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At least 19 recordsLinked to original sources
PubMed1983

Afferent connections to the tectum mesencephali in the hagfish, Eptatretus burgeri: an HRP study.

The afferent connections to the tectum mesencephali were determined by unilateral injections of HRP in the hagfish, Eptatretus burgeri, whose eyes are degenerate and buried below the skin. Retrogradely labeled cells were observed ipsilaterally in the hypothalamus, lateral part of the pars ventralis thalami of Jansen, and nucl. reticularis mesencephali, and contralaterally in the tectum, nucl. sensorius n. V, area acoustico-lateralis, and "nucl. funiculi dorsalis". Of these non-visual afferents to the tectum, the trigeminal sensory nucleus contributed the greatest number, which ascended along the lemniscus bulbaris after crossing in the commissura ventralis. Retrogradely labeled fibers of the optic nerve could not be recognized in this study, although in a previous study the superficial layer of the tectum mesencephali received a few projections from the contralateral eye. These data are compared with the data from other animals and previous histochemical investigations.

Afferent Pathways↗
PubMed1982

The afferent connections of the tectum mesencephali in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.

The afferent connections of the tectum mesencephali were studied in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata by means of the horseradish peroxidase (HRP) technique. Following unilateral injections in the tectum, labeled neurons could be identified in all main divisions of the brain and in the cervical spinal cord. Telencephalic neurons which project to the tectum mesencephali were observed in the caudal part of the pallium. Diencephalic projections to the tectum originate from the thalamus dorsalis pars medialis, the thalamus ventralis pars lateralis, the nucleus medius infundibuli, and the pretectal area. In Scyliorhinus labeled neurons could also be found in the corpus geniculatum laterale. Mesencephalic cells of origin of tectal afferent pathways were identified in the stratum cellulare externum of the contralateral tectum, in the nucleus tegmentalis lateralis, in the ventrolateral tegmentum, and in the nucleus ruber. Rhombencephalic cells projecting to the tectum could be identified in the nucleus cerebelli (only in Scyliorhinus), the nucleus vestibularis superior, the reticular formation, the nucleus funiculi lateralis, the nucleus tractus descendens nervi trigemini, and the nucleus dorsalis and intermedius areae octavolateralis. In addition a number of small-and medium-sized cells of the reticular formation were found labeled. Diffusely scattered labeled cells could be observed in the dorsal part of the cervical spinal cord. It is concluded that the tectal afferent connections in the chondrichthyans studied in general resemble those of other vertebrates, but that some striking differences exist. In particular, tectal afferents originating from the nucleus medius infundibuli, the nucleus cerebelli, and the nucleus dorsalis and intermedius areae octavolateralis have not been reported in other vertebrates.

Afferent Pathways↗
PubMed1976

[Linear dimensions of the lamina of the tectum mesencephali during human ontogenesis].

The dynamics of the establishment of linear dimensions of the lamina of tectum mesencephali in ontogenesis was studied in 145 preparations of human brain. The investigation was performed with by the M. M. Sauliak-Savitskaja apparatus (1953). The obtained data were processed by the method of mathematical analysis. The relief of the superior colliculi was found to be formed earlier than that of the inferior colliculi. The linear dimensions of both colliculi are practically equal to those of adult men during the third year of life. No correlative relationship between the sex of the objects under study and the linear dimensions of the lamina of tectum mesencephali was found as well as between thr right and left parts of the lamina tecti. The linear dimensions of it in all age groups are very variable.

Adolescent↗
PubMed1990

Cytoarchitecture of the tectum mesencephali in salamanders: a Golgi and HRP study.

The tectum mesencephali of salamanders shows a morphology that has long been considered primitive when compared with that of frogs. The alternative hypothesis is that the salamander brain is secondarily simplified. In order to test these two hypotheses, the cytoarchitecture of the tectum and the projections of tectal neurons were studied in 11 species of salamanders. Application of the Golgi method reveals three major morphological types. Type 1 has a very wide dendritic arborization mostly confined to the deep fiber layers, and somata are always located within the most superficial part of the periventricular gray matter. Type 2 possesses a wide to medium-size dendritic arborization. In subtype 2a the somata are located in the uppermost part of the gray, and dendrites always reach the uppermost layer of retinal afferents; in subtype 2b the somata are found in deeper parts of the gray, and dendrites arborize in the deeper layers of retinal afferents; and in subtype 2c the somata are also located in deeper parts, but the wide dendritic arborization is confined to deep fiber layers. Type 3 shows the narrowest dendritic arbors that always reach the upper two tectal fiber layers. The somata are found at any depth of the gray matter. HRP experiments reveal a correlation between morphological differences and the projections of tectal neurons. Type 1- and type 2c-like cells constitute the uncrossed tecto-bulbo-spinal tract, whereas type 1- and type 2a-like cells and migrated large spindle-shaped cells (Salamandra) constitute the crossed tecto-bulbo-spinal tract. Type 3-like neurons project to thalamic, pretectal, and isthmic termination sites. The HRP experiments also demonstrate the existence of two classes of mesencephalic trigeminal cells. A comparison shows that salamanders and frogs possess very similar functional and morphological types of tectal cells. However, tectal cells of salamanders show a "juvenile" morphology, and the number of migrated cells is about 10 times higher in frogs compared to salamanders. Both phenomena are seen as the result of secondary simplification of brain structures in the context of paedomorphosis.

Animals↗
PubMed1976

The venous drainage of the tectum mesencephali. An anatomical angiographic study of the quadrigeminal veins.

The normal course and appearance of the veins draining the tectum mesencephali proper are described in detail on the basis of the anatomical radiological study. These specific veins, the quadrigeminal veins, were constantly present on autopsy study. There are two types of variations of these quadrigeminal veins. They have a close anatomical and angiographic correlation with the quadrigeminal plate proper, and also outline the posterior aspects of the quadrigeminal plate. The whole structure of the mesencephalon may be delineated by these veins in combination with the other veins of the mesencephalon. They may be of diagnostic value in the early recognition of the brain stem lesions.

Atrophy↗
PubMed1977

Cytoarchitecture of the tectum mesencephali in two types of siluroid teleosts.

The cytoarchitecture of the tectum mesencephali in the siluroid teleosts Bagrus and Ictalurus was studied by means of the Golgi method. These animals are known to have a restricted visual system and it seemed important to study whether this fact would affect the existence or the shape of the main neuron types which have been described for highly visual teleosts. It had been shown for a variety of teleosts that the retinotectal axons and terminals occupy almost exclusively the stratum opticum and the stratum fibrosum et griseum superficiale. The thickness of these strata in Bagrus and Ictalurus was found to be reduced. However, the main types of especially the vertically oriented neurons, such as the pyramidal, fusiform, large pyriform and periventricular neurons which have been described for highly visual species of teleosts, were also found in Bagrus and Ictalurus. Although their shape was somewhat distorted, these neurons, nevertheless, showed processes distributed to the same tectal layers as in highly visual teleosts and are accessible to horizontally distributed fiber systems such as marginal, telencephalotectal and commissural tectal fibers, as well as the retinotectal fibers. Nonvisual inputs appear to be considerably involved in the maintenance of the main neuron types in the siluroid tectum. For example, the pyramidal neuron's apical dendritic tree, which receives the excitatory input from the marginal fibers, is as well developed in siluroids as in highly visual teleosts.

Animals↗
PubMed2000

[The prenatal development of the tectum mesencephali and substantia nigra in man].

The development of tectum of the midbrain was studied in situ in human 6-11 wks embryos. Using electron microscopy and immunocytochemistry processes that occur in the anlage of tectum of the midbrain at early stages of formation of dopaminergic populations of cells were followed up. Growth of pallium zone due to migration of cells from ventricular zone and their differentiation is proportional to growth of the terms of embryonal development. Proliferating cells were located not only in ventricular zone. Expression of tyrosine hydroxylase was found in 6.5 wks embryos in the fraction of cells that migrated from ventricular zone and was observed only during neuroblast migration. Cells migrate along the radial glia fibres in dorsoventral direction. Microgliocytes with short processes near to vessels located in the vicinity of ventricular zone were found in 7 wks embryos for the first time. Peculiarities of morphogenetic processes participating in anlage of tectum of the midbrain and possible role of microgliocytes in development of embryonal nerve tissue are discussed.

Cell Differentiation↗
PubMed1981

[Comparative study of the neuronal and synaptic organization of the tectum mesencephali in the Caspian (Clemmys caspica Gmel.) and pond (Emys orbicularis L.) tortoises].

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 Clemmys caspica tectum differs from that of the Emys orbicularis in a greater diversity of neuronal composition; a greater variety and quantity of cells with short axons, the presence of neurons with relatively short dendrites, in a greater relative thickness of the upper and deep systems of horizontal neurons, in a small number of axo-axonal synapses in sublayer Ia, a more diverse composition of synaptic zones in sublayers IIa and IIb, the presence of axons in layers Ib and IIb with certain species specific features of degeneration, the pattern of localization of tectal ganglionic cell projections. The above mentioned specific features appear to be connected with the species differences of these tortoises.

Afferent Pathways↗
PubMed1988

[Effect of baclofen and muscimol on the evoked potentials of the tectum mesencephali in the carp in response to stimulation of the visual and somatosensory afferent inputs].

The perfusion of (+/-) 10(-5) M baclofen to the optic tectum of the carp greatly reduced evoked potential to the optic nerve stimulation and slightly inhibited evoked potential to the spinal cord stimulation. The perfusion of 10(-4) M muscimol reduced the former evoked potential as well as the latter one. The results permit supposing that tectal visual input is more sensitive to the presynaptic inhibitory influences through GABAB-receptors than the somatosensory afferent input.

Afferent Pathways↗