Projections of the Intraotic Ganglion to the Medullary Nuclei in the Tegu Lizard, &lt;i&gt;Tupinambis nigropunctatus&lt;/i&gt;

DeFina, Anthony V.; Webster, Douglas B.

doi:10.1159/000124312

Cited by 19 publications

(2 citation statements)

References 21 publications

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“…The pattern of label thereby reflects the dual auditory and vestibular function of this nerve. Similar results of the central projections of the posterior branch of the eighth cranial nerve to the ipsilateral cochlear nucleus and vestibular system have been described in the lizards Iguana [Foster and Hall, 1978] and Tupinambis [DeFina and Webster, 1974], the alligator Caiman crocodilus [Leake, 1974], and two species of birds [Boord and Rasmussen, 1963;Parks and Rubel, 1978;Correia et al, 1982]. Direct projections from the posterior eighth nerve to the ipsilateral cerebellar cortex were observed in all cases examined.…”

Section: Labeled Pathways Following Posterior Eighth Nerve Injectionssupporting

confidence: 83%

Central Trigeminal and Posterior Eighth Nerve Projections in the Turtle <i>Chrysemys picta</i> Studied in vitro

Herrick

Keifer²

1998

Brain Behav Evol

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Recent electrophysiological studies in the turtle Chrysemys picta have suggested that a neural correlate of the eye-blink reflex can be evoked in an in vitro brainstem-cerebellum preparation by electrical rather than natural stimulation of the cranial nerves. Discharge recorded in the abducens nerve, which is similar to EMG recordings from extraocular muscles during eye retraction, is triggered by a brief electrical stimulus applied to the ipsilateral trigeminal nerve. Evidence also suggests that pairing a one-second electrical stimulus applied to the posterior eighth nerve immediately prior to a single shock to the trigeminal nerve results in classically conditioned abducens nerve discharge in response to the previously neutral eighth nerve stimulus. In view of these physiological findings, the aim of the present study was to examine the central projections of trigeminal and posterior eighth nerve inputs to elucidate the anatomical substrates that may underlie the in vitro eye-blink reflex and possible pathways involved in reflex conditioning. Neurobiotin (NB) or fluorescein dextran (FD) was pressure injected into the cut end of either the trigeminal or posterior eighth nerve of the in vitro brainstem-cerebellum. Following trigeminal nerve injections, both tracers showed label in the ipsilateral trigeminal nuclear complex. Direct projections to the ipsilateral principal and accessory abducens motor nuclei were observed, suggesting that the eye-blink reflex is monosynaptic. Trigeminal nerve axons were also observed to terminate in the ipsilateral cerebellar cortex. The results of the posterior eighth nerve injections showed axonal projections and terminals in the cochlear, vestibular and principal sensory trigeminal nuclei. Terminal label was also observed in the ipsilateral cerebellar cortex, deep cerebellar nuclei, and in the principal and accessory abducens motor nuclei. Results from the NB cases suggested transneuronal transport of this tracer substance, whereas the FD cases did not. The present findings suggest that convergence of trigeminal and posterior eighth nerve inputs occurs in the ipsilateral cerebellar cortex, the principal sensory trigeminal nucleus, and the principal and accessory abducens motor nuclei. These regions of convergence may therefore be considered as potential sites of synaptic modification during in vitro studies of the conditioned abducens nerve reflex.

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Section: Labeled Pathways Following Posterior Eighth Nerve Injectionssupporting

confidence: 83%

Central Trigeminal and Posterior Eighth Nerve Projections in the Turtle <i>Chrysemys picta</i> Studied in vitro

Herrick

Keifer²

1998

Brain Behav Evol

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“…Within the osseous cochlear canal, both the cochlear and lagenar ganglia are supported by the dense surrounding connective tissue (but are not enclosed by bone). The stabilizing support of the inner ear ganglia by connective tissue is a general condition of non‐mammalian amniotes, and is well documented for the inner ear of Lacerta agilis (Frick, ) and other lizards (DeFina and Webster, ). A similar condition of the ganglia is also known from birds (e.g., Boord, ; Fischer et al, ).…”

Section: Discussionmentioning

confidence: 99%

Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

Schultz

Zeller

Luo

2016

Journal of Morphology

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The monophyletic clade Monotremata branches early from the rest of the mammalian crown group in the Jurassic and members of this clade retain many ancestral mammalian traits. Thus, accurate and detailed anatomical descriptions of this group can offer unique insight into the early evolutionary history of Mammalia. In this study, we examine the inner ear anatomy of two extant monotremes, Ornithorhynchus anatinus and Tachyglossus aculeatus, with the primary goals of elucidating the ancestral mammalian ear morphology and resolving inconsistencies found within previous descriptive literature. We use histological serial sections and high-resolution microcomputed tomography (µCT) for correlating soft tissue features of the vestibule and cochlea to the osseous labyrinth endocast. We found that in both monotremes the scala tympani coils to a lesser degree than scala vestibuli and scala media, although all three scalae show an apical coil inside the osseous cochlear tube. The helicotrema (conduit between scala tympani and scala vestibuli) is in subapical position, and the cochlear and lagenar ganglia and their associated nerve fibers are not enclosed by bone. In comparison, in extant therian mammals (i.e., marsupials and placentals) the helicotrema is located at the apex of the osseous cochlear canal, the three scalae coil to the same degree and the cochlear ganglion is enclosed by the primary bony lamina. Whether the lagenar ganglion is lost in therian mammals or integrated into the cochlear ganglion is still debated. The presence of a sensory lagenar macula at the apex of the membranous cochlear duct, innervated by a separate lagenar nerve and ganglion is a plesiomorphic condition of amniotes that monotremes share. A separate osseous lagenar canaliculus for the lagenar nerve, and the coiling of the distended lagenar sac at the end of the cochlear duct are autapomorphies of monotremes. Based on our findings we hypothesize that the ancestral inner ear of stem mammaliaforms is characterized by a straight or slightly curved osseous cochlear canal, a lagenar macula, lagenar nerve fibers separated from a larger bundle of cochlear nerve fibers, the presence of an organ of Corti and an intra-otic cochlear ganglion suspended by membranous connective tissue. Among the major Mesozoic clades of crown mammals, cladotherians and gondwanatherians most likely acquired a fully functioning organ of Corti but lost the sensory lagenar macula, like extant therians. However, Mesozoic spalacotherioids, multituberculates and eutriconodonts likely retained the mammaliaform condition. J. Morphol. 278:236-263, 2017. © 2016 Wiley Periodicals,Inc.

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Neuronal architecture of the dorsal nucleus (Cochlear nucleus) of the frog,Rana pipiens pipiens

Feng

Lin

1996

J. Comp. Neurol.

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The neuronal architecture of the dorsal nucleus of the Northern leopard frog (Rana pipiens pipiens), which is a homolog of the cochlear nucleus of mammals and birds, was investigated. Our study showed that the frog dorsal nucleus contains a number of morphologically distinct cell types that are discernible in terms of the cellular architecture as derived from Nissl-stained material and in terms of the dendritic profile as revealed by horseradish peroxidase-filled single neurons. These cell types are bushy cells, bipolar (or fusiform) cells, octopus cells, stellate cells, giant cells, radiate (or round) cells, and a variety of small cells. The different cell types occupy different regions of the nucleus. Therefore, our results suggest that the dorsal nucleus should no longer be considered to be a uniform nucleus containing a homogeneous population of neurons. Homologies of these cell types with those described in other vertebrate species, including mammals, are proposed.

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Projections of the Intraotic Ganglion to the Medullary Nuclei in the Tegu Lizard, <i>Tupinambis nigropunctatus</i>

Cited by 19 publications

References 21 publications

Central Trigeminal and Posterior Eighth Nerve Projections in the Turtle <i>Chrysemys picta</i> Studied in vitro

Central Trigeminal and Posterior Eighth Nerve Projections in the Turtle <i>Chrysemys picta</i> Studied in vitro

Inner ear labyrinth anatomy of monotremes and implications for mammalian inner ear evolution

Neuronal architecture of the dorsal nucleus (Cochlear nucleus) of the frog,Rana pipiens pipiens

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