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1.
Sci Rep ; 14(1): 14734, 2024 06 26.
Article in English | MEDLINE | ID: mdl-38926520

ABSTRACT

Based on the auditory periphery and the small head size, Etruscan shrews (Suncus etruscus) approximate ancestral mammalian conditions. The auditory brainstem in this insectivore has not been investigated. Using labelling techniques, we assessed the structures of their superior olivary complex (SOC) and the nuclei of the lateral lemniscus (NLL). There, we identified the position of the major nuclei, their input pattern, transmitter content, expression of calcium binding proteins (CaBPs) and two voltage-gated ion channels. The most prominent SOC structures were the medial nucleus of the trapezoid body (MNTB), the lateral nucleus of the trapezoid body (LNTB), the lateral superior olive (LSO) and the superior paraolivary nucleus (SPN). In the NLL, the ventral (VNLL), a specific ventrolateral VNLL (VNLLvl) cell population, the intermediate (INLL) and dorsal (DNLL) nucleus, as well as the inferior colliculus's central aspect were discerned. INLL and VNLL were clearly separated by the differential distribution of various marker proteins. Most labelled proteins showed expression patterns comparable to rodents. However, SPN neurons were glycinergic and not GABAergic and the overall CaBPs expression was low. Next to the characterisation of the Etruscan shrew's auditory brainstem, our work identifies conserved nuclei and indicates variable structures in a species that approximates ancestral conditions.


Subject(s)
Shrews , Superior Olivary Complex , Animals , Shrews/anatomy & histology , Superior Olivary Complex/anatomy & histology , Superior Olivary Complex/metabolism , Auditory Pathways/anatomy & histology , Neurons/metabolism , Inferior Colliculi/anatomy & histology , Inferior Colliculi/metabolism , Calcium-Binding Proteins/metabolism , Calcium-Binding Proteins/genetics , Brain Stem/anatomy & histology , Brain Stem/metabolism , Male , Olivary Nucleus/anatomy & histology , Olivary Nucleus/metabolism
2.
Hear Res ; 449: 109036, 2024 Aug.
Article in English | MEDLINE | ID: mdl-38797037

ABSTRACT

Although rats and mice are among the preferred animal models for investigating many characteristics of auditory function, they are rarely used to study an essential aspect of binaural hearing: the ability of animals to localize the sources of low-frequency sounds by detecting the interaural time difference (ITD), that is the difference in the time at which the sound arrives at each ear. In mammals, ITDs are mostly encoded in the medial superior olive (MSO), one of the main nuclei of the superior olivary complex (SOC). Because of their small heads and high frequency hearing range, rats and mice are often considered unable to use ITDs for sound localization. Moreover, their MSO is frequently viewed as too small or insignificant compared to that of mammals that use ITDs to localize sounds, including cats and gerbils. However, recent research has demonstrated remarkable similarities between most morphological and physiological features of mouse MSO neurons and those of MSO neurons of mammals that use ITDs. In this context, we have analyzed the structure and neural afferent and efferent connections of the rat MSO, which had never been studied by injecting neuroanatomical tracers into the nucleus. The rat MSO spans the SOC longitudinally. It is relatively small caudally, but grows rostrally into a well-developed column of stacked bipolar neurons. By placing small, precise injections of the bidirectional tracer biotinylated dextran amine (BDA) into the MSO, we show that this nucleus is innervated mainly by the most ventral and rostral spherical bushy cells of the anteroventral cochlear nucleus of both sides, and by the most ventrolateral principal neurons of the ipsilateral medial nucleus of the trapezoid body. The same experiments reveal that the MSO densely innervates the most dorsolateral region of the central nucleus of the inferior colliculus, the central region of the dorsal nucleus of the lateral lemniscus, and the most lateral region of the intermediate nucleus of the lateral lemniscus of its own side. Therefore, the MSO is selectively innervated by, and sends projections to, neurons that process low-frequency sounds. The structural and hodological features of the rat MSO are notably similar to those of the MSO of cats and gerbils. While these similarities raise the question of what functions other than ITD coding the MSO performs, they also suggest that the rat MSO is an appropriate model for future MSO-centered research.


Subject(s)
Auditory Pathways , Axons , Sound Localization , Superior Olivary Complex , Animals , Superior Olivary Complex/physiology , Superior Olivary Complex/anatomy & histology , Auditory Pathways/physiology , Auditory Pathways/anatomy & histology , Axons/physiology , Rats , Male , Dextrans/metabolism , Biotin/analogs & derivatives , Acoustic Stimulation , Efferent Pathways/physiology , Efferent Pathways/anatomy & histology , Olivary Nucleus/physiology , Olivary Nucleus/anatomy & histology , Female , Neuroanatomical Tract-Tracing Techniques , Rats, Wistar
3.
Neurocirugia (Astur : Engl Ed) ; 35(3): 152-163, 2024.
Article in English | MEDLINE | ID: mdl-38244925

ABSTRACT

OBJECTIVES: Throughout neurosurgical history, the treatment of intrinsic lesions located in the brainstem has been subject of much controversy. The brainstem is the anatomical structure of the central nervous system (CNS) that presents the highest concentration of nuclei and fibers, and its simple manipulation can lead to significant morbidity and mortality. Once one of the safe entry points at the medulla oblongata has been established, we wanted to evaluate the safest approach to the olivary body (the most used safe entry zone on the anterolateral surface of the medulla oblongata). The proposed objective was to evaluate the working channel from the surface of each of the far lateral and retrosigmoid approaches to the olivary body: distances, angles of attack and channel content. MATERIAL AND METHODS: To complete this work, a total of 10 heads injected with red/blue silicone were used. A total of 40 approaches were made in the 10 heads used (20 retrosigmoid and 20 far lateral). After completing the anatomical study and obtaining the data referring to all the approaches performed, it was decided to expand the sample of this research study by using 30 high-definition magnetic resonance imaging of anonymous patients without cranial or cerebral pathology. The reference points used were the same ones defined in the anatomical study. After defining the working channels in each of the approaches, the working distances, angle of attack, exposed surface, and the number of neurovascular structures present in the central trajectory were analyzed. RESULTS: The distances to the cranial and medial region of the olivary body were 52.71 mm (SD 3.59) from the retrosigmoid approach and 27.94 mm (SD 3.99) from the far lateral; to the most basal region of the olivary body, the distances were 49.93 (SD 3.72) from the retrosigmoid approach and 18.1 mm (SD 2.5) from the far lateral. The angle of attack to the caudal region was 19.44° (SD 1.3) for the retrosigmoid approach and 50.97° (SD 8.01) for the far lateral approach; the angle of attack to the cranial region was 20.3° (SD 1.22) for the retrosigmoid and 39.9° (SD 5.12) for the far lateral. Regarding neurovascular structures, the probability of finding an arterial structure is higher for the lateral far, whereas a neural structure will be more likely from a retrosigmoid approach. CONCLUSIONS: As conclusions of this work, we can say that far lateral approach presents more favorable conditions for the microsurgical treatment of intrinsic bulbar and bulbomedullary lesions approached through the caudal half of the olivary body. In those cases of bulbar and pontine-bulbar lesions approached through the cranial half of the olivary body, the retrosigmoid approach can be considered for selected cases.


Subject(s)
Olivary Nucleus , Humans , Olivary Nucleus/diagnostic imaging , Olivary Nucleus/anatomy & histology , Neurosurgical Procedures/methods , Magnetic Resonance Imaging , Cadaver , Medulla Oblongata/anatomy & histology , Medulla Oblongata/diagnostic imaging , Medulla Oblongata/blood supply
4.
J Morphol ; 283(4): 446-461, 2022 04.
Article in English | MEDLINE | ID: mdl-35066941

ABSTRACT

In all mammals, the superior olivary complex (SOC) comprises a group of auditory brainstem nuclei that are important for sound localization. Its principal nuclei, the lateral superior olive (LSO) and the medial superior olive (MSO) process interaural time and intensity differences, which are the main cues for sound localization in the horizontal plane. Toothed whales (odontocetes) rely heavily on hearing and echolocation for foraging, orientation, and communication and localize sound with great acuity. The investigation of the SOC in odontocetes provides insight into adaptations to underwater hearing and echolocation. However, quantitative anatomical data for odontocetes are currently lacking. We quantified the volume, total neuron number, and neuron density of the LSO of six common dolphins (Delphinus delphis) using the Cavalieri principle and the unbiased stereology optical fractionator. Our results show that the LSO in D. delphis has a volume of 150 + (SD = 27) mm3 , which is on average 69 (SEM = 19) times larger than the LSO in human, or 37 (SEM = 11) times larger than the human LSO and MSO combined. The LSO of D. delphis contains 20,876 ± (SD = 3300) neurons. In comparison, data reported for the human brainstem indicate the LSO has only about » that number but about the same number for the LSO and MSO combined (21,100). LSO neurons range from 21 to 25 µm (minor axis) and from 44 to 61 µm (major axis) in transverse sections. The LSO neuron packing density is 1080 ± (SD = 204) neurons/mm3 , roughly half of the LSO neuron density in human. SMI-32-immunohistochemistry was used to visualize projection neurons in the LSO and revealed the presence of principal, marginal, and multipolar neurons in transverse sections. The distinct morphology of the LSO likely reflects the common dolphin's superb sensitivity to ultra-high frequencies and ability to detect and analyze sounds and their location as part of its underwater spatial localization and echolocation tasks.


Subject(s)
Common Dolphins , Echolocation , Superior Olivary Complex , Animals , Cetacea , Echolocation/physiology , Olivary Nucleus/anatomy & histology , Olivary Nucleus/physiology
5.
Neurosci Lett ; 707: 134302, 2019 08 10.
Article in English | MEDLINE | ID: mdl-31152849

ABSTRACT

INTRODUCTION: This study describes the prenatal development of the principal inferior olivary nucleus (PO) in humans. MATERIAL/METHODS: Ten brains were obtained from preterm infants aged 21-43 postmenstrual weeks (PW). After fixation, the brains were processed into 30-µm serial sections, which were stained using the Klüver-Barrera method. RESULTS: At mid-gestation, the dorsal and ventral lamellae were distinguishable. The dorsal lamella (DL) was composed of ballooned and folded portions, with many neurons peripherally gathered in the ballooned portion, and neurons densely packed in the folded portion. Clusters of pyknotic neurons were observed in the lateral portion of the PO at 21PW. The PO acquired thin complicated folds by 28-29 PW. Then, it regained the width of a nuclear band, and further elaborated the folds. The 3D-reconstruction models showed that the basic pattern of folding like in adults was attained at 28-29PW, and that the rostro-medial region of DL was microgyric. The nuclear volume increased exponentially with age. The total surface area increased progressively, while the surface density varied in a biphasic manner, wherein it increased initially and then decreased. The neuronal profile area increased uniformly. The total neuronal number increased uniformly, while the numerical density decreased rapidly during 21-29 PW. CONCLUSION: After mid-gestation, the period of 21-29 PW may be critical, because the PO undergoes extensive folding after massive neuronal death.


Subject(s)
Olivary Nucleus/embryology , Cell Count , Gestational Age , Humans , Imaging, Three-Dimensional , Infant, Premature , Neurons/cytology , Olivary Nucleus/anatomy & histology
6.
J Comp Neurol ; 526(15): 2406-2427, 2018 10 15.
Article in English | MEDLINE | ID: mdl-30004589

ABSTRACT

Topographic connection between corresponding compartments of the cerebellar cortex, cerebellar nuclei, and inferior olive form parallel modules, which are essential for the cerebellar function. Compared to the striped cortical compartmentalization which are labeled by molecular markers, such as aldolase C (Aldoc) or zebrin II, the presumed corresponding organization of the cerebellar nuclei and inferior olivary nucleus has not been much clarified. We focused on the expression pattern of pcdh10 gene coding cell adhesion molecule protocadherin 10 (Pcdh10) in adult mice. In the cortex, pcdh10 was strongly expressed in (a) Aldoc-positive vermal stripes a+//2+ in lobules VI-VII, (b) paravermal narrow stripes c+, d+, 4b+, 5a+ in crus I and neighboring lobules, and (c) paravermal stripes 4+//5+ across all lobules from lobule III to paraflocculus. In the cerebellar nuclei, pcdh10 was expressed strongly in the caudal part of the medial nucleus and the lateral part of the posterior interposed nucleus which project less to the medulla or to the red nucleus than to other metencephalic, mesencephalic, and diencephalic areas. In the inferior olive, pcdh10 was expressed strongly in the rostral and medioventrocaudal parts of the medial accessory olive which has connection with the mesencephalic areas rather than the spinal cord. Olivocerebellar and corticonuclear axonal labeling confirmed that the three cortical pcdh10-positive areas were topographically connected to the nuclear and olivary pcdh10-positive areas, demonstrating their coincidence with modular structures in the olivo-cortico-nuclear loop. We speculate that some of these modules are functionally involved in various nonsomatosensorimotor tasks via their afferent and efferent connections.


Subject(s)
Cadherins/metabolism , Cerebellar Nuclei/metabolism , Cerebral Cortex/metabolism , Olivary Nucleus/metabolism , Animals , Cadherins/genetics , Cerebellar Cortex/anatomy & histology , Cerebellar Cortex/metabolism , Cerebellar Nuclei/anatomy & histology , Cerebral Cortex/anatomy & histology , Immunohistochemistry , Male , Mice , Mice, Inbred C57BL , Neural Pathways/anatomy & histology , Neural Pathways/metabolism , Olivary Nucleus/anatomy & histology , Phenotype , Protocadherins , Purkinje Cells/physiology
7.
Elife ; 72018 06 14.
Article in English | MEDLINE | ID: mdl-29901438

ABSTRACT

The brainstem's lateral superior olive (LSO) is thought to be crucial for localizing high-frequency sounds by coding interaural sound level differences (ILD). Its neurons weigh contralateral inhibition against ipsilateral excitation, making their firing rate a function of the azimuthal position of a sound source. Since the very first in vivo recordings, LSO principal neurons have been reported to give sustained and temporally integrating 'chopper' responses to sustained sounds. Neurons with transient responses were observed but largely ignored and even considered a sign of pathology. Using the Mongolian gerbil as a model system, we have obtained the first in vivo patch clamp recordings from labeled LSO neurons and find that principal LSO neurons, the most numerous projection neurons of this nucleus, only respond at sound onset and show fast membrane features suggesting an importance for timing. These results provide a new framework to interpret previously puzzling features of this circuit.


Subject(s)
Action Potentials/physiology , Auditory Pathways/physiology , Gerbillinae/physiology , Olivary Nucleus/physiology , Sensory Receptor Cells/physiology , Sound Localization/physiology , Acoustic Stimulation/methods , Animals , Electrodes, Implanted , Female , Gerbillinae/anatomy & histology , Lysine/analogs & derivatives , Lysine/chemistry , Male , Olivary Nucleus/anatomy & histology , Olivary Nucleus/cytology , Patch-Clamp Techniques , Sensory Receptor Cells/cytology , Staining and Labeling/methods
8.
Hear Res ; 362: 38-47, 2018 05.
Article in English | MEDLINE | ID: mdl-29291948

ABSTRACT

The anatomy and physiology of olivocochlear (OC) efferents are reviewed. To help interpret these, recent advances in cochlear mechanics are also reviewed. Lateral OC (LOC) efferents innervate primary auditory-nerve (AN) fiber dendrites. The most important LOC function may be to reduce auditory neuropathy. Medial OC (MOC) efferents innervate the outer hair cells (OHCs) and act to turn down the gain of cochlear amplification. Cochlear amplification had been thought to act only through basilar membrane (BM) motion, but recent reports show that motion near the reticular lamina (RL) is amplified more than BM motion, and that RL-motion amplification extends to several octaves below the local characteristic frequency. Data on efferent effects on AN-fiber responses, otoacoustic emissions (OAEs) and human psychophysics are reviewed and reinterpreted in the light of the new cochlear-mechanical data. The possible origin of OAEs in RL motion is considered. MOC-effect measuring methods and MOC-induced changes in human responses are also reviewed, including that ipsilateral and contralateral sound can produce MOC effects with different patterns across frequency. MOC efferents help to reduce damage due to acoustic trauma. Many, but not all, reports show that subjects with stronger contralaterally-evoked MOC effects have better ability to detect signals (e.g. speech) in noise, and that MOC effects can be modulated by attention.


Subject(s)
Auditory Perception , Cochlea/innervation , Cochlear Nerve/physiology , Hearing , Mechanotransduction, Cellular , Olivary Nucleus/physiology , Acoustic Stimulation , Animals , Attention , Cochlear Nerve/anatomy & histology , Efferent Pathways/anatomy & histology , Efferent Pathways/physiology , Humans , Noise/adverse effects , Olivary Nucleus/anatomy & histology , Perceptual Masking , Signal Detection, Psychological , Speech Perception
9.
J Comp Neurol ; 525(14): 3158-3173, 2017 Oct 01.
Article in English | MEDLINE | ID: mdl-28649766

ABSTRACT

Zebrin II (ZII; a.k.a. aldolase C) is expressed heterogeneously in Purkinje cells (PCs) such that there are sagittal stripes of high expression (ZII+) interdigitated with stripes of little or no expression (ZII-). The pigeon flocculus receives visual-optokinetic information and is important for generating compensatory eye movements. It consists of 4 sagittal zones based on PC complex spike activity (CSA) in response to rotational optokinetic stimuli. There are two zones where CSA responds best to rotation about the vertical axis (VA), interdigitated with two zones where CSA responds best to rotation about an horizontal axis (HA). These optokinetic zones relate to the ZII stripes in folium IXcd of the flocculus, such that an optokinetic zone spans a ZII+/- pair: the HA zones span the P5+/- and P7+/- ZII stripe pairs, whereas the VA zones correspond to ZII stripe pairs P4+/- and P6+/-. In the present study, we used fluorescent retrograde tracing to determine the olivary inputs to the ZII+ and ZII- stripes within the functional pairs. We found that separate but adjacent areas of the medial column of the inferior olive (mcIO) project to the ZII+ and ZII- stripes within each of the functional pairs. Thus, although a ZII+/- stripe pair represents a functional unit in the pigeon flocculus insofar as the CSA of all PCs in the stripe pair encodes similar sensory information, the olivary inputs to the ZII+ and ZII- stripes arise from different, although adjacent, regions of the mcIO.


Subject(s)
Avian Proteins/metabolism , Cerebellar Vermis/anatomy & histology , Columbidae/anatomy & histology , Nerve Tissue Proteins/metabolism , Olivary Nucleus/anatomy & histology , Animals , Cerebellar Vermis/metabolism , Columbidae/metabolism , Immunohistochemistry , Neural Pathways/anatomy & histology , Neural Pathways/metabolism , Neuroanatomical Tract-Tracing Techniques , Olivary Nucleus/metabolism , Visual Perception/physiology
11.
Cerebellum ; 14(5): 584-96, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26142291

ABSTRACT

Enrico Mugnaini has devoted part of his long and fruitful neuroscientific career to investigating the structural similarities between the cerebellar cortex and one of the first relay stations of the mammalian auditory pathway: the dorsal cochlear nucleus. The hypothesis of the cerebellar-like nature of the superficial layers of the dorsal cochlear nucleus received definitive support with the discovery and extensive characterization in his laboratory of unipolar brush cells, a neuron type unique to certain regions of the cerebellar cortex and to the granule cell domains of the cochlear nuclei. Paradoxically, a different line of research carried out in his laboratory revealed that, unlike the mammalian cerebellar cortex, the dorsal cochlear nucleus receives direct projections from the cerebral cortex, a fact that constitutes one of the main differences between the cerebellum and the dorsal cochlear nucleus. In an article published in 1995, Mugnaini's group described in detail the novel direct projections from the rat auditory neocortex to various subcollicular auditory centers, including the nucleus sagulum, the paralemniscal regions, the superior olivary complex, and the cochlear nuclei (Feliciano et al., Auditory Neuroscience 1995; 1:287-308). This review gives Enrico Mugnaini credit for his seminal contribution to the knowledge of auditory corticosubcollicular projections and summarizes how this growing field has evolved in the last 20 years.


Subject(s)
Auditory Pathways/physiology , Cerebral Cortex/anatomy & histology , Cerebral Cortex/physiology , Olivary Nucleus/anatomy & histology , Olivary Nucleus/physiology , Animals , Humans , Neurons
12.
Cerebellum ; 14(5): 557-69, 2015 Oct.
Article in English | MEDLINE | ID: mdl-25592068

ABSTRACT

Although the major emphasis of Enrico Mugnaini's research has been on investigations of the cerebellum, a significant amount of work over a relatively short span of time was also done in his lab on a number of other brain systems. These centered on sensory systems. One of these extra-cerebellar systems that he embraced was the auditory system. Portions of the cochlear nucleus, the first synaptic relay station along the central auditory pathways, possess a cerebellar-like circuitry and neurochemistry, and this no doubt lured Enrico into the auditory field. As new tools became available to pursue neuroanatomical research in general, which included a novel antibody to glutamic acid decarboxylase (GAD), Enrico's lab soon branched out into investigating many other brain structures beyond the cerebellum, with an overall goal of producing a map illustrating GAD expression in the brain. In collaboration with long-term colleagues, one of these many non-cerebellar regions he took an interest in was an efferent pathway originating in the superior olive and projecting to the cochlea, the peripheral end organ for hearing. There was a need for a more complete neurochemical map of this olivocochlear efferent system, and armed with new antibodies and well-established tract tracing tools, together we set out to further explore this system. This short review describes the work done with Enrico on the olivocochlear system of rodents, and also continues the story beyond Enrico's lab to reveal how the work done in his lab fits into the larger scheme of current, ongoing research into the olivocochlear system.


Subject(s)
Cerebellum/physiology , Mammals/anatomy & histology , Olivary Nucleus/anatomy & histology , Olivary Nucleus/physiology , Animals , Auditory Pathways/physiology , History, 20th Century , Humans , Neuroanatomy/history , Neurochemistry/history
14.
Eur J Neurosci ; 40(5): 2811-21, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24964034

ABSTRACT

Axon collateral projections to various lobules of the cerebellar cortex are thought to contribute to the coordination of neuronal activities among different parts of the cerebellum. Even though lobules I/II and IX/X of the cerebellar vermis are located at the opposite poles in the anterior-posterior axis, they have been shown to receive dense vestibular mossy fiber projections. For climbing fibers, there is also a mirror-image-like organisation in their axonal collaterals between the anterior and posterior cerebellar cortex. However, the detailed organisation of mossy and climbing fiber collateral afferents to lobules I/II and IX/X is still unclear. Here, we carried out a double-labeling study with two retrograde tracers (FluoroGold and MicroRuby) in lobules I/II and IX/X. We examined labeled cells in the vestibular nuclei and inferior olive. We found a low percentage of double-labeled neurons in the vestibular nuclei (2.1 ± 0.9% of tracer-labeled neurons in this brain region), and a higher percentage of double-labeled neurons in the inferior olive (6.5 ± 1.9%), especially in its four small nuclei (18.5 ± 8.0%; including the ß nucleus, dorsal cap of Kooy, ventrolateral outgrowth, and dorsomedial cell column), which are relevant for vestibular function. These results provide strong anatomical evidence for coordinated information processing in lobules I/II and IX/X for vestibular control.


Subject(s)
Cerebellar Vermis/anatomy & histology , Neurons/cytology , Olivary Nucleus/anatomy & histology , Vestibular Nuclei/anatomy & histology , Animals , Female , Neural Pathways/anatomy & histology , Neuroanatomical Tract-Tracing Techniques , Photomicrography , Rats, Long-Evans
15.
J Assoc Res Otolaryngol ; 15(4): 571-83, 2014 Aug.
Article in English | MEDLINE | ID: mdl-24825663

ABSTRACT

Morphological studies of inner hair cell (IHC) synapses with cochlear nerve terminals have suggested that high- and low-threshold fibers differ in the sizes of their pre- and postsynaptic elements as well as the position of their synapses around the hair cell circumference. Here, using high-power confocal microscopy, we measured sizes and spatial positions of presynaptic ribbons, postsynaptic glutamate receptor (GluR) patches, and olivocochlear efferent terminals at eight locations along the cochlear spiral in normal and surgically de-efferented mice. Results confirm a prior report suggesting a modiolar > pillar gradient in ribbon size and a complementary pillar > modiolar gradient in GluR-patch size. We document a novel habenular < cuticular gradient in GluR patch size and a complementary cuticular < habenular gradient in olivocochlear innervation density. All spatial gradients in synaptic elements collapse after cochlear de-efferentation, suggesting a major role of olivocochlear efferents in maintaining functional heterogeneity among cochlear nerve fibers. Our spatial analysis also suggests that adjacent IHCs may contain a different synaptic mix, depending on whether their tilt in the radial plane places their synaptic pole closer to the pillar cells or to the modiolus.


Subject(s)
Cochlea/innervation , Cochlear Nerve/anatomy & histology , Habenula/anatomy & histology , Olivary Nucleus/anatomy & histology , Synapses , Animals , Cochlea/anatomy & histology , Hair Cells, Auditory, Inner/cytology , Mice , Mice, Inbred CBA , Models, Animal , Neurons, Efferent/cytology , Peripheral Nerves/cytology
16.
J Comp Neurol ; 522(18): 3960-77, 2014 Dec 15.
Article in English | MEDLINE | ID: mdl-24706328

ABSTRACT

The central pathways subserving the feline pupillary light reflex were examined by defining retinal input to the olivary pretectal nucleus (OPt), the midbrain projections of this nucleus, and the premotor neurons within it. Unilateral intravitreal wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) injections revealed differences in the pattern of retinal OPt termination on the two sides. Injections of WGA-HRP into OPt labeled terminals bilaterally in the anteromedian nucleus, and to a lesser extent in the supraoculomotor area, centrally projecting Edinger-Westphal nucleus, and nucleus of the posterior commissure. Labeled terminals, as well as retrogradely labeled multipolar cells, were present in the contralateral OPt, indicating a commissural pathway. Injections of WGA-HRP into the anteromedian nucleus labeled fusiform premotor neurons within the OPt, as well as multipolar cells in the nucleus of the posterior commissure. Connections between retinal terminals and the pretectal premotor neurons were characterized by combining vitreous chamber and anteromedian nucleus injections of WGA-HRP in the same animal. Fusiform-shaped, retrogradely labeled cells fell within the anterogradely labeled retinal terminal field in the OPt. Ultrastructural analysis revealed labeled retinal terminals containing clear spherical vesicles. They contacted labeled pretectal premotor neurons via asymmetric synaptic densities. These results provide an anatomical substrate for the pupillary light reflex in the cat. Pretectal premotor neurons receive direct retinal input via synapses suggestive of an excitatory drive, and project directly to nuclei containing preganglionic motoneurons. These projections are concentrated in the anteromedian nucleus, indicating its involvement in the pupillary light reflex.


Subject(s)
Olivary Nucleus/anatomy & histology , Pretectal Region/anatomy & histology , Reflex, Pupillary , Animals , Cats , Edinger-Westphal Nucleus/anatomy & histology , Edinger-Westphal Nucleus/physiology , Female , Male , Microscopy, Electron , Motor Cortex/anatomy & histology , Motor Cortex/physiology , Neurons/cytology , Neurons/physiology , Olivary Nucleus/physiology , Photomicrography , Pretectal Region/physiology , Reflex, Pupillary/physiology , Retina/anatomy & histology , Retina/physiology , Synapses/physiology , Synapses/ultrastructure , Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
17.
J Comp Neurol ; 522(9): 2179-90, 2014 Jun 15.
Article in English | MEDLINE | ID: mdl-24357064

ABSTRACT

The gracile nucleus (GN) and lateral part of rostral dorsal accessory olive (rDAO) are important relays for indirect, postsynaptic dorsal column, and direct ascending pathways, respectively, that terminate as climbing fibers in the "hindlimb-receiving" parts of the C1 and C3 zones in the cerebellar cortex. While the spinal cells of origin of that project to GN and rDAO are from largely separate territories in the spinal cord, previous studies have indicated that there could be an area of overlap between these two populations in the medial dorsal horn. Given the access of these two ascending tracts to sensory (thalamic) versus sensorimotor (precerebellar) pathways, the present study therefore addresses the important question of whether or not individual neurons have the potential to contribute axons to both ascending pathways. A double-fluorescent tracer strategy was used in rats (red Retrobeads and Fluoro-Ruby or green Retrobeads and Fluoro-Emerald) to map the spatial distribution of cells of origin of the two projections in the lumbar spinal cord. The two pathways were found to receive input from almost entirely separate territories within the lumbar cord (levels L3-L5). GN predominantly receives input from lamina IV, while rDAO receives its input from three cell populations: medial laminae V-VI, lateral lamina V, and medial laminae VII-VIII. Cells that had axons that branched to supply both GN and rDAO represented only about 1% of either single-labeled cell population. Overall, the findings therefore suggest functional independence of the two ascending pathways.


Subject(s)
Medulla Oblongata/anatomy & histology , Neurons/cytology , Olivary Nucleus/anatomy & histology , Spinal Cord/anatomy & histology , Animals , Axons , Fluorescent Dyes , Lumbar Vertebrae , Male , Neural Pathways/anatomy & histology , Neuroanatomical Tract-Tracing Techniques , Neuronal Tract-Tracers , Photomicrography , Rats, Wistar
18.
Dev Neurosci ; 35(1): 69-81, 2013.
Article in English | MEDLINE | ID: mdl-23689557

ABSTRACT

Precise temporal and spatial sequences of synaptogenesis occur in the cerebellar system, as in other synaptic circuits of the brain. In postmortem brain sections of 172 human fetuses and neonates, synaptophysin immunoreactivity was studied in nuclei of the Guillain-Mollaret triangle: dentato-olivo-rubro-cerebellar circuit. Synaptophysin demonstrates not only progressive increase in synaptic vesicles in each structure, but also shows the development of shape from amorphous globular neuronal aggregates to undulated nuclei. Intensity of synaptophysin reactivity is strong before the mature shape of these nuclei is achieved. Accessory olivary and deep cerebellar nuclei are intensely stained earlier than the principal olivary and dentate nuclei. The dorsal blades of both form earlier than the ventral, with reactivity initially peripheral. Initiation of synaptophysin reactivity is at 13 weeks in the inferior olive (r6, r7) and at 16 weeks in the dentate (r2). Initial synaptic vesicles are noted at 13 weeks in the red nucleus (r0); synapses form initially on the small neurons at 13 weeks but thereafter simultaneously on small and large neurons. Form and reactivity follow caudorostral, dorsoventral and mediolateral gradients in the axes of the rhombencephalon. This study provides control data to serve as a basis for interpreting aberrations in synaptogenesis in malformations of the cerebellar system, genetic disorders and acquired insults to the cerebellum and brainstem during fetal life, applicable to tissue sections and complementing biochemical and molecular techniques.


Subject(s)
Cerebellar Nuclei/growth & development , Olivary Nucleus/growth & development , Red Nucleus/growth & development , Synapses/metabolism , Cerebellar Nuclei/anatomy & histology , Cerebellar Nuclei/embryology , Female , Fetus/anatomy & histology , Fetus/embryology , Humans , Infant, Newborn , Male , Neural Pathways , Olivary Nucleus/anatomy & histology , Olivary Nucleus/embryology , Red Nucleus/anatomy & histology , Red Nucleus/embryology , Synaptophysin/metabolism
19.
Article in English | MEDLINE | ID: mdl-23509001

ABSTRACT

Projections to the inferior colliculus (IC) from the lateral and medial superior olivary nuclei (LSO and MSO) were studied in the gerbil (Meriones unguiculatus) with neuroanatomical tract-tracing methods. The terminal fields of projecting axons were labeled via anterograde transport of biotinylated dextran amine (BDA) and were localized on series of horizontal sections through the IC. In addition, to make the results easier to visualize in three dimensions and to facilitate comparisons among cases, the data were also reconstructed into the transverse plane. The results show that the terminal fields from the low frequency parts of the LSO and MSO are concentrated in a dorsal, lateral, and rostral area that is referred to as the "pars lateralis" of the central nucleus by analogy with the cat. This region also receives substantial input from both the contralateral and ipsilateral cochlear nuclei (Cant and Benson, 2008) and presumably plays a major role in processing binaural, low frequency information. The basic pattern of organization in the gerbil IC is similar to that of other rodents, although the low frequency part of the central nucleus in gerbils appears to be relatively greater than in the rat, consistent with differences in the audiograms of the two species.


Subject(s)
Auditory Pathways/physiology , Inferior Colliculi/physiology , Olivary Nucleus/physiology , Animals , Auditory Pathways/anatomy & histology , Cats , Female , Gerbillinae , Inferior Colliculi/anatomy & histology , Olivary Nucleus/anatomy & histology , Rats , Species Specificity
20.
Article in English | MEDLINE | ID: mdl-24478634

ABSTRACT

The reflexological view of brain function (Sherrington, 1906) has played a crucial role in defining both the nature of connectivity and the role of the synaptic interactions among neuronal circuits. One implicit assumption of this view, however, has been that CNS function is fundamentally driven by sensory input. This view was questioned as early as the beginning of the last century when a possible role for intrinsic activity in CNS function was proposed by Thomas Graham Brow (Brown, 1911, 1914). However, little progress was made in addressing intrinsic neuronal properties in vertebrates until the discovery of calcium conductances in vertebrate central neurons leading dendritic electroresponsiveness (Llinás and Hess, 1976; Llinás and Sugimori, 1980a,b) and subthreshold neuronal oscillation in mammalian inferior olive (IO) neurons (Llinás and Yarom, 1981a,b). This happened in parallel with a similar set of findings concerning invertebrate neuronal system (Marder and Bucher, 2001). The generalization into a more global view of intrinsic rhythmicity, at forebrain level, occurred initially with the demonstration that the thalamus has similar oscillatory properties (Llinás and Jahnsen, 1982) and the ionic properties responsible for some oscillatory activity were, in fact, similar to those in the IO (Jahnsen and Llinás, 1984; Llinás, 1988). Thus, lending support to the view that not only motricity, but cognitive properties, are organized as coherent oscillatory states (Pare et al., 1992; Singer, 1993; Hardcastle, 1997; Llinás et al., 1998; Varela et al., 2001).


Subject(s)
Cerebellum/physiology , Nerve Net/physiology , Neurons/physiology , Olivary Nucleus/physiology , Animals , Cerebellum/anatomy & histology , Humans , Models, Neurological , Nerve Net/anatomy & histology , Olivary Nucleus/anatomy & histology , Periodicity
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