Superficial Layers Of Superior Colliculus Research Articles

Effects of eye enucleation on NADPH-diaphorase positive neurons in the superficial layers of the rat superior colliculus

Dihydronicotinamide adenine-dinucleotide phosphate diaphorase (NADPH-d) positive neurons in the superficial layers of superior colliculus (SC) were studied in the adult rat after eye enucleation at postnatal day 5 (P5). Bilaterally, NADPH-d histochemistry revealed either weakly or intensely labeled neurons. In the SC contralateral to the enucleation, the volume of superficial layers decreased significantly, whereas the total number of NADPH-d positive neurons was only slightly reduced, thus resulting in an increased cell density. Bilaterally, the number of NADPH-d positive neurons was around 20% of Nissl-stained neurons. While the number of neurons which were weakly positive for NADPH-d was unchanged contralateral to the enucleation (thus resulting in a significant increase in their percentage on the overall NADPH-d population), the number of intensely labeled neurons decreased by 30%. Intensely labeled neurons were classified with respect to cell size and dendritic distribution. Some (126) were reconstructed and analyzed on the computer, in order to quantitate morphological differences in dendritic distribution in the denervated and control SC. The percent of neurons which could be assigned to some classes (marginal, stellate, narrow field vertical and wide field vertical) was reduced contralateral to the enucleation. In addition, vertically-oriented neurons (narrow field vertical, wide field vertical and pyriform) showed a significant decrease in soma size, dendritic length and number of branch points. And finally, the overall orientation of dendrites on narrow and wide field vertical neurons was more dispersed, when compared to the control colliculus. Thus, P5 eye enucleation affects the adult morphology of NADPH-d positive neurons in the superficial layers of the rat SC, resulting in increased cell density, changed relative number of cells in each morphological type, and altered soma size, dendritic length and orientation in specific neurons.

Excitatory amino acid receptors participate in synaptic transmission of visual responses in the superficial layers of the cat superior colliculus.

The contribution of NMDA and non-NMDA receptors to visual synaptic transmission in the superficial layers of the superior colliculus of the cat has been studied using extracellular recording and iontophoretic techniques. Neuronal responses to natural visual stimulation and the ejection of NMDA and AMPA were observed in the absence and presence of the antagonists CNQX, CPP and AP5. CNQX routinely reduced the responses to visual stimulation at ejection currents which selectively blocked the responses to AMPA but not those to NMDA. Agonist selective ejection currents of CPP and AP5 also reduced visual responses of most SC neurons, but there was a substantial majority whose visual responses were resistant to these antagonists. Neurons with CPP/AP5 resistant visual responses were more commonly found 750-1000 microns from the dorsal surface of the SC. The data indicate that, while non-NMDA receptors are heavily involved in visual synaptic transmission in the superficial SC, the involvement of NMDA receptors varies with recording depth.

Corticostriatal and corticotectal projections from visual cortical areas 17, 18 and 18a in the pigmented rat.

Regions of the visual cortex and the deep layers of the superior colliculus (SC) have been suggested to be functionally linked via an 'indirect' pathway through the basal ganglia. The present report demonstrates projections from the striate (area 17) and extrastriate (areas 18 and 18a) visual cortex in Long-Evans hooded rats to the striatum (ST) and SC with anterograde (biocytin) and retrograde (WGA-HRP and fluorescent dyes) tracers. Biocytin injections into each cortical area produced markedly different patterns of labeling in ST and SC. Injections into area 17 resulted in a dense labeling in the superficial layers of SC, with little labeling present in the deep layers of SC or ST. In contrast, injections into area 18a, which produced marked labeling in the deep layers of SC with moderate in the superficial layers, resulted in dense labeling in the caudal two-thirds of the dorsal region of ST; injections into area 18 produced numerous terminals mainly in the deep layers of SC and in the rostral two-thirds of the dorsal aspect of ST. WGA-HRP injections into ST resulted in numerous retrogradely labeled pyramidal neurons in areas 18 and 18a, but only a few labeled neurons were observed in area 17. Corticostriatal neurons in extrastriate visual cortex were distributed predominantly in layer V, with smaller numbers in layers II and III, whereas corticotectal neurons were located only in layer V of both the striate and extrastriate visual cortex. Although corticostriatal and corticotectal neurons were intermingled in layer V, no double-labeled neurons were observed following injections of different fluorescent dyes into ST and SC. It appears, therefore, that: 1) the major source of visual input to both ST and the deep layers of SC in the rat arises not from the primary visual cortex but from extrastriate visual areas; and that 2) the projections from the extrastriate visual area to ST and SC originate from different populations of corticofugal neurons.

The cholinergic input to the superficial layers of the superior colliculus: an ultrastructural immunocytochemical study in the ferret

The cholinergic innervation of the superficial layers of the ferret's superior colliculus was investigated with a combination of electron microscopy and choline acetyltransferase immunohistochemistry. Cholinergic boutons in the superficial layers of the superior colliculus possess spherical vesicles and make predominantly asymmetrical synapses onto the profiles of small dendrites, as do the terminals of cortical and retinal axons. In most areas of the brain studied so far, cholinergic terminals tend to form synapses of the symmetrical variety.

Interactions between natural and electrically evoked saccades

Electrical microstimulation was applied at brain sites (thalamic internal medullary lamina complex and superficial layers of superior colliculus) of alert, trained monkeys to evoke fixed-vector saccades. When the stimulation was timed to occur during or after an eye movement, the evoked saccade had a modified trajectory, compensating for, at least, the last portion of the ongoing eye movement. The hypothesis proposed to explain this compensatory effect (Schlag-Rey et al. 1989) is that the electrical stimulation produces a saccade by generating a signal, equivalent to a retinal error, specifying the saccade goal at a fixed location with respect to some eye position (called reference eye position). If the eyes are moving at the time of stimulation, the reference eye position lies somewhere along the trajectory of the ongoing movement. In the present study, we tried to determine this reference eye position, and deduce from it the instant at which the goal was specified. A significant timing difference was observed between thalamic and collicular stimulations. The goal appeared to be referred to an eye position existing at stimulation onset in superior colliculus (SC), and 35-65 ms before stimulation onset in central thalamus. In the latter case, the results suggest that the evoked saccade was aimed at the spatial location that the brain computed by summing a retinal error signal (evoked by stimulation) with the eye position at the time such a signal would have been elicited by a real target. In contrast, the collicular results suggest that the evoked saccade was directed to the retinal location specified by the retinal error signal. The findings imply that if the eyes are not steady while the target position is calculated, signals conveyed in the superficial layers of SC (in contrast to the thalamus) cannot direct the eyes correctly to a visual target.

Enkephalin-like immunoreactive neurons appear in superficial layers of superior colliculus after enucleation

Enkephalin-like immunoreactive neurons appear in superficial layers of superior colliculus after enucleation

The distribution of beta-1- and beta-2-adrenergic receptors of normal and reeler mouse brain: An in vitro autoradiographic study

The densities of beta-1 and beta-2-adrenergic receptors in normal and reeler mice brains were compared using in vitro autoradiography. For the most part, the regional distribution of the beta-receptor subtypes in mouse brain was similar to that of rat [Rainbow et al. (1984) Proc. natn. Acad. Sci. U.S.A. 81, 1585–1589]. The most striking differences in beta-adrenergic receptor localization between the mouse and rat brain were in the superficial layer of the superior colliculus and the bed nucleus of stria terminalis. The superficial layer of the mouse superior colliculus had high densities of beta-1 receptors and much lower densities of beta-2 receptors, while the superficial layer of the rat superior colliculus had moderately high densities of beta-2 and lower densities of beta-1 receptors. The mouse bed nucleus of stria terminalis had greater densities of beta-1 receptors than beta-2 receptors. This structure in the rat possessed roughly equivalent densities of beta-1 and beta-2 receptors. In general, the distributional pattern of beta-1 and beta-2 receptors in the reeler mouse brain matched that of the normal mouse brain. In regions which neuronal malpositioning had been reported, such as the cerebral cortex, hippocampus, and cerebellum, beta-1 and beta-2 receptors were still present in proportions similar to normal mice; however, the pattern of beta-receptors within each of these regions was altered. The beta-receptor subtypes in these structures showed an abnormal radial distribution similar to the abnormal radial positioning of neurons in these structures.

Postnatal development of the ipsilateral retinocollicular projection and the effects of unilateral enucleation in the golden hamster.

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to study the normal development of the ipsilateral retinocollicular projection in golden hamsters, and to examine the effect of enucleation of the other eye at birth. In neonatal animals there were retinal fibers and sparsely distributed granular labeling in the superficial layers of the ipsilateral superior colliculus over its entire areal extent. Differences in the uncrossed projections of normal and enucleated animals first became clear at day 5. In normal animals, retinal fibers withdrew from the superficial layers of the superior colliculus, and the projection became concentrated in the stratum opticum, where denser clumps of label in the rostral part of the superior colliculus were first seen at day 5. In enucleated animals, the retinal projection persisted in the most superficial layers, and the density of labeling was higher than in normals. The very sensitive WGA-HRP technique showed retinal fibers extending to the caudal pole of the superior colliculus at all ages: even in normal animals more than 2 weeks of age some fibers reached as far as the inferior colliculus. When the shrunken size of the superior colliculus in the enucleated animals was taken into account, the total areal distribution of the ipsilateral projection was similar in normal animals and enucleates. The major difference between the two groups was in the higher density of ipsilateral labeling, especially in the caudal part of the superior colliculus, and in its more superficial laminar distribution in the enucleated animals.

Optokinetic visual detection in the rat visual centres. A [14C]-2-deoxy-D-glucose study.

Following forty-five min of binocular optokinetic stimulation (OKS) the autoradiographic maps of [14C]-2-deoxy-D-glucose (2DG) assumption of Long-Evans brain reveal clearly different patterns of optical density within visual centres. The most superficial layers of superior colliculus (SC) and a pretectal area including the nucleus of the optic tract (NOT) appear symmetrically, strongly darker than other visual structures such as lateral geniculate nucleus (LGN) and visual cortex (VC). Whereas the lack of metabolic increase at LGN and VC levels entirely confirms the non-involvement of the geniculo-cortical path in mediating the optomotor response following OKS in Rodents, it is postulated that the symmetrical increase of 2DG uptake even upon unidirectional OKS found even at pretectal level may represent a commissural transfer of visual information between homologous pretectal areas like the nuclei of the optic tract.

Retinotectal connectivities within the superficial layers of the cat's superior colliculus

Intracellular staining of neurons located in the superficial layers of the superior colliculus (SC) of the cat was carried out through an intracellular recording micropipette with which responses to stimulation of the optic chiasm (OX) and the optic tract (OT) ipsilateral to the explored SC were recorded. A total of 16 SC neurons were successfully stained. Retinotectal fibers which were synaptically connected to those morphologically identified neurons were classified as either W- or Y-fibers according to their conduction velocities. The conduction velocity of W-fibers ranged from 4.0 to 13.1 m/sec and that of Y-fibers from 35.5 to 42.0 m/sec. Neurons located in the upper part of the stratum griseum superficiale (SGS) were found to be monosynaptically or polysynaptically supplied by W-fibers, while some neurons located in the lower part of SGS were monosynaptically connected to Y-fibers and others monosynaptically or polysynaptically to W-fibers. Morphologically SC neurons were classified as horizontal (1), narrow-field vertical (3), wide-field vertical type II (6) and type III cells (3) with 3 unidentified neurons. W-fibers were connected to the horizontal, narrow-field vertical and wide-field vertical type-II cells while Y-fibers contacted only wide-field vertical type-III cells.

Innervation by W-type retinal ganglion cells of superior colliculus neurons projecting to pulvinar nuclei in cats

Neurons of the cat superior colliculus (SC) sending their axons to the pulvinar nuclei were identified electrophysiologically as the ones responding antidromically to electrical stimulation of the pulvinar nuclei. They were located in the superficial layers of SC and found to be innervated by axons of W-type ganglion cells of the retina.

Altered retinal projections in brushtailed possum, Trichosurus vulpecula, following removal of one eye.

AbstractOne eye was removed from ten brushtailed prossums aged 18 to 102 days. The possums were kept until they reached 8‐13 months of age and the remaining eye was injected with 3H leucine to show the retinal projections. Retinal projections were also mapped in five normal possums.In the one‐eyed possums we found an altered retinal projection to the medial terminal nucleus (MTN), the dorsal lateral geniculate nucleus (LGNd) and the superior colliculus (SC). In normal possums the MTN receives an contralateral retinal projection. The LGNd has a laminar structure, there being three contralateral laminae and five ipsilateral laminae. In normal possums there is a contralateral retinal input to the superficial layers of the SC and in the front half of the SC there is an ipsilateral input top the deeper layers.In the one‐eyed possums we observed a bilateral retinal projection to the MTN. This was best developed in possums which had lost one eye at an early age (about 25 days). In the one‐eyed possums there was an extensive retinal projection to the superficial layers of the ipsilateral SC in addition to the normal retinal projection to the contralateral SC. In animals which had lost one eye at about 25 days the retinal fibers covered about three‐quarters of the ipsilateral SC, whereas in animals which had been operated at about 80 days the retinal fibers occupied only part of the front half of the ipsilateral SC. Animals which had lost one eye at about 80 days showed some growth of retinal axons into the deafferented layers of the LGNd and these layers were thinner than the layers with a normal nerve input. In animals which had lost one eye at 25 to 50 days retinal fibers form the remaining eye covered the whole of the LGNd on both sides.The possum which lost one eye at age 102 days, when its eyes were open, had retinal pathways which were nearly normal.

Estimation of lipoproteins using capillary blood.

The superior colliculus (SC) receives direct input from the retina and integrates it with information about sound, touch, and state of the animal that is relayed from other parts of the brain to initiate specific behavioral outcomes. The superficial SC layers (sSC) contain cells that respond to visual stimuli, whereas the deep SC layers (dSC) contain cells that also respond to auditory and somatosensory stimuli. Here, we used a large-scale silicon probe recording system to examine the visual response properties of SC cells of head-fixed and alert male mice. We found cells with diverse response properties including: (1) orientation/direction-selective (OS/DS) cells with a firing rate that is suppressed by drifting sinusoidal gratings (negative OS/DS cells); (2) suppressed-by-contrast cells; (3) cells with complex-like spatial summation nonlinearity; and (4) cells with Y-like spatial summation nonlinearity. We also found specific response properties that are enriched in different depths of the SC. The sSC is enriched with cells with small RFs, high evoked firing rates (FRs), and sustained temporal responses, whereas the dSC is enriched with the negative OS/DS cells and with cells with large RFs, low evoked FRs, and transient temporal responses. Locomotion modulates the activity of the SC cells both additively and multiplicatively and changes the preferred spatial frequency of some SC cells. These results provide the first description of the negative OS/DS cells and demonstrate that the SC segregates cells with different response properties and that the behavioral state of a mouse affects SC activity. <b>SIGNIFICANCE STATEMENT</b> The superior colliculus (SC) receives visual input from the retina in its superficial layers (sSC) and induces eye/head-orientating movements and innate defensive responses in its deeper layers (dSC). Despite their importance, very little is known about the visual response properties of dSC neurons. Using high-density electrode recordings and novel model-based analysis, we found several novel visual response properties of the SC cells, including encoding of a cell9s preferred orientation or direction by suppression of the firing rate. The sSC and the dSC are enriched with cells with different visual response properties. Locomotion modulates the cells in the SC. These findings contribute to our understanding of how the SC processes visual inputs, a critical step in comprehending visually guided behaviors.

The ascending projections of the superior colliculus in the rhesus monkey (Macaca mulatta).

We studied and compared the ipsilateral efferents of the superficial and deep layers of the superior colliculus of the rhesus monkey. Using a stereotaxic method, microelectrodes were inserted through the contralateral hemisphere in order to make electrolytic lesions of the superior colliculus. Large lesions involved all layers of the superior colliculus, while smaller lesions involved either the superficial or the deep layers of the superior colliculus. Following various survival times, the brains were prepared with the Fink-Heimer technique ('67). Following lesions of the superficial layers of the superior colliculus, definite degenerated axonal endings were found in the dorsal and ventral lateral geniculate nuclei, inferior pulvinar, centrointermediate nucleus, magnocellular dorsomedial nucleus, anterior pretectal nucleus and pretectal region. Sparse degenerated axonal endings were found in the limitans nucleus, lateral posterior nucleus and some intralaminar nuclei following lesions of the superficial layers in the rostral portion of the superior colliculus. Following lesions of the deep layers of the superior colliculus, degenerated axonal endings were found in the central gray, magnocellular medial geniculate nucleus, suprageniculate nucleus, limitans nucleus, lateral posterior nucleus, medial and oral pulvinar, nucleus of the accessory optic tract, zona incerta, subdivisions of the ventral lateral and ventral posterior lateral nuclei, ventral posterior inferior nucleus, denosocellular and multiform dorsomedial nuclei, all intralaminar nuclei, inferior colliculus, parabigeminal nucleus, olivary nucleus, reunions nucleus, Forel's Field H and an undefined midbrain nucleus. In general the projections were topographically organized in that the caudal portion of the superior colliculus projected to the rostral portions of thalamic nuclei and the rostral portion of the superior colliculus projected to the caudal portions of thalamic nuclei. All the degeneration patterns seen after lesions of the superficial and deep layers were accounted for by large lesions which involved all layers of the superior colliculus. It is concluded that the superficial and deep layers of the rehesus monkey superior colliculus have different ascending projections. The finding, are related to the organization of visual and multimodal thalamocortical systems in primates and other mammals.

The upper layers of the superior colliculus of the rat: a Golgi study.

AbstractA number of questions deriving from a previous electron microscopic study of the superficial layers of the rat superior colliculus pointed out the need for a comprehensive study of the cell types of the superior colliculus and their detailed morphology. In the present Golgi study the cells of the superficial layers of the superior colliculus were found to be of five major types; marginal cells, horizontal cells, narrow field vertical cells, wide field vertical cells, and stellate cells. Some of these categories were further subdivided. Each cell type has a distinctive set of dendritic field characteristics, a regional distribution, and consistent axon characteristics. The horizontal cells were found to have a preference in the orientation of their dendrites along the vertical and horizontal axes of the visual field projection upon the superior colliculus. It is argued that the horizontal cells are the presynaptic elements in the majority of the dendrodendritic synapses.

Early lesions of superior colliculus: factors affecting the formation of abnormal retinal projections.

The longest fibers of the main optic tract reach the upper layers of the superior colliculus (SC) of the midbrain. Destruction of this terminal area in newborn hamsters caused striking anomalies in the distribution of the optic tract, studied after the animals were fully grown. Evidence of termination was found in areas normally devoid of such termination: in the remaining tissue of the colliculus and in the thalamic nucleus lateralis posterior (LP). An abnormally high density of termination was found in part of the ventral nucleus of the lateral geniculate body. These thalamic regions normally receive connections from SC. Retinofugal axons could also be induced to terminate in the medial geniculate body of the thalamus if the brachium of the inferior colliculus, which normally carries auditory information to this cell group, was ablated at birth together with the lesion of SC.If the superficial layers of SC were destroyed unilaterally at birth, axons from the eye contralateral to the lesion not only reached the area of early damage, but also formed an abnormal decussation, crossing the tectal midline to terminate in the medial zone of the undamaged colliculus. Axons from the two eyes <i>competed for terminal space </i>in this intact colliculus, for they terminated in a nonoverlapping manner, and if the axons from the eye contralateral to the remaining SC were eliminated at birth, the anomalously recrossing axons increased in quantity and spread across the entire SC on the 'wrong' side of the midbrain. Hamsters with such an anomaly showed wrong-direction turning in response to visual stimuli in a large part of the visual field.The less the amount of termination found in SC, the greater was the amount in LP. Thus, optic tract axons showed a <i>'pruning effect' </i>which may be attributed to a tendency for axons to conserve the quantity of their terminal arborizations. The pruning effect alone may account for the hypertrophy we found, after early SC lesions, of the dorsal terminal nucleus of the accessory optic tract. The tendency to invade vacated terminal space may be sufficient to account for an effect of early unilateral eye removal, namely, a pronounced increase in an ipsilateral retinal projection to the medial terminal nucleus of the accessory optic tract.The greatest alterations in axonal projections were seen when the two effects, competition and pruning, seemed to act jointly. Additional factors may have to be considered in fully explaining such neuroplasticity; some of these have been suggested.