Tectum Opticum

(1) Neurogenesis occurred in the stratum griseum centrale of the tectum opticum from S11-12 to S16 with a peak at S12.  

Acute chlorisondamine increased the level of c-fos mRNA in the cerebellum, hippocampus, hyperstriatum accessorium, locus parolfactorius, nucleus accumbens, tectum opticum, paleostriatum augmentatum, and stratum griseum et fibrosum superficiale but had no effect on its own 24 hr after administration.  

Nevertheless, tectum opticum regions of teleost and rat express high levels of NR1 splicing variant with N1 cassette..  

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.  

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).  

Retinofugal terminals were located in 8 brain nuclei, the suprachiasmatic nucleus, nucleus pretectalis superficialis, nucleus dorsolateralis thalami, area pretectalis pars dorsalis (APd), area pretectalis pars ventralis (APv), nucleus of the posterior commissure (NPC), accessory optic nucleus, and the tectum opticum.  

After an injection of WGA-HRP into the GLv, many labelled neurons were observed in layer i of the stratum griseum et fibrosum superficiale (SGFS) in the ipsilateral tectum opticum (TO) and in the nucleus lentiformis mesencephali (LM).  

Nogo-A/RTN4-A specific antisera detect the protein in myelinated fiber tracts of the spinal cord, hindbrain, optic nerve, tectum opticum and in isolated oligodendrocytes.  

In the brain, a few positive cells were detected in the tectum opticum.  

The DMA is also connected to the periaqueductal gray, deep tectum opticum, intercollicular nucleus, ventral tegmental area, substantia nigra, locus coeruleus, dorsal lateral mesencephalic nucleus, lateral reticular formation, nucleus papillioformis, and vestibular and cranial nerve nuclei.  

Extracellular recordings from the nucleus of the basal optic root and the tectum opticum identified units that responded to changes in magnetic North.  

These recrossing projections connect the contralateral tectum opticum with the ipsilateral nucleus rotundus, which in turn projects to the ectostriatum.  

The avian isthmic nuclei are constituted by a group of structures reciprocally connected with the tectum opticum and considered to play a role in the modulation of intratectal processes.  

In the chick visual system, retinal ganglion cells (RGCs) extend their axons into the tectum opticum, but not into glial somata containing retina layers. We addressed the question whether the different glia of retina and tectum opticum differentially affect axon growth. Glial cells were purified from retina and tectum opticum by complement-mediated cytolysis of non-glial cells.  

Visual information processing within the ascending tectofugal pathway to the forebrain undergoes essential rearrangements between the mesencephalic tectum opticum and the diencephalic nucleus rotundus of birds.  

Based on their axonal projections, labeled neurons (n = 76) were divided into the following groups: TH1 neurons, with mostly ipsilateral projections to the striatum; TH2 neurons, with ipsilateral or bilateral projections to the medial amygdala and nucleus accumbens; TH3 neurons, with bilateral projections to the medial and dorsal pallium; TH4 neurons, with mostly ipsilateral projections to the striatum and ipsilateral projections to the tectum opticum, tegmentum, and rostral medulla oblongata; and TH5 neurons, with ipsilateral projections to the tegmentum, medulla oblongata, and rostral spinal cord without (TH5.1) or with (TH5.2) additional projections to the optic tectum.  

In the tectum opticum, intensely stained cells occupied the stratum fibrosum et griseum superficiale.  

These connections were to the area dorsalis pars medialis of the telencephalon, the nucleus ventromedialis (NVM) of the thalamus, the tectum opticum (TO), and the nucleus posterioris periventricularis.  

In the mesencephalon, abundant PV-immunoreactive elements were found in the tectum opticum, torus semicircularis, and tegmentum. In the tectum opticum, PV-immunoreactivity presented a laminar distribution.  

We show that the ventral tectum opticum (TO) has significantly more projections onto the nucleus rotundus (Rt) than dorsal tectal areas.  

Within the visual system of chick and rat, extension of retinal ganglion cell axons is essentially restricted to distinct layers of the retina and distinct brain regions such as the tectum opticum.  

Our results reveal a large number of different types of interneurons in the quail tectum opticum, only part of which are described in the chick or pigeon. We consider horizontal cells, bitufted cells, multiform cells and small radial cells to be GABAergic interneurons of the stratum griseum et fibrosum superficiale which seem to be more numerous than in the pigeon tectum opticum.  

Cell groups were labeled bilaterally within the dorsal region along the diencephalic-mesencephalic border (caudal pretectum and rostral tectum opticum), in tectum opticum, torus semicircularis, and tegmentum mesencephali.  

These neurons are thought to send axon collaterals to the parvocellular nucleus; their axons enter the tectum opticum.  

Up to 3.4 cm CRL the primordium of the tectum opticum exhibits still a trilaminate pattern (ventricular-intermediate- and marginal zone), but at 4.5 cm CRL, the formation of the specific tectal layers is marked by the origin of the stratum profundum and intermedium.  

In the mesencephalon, only a few immunopositive cells were observed in the tectum opticum.  

Regarding the anatomical distribution, the areas with the highest densities of alpha2-adrenoceptors in the pigeon brain included the hyperstriatum, nuclei septalis, tectum opticum and some brainstem nuclei.  

A detailed analysis of the binding capacity for [ 125I]CLO was performed for parts of several functional systems: hypothalamic structures (nucleus inferior hypothalami, nucleus magnocellularis preopticus, nucleus paraventricularis), limbic system (habenula, nucleus septalis lateralis, nucleus striae terminalis), circumventricular organs (organum pineale, organum subfornicale, plexus choroidei ventriculi tertii and ventriculi lateralis), visual system (hyperstriatum accessorium, nucleus reticularis superior, tectum opticum), and associative cortex (hyperstriatum ventrale).  

By employing in vitro tract-tracing techniques, we have, in the present investigation, demonstrated that this complex receives input from the tectum opticum.  

Several ontogenetic studies have been devoted to the structural organization of the developing tectum opticum. The present work is a dynamic description of the tectum opticum lamination based on sections coinciding with the developmental gradient.  

This paper describes the development of the serotonergic innervation of the chick tectum opticum as revealed by an immunohistochemical methodology.  

In comparison with the lamprey, the hagfish has subcutaneous eyes under an unpigmented patch of skin, 4 paired tentacles at the rostral tip of the head, one semicircular canal on each side, a regressed ventricular system, a "primordium hippocampi" of unresolved homology in the telencephalon, no pineal body, fusion of the habenula of both sides, a tectum opticum with unclear laminations, no macroscopical cerebellum, and optic decussation within the hypothalamus.  

The distribution of nitric oxide synthase-containing neurons in certain areas, e.g., the tectum opticum and the spinal cord, indicates an evolutionarily conserved pattern.  

After PhA-L injection into the tectum opticum of chickens, column-like labelled terminal arborizations were found in tectum and also labelled neurons of Ipc and Imc in the corresponding sections.  

It is hypothesized that the likely location for the interaction between the visual system and the lateral line is the tectum opticum..  

Target neurons were present in ventral periventricular brain regions including tuberculum olfactorium, nucleus accumbens, cortex piriformis, primordium hippocampi, nucleus striae terminalis, dorsal ventricular ridge, amygdala, nucleus infundibularis and tectum opticum. With the exception of the nucleus infundibularis and the tectum opticum, target neurons can be continuously followed from the ventrolateral nucleus accumbens throughout the nucleus striae terminalis into the amygdala.  

Neuronal transcriptional activity is found mostly in the glomerular layer of the olfactory bulb, in the striatum, nucleus accumbens septi, lateral and medial septal nuclei of the telencephalon, in the habenulae and various nuclei of the diencephalon, in the tectum opticum (particularly in the stratum griseum centrale), in the molecular layer of the cerebellum and in various nuclei of the rhombencephalon.  

The tectum opticum was virtually devoid of stain except for two light bands in the stratum griseum et fibrosum superficiale.  

Immunoreactive fibers were seen in these locations and in the lamina terminalis, lateral forebrain bundle, supraoptic nucleus, median eminence, neurohypophysis, tectum opticum, torus semicircularis and deep mesencephalic nucleus.  

Moreover, the fish retinal ganglion cells re-express upon injury a set of growth-associated cell surface molecules and equip the regenerating axons throughout their path and up into their target, the tectum opticum with these molecules.  

Circumventricular organs, such as the plexus choroidei, organum subfornicale, organum paraventriculare and the corpus pineale, were endowed with alpha 2-specific binding sites, as were the cell layers of the tectum opticum.  

This was also found in homogenates of the telencephalon and diencephalon, but not in homogenates of the tectum opticum.  

The highest densities of binding sites were observed in the hyperstriatum dorsale, archistriatum, auditory field L of neostriatum, area corticoidea dorsolateralis and temporo-parieto-occipitalis, area parahippocampalis, tectum opticum, nucleus dorsomedialis anterior thalami, and in the periventricular area of the hypothalamus. A striking mismatch occurred in the hyperstriatum ventrale, neostriatum, tectum opticum (high to moderate density of binding sites but only few immunoreactive profiles), and in the tuberculum olfactorium, median eminence, and spinal cord (lower density of binding sites but abundant immunoreactive profiles).  

The retinal afferents of the tectum opticum and the n. Injections into the tectum opticum revealed topographically related areas of high density labelling in the contralateral retina.  

In the brain, [ 125I]GAL binding was found to occur in all parts of the dorsal and ventral telencephalon, in the anterior, tuberal and posterior hypothalamus, in the thalamus and in the tectum opticum, in the inferior lobe and in the ventral medulla oblongata.  

High or very high densities of binding sites were found in the hyperstriatum, tuberculum olfactorium, hypothalamic nuclei, tectum opticum and some medullary nuclei.  

During the subsequent period of axon outgrowth, the antigen becomes restricted to ganglion cell axons but disappears during the innervation of the tectum opticum, suggesting a tectal inhibition of antigen expression in retinal axons.  

The projection of the nucleus isthmi pars parvocellularis (Ipc) onto the tectum opticum was studied with tectal injections of three different fluorescent tracers and wheat germ-agglutinated horseradish peroxidase (WGA-HRP) in 21 pigeons.  

In all species the tectum opticum decreases in relative size during growth, whereas the corpus cerebelli increases.  

NPY-fibres occurred in the medial and deep layers of the tectum opticum, in the marginal areas of the tegmentum and the torus semicircularis, and as a lateral fibre tract through the medulla oblongata, connecting to the rostral parts of the spinal cord..  

SRIF-positive fibres could be found in the lateral and dorsal telencephalon, below most of the diencephalic nuclei, in the pituitary, the tectum opticum, the torus semicircularis, and in the lateral medulla oblongata..  

In the brain [ 3H]AVP binding was found to occur in the pars lateralis and the pars ventralis of the ventral telencephalon, in the pars centralis of the dorsal telencephalon, in the hypothalamic region (especially in the nucleus preopticus, in the tuberal hypothalamus and around the posterior recess), in the tectum opticum and in the noncellular layer of the corpus cerebelli.  

Using a special in vitro assay, we tested whether retinal ganglion cell axons in an adult vertebrate, the goldfish (which can regenerate a retinotopic projection after optic nerve section), recognize position-specific differences in cell surface membranes of their target, the tectum opticum.  

In the chicken brain apamin binds preferentially to the tectum opticum and nuclei isthmi.  

Some FMRFi fibres traversed through the commissura anterior while others occurred close to the hypothalamic nuclei, in the medial layers of the tectum opticum, in the brain stem, in the vagal lobe and in the ventral medulla oblongata.  

SRIFi mesencephalic fibres were only found in the rostral tectum opticum.  

FMRFi fibres also appeared in the deep layers of the tectum opticum, in the torus semicircularis, in the medial and lateral medulla and below the pacemaker nucleus.  

Also a high activity was detected in the mesencephalic tectum opticum and the dorsolateral part of the torus semicircularis.  

tectum opticum, nucleus rotundus of thalamus and ectostriatum of telencephalon--of 13-day chick embryos. Being phylogenetically more ancient structures, tectum opticum and nucleus rotundus reveal differentiation earlier than ectostriatum which is phylogenetically younger..  

vagus, central acustic area, Crista cerebellaris, Bulbus olfactorius, Eminentia granularis, Stratum opticum (of the optic tectum), Torus longitudinalis, Nucleus habenularis, Valvula cerebelli, Corpus cerebelli, Telencephalon, tectum opticum, Diencephalon, Torus semicircularis, mesencephalic tegmentum.  

In the mesencephalon, FMRF-amide-containing fibres appeared in the dorsal tegmentum, in the torus semicircularis and in the deep layers of the tectum opticum.  

The excitatory projection probably leads from the eye to the contralateral tectum opticum, then recrosses back to the nucleus rotundus of the ipsilateral side where it reaches the ectostriatum.  

Tectal connections were studied in two urodele species following horseradish peroxidase injections into the tectum opticum. In both species retrogradely labelled cells were observed: ipsilaterally in the corpus striatum, lateral amygdala, ventral and dorsal thalamus and nucleus of DARKSCHEWITSCH--bilaterally in the pretectal nucleus, dorsal tegmentum and nucleus reticularis medius--contralaterally in the tectum opticum and area octavo lateralis. Rostral efferent projections of the tectum opticum terminated in the ipsilateral pretectal area and the ipsilateral dorsal and ventral thalamus ipsilaterally coursing to the contralateral tectum via the commissura postoptica. Comparison of the results of a series of tectal horseradish peroxidase injections differing in depth, tangential extension and location, indicated that tectal afferents from the telencephalon, the contralateral tectum opticum and the medulla were sparse and widely branching. Projections of the telencephalon and all diencephalic nuclei terminated deep in the rostral tectum opticum. Projections of the medulla terminated preferentially deep in the caudal tectum opticum. The isthmo-tectal projection innervated the whole tectum opticum on the ipsilateral side and was highly topographic. On the contralateral side the caudal part of the tectum opticum was not innervated. The isthmo-tectal fibers terminated superficially in the tectum opticum on both sides of the brain.  

Afferent projections to the tectum opticum of the clawed toad Xenopus laevis were studied by injections of horseradish peroxidase (HRP) into the tectum.  

A similar activity was found in the most rostral part of the telencephalon and the dorsal parts of the mesencephalon, i.e., the tectum opticum and torus semicircularis (2.3 pmol). Since both the torus semicircularis and the tectum opticum display a high aromatase activity, it is suggested that also these structures are involved in reproductive processes..  

ChAT-IR neurons were located in the brainstem cranial nerve motor nuclei, in the brainstem reticular formation, in the nucleus lateralis valvulae and an adjacent subnucleus "a," in the nucleus isthmi, and in the stratum griseum periventriculare of the tectum opticum.  

Remarkable are the reduction values of the tectum opticum (21.8%), the tractus opticus (37.3%), the hyperstriatum ventrale (26.1%), the archistriatum (22.4%), and the hippocampus (31%).  

Mathematical description of the operations in the tectum opticum include (i) spatial summation of retinal output (mainly of class-2 and class-3 retina ganglion cells), and (ii) direct or indirect lateral inhibition between tectal cells.  

Many fluorescent fibres were found in the middle layers of the tectum opticum, in the torus semicircularis, in the lobus inferior and in the medulla oblongata.  

Visual system: The tectum opticum (TO) exhibited strong or moderate AChE and SDH activity in areas receiving retinal projections, i.e.  

ventrolateralis thalami, caudal dorsal tegmentum and the tectum opticum.  

The formation of a blood-brain barrier to horseradish peroxidase was microscopically and ultrastructurally investigated in the tectum opticum of the chick during development of the intraneural blood vessel network from the 6th incubation day to hatching, and in adult specimens.  

With the aid of the method of Karnovsky and Roots (1964) which was adapted to the semi-permeable membrane technique and a scanning recording method the relative activity of soluble and membrane bound AChE as well as the influence of fixation with 5% paraformaldehyde on the enzyme activity was investigated quantitative-histochemically in the tectum opticum of the rudd. Approximately 38% of the AChE activity which can be demonstrated in the whole tectum opticum on native untreated cryostat sections are puffer-soluble and only 68% are detectable after fixation.  

Labelled cells were found (i) ipsilaterally in the visual Wulst, neostriatum pars intermedia and caudalis, the posterior part of the hyperstriatum ventrale, the dorsal part of the archistriatum, paleostriatum augmentatum, dorsomedial part of the thalamus, and (ii) bilaterally in the hippocampus, area septalis, ventromedial part of the thalamus and the stratum album centrale of the tectum opticum.  

It was found to have a large cerebellum, large medulla oblongata and a tendency to macrosmy, but a small telencephalon and tectum opticum (tendency to micropty).  

The initial formation and further development of the intraneural blood vessel network in the tectum opticum of the chick from the 4th to the 14th incubation day have been analyzed and some quantitative data morphometrically recorded.  

These amines are fairly specifically taken up by catecholaminergic and serotoninergic neurons, respectively, which are located in structures like the catecholaminergic preoptic recess organ; the mixed catecholaminergic-serotoninergic paraventricular organ/nucleus infundibularis-complex and nucleus reticularis mesencephali; the telencephalic septal and striatal areas and the tectum opticum, which contain many catecholaminergic axon terminals; the habenular area, which contains serotoninergic axon terminals.  

In order to clarify physiological mechanisms underlying colour-specific visually guided behaviour, we measured spectral sensitivities of On-fibres projecting to the thalamus and class 2 and 3 fibres passing to tectum opticum.  

Pineal efferents also innervate the habenular nuclei and dorsal hypothalamus, while retinal efferents innervate rostral hypothalamus, ventrolateral thalamus, and tectum opticum.  

In the mesencephalon, the dorsal periventricular tegmentum and the central gray receive only small numbers of serotoninergic axons, while torus semicircularis and the visual layers of tectum opticum are profusely innervated.  

tectum opticum and nuclei isthmi are labelled in chicken brain.  

Electrical and visual information converge in the tectum opticum, which harbors a multimodal representation of sensory space..  

The tectum opticum is then reviewed as regards its afferent connections from retina, telencephalon, diencephalon, mesencephalon and brainstem, with details on distribution of terminals, cell types contacted and synaptic structure.  

Concerning the efferent connections, the nMD projects to the ipsilateral tectum opticum and valvula cerebelli..  

Changes in the activity of 13 enzymes are described in the process of cytodifferentiation of the nerve cells of spinal ganglion, the motor neurons of spinal cord and large nerve cells of the III layer of tectum opticum in 7, 10 and 21 day old chick embryos.  

The space and time organization of neuronal activity was studied in the frog tectum opticum under the action of different visual stimuli.  

The changes in the glial and nerve cells in dissociated cultures of the hen embryo tectum opticum have been studied. Particular attention has been paid to the changes of another type leading to the plane reconstruction of the structure of tectum opticum on the surface of collagen. Plane reconstruction of the structure of tectum opticum may be considered as a manifestation of histogenesis in the conditions of tissue culture..  

The retinal projections of the latter range from weakly labeled terminal fields restricted to the thalamus to heavily labeled fields covering the entire tectum opticum..  

The relative importance of acetylcholine, dopamine, endogenous opiates, gamma-aminobutyric acid (GABA), glutamate, glycine, noradrenaline, and serotonin as transmitters in the pigeon visual system was estimated by measuring the activity of choline acetyltransferase (ChAT), glutamic acid decarboxylase (GAD), and aromatic amino acid decarboxylase (AAD) as well as the binding of dihydroalprenolol, etorphine, kainic acid, muscimol, serotonin, spiroperidol, strychnine, and quinuclidinyl benzilate (QNB) in the tectum opticum, nucleus rotundus, ectostriatum, dorsolateral thalamus, and hyperstriatum (Wulst).  

Projections were found in the suprachiasmatic nucleus, ventral thalamus, dorsal thalamus, the pretectal complex, and the tectum opticum.  

By means of doublewave cytophotometry of the histological sections and smears performed with the device mtsfv-1 (lomo) it has been demonstrated that differentiation of some neurons of the spinal ganglia and the spinal cord is accompanied with hyperreplication of DNA amount exceeding the diploid contents, while the large neurons in layer III of the tectum opticum remain diploid.  

The morpho-functional characteristics of the optic nerve and tectum opticum were studied electronmicroscopically and electrophysiologically after unilateral enucleation in 4 Chelonia species.  

Several methods (light optic, electron microscope and electrophysiological) were used to study the optic nerve and the tectum opticum of water turtles (two species) and of land tortoises (two species).  

In the tectum opticum of Hydromantes italicus neurons were recorded extracellularly which responded selectively to moving visual stimuli.  

Furthermore, a moderate number of SRIF-positive neurons were seen in the tectum opticum, nucleus tractus solitarii, and spinal cord.  

The neuronal and synaptic organization of tectum opticum was studied in two species of tortoises (Clemmys caspica Gmel, and Emys orbicularis L.) by means of Nissl, Golgi and electron microscopical methods.  

The afferent and efferent connections of the tectum opticum in the carp (Cyprinus carpio L.) were studied with the HRP method.  

The neurons related to movement direction--velocity are equally distributed in the tectum opticum layers with representation in the latters of sensory, associative and effector structures which suggests equal participation of these structures in estimation of parameters of the visual stimulus movement. In the tectum opticum neurons, the inhibition restricting the excitation, seems to facilitate responses of separate groups of neurons related to analysis of direction--velocity parameters..  

By the method of anterograde degeneration, distribution of projections of functionally definite AI and AIV zones of the cat auditory cortex have been studied in the posterior calculi of the tectum opticum. Peculiarities of the degenerative rates, specific for short- and long-axonal systems of the fibres and possible mechanisms for the influence of the auditory cortex on the neurons of the posterior colliculi of the tectum opticum are discussed..  

Color coding 'on-off' cells project to the tectum opticum.  

Labelled neurons were observed bilaterally in part of the visual Wulst (Hyperstriatum accessorium and Hyperstriatum intercalatum superior) following unilateral injection of the enzyme horseradish peroxidase into the tectum opticum of pigeons. Horseradish peroxidase positive fibres running through the Tractus septomensencephalicus and ending bilaterally in the tectum opticum were found following injection of the enzyme into Hyperstriatum accessorium.  

Analysis and comparison of the parameters of the components of the evoked potentials in the telencephalon and tectum opticum indicate the existence of two visual subsystems (the retino-thalamo-telencephalic and the retino-tecto-thalamo-telencephalic ones) in the dogfish..  

The tectum opticum displays as many as four dense layers of retinofugal fibers and terminals in the rostral part and, in addition, a more densely stained strip of neuropil running from rostral to caudal over the tectum. They supply the medial and the lateral parts of the neuropoil of Bellonci, the uncinate field, and reach the tectum opticum via the medial optic tract.  

Evoked responses in the dogfish tectum opticum were studied during electrical stimulation of the spinal cord, its dorsal roots and ramus ophthalmicus of the facial nerve. Evoked responses could be detected mainly on the contralateral side of the tectum opticum either as slow positive (spinal cord stimulation) or negative-positive (facial stimulation) waves which were preceeded by one or two fast, probably, presynaptic deflections and followed by a very slow low-amplitude negative wave. These findings evidence that the tectum opticum performs a double function: a primary projecting and an integrative centre..  

Somatostatin fibers were found among the classical neurosecretory fibers of the supraoptico-paraventricular system (tract, median eminence, neural lobe), near to and within the epiphysis, in the septum, in the vicinity of the tectum opticum and the cerebellum, and in the tegmentum..  

In Rana, somatostatin neurons are also present in (as well as in the vicinity of) the subfornical organ, in the thalamus, the tectum opticum, the interpeduncular nucleus and the caudal end of the roof of the calamus scriptorius.  

Compared to cells examined in the in vivo conditions, neurons of the nucleus cochlearis laminaris, grown in tissue culture conditions, do not make plate-forming structures; dendrites of the neurons of III layer of tectum opticum do not develop.  

38 cells with large elongated bodies have one ventral dendrite which originates directly from the body and produces several ventro-lateral processes intersecting the efferent bundle in the tectum opticum.  

The tectum opticum is of secondary simplicity and does not exhibit a clearly recognizable stratification..  

The proliferation and directions of cell differentiation in tectum opticum were studied in the young frogs under the conditions of normal development and upon brain trauma by means of 3H-thymidine autoradiography.  

The stratification, neuronal structure and synaptic organization of tectum opticum have been studied in two species of tortoises (Testudo graeca and Testudo horsfieldi, Gray) by means of Golgi methods and electron microscopy.  

Stratigenesis is influenced by "guiding structures" (fibrillar plate in the tectum opticum), by the elongations of ependymal cells and by the similarly oriented vascular-connectives..  

In the 5 species the retinal ganglion cells project to the contralateral hypothalamus (nucleus suprachiasmaticus), thalamus (nucleus geniculatus lateralis pars ventralis, nucleus geniculatus lateralis pars dorsalis), pretectum (nuclei lentiformis mesencephali, geniculatus pretectalis, postero-dorsalis griseus tectalis), tectum opticum (layer 2 to layer 6 of the stratum griseum et fibrosum superficiale) and tegmentum mesencephali (nucleus opticus tegmenti).  

The construction of "chains of excitation" based on latent periods of responses of silent neurons of the frog tectum opticum to repetitive visual stimuli revealed significant differences in the course of excitation of the neuronal structures during the action of simple (flashes) and complex (movement of a visual object) stimuli.  

A layer-by-layer study of ultrastructural synaptic organization of mesencephalic optic centre (tectum opticum) of T. In the external layers of the tectum opticum where the terminals of optic afferents are disposed, a considerable morphological variety of nerve terminals is revealed which are distinguished not only by their ultrastructural parameters but also by the character of organization in synaptic complexes at different levels of the cortical plates of the investigated centre..  

However, some retinofugal fibers reach the posterolateral part of the ipsilateral tectum opticum.  

In the tectum opticum of the adult neotenic A.  

Slow and sharp-pointed theta waves appear on EEG tracings of the telencephale, and especially of the tectum opticum (fig.  

A study of ultrastructural changes in the neuronal terminals of optic fibres at the level of tectum opticum (TO) in different periods after unilateral enucleation has revealed the process of degeneration in the optic system of Testudo horsfieldii as well as in Emysorbicularis L.  

The evoked potentials in the carp tectum opticum in response to stimulation of the afferent pathway for chemical nonolfactory reception, the facial nerve, are positive deflections of 5-25 ms latency which do not reverse during microelectrode submersion. The dependence of the response evoked by facial nerve stimulation in the tectum opticum on the impulsation from the medulla is proved by the difference in latency and by disappearance of the response in the tectum while persisting in the medulla after disconnection of both areas of the brain.  

The optic nerve and mesencephalic optic centre (tectum opticum, TO) of the tortoise, Testudo horsfieldi, Gray, in the norm and after the enucleation have been studies using Golgi's method, electron microscopy and the electrophysiological technique.  

Optic tract axons cross completely in the optic chiasma and are distributed to the hypothalamus (nucleus opticus hypothalamicus pars magnocellularis), the thalamo-pretectal region (11 distinct primary optic centers), and the tectum opticum (stratum fibrosum et griseum superficiale, stratum griseum centrale and stratum album centrale).  

A comparison of these results with those on tectum opticum by authors brings up the question of the exact nature of retino-thalamic connections and of their morphogenetic role.  

2 EEG's records from the cerebellum, tectum opticum, telencephalon and olfactory bulb of the eel are compared with other fish previously studied by other authors. 3 Averaged evoked visual potentials from the telencephalon, tectum opticum and cerebellum are presented.  

Following the intraocular injection of a mixture of [ 3H]proline and [ 3H]fucose, label transported in the rapid phase of axonal flow was found only on controlateral side to the injection in the nuceli, supra-opticus, ovalis, geniculatus lateralis pars dorsalis and pars ventralis, geniculatus pretectalis, lentiformis mesencephali, griseus tectalis, opticus tegmenti and in the superficial layers of the tectum opticum (layers 1 to 6).  

The architectonics of primary visual centres (nuclei ectomamillaris, geniculatus lateralis, lateralis anterior superficialis synencephali, griseus tectalis and the tectum opticum superficiale) and of the isthmo-opticus nucleus were compared with the architectonics of the same centres in anophthalms. Optic fibres coming from limited ocular formation in microphthalms can reach the ectomamillaris nucleus in most cases and sustain existence; they may reach the tectum opticum without playing a qualitatively discernable morphogenetic role and act upon the isthmo-opticus nucleus.  

During metamorphosis, opitcal morphogenetic influences would come from the tectum opticum to the dorsal thalamus.  

The unit activity studies in the fish (Serranus scriba) tectum opticum showed that, after surgical isolation of a retinal segment, there was a slowing of spontaneous unit activity in the partially deafferented portion of the projection area, whereas the firing rate of responses to illumination of the remaining retina increased.  

In the matrical zones of the non-operated tectum opticum too, the number of DNA synthesizing cells is increased..  

After a damage of tectum opticum, the heterogeneity of the receptive areas and the specific responses to movement in cells of n.  

The changes in the receptive fields of neurons in the deep layers of the tectum opticum were studied as induced by labyrinthine and sound stimulation. The results obtained and data from the literature allow one to suggest an active role of tectum opticum in the transformation of signals from the retina depending on the kind of information from other sensory systems..  

In contrast, the weak nonspecific reactions, in the neighbouring brain structures (dorsal telencephalon, tectum opticum and paraphysis), stay constant.  

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