All subtype genes were expressed in the optic tectum, diencephalon, mesencephalon, vagal lobe, retina and spleen. The real-time PCR analyses showed that significant differences among time were observed for Mel(1a) 1.4 in the optic tectum and for Mel(1a) 1.7 and Mel(1b) in the retina. Mel(1a) 1.4 in the optic tectum and Mel(1a) 1.7 in the retina.. 
Rich VGLUT2 mRNA expression was found in the optic tectum, nucleus mesencephalicus lateralis, pars dorsalis, nucleus isthmi, pars parvocellularis, isthmo-optic nucleus, pontine nuclei, and granular layer of the cerebellum.
Double-labeling experiments revealed nNOS/ChAT-positive cells in (1) the diencephalon: the preoptic and suprachiasmatic nuclei, the habenula, the dorsal thalamus, and the nucleus of the medial longitudinal fasciculus; (2) the mesencephalon: the optic tectum, the mesencephalic portion of the trigeminal nucleus, the oculomotor and trochlear nuclei, and the Edinger-Westphal nucleus; and (3) the rhombencephalon: the secondary gustatory nucleus, the nucleus isthmi, the lateral lemniscus nucleus, the cerebellum, the reticular formation, different nuclei of the octaval column, the motor zone of the vagal lobe, and the trigeminal, facial, abducens, glosso-pharyngeal, vagal, and hypobranchial motor nuclei.
Stimulated birds showed a greater number of ZENK-immunopositive cells per unit volume of brain tissue in deep optic tectum, a midbrain region strongly implicated in multimodal function.
MRI revealed hyperintensities within the thalami, hypothalami, corpora mammillaria, the tectum and the cortex. Finally, small infarctions affecting the tectum, tegmentum, corpora mammillaria and global hypoxic-ischaemic changes could be identified as the probable reason for the changes interpreted as CJD-related pathology.
The midbrain tectum structures, dorsal periaqueductal gray (dPAG) and inferior colliculus (IC), are involved in the organization of fear and anxiety states during the exposure to dangerous stimuli. Since opiate withdrawal is associated with increased anxiety in both humans and animals, this study aimed to investigate the possible sensitization of the neural substrates of fear in the midbrain tectum and its influence on the morphine withdrawal-induced anxiety.
In this review, the historical background of the means of identifying the isthmus organizer and the molecular mechanisms of signal transduction for tectum and cerebellum differentiation is reviewed..
Basilar pons, cerebral crus and cerebellum hemisphere were more susceptible than pontine tegmentum, vermis, midbrain tegmentum and tectum.
The avian optic tectum is reciprocally connected with the isthmic nuclei.
It has been demonstrated that mRNA of C-RFa is present in the telencephalon, optic tectum, medulla oblongata, and proximal half of the eyeball in abundance. However, in the optic tectum the immunopositive perikarya and fibers were less abundant.
Morphometric analysis showed bilateral cell-type dependent effects within the optic tectum.
The coordination of anterior-posterior (AP) and dorsal-ventral (DV) patterning of the mesencephalon (mes) and rhombomere 1 (r1) is instrumental for the development of three distinct brain structures: the tectum and cerebellum dorsally and the tegmentum ventrally. We demonstrate that before E9.0, Gli3 is required for establishing a distinct posterior tectum, isthmus and cerebellum, but does not play a role in the development of the tegmentum.
Expression of NTERM in ventral optic axons dispersed and induced anterior and lateral shifts in their targeting locations in the dorsal tectum.
In this projection, the temporal (posterior) retina is connected to the rostral (anterior) part of the contralateral optic tectum, the nasal (anterior) retina to the caudal (posterior) tectum, and likewise the dorsal and ventral retina to the ventral (lateral) and dorsal (medial) tectum, respectively. Thus, images received by the retina are precisely projected onto the tectum in a reversed manner.
By external examination, the sea bass exhibits a prominent Optic tectum and Corpus cerebelli as expected in a predator species with a highly developed visual system.
Considerable interspecies differences were noted mainly related to innervation of the olfactory and visual centers (thalamus and mesencephalic tectum) and the precise localization of immunoreactive cell bodies, which was assessed by double labeling with tyrosine hydroxylase.
The largest number of immunoreactive puncta were seen in the mesencephalic tectum in addition to the hypothalamus. Immunoelectron microscopic analysis revealed the presence of synaptoid connections of immunoreactive fibers on neuronal somata in the tectum.
Neighbouring retinal ganglion cells (RGCs) project their axons to neighbouring positions in the optic tectum, thus re-establishing a continuous neural representation of visual space. High concentrations of ephrin A, increasing from anterior to posterior, prevent temporal axons from invading the posterior tectum. However, the force that drives nasal axons to extend past the anterior tectum and terminate in posterior regions remains to be identified. We tested whether axon-axon interactions, such as competition, are required for posterior tectum innervation. These solitary RGCs often extended axons into the tectum, where they branched to form a terminal arbor. Here we show that the distal tips of these arbors were positioned at retinotopically appropriate positions, ruling out an essential role for competition in innervation of the ephrin-A-rich posterior tectum. We conclude that dense innervation is not required for targeting of retinal axons within the zebrafish tectum but serves to restrict arbor size and shape..
We sought to examine the early development and plasticity of local excitatory circuits in the optic tectum of Xenopus laevis tadpoles.
The magnocellular superficial pretectal nucleus does not receive retinal projections, but receives ipsilateral projections from the optic tectum and the mesencephalic tegmentum. The organization of the trout pretectum was compared with the pretectal organization patterns proposed in various teleosts..
Formation of the optic fiber layer of the zebrafish retina is also impaired, exhibited as both reduced size of the optic fiber layer, and disruption of retinal ganglion cell axon growth to the optic tectum. The retinotectal topographic projection to the optic tectum is perturbed in agrin morphants in association with a marked loss of heparan sulfate expression in the retinotectal pathway, with this phenotype resembling retinotectal phenotypes observed in mutant zebrafish lacking enzymes for heparan sulfate synthesis. Collectively, these agrin morphant phenotypes provide support for a crucial role of agrin in retina development and formation of an ordered retinotectal topographic map in the optic tectum of zebrafish..
In this study, we have utilized immunohistochemical and retroviral lineage tracing methods to characterize the developmental profiles of astrocytes in the chick optic tectum, which develops from both the neural tube and invasion of optic tract. The extrinsic astrocytes arose from the ventral neuroepithelium of the third ventricle, dispersed bilaterally to the optic tract, and subsequently to the outer layer of optic tectum, indicating migration of astrocytes along retinal ganglion cell axons. On the other hand, the intrinsic astrocytes from the tectal ventricular neuroepithelium appeared first in the ventral part of the optic tectum, and then in the lateral and dorsal tectum. These results demonstrated that the optic tectum contains heterogeneous populations of astrocytes developed from the different origins and routes of migration..
From there, information is sent to various midbrain structures, including the tectum. Here we recorded the responses of single units in the midbrain tectum and DON to uniform electric fields.
The rostral part of the dorsal midbrain, known as the superior colliculus in mammals or the optic tectum in birds, receives a substantial retinal input and plays a diverse and important role in sensorimotor integration. However, little is known about the development of specific subtypes of neurons in the tectum, particularly those which contribute tectofugal projections to the thalamus, isthmic region, and hindbrain. Neurons expressing these factors are generated at characteristic developmental times, and have specific laminar fates within the tectum. Using misexpression of Brn3a and Pax7 by electroporation in the chick tectum, combined with GFP reporters, we show that Brn3a determines the laminar fate of subsets of tectal neurons.
The repulsive guidance molecule (RGMa) is involved in controlling the topography of retinal ganglion cell axons along the anterioposterior axis of the tectum. These included the absence of terminal zone, the premature stalling of arborization of fibers, overshooting of terminal zone, aberrant axonal turns in the optic tectum and abnormal projections into deeper tectal layers.
Prominent binding sites were seen in the olfactory bulb and on retinal axons growing into the optic tectum. In the developing retinotectal system, APP, contactin 4 and NgCAM are expressed in the retina and tectum in suitable locations to interact.
In the present study, we examined two gaze control centers of the barn owl: the optic tectum (OT) and the arcopallium gaze fields (AGFs).
We have recently suggested that a slow negative wave (sNW), extracellularly observed in the frog tectum during the burst discharge of a single retinal ganglion cell, can be generated as a result of the persistent inward current in dendrites of tectal pear-shaped neurons. The evoked electrical activity of the tectum was recorded using a carbon-fiber microelectrode inserted into tectum layer F. (2) The sNW evoked by the burst discharge of a single retinal ganglion cell projecting to frog tectum layer F is generated by the activation of L-type calcium channels in the dendrites of pear-shaped neurons.
The second major finding is that the tectum is much smaller in parakeets than in quail at all developmental stages examined, suggesting that the tectum's reduced size is due to an evolutionary change in how much tissue was allocated to become tectum at the time of brain regionalization.
Developing binocular projections to the Xenopus tectum require visual input in order to establish matching topographic maps.
When the optic nerve is severed in adult goldfish, all axons regenerate back to the tectum to reestablish accurate connections. These conditions were mimicked in the adult goldfish by surgically deflecting 10-20% of optic fibers from one tectum into the opposite tectum which was denervated of all other optic fibers by removing its corresponding eye.
We also observed glycine-immunoreactive populations in the optic tectum, the torus semicircularis and the midbrain tegmentum, the isthmus, the octavolateral area, the dorsal column nucleus, the abducens nucleus, the trigeminal motor nucleus, the facial motor nucleus, and the rhombencephalic reticular formation.
After tracer injections into the inferior olive, labeled somata were observed bilaterally in the pretectum, nucleus ruber, principal sensory trigeminal nucleus, descending trigeminal nucleus, inferior reticular formation, and cerebellar valvula. Labeled somata were also seen ipsilaterally in the descending octaval nucleus, and contralaterally in the optic tectum, lateral funicular nucleus, cerebellar corpus, and inferior olive.
Here we report that the activation of ephrin-B reverse signaling in the developing Xenopus laevis optic tectum promotes morphological and functional maturation of retinotectal synapses.
The aim of this study was to evaluate the effects of unilateral retinal ablation on the expression of the cannabinoid receptor subtype 1 (CB(1)) at both protein and mRNA levels in the optic tectum of the adult chick brain. No cell death could be observed in the deafferented tectum, at least up to 30 days postlesion, although Fluoro-Jade B could reveal degenerating axons and terminals. Retinal ablation seems to generate an increase of CB(1) protein in the optic tectum and other retinorecipient visual areas, which paralleled an increase in MAP-2 staining. The increase of CB(1) receptor expression observed after retinal removal indicates that these receptors are not presynaptic in retinal axons projecting to the tectum and suggests a role of the cannabinoid system in plasticity processes ensuing after lesions..
We wanted to examine how the retinotectal projections regenerate after removal of the brain's optic tectum and establish this animal as a model for retinal projection as well as a central nervous system regeneration model. METHODS: A major portion of the left optic tectum was removed in several adult newts, and the animals were monitored postoperatively for eight months to observe regeneration and innervation. RESULTS: We observed that adult newts have the capability to the excised optic tectum. The ependymal cells that line the ventricle were the most likely source of the regenerated tectum. CONCLUSIONS: The retinotectal projections after removal of the adult newt optic tectum can be readily re-established.
We studied the effects of electrically microstimulating a gaze-control area in the owl's forebrain, the arcopallial gaze fields (AGFs), on the responsiveness of neurons in the optic tectum (OT) to visual and auditory stimuli.
Basic histologic stains, tract-tracing techniques and three-dimensional reconstructions reveal that the rat TLC is a narrow, elongated structure spanning the midbrain tectum longitudinally. The discovery of the TLC reveals an unexpected level of longitudinal organization in the mammalian tectum and raises questions as to the participation of this mesencephalic region in essential, yet completely unexplored, aspects of multisensory and/or sensorimotor integration..
After injections of horseradish peroxidase or biotinylated dextran amine into the optic tectum, electron microscopic observations showed that the vast majority of ipsilateral tectorotundal axon terminals were small in size, had smooth contours and contained small, round, densely packed synaptic vesicles. Occasional GABA-ir-labelled axon terminals were observed; these may arise from the rare GABAergic neurons in the central tectal layer, or from neurons in the ventral pretectal nucleus, which projects both to the optic tectum and nucleus rotundus. The existence in reptiles of reciprocal connections between the nucleus rotundus and the optic tectum as a phylogenetically ancient feedback system is discussed..
They were located in the anterodorsal tegmental nucleus, anteroventral tegmental nucleus, nucleus profundus mesencephali, and superficial isthmal reticular nucleus, with axons projecting to the tectum, nucleus isthmi, and spinal cord. It appears that the striatum can control visually guided behaviors through the striato-tegmento-spinal pathway and the tegmento-spinal pathway mediated by the tectum and nucleus isthmi..
In zebrafish, individual axons choose one of four retinorecipient layers upon entering the tectum and remain restricted to this layer, despite continual remodeling and shifting of their terminal arbors. The dragnet gene, drg, encodes collagen IV(alpha5) (Col4a5), a basement membrane component lining the surface of the tectum. Heparan sulfate proteoglycans (HSPGs) are normally associated with the tectal basement membrane but are dispersed in the dragnet mutant tectum. Our results show that the collagen IV sheet anchors secreted factors at the surface of the tectum, which serve as guidance cues for retinal axons..
This review presents the fascinating neurobiology underlying the development of the frog optic tectum, the brain structure where the two separate inputs from the two eye are combined into a single, integrated map.
In the present work, we reviewed critically current data about nitric oxide synthase (NOS) expression in the superior colliculus/optic tectum, as well as the roles of NO in the formation of the retinotopic map and in synaptic plasticity.
The proaversive effects of oCRF in the dmPAG gain further relevance when combined with previous immunohistochemical studies showing that CRF-containing projections from the periventricular hypothalamic system arch dorsomedially to the PAG, which could function as an important relay station in the midbrain tectum for avoidance behaviors..
Finally, if AA is the retrograde messenger, the application of exogenous AA to the tectum should reverse the increased branch turnover caused by blocking either NMDARs or cPLA2.
No gross histopathologies were observed (H&E stain) in the retina or optic tectum at any MeHg concentration.
Using retrograde HRP labeling from the optic nerve (ON) or optic tectum (OT), we have visualized large ganglion cells (LGCs) in wholemounted retinas of the teleost Pholidapus dybowskii and studied their morphology and spatial properties. Biplexiform ganglion cells in the retina of the perciform fish Pholidapus dybowskii revealed by HRP labeling from the optic nerve and optic tectum.
Brain stem lesions involved the following: tectum (n = 5), tegmentum (n = 4), red nucleus (n = 3) of the midbrain, vestibular nucleus (n = 6), and a focal tegmental lesion involving the superior olivary nucleus (n = 6) and abducens nucleus (n = 4) of the pons and vestibular nucleus (n = 4) and inferior olivary nucleus (n = 1) of the medulla.
Retinal ganglion cells (RGCs) extend axons that exit the eye, cross the midline at the optic chiasm, and synapse on target cells in the optic tectum. Finally, the optic tectum expresses sema3Aa, 3Fa, 3Fb, and 3Gb.
These labeled cells were particularly numerous in the dorsal and ventral hypothalamus, preoptic area, optic tectum, and laminar and principal nuclei of the torus semicircularis, with label also present, but at qualitatively reduced levels, in thalamic and telencephalic nuclei. Double-label immunohistochemistry using glial and early neural markers indicated that gliogenesis and neurogenesis both occurred, with new neurons observed particularly in the hypothalamus, optic tectum, and torus semicircularis.
The three regions investigated were telencephalon (Tel), optic tectum (OT) and cerebellum (Ce).
When pretreated for 7 days, rats receiving 1.5 mg/kg AM also showed inhibitory activity of the cortical centres, whereas desynchronization of the optic tectum and reticular formation was observed in rats pretreated with 7.5 and 15 mg/kg AM.
The overall size of the pretectum in both monotremes was found to be at least comparable in size, if not larger than, the pretectum of representative therian mammals of similar brain and body size. Our findings suggest that the pretectum of these two monotreme species is comparable in both size and organization to that of eutherian mammals, and is more than just an undifferentiated area pretectalis. The presence of a differentiated pretectum with similar chemoarchitecture to therians in both living monotremes lends support to the idea that the stem mammal for both prototherian and therian lineages also had a differentiated pretectum. This in turn indicates that a differentiated pretectum appeared at least 125 million years ago in the mammalian lineage and that the stem mammal for proto- and eutherian lineages probably had similar pretectal nuclei to those identified in its descendants..
Although RA has been suggested to regulate development of the retina and its central projection, little is known about the distribution of retinoid receptors and binding proteins in the optic tectum, which in birds is the direct target of most retinofugal axons. In addition, we detected retinoid receptors RARalpha, RARbeta, RXRalpha, RXRbeta and RXRgamma in the developing tectum.
We examined activity changes in the human tectum and the lateral geniculate nuclei (LGN) in a visual search task using functional magnetic resonance imaging (fMRI) and anatomically defined regions of interest (ROI).
It is suggested that an enhanced neural activation of neural substrates of fear in the midbrain tectum may underlie the aversive state elicited in diazepam-withdrawn rats..
This mechanism is based on a topographically organized cholinergic signal reentering the optic tectum (TeO). We have shown previously that, whenever a visual stimulus activates neurons in a given tectal location, this location receives a strong bursting feedback from cholinergic neurons of the nucleus isthmi pars parvocellularis (Ipc), situated underneath the tectum.
This investigation analyzes the effect of an acute hypoxic treatment on the level of four (alpha(1), alpha(2), beta(2), and gamma(2)) subunit mRNAs of the GABA(A) receptor in layer "i" of the developing chick optic tectum.
To identify Pbx-dependent genes involved in regulating retino-tectal pathfinding, we conducted a microarray screen for Pbx-dependent transcripts in zebrafish, and detected genes that are specifically expressed in the eye and tectum. CONCLUSION: These data define a novel role for Pbx in patterning the vertebrate retina and tectum in a manner required for proper retinal ganglion cell axon outgrowth..
Immunoreactivity for GH is also traced through the optic nerve head, at the back of the eye, into the optic nerve, through the optic chiasm, into the optic tract and into the stratum opticum and the retinorecipient layer of the optic tectum, where the RGC axons synapse. The presence of GH immunoreactivity in the tectum occurs prior to synaptogenesis with RGC axons and thus reflects the local expression of the GH gene, especially as GH mRNA is also distributed within this tissue. The distribution of GH-immunoreactivity in the visual system of the E7 embryo is consistent with the distribution of the GH receptor (GHR), which is also expressed in the neural retina and tectum.
In the diencephalon, the cells were found in some nuclei of the preoptic area and hypothalamus, habenula, pretectum, and dorsal and ventral thalamic regions. In the midbrain, cells were observed in the optic tectum, torus longitudinalis, and tegmental nuclei.
Staining was identified in the olfactory glomeruli, pallium and subpallium of the telencephalon; epithalamus, thalamus, preoptic area, and hypothalamus of the diencephalon; pretectal area, optic tectum, torus semicircularis, and tegmentum of the mesencephalon; all layers of the cerebellum; reticular formation; nucleus of the solitary tract, octaval nuclei, and dorsal column nuclei of the medulla; and dorsal and motor fields of the spinal cord.
OBJECTIVE: A few investigations have been reported about pretectal suppressive influences on the optic tectum of frog, but characteristics of tectal activity to pretectal input are left unknown. RESULTS: The pretectal stimulation mainly elicited two types of responses in the ipsilateral tectum: an excitatory postsynaptic potential (EPSP) followed by an inhibitory postsynaptic potential (IPSP) and a pure IPSP. The spikes of tecto-pretectal projecting cells elicited by antidromical stimulation were recorded in the ipsilateral tectum, which revealed reciprocal connections between the tectum and particular pretectal nuclei. Most IPSPs were generated through polysynaptic paths, but monosynaptic IPSPs were also recorded in the tectum.
Other smaller veins were also differentiated according to whether they drained mainly the cerebral peduncle, the lemniscal trigone, or the tectum.
The engrailed (En) homeobox transcription factors are candidate regulators of this process in the dorsal midbrain (tectum) and anterior hindbrain (cerebellum). En1 mutants lack most of the tectum and cerebellum and die at birth, whereas En2 mutants are viable with a smaller cerebellum and foliation defects. First, using a conditional allele we demonstrate that En1 is required for cerebellum development only before embryonic day 9, but plays a sustained role in forming the tectum. Third, based on a differential sensitivity to the dose of En1/2, our studies reveal a genetic subdivision of the tectum into its two functional systems and the medial cerebellum into four regions that have distinct circuitry and molecular coding. Our study suggests that an ;engrailed code' is integral to partitioning the tectum and cerebellum into functional domains..
Transciptome profiles were obtained from the inferior colliculus (IC), the major site of synaptic plasticity, and the optic tectum (OT), which provides an instructive signal that controls the direction and extent of plasticity.
Electrographic activity was monitored by using a field-recording electrode placed in the optic tectum of agar-immobilized zebrafish.
We show that injection of anti-dystroglycan Fab fragments, knockdown of dystroglycan using RNAi, and overexpression of a dominant-negative dystroglycan protein by microelectroporation in neuroepithelial cells of the chick retina and optic tectum in vivo leads to the loss of their radial morphology, to hyperproliferation, to an increased number of postmitotic neurons, and to an altered distribution of several basally concentrated proteins.
The optic tectum is a visual center in vertebrates. These results may provide a neuroanatomical and molecular basis for the motor command map in the tectum..
In contrast large cysts can be symptomatic due to compression of the aqueduct of Sylvius, compression of the midbrain tectum or mass effect in the posterior fossa.
Previous work has found that the optic tectum is an important structure responsible for the mediation of feeding behaviors, and combined electrical and visual stimulation of the optic tectum was found to increase the animals feeding behaviors. However, the pretectal thalamus has an inhibitory influence upon the optic tectum and its lesion results in disinhibited feeding behaviors. The application of DC stimulation increased the incidence of avoidance behaviors to a visual prey stimulus while reducing the prey catching behavior component of approach, suggesting that the DC current applied to the pretectum increased the inhibition upon the feeding elements of the optic tectum.
Proteomic analyses of zebra finch (Taeniopygia guttata) optic tectum resulted in identification of 176 proteins. A number of identified proteins have been previously reported to exist in the avian optic tectum. The immunohistochemical localization of selected proteins showed their distribution in similar laminae of the owl (Tyto alba) and chicken (Gallus gallus) tectum. Immunohistochemical analysis of identified proteins can provide clues about cell types and circuit layout of the avian optic tectum in general. As the optic tectum of nonmammals is homologous to the superior colliculus of mammals, the analysis of the tectal and collicular proteome may provide clues about conserved cell and circuit layout, circuit function, and evolution..
Neuropathologically, the subthalamic nucleus and brainstem, especially the midbrain tectum and the superior cerebellar peduncle, show atrophy.
The torus longitudinalis (TL) is a tectum-associated structure of actinopterygian fishes. Small GABAergic cells were also observed in marginal and periventricular strata of the optic tectum. Toropetal neurons were observed in the optic tectum, in pretectal (central, intermediate, and paracommissural) nuclei, in the subvalvular nucleus, and associated with the pretectocerebellar tract. Torofugal fibers were numerous in the stratum marginale of the optic tectum. The pyramidal cells of the trout tectum were also studied by Golgi methods and local DiI labeling.
The dependence of visual orienting ability in hamsters on the axonal projections from retina to midbrain tectum provides experimenters with a good model for assessing the functional regeneration of this central nervous system axonal pathway.
Total GAD and GABA-T specific enzyme activity was highest in the hypothalamus and optic tectum and GABA-T activity was significantly higher than total GAD enzyme activity.
In Xenopus, BDNF applications in the optic tectum influence retinal ganglion cell (RGC) axon branching and promote synapse formation and stabilization.
We intraocularly injected radio-iodinated fragments of recombinant chicken PrP(c) and then examined their anterograde axonal transport from retina into optic tectum.
The frog nucleus isthmi (homolog of the mammalian parabigeminal nucleus) is a visually responsive tegmental structure that is reciprocally connected with the ipsilateral optic tectum; cells in nucleus isthmi also project to the contralateral optic tectum. Dye solutions were pressure-injected into separate sites in the superficial optic tectum. Injection of the different labels at separate, discrete locations in the optic tectum result in retrograde filling of singly labeled clusters of cells in both the ipsilateral and contralateral nucleus isthmi. The set of cells that project to the ipsilateral tectum and the set of cells that project to the contralateral tectum form a visuotopic map in a roughly vertical, transverse slab. Our results suggest that nucleus isthmi can be separated into two regions with cells in the dorsolateral portion projecting primarily to the ipsilateral optic tectum and cells in the ventrolateral nucleus isthmi projecting primarily to the contralateral optic tectum..
This study addresses the role of tectum in integrating eye, body orientation, and locomotor movements as in steering and goal-directed behavior. Electrical stimuli were applied to different areas within the optic tectum in head-restrained semi-intact lampreys (n = 40). These results show that tectum can provide integrated motor responses of eye, body orientation, and locomotion of the type that would be required in goal-directed locomotion..
EPSCs were increased by application of each of two types of GnRH (GnRH2 and GnRH3) in the trout tectum.
The morphology of retinotectal ganglion cells was investigated by retrograde transport of dextran amines applied into the optic tectum in vitro.
E-cadherin is also expressed in the optic tectum.
Our in vitro experiments with avian tectum reveal two distinct GABAergic pathways that mediate the spatiotemporal tectal interaction of retinal inputs. Simulations of an experimentally constrained model including the two pathways reproduce the observed avian tectum wide-field neuron's sensitivity to small and moving stimuli, while being insensitive to whole-field motion..
Retinal ganglion cells (RGCs) anterogradely transport neurotrophins to the midbrain tectum/superior colliculus with significant downstream effects.
In particular, canonical Wnt signaling is crucial for normal development of the dorsal midbrain, the future optic tectum. In the developing tectum, Wnt signaling is mitogenic; however, the mechanism of Wnt function is not known. Zic2a and Zic5, in turn, have essential, cooperative roles in promoting cell proliferation in the tectum, but lack obvious patterning functions.
In addition, mutant axons arborize more extensively, thus increasing the number of synaptic terminals and effectively normalizing the combined input to postsynaptic cells in the tectum. As predicted, mutants have a selective deficit in the capture of small prey objects, a behavior dependent on the tectum.
We revealed that the precise temporal interaction and order of ascending and descending inputs to the tectum decide about late responses with burst or tonic characteristics. When descending signals reached the tectum before the ascending signals, rotundal cells showed late responses that were characterized by burst activity patterns. When ascending input reached the tectum first, responses with tonic characteristic were observed.
In other cases, neurons were retrogradely labeled from the thalamus or tectum and immunocytochemically identified to determine their projection sites. Retrograde tracing experiments revealed that both parvalbumin- and calretinin-containing neurons project nonpreferentially to the thalamus or tectum.
As a result of these molecular defects, the development of the tectum and cerebellum was severely impaired in Lmx1b-/- mice. Taken together, our results indicate that Lmx1b plays an essential role in the development of the tectum and cerebellum by regulating expression of Fgf8, Wnt1 and several isthmus-related transcription factors in the MHB, and is a crucial component of a cross-regulatory network required for the induction activity of the isthmic organizer in the MHB..
As exogenous nicotine alters neuronal activity, we investigated whether it would affect the visual map created by retinal ganglion cell terminals in the frog optic tectum. Chronic exposure of the tectum to nicotine decreased the retinal area from which cells project to a given tectal site. The developing optic tectum was more sensitive to nicotine than the adult tectum and nicotine induced both map refinements and map disruptions in a concentration-dependent manner. Blockade of the N-methyl-D-aspartate (NMDA) receptor with D(-)-2-amino-5-phosphonopentanoic acid (D-APV) prevented nicotine from refining the map in the adult tectum.
The medium from cultured optic tectum of the goldfish intact or at various days after optic nerve crush, or the co-culture of this optic tectum with post-crush goldfish retinal explants plating in the absence of fetal calf serum, but in the presence of glucose, modulate its outgrowth. The a dition of taurine did not further stimulate outgrowth but rather inhibited it in the presence of optic tectum. The goldfish optic tectum, either medium or in co-culture with the retina, stimulated retinal outgrowth.
The nucleus isthmi pars parvocellularis (Ipc) is a midbrain cholinergic nucleus that shares reciprocal, topographic connections with the optic tectum (OT).
The present study was designed to explore whether a discharge of a certain type of frog retinal ganglion cell [ likely changing contrast (third) detector] can evoke NMDA response in frog tectum neurons and higher level of activity of tectal neuron network. Evoked electrical activity of the tectum was recorded by the carbon-fiber microelectrode brought into the optic fiber layer F.
At 24hpf, strong nr2e1 expression was detected in telencephalon, hypothalamus, dorsal thalamus, pretectum, midbrain tectum, and retina.
The same degree of hypertrophy is not, however, present in nBOR or the other visual nuclei measured: nucleus geniculatus lateralis, pars ventralis, and optic tectum.
Then, we analyzed the labeling in the optic tectum. 1) The MRF and the optic tectum were connected by separate axons of the tectobulbar tract. 4) The distribution of labeled neurons in the tectum shifted with the different MRF sites in a manner consistent with the tectal motor map. In addition to this high-density topographic projection, there was a low-density one spread throughout the tectum.
After tracer injections into the periventricular pretectal nucleus, labeled neurons were observed ipsilaterally in the area pretectalis pars ventralis, area pretectalis pars dorsalis, optic tectum and ventrolateral nucleus of semicircular torus, bilaterally in the ventromedial thalamic nucleus, principal sensory trigeminal nucleus and descending trigeminal nucleus, and contralaterally in the periventricular pretectal nucleus and corpus cerebelli. Anterogradely labeled terminals were present in the ipsilateral area pretectalis pars dorsalis, optic tectum and corpus cerebelli, the bilateral ventromedial thalamic nucleus, lateral valvular nucleus, oculomotor nucleus and inferior olive, and the contralateral periventricular pretectal nucleus.
Pax7 is pivotal in specifying the superior colliculus/tectum, an important centre for integration of visuomotor responses and a target for Pax6+ retinal ganglion cell axons during retinocollicular mapping. Whilst initial Pax7-specification of the mesencephalon is well-established, a role in regulating polarity within the maturing mouse superior colliculus is yet to be defined, although already detailed for the chick tectum.
We show by extracellular recording that all motion-sensitive neurons in the pigeon's pretectum respond similarly to real and illusory contours, and their preferred directions are identical for both contours in unidirectional cells, whereas these directions are changed by 90 deg for real versus illusory contours in bidirectional cells.
By the long-pec stage (48 hpf), spinal cord expression is undetectable, but strong expression is observed in the rhombencephalon, telencephalon, tectum opticum, midbrain-hindbrain boundary, in the first pharyngeal arch and in the eyes.
The efferent connections and axonal and dendritic morphologies of periventricular neurons were examined in the optic tectum of rainbow trout to classify periventricular efferent neurons in salmonids. This cell type also possessed axonal branches that terminated within the tectum.
The nucleus isthmi (NI) of the frog receives input from the ipsilateral optic tectum and projects back to both optic tecta.
The optic tectum of the barn owl contains a map of auditory space.
In most vertebrates, the major synaptic target of RGCs is the optic tectum.
The optic tectum in the lamprey midbrain, homologue of the superior colliculus in mammals, is important for eye movement control and orienting responses. There is, however, only limited information regarding the afferent input to the optic tectum except for that from the eyes. The objective of this study was to define specifically the gamma-aminobutyric acid (GABA)-ergic projections to the optic tectum in the river lamprey (Lampetra fluviatilis) and also to describe the tectal afferent input in general. The origin of afferents to the optic tectum was studied by using the neuronal tracer neurobiotin. Injection of neurobiotin into the optic tectum resulted in retrograde labelling of cell groups in all major subdivisions of the brain. The main areas shown to project to the optic tectum were the following: the caudoventral part of the medial pallium, the area of the ventral thalamus and dorsal thalamus, the nucleus of the posterior commissure, the torus semicircularis, the mesencephalic M5 nucleus of Schober, the mesencephalic reticular area, the ishtmic area, and the octavolateral nuclei. GABAergic projections to the optic tectum were identified by combining neurobiotin tracing and GABA immunohistochemistry. On the basis of these double-labelling experiments, it was shown that the optic tectum receives a GABAergic input from the caudoventral part of the medial pallium, the dorsal and ventral thalamus, the nucleus of M5, and the torus semicircularis. The afferent input to the optic tectum in the lamprey brain is similar to that described for other vertebrate species, which is of particular interest considering its position in phylogeny..
In addition to the spinal cord, cBM88 is expressed in the HH stage 45 (embryonic day 19) brain, including the telencephalon, diencephalon, mesencephalon, optic tectum and cerebellum.
Using the medium in the presence of glucose, but in the absence of fetal calf serum, we explored the effect of optic tectum medium from cultures of them coming from goldfish without crush of the optic nerve or 3, 5, 10, 14 and 20 days after crush. Retinal explants, intact or from goldfish with crush of the optic nerve 10 days prior to starting the culture, were employed in order to measure the possible effect of optic tectum media and the inter action with taurine. In other type of experiments the optic nerve was crushed 1, 2, 4, 7 and 10 days before dissection of the optic tectum, and then co-cultured with intact or 10 days post-crush retinal explants. Optic tectum media produced a time-dependent effect on outgrowth in lesioned retinas with a maximum effect around 5 days after the lesion for the corresponding optic tectum. Taurine, 4 mM, did not further affect the outgrowth in the presence of optic tectum media, but did significantly increase length of neurites either in intact or in post-lesion retinas. Co-culture of optic tectum at different days post-lesion and retinas at 10 days post-lesion increased the outgrowth around 4 days post-lesion, in a preparation resulting in mutual effects of both types of tissues. The addition of taurine in these conditions did not further increase outgrowth, rather inhibited it according to the time after lesion of optic nerve corresponding to the co-cultured optic tectum. The effect of taurine was concentration-dependent, since 0.2 mM was more effective than 2 or 4 mM in the presence of optic tectum with lesion of 2 days. These results demonstrate the time-course of the regeneration processes in the visual system of goldfish, indicating the crucial periods after crush in which the tectum could produce stimulation and later decrease or no effect on outgrowth from the retina. In addition, they are evidences of the interaction between taurine and optic tectum production of time-produced specific agents. The mechanisms underlying these effects are closely related to calcium, as it was demonstrated by the addition of extracellular or intracellular chelators to the medium, which inhibited the effects of the optic tectum and the trophic properties of taurine in this system. The inhibitor of taurine transport, guanidoethylsulfonate, also decreased the stimulatory effects of the optic tectum and of taurine, indicating an interaction of substances produced by the tectum with taurine, and an effect of taurine mediated through its entrance to the cells. Overall, retinal explants outgrowth in the absence of fetal calf serum, the interaction of agents of the optic tectum and taurine modulates outgrowth from the retina, and these effects are mediated by calcium levels and by the levels of intracellular taurine..
Tectal afferents were studied in adult lampreys of three species (Ichthyomyzon unicuspis, Lampetra fluviatilis, and Petromyzon marinus) following unilateral BDA injections into the optic tectum (OT).
Several endpoints related to histoarchitectural and acetylcholine-acetylcholinesterase (ACh-AChE) profile in the optic tectum were evaluated. Histological examination showed aggregated, disorganized and necrotic cells with irregular outlines in the different layers of optic tectum in the As-treated fish.
We build on our analysis to provide a model for the tectum-pretectum loop in the nonmammalian midbrain. It also agrees with our knowledge of the pretectotectal projection (divergent and inhibitory), and with the results of lesion studies in which the pretectal input to the tectum was removed, leading to hyperactivity of the tectal neurons and the animal. Our model also makes a testable prediction regarding the tectopretectal projection, i.e., that the presence of a larger object and a bigger discrepancy between the directions of motion for the object and the background lead to a larger error by the pretectum in estimating the background motion when the tectal input is abolished..
The chick optic tectum displays an alternating pattern of cellular and plexiform layers and at embryonic day (ED) 12 there are mainly four cellular layers: transient cell compartment 3 (TCC3), compartment "h-i-j"(C"h-i-j"), stratum griseum centrale (SGC) and subventricular zone (SvZ). In conclusion, our findings demonstrate that in the chick optic tectum at ED12, PCD is layer dependent and that acute hypoxia causes a transient increase in neuronal death in a delayed fashion, which is also layer dependent.
Our recordings in voltage-clamp mode indicate that the small fast inward currents (spikelet currents), which were several times smaller than action potential (AP) currents, are a distinguished feature of 33% of neurons from 8 to 6 layers of the frog tectum.
The midbrain roof is a retinorecipient region referred to as the optic tectum in lower vertebrates, and the superior colliculus in mammals. The retinal fibers projecting to the tectum transmit visual information to tectal retinorecipient neurons. Periventricular neurons are a subtype of these neurons that have their somata in the deepest layer of the teleostean tectum and apical dendrites ramifying at more superficial layers consisting of retinal fibers. We demonstrated that periventricular neurons play a principal role in visual information processing in the teleostean optic tectum; the effects of tectal output on behavior is discussed also in the present review..
Extensive fiber staining also occurred in the nucleus accumbens and the midbrain tectum.
Consistent with a lateralization of visual processing during communication, there were higher levels of expression of both egr-1 and c-fos in the left optic tectum after directed singing.
Electrolytic or chemical lesions of the substantia nigra, pars reticulata (SNpr), decreased the freezing and escape behaviors thresholds elicited by electrical stimulation of the IC, and increased the behavioral responses evoked by the GABAA blockade in the same sites of the mesencephalic tectum (MT) electrically stimulated. The GABAA blockade in the SNpr caused a significant increase in the defensive behavior thresholds elicited by electrical stimulation of the IC and a decrease in the mean incidence of panic-like responses induced by microinjections of bicuculline in the mesencephalic tectum (inferior colliculus).
Outside of the telencephalon at P9, we found distinct label in nucleus ovoidalis (OV), nucleus spiriformis lateralis (SpL), and nucleus subpretectalis (SP) in the midbrain, almost the entire diencephalon including nucleus dorsomedialis posterior thalami (DMP), stratum griseum et fibrosum superficiale (SGF) in optic tectum, and Purkinje cells in cerebellum.
In this study, we examine the effects of axotomy and FGF-2 treatment upon the distribution of nitric oxide synthase (NOS) and NADPH diaphorase (NADPH-d) activity in the frog retina and tectum. FGF-2 application to the optic nerve down-regulates NOS expression and activity in the retina and up-regulates it in the tectum, particularly in retinorecipient layers. Electron microscopy of the optic nerve and neurofilament immunostaining of the tectum suggests that FGF-2 treatment increases the number of regenerating retinal axons arriving at the tectum. The effects in the retina and tectum are probably indirect, that in the retina being due to retrograde signaling from RGCs to amacrine neurons, and that in the tectum being due to re-induction of NOS expression in tectal neurons by the arrival of regenerating axons.
E4 chick embryos were injected with 4F7 hybridoma cells or with the purified monoclonal antibody into the ventricular cavity of the optic tectum.
The avian optic tectum has become a reliable model system to study the basic mechanisms that underlie the computation of visual stimuli. As a prerequisite to understand a possible functional role of the monoaminergic neurotransmitters, the serotonergic, noradrenergic, and dopaminergic innervation of the optic tectum as well as the distribution of serotonin 2A receptors, the dopamine- and cAMP-regulated phosphoprotein DARPP-32 and calbindin D-28K was studied in domestic chicks by immunohistochemical techniques. Serotonergic, noradrenergic, and tyrosine hydroxylase positive axons and axon terminals were present in all layers of the optic tectum. These findings indicate that the catecholaminergic innervation of the optic tectum consists of a noradrenergic and a dopaminergic component and that the noradrenergic, serotonergic, and dopaminergic system may be potentially involved in the modulation of retinal input in the superficial layers of the optic tectum as well as in the modulation of tectal output via the deep tectal layers..
This suggests that the guiding principle behind the formation of ordered maps of nerve connections between vertebrate retina and superior colliculus, or optic tectum, is that axons carrying similar amounts of Eph receptor terminate near to one another on the target structure.
Experimentally, we found that calcium signals processed in this way were synchronous with simultaneously measured synaptic responses and could be used with reverse correlation to determine temporal filters of neurons in the zebrafish optic tectum.
Increasing BDNF levels in the optic tectum of Xenopus tadpoles significantly increases both axon arborization and synapse density per axon terminal within a few hours of treatment. Microinjection of BDNF into the optic tectum significantly increased synapse number in tectal neuron dendritic arbors within 24 hours, without significantly influencing arbor morphology.
Rat behaviors in the elevated T-maze (ETM) were evaluated following tectum microinjections of either glycine (GLY, 1, 10, 80 and 120 nmol) or d-serine (D-SER, 160 and 320 nmol), the putative endogenous agonists of GLY-B site at NMDA receptor, or the respective antagonist 7-chloro-kynurenic acid (7CK, 8 nmol).
Magnetic resonance (MR) imaging was performed, and the images were used to classify patients into three groups: those with hypertrophy of the tectum in whom isointensity appeared on T1-weighted images (Group 1); those with a tectal tumor occupying the cerebral aqueduct in whom decreased signal intensity appeared on T1-weighted images, as well as no enhancement after gadolinium administration (Group 2); and those with a tectal tumor in whom mixed signal intensity appeared on T1-weighted images and conspicuous evidence of contrast enhancement (Group 3).
It lies between the tectum and the tegmentum of the mesencephalon and is surrounded by the periaqueductal gray matter.
Five species of parasites were found: Myxobolus diaphanus (Fantham, Porter, and Richardson, 1940) (connective tissue throughout the body and head), Myxobolus funduli (Kudo, 1918) (interlamellar), Myxobolus neurophilus (Guilford, 1963) (optic tectum of the brain), Myxobolus sp.
In the mesencephalon, layers of optic tectum displayed different intensities, with the strongest reaction in layers B, D, F, 3, and 5.
Moreover, we have investigated cytoarchitectural alterations in the main components of the visual pathway-retina and optic tectum-and ethanol treatment affects both the retina and the optic tectum. With regard to the optic tectum, treatment with ethanol alters the normal pattern of tectal lamination.
Unlike in the spinal cord, Shh signaling plays a major role in patterning of dorsal structures (tectum and cerebellum).
bufo) had stimulating electrodes implanted on the surface of each optic tectum.
The developing optic tectum becomes the major area of FoxP2 expression. In the adult brain, the highest concentrations of the FoxP2 transcript can be observed in the optic tectum.
More recent reports of brainstem tumors include diverse sites such as the cervicomedullary junction, pons, midbrain, or the tectum. Today, these tumors are broadly categorized as either diffuse intrinsic gliomas, most often in the pons, or the nondiffuse brainstem tumors originating at the tectum, focally in the midbrain, dorsal and exophytic to the brainstem, or within the cervicomedullary junction.
In the optic tectum, derived from the mesencephalon, no immunolabeled neurons were observed in any of the stages analyzed. At the 30-day postfertilization, the tyrosine hydroxylase immunoreactive neuropile in the optic tectum presents two bands located within the retinorecipient strata and deeper strata, respectively. All diencephalic regions, which receive direct retinal inputs, show immunolabeled cells in the preoptic area, in the pretectum, and in the ventral thalamus from embryonic stages onwards. During the fry development, the immunolabeled neurons can be observed in the periventricular pretectum from 15-days postfertilization and in both the ventrolateral thalamic nucleus and suprachiasmatic nucleus from 30-days postfertilization.
EphAs and ephrinAs are expressed in multiple areas of the developing brain in overlapping countergradients, notably in the retina and tectum. Here they are involved in targeting retinal axons to their correct topographic position in the tectum.
FGF signaling from the midbrain-hindbrain boundary (MHB, isthmus) plays a major role both in maintenance of the MHB and induction of the tectum and cerebellum. This study highlights a positive-feedback loop between the FGFR pathway and Cnpy1 that may ensure the strength of FGF signaling in the MHB, leading to correct development of the tectum and cerebellum..
The response pattern distribution differed significantly across the optic tectum and torus semicircularis magnocellularis (chi-square test, P < 0.05). These neurones were registered mainly in the dorsal tectum and magnocellular torus semicircularis (chi-square test, P < 0.05).
In this study, we investigate oligodendrocyte lineage cells in the embryonic optic tectum of chick, which develops from the dorsal region of the neural tube and invasion of optic tract. With further development, OPCs increased and spread laterally and dorsally to populate the optic tectum. Our results reveal that OPCs dispersed bilaterally along the optic tract and then migrated to the optic tectum in the stratum opticum (SO). These data support stage-specific dorsoventral origins and distribution of oligodendrocytes populating the optic tectum..
In contrast, GnRH-R2 is expressed in many more brain areas, including the olfactory bulb, telencephalon, preoptic area, hypothalamus, thalamus, midbrain, optic tectum, cerebellum, hindbrain, and pituitary.
The optic tectum differentiates from the mesencephalic alar plate and matures into a characteristically laminated structure.
Both the forebrain and tectum of the owl contain such neurons.
The labeling of CB1 mRNA was also found in regions of the preoptic area, thalamus, midbrain tegmentum and tectum, cerebellum, and the stratum griseum of the hindbrain.
The results reveal that CR is a marker of various neuronal populations distributed throughout the brainstem, including numerous cells in the optic tectum, torus semicircularis, secondary gustatory nucleus, reticular formation, somatomotor column, gustatory lobes, octavolateral area, and inferior olive, as well as of characteristic tracts of fibers and neuropil.
A paradigm example is the topographic representation of the visual world in the optic tectum/superior colliculus. This map initially forms during neural development using activity-independent molecular cues, most notably some type of chemospecific matching between molecular gradients in the retina and corresponding gradients in the tectum/superior colliculus.
Peak expression occurred during retinal axon innervation of the tectum. Our results suggest a molecular mechanism whereby ingrowth of retinal axons into the tectum can be regulated by Sema3E/BDNF modulation without disturbing tectal axon growth out of the tectum mediated by Sema3A..
The anatomical connection of the magnocellular isthmic nucleus with the optic tectum was investigated with the axonal tracer biotinylated dextran amine. Following iontophoretic injection of this tracer into different areas of the chick optic tectum, neurones of both magno- and parvocellular isthmic nuclei were labelled together in a topographical arrangement. The labelled axons were seen to course along the shortest possible distance between the injection site and the cells of origin, i.e., the ventral part of the tectum received projections from neurones located ventrally in the isthmic nuclei, the dorsal tectum from neurones in the dorsal part, and the lateral extension of the tectum from neurones lying midway along the nuclei. After tracer injections into the magnocellular nucleus, the terminal arbours were seen to extend from the deep layers (11-12) to layer 2 of the tectum.
1) Both nuclei have reciprocal homotopic connections with the ipsilateral optic tectum.
Serotonin was localized to somata and projections of the neural networks of the mesencephalic tectum. These findings support the contention that serotonin and GABAergic neurons may act in concert in the modulation of defense reaction in the midbrain tectum. The midbrain tectum-gigantocellularis complex and midbrain tectum-nucleus raphe magnus neural pathways may provide an alternative output allowing the organization of the fear-induced anti-nociception by mesencephalic networks..
This is the first report of current source density (CSD) and intracellular analyses of non-optic processing in the frog optic tectum. Sciatic nerve stimulation was used to test for somatosensory input to the optic tectum. An early component was found in the whole area, but a late component was detected only in medial and caudal regions of the contralateral tectum. The effect of different stimulus intensity suggested that the optic tectum receives mainly the tactile sensation with fast conducting, low threshold level afferents from the sciatic nerve. The result of CSD analysis suggests that somatosensory afferents terminate on the tectal neurons with vertically expanding dendrites at the medial site of the contralateral optic tectum where the late component was found. The responses of those in the middle layers appeared to participate in avoidance behavior, based upon previous CSD analysis of the tectum using optic tract stimulation. The findings imply that the somatosensory input to the optic tectum gives a suppressive effect on avoidance behavior.
Other fibers were observed in the outer zone of the median eminence close to the portal vessels and in the septum, lamina terminalis, retrochiasmatic nucleus, deep layers of the tectum, periventricular gray and granular layer of the cerebellum.
Two model systems for addressing map formation are the retinotopic map formed by retinal projections to the superior colliculus (SC) (or its non-mammalian homolog, the optic tectum (OT)), and the eye-specific map formed by retinal projections to the lateral geniculate nucleus of the thalamus.
This immunoreactivity was also observed in extra-ependymal areas: in the internal granular layer of the olfactory bulbs in Triturus carnifex and Rana esculenta; in the diencephalic nuclei of the habenula in Podarcis sicula, in both Amphibians and in Carassius carassius; in the mesencephalic tectum in Podarcis sicula and in the two Amphibians.
Engrailed-2 (En-2), a homeodomain transcription factor, is expressed in a caudal-to-rostral gradient in the developing midbrain, where it has an instructive role in patterning the optic tectum--the target of topographic retinal input.
Although the optic tectum in non-mammals and its mammalian homolog, the superior colliculus, are involved in avoidance behaviors, whether and how tectal neurons respond to an object approaching on a collision course towards the animal remain unclear.
While Ras activation levels did not differ between light- and dark-incubated pigeons during embryonic development, directly after hatching Ras activity was significantly decreased in the stronger stimulated left tectum of light-incubated animals. These cells were TrkB-positive and developed enlarged soma sizes within the right tectum during the first week after hatching.
They are detected in the ventral and lateral regions of the diencephalon and mesencephalon, in the superficial layer of the optic tectum, in the ventral medulla oblongata, and in the ventral and lateral spinal cord.
The paradigm for such maps is the precisely ordered wiring of the output cells of the eye to their synaptic targets in the tectum of the midbrain. These signaling proteins are arrayed in complementary expression gradients along the orthogonal axes of the retina and tectum, and provide both input and recipient cells with Cartesian coordinates that specify their location. Molecular genetic studies in the mouse indicate that these coordinates are interpreted in the context of neuronal competition for termination sites in the tectum.
Neuropeptide Y (NPY) experimentally administered to the surface of the optic tectum in visually stimulated fire bellied toads diminishes local glucose utilization in the retinorecipient tectal laminae. Strong NPY-induced suppression of tectal glucose utilization was found even when visual retinal input to the tectum was boosted pharmacologically under systemic apomorphine treatment.
Wild-type fish tested in darkness, as well as blind mutants, were impaired similarly to tectum-ablated animals, suggesting that prey capture is mainly visually mediated. These two neurons extend dendrites into the ipsilateral tectum and project axons into the spinal cord. Ablating MeLc and MeLr neurons unilaterally in conjunction with the contralateral tectum also mostly abolished prey capture, but ablating them together with the ipsilateral tectum had a much smaller effect. These results suggest that MeLc and MeLr function in series with the tectum, as part of a circuit that coordinates prey capture movements..
Behavioral studies in barn owls indicate that both the optic tectum (OT) and the auditory arcopallium (AAr) mediate sound localization through the presence of neurons that respond only when sound comes from a circumscribed direction in space.
The map of the retina onto the optic tectum is a highly conserved feature of the vertebrate visual system; the mechanism by which this mapping is accomplished during development is a long-standing problem of neurobiology. The early suggestion by Roger Sperry that the map is formed through interactions between retinal ganglion cell axons and target cells within the tectum has gained significant experimental support and widespread acceptance. Furthermore, this dorsoventral retinotopic order is well established by the day after birth, long before the final target zone is discernible within the tectum.
In the embryonic chick optic tectum, versican is expressed selectively by subsets of interneurons confined to the retinorecipient laminae, in which retinal axons arborize and form synapses.
In color matching experiments with extracellular recordings from axon terminals of ganglion cells in the tectum opticum of immobilized goldfish, direction-selective ganglion cells were shown to be color-blind.
Responses of direction-selective (DS) ganglion cells (GCs) were recorded extracellularly from their axon terminals in the superficial layer of the tectum opticum (TO) of immobilized goldfish, Carassius auratus gibelio (Bloch). Coincidence in number of preferred directions with number of semicircular canals implies that DS GCs projecting to tectum are involved in some multimodal sensory integration in postural, locomotor, and oculomotor control in the three-dimensional aquatic world.
The optic tectum of vertebrates bears a set of visual neurons which can be differentiated by the expression of distinct calcium-binding proteins (CaBPs). Using immunohistochemistry, we mapped the distribution of the CaBPs calbindin (CB) and parvalbumin (PV) in the pigeon's optic tectum and examined if their differentiation is affected by retinal brain-derived neurotrophic factor (BDNF)-injections.
The tegmental ventricular zone was composed of a large caudal region located ventral to the pretectum and the midbrain tectum, and of a smaller rostral wedge-shaped region that extended dorsally between the dorsal and the ventral thalamus, in the last one, ventricular crests coursing in the zona limitans intrathalamica.
In the mesencephalon, ChAT-ir cells are observed in both the optic tectum and the tegmentum. Stained cells in the tegmentum are observed from 60 hpf onwards, while in the optic tectum they appear after hatching.
Therefore, we studied the contribution of the optic tectum and the mesencephalic reticular formation to the performance of the orienting response in goldfish, using behavioural, physiological, and anatomical tracer techniques. Electrical microstimulation of the optic tectum suggested the presence of a motor map, which is in correspondence with the overlying visual representation, as previously reported in other vertebrates.
Green fluorescent protein (GFP)-tagged synaptobrevin II was used to visualize presynaptic specializations in individual DsRed2-labeled Xenopus retinal axons arborizing in the optic tectum. To obtain a second measure of the role of BDNF during synapse stabilization, we injected recombinant BDNF in tadpoles with altered glutamate receptor transmission in the optic tectum.
In the present study, the functional neuroanatomy of nigrotectal-tectonigral pathways as well as the effects of central administration of opioid antagonists on aversive stimuli-induced responses elicited by electrical stimulation of the midbrain tectum were determined. Central microinjections of naloxonazine, a selective mu(1)-opiod receptor antagonist, in the mesencephalic tectum (MT) caused a significant increase in the escape thresholds elicited by local electrical stimulation. Labeled neurons of the midbrain tectum send inputs with varicosities to ipsi and contralateral dlSC/dlPAG and ipsilateral substantia nigra, pars reticulata and compacta, in which the anterograde and retrograde tracing from a single injection indicates that the substantia nigra has reciprocal connections with the dlSC/dlPAG featuring close axo-somatic and axo-dendritic appositions in both locations.
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