans 1975 4 stellate (DCN) Inhibitory Synapse Excitatory Synapse DAS to inferior colliculus cartwheel fusiform SUPERIOR OLIVARY giant COMPLEX INFERIOR COLLICULUS granule vertical vertical OCB AANN to CN & IC via TB golgi DORSAL
    [Show full text]
  • Universität Leipzig Fakultät Für Biowissenschaften, Pharmazie Und Psychologie
    Universität Leipzig Fakultät für Biowissenschaften, Pharmazie und Psychologie IMPRS NeuroCom" Marc Schönwiesner" " " Auditory and vestibular system Michael Hawke MD / CC-BY-SA-4.0 The middle ear The middle ear Bekesy’s fluid model The traveling wave Problem: traveling waves have very broad peaks – frequency discrimination can not be based on the location of the peak vibration! Masking masker Sound intensity Sound frequency inaudible audible Masking and mp3 encoding Idea: signals that are inaudible because of masking can be removed from the file to save space. The organ of Corti Hair cells Outer hair cell motility The active cochlea model (video by J. Ashmore 1987) Connections from outer and inner hair cells Microtubule inside of a cilium 9 doublet microtubules + 2 central microtubule Dynein arms http://scienceblogs.com/transcript/upload/2006/08/axoneme.gif /www.uni-mainz.de/FB/Medizin/Anatomie Tilting of stereocilia bundles cause graded de- or hyperpolarization in hair cells (and modulation of action potential rates in afferent nerve fibers) Intracellular recording Mechanical stimulation Extracellular recording from afferent nerve fiber The lateral line system Adequate stimulus: Tilting of stereovilli by water movement Lateral line Afferent and efferent innervation Dudel, Menzel, Schmidt Hair cell: One type of sensory cell, different functions through specific accessory structures A. Perception and integration of water-flow pattern at the body surface Vestibular system Vestibular system The vestibular labyrinth answers two basic questions: Where am I going? Which way is up? The vestibular labyrinth answers the two questions by sensing: Head angular acceleration (semicircular canals) = Head rotation Head linear acceleration (saccule and utricle)" = Translational motion.
    [Show full text]