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Results for “Superior Colliculi”

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At least 19 recordsLinked to original sources
PubMed1986

The nature of the visual discrimination impairment after neonatal or adult ablation of superior colliculi in rats.

The superior colliculi were removed in rats at either one or five days of age or in adulthood. Seven months later they were tested on four successively presented two-choice intensity discriminations. The intensity difference between the discriminanda was reduced across the four problems to encourage choice by comparison. The purpose was to establish whether impoverished scanning is a feature of rats with collicular lesions and whether the age at which the lesion is incurred is important. The number of door-push and approach errors made in reaching criterion were used as measures of performance and the number of head-scans during acquisition was counted. The results provide no evidence that either one- or five-day operated rats exhibit sparing or recovery of the ability to scan discriminanda since all operated animals were impaired. Furthermore, novel retinal projections, present in one-day operated animals, fail to mediate such sparing. Finally, the results did not demonstrate a selective increase in approach errors following collicular lesions and were therefore inconsistent with the view that the impairment is one of visually-guided locomotion. It is concluded that visual discrimination learning is impaired following collicular lesions in circumstances where scanning of discriminanda is required for efficient performance.

Age Factors↗
PubMed1991

Scrapie inoculation of mice: light and electron microscopy of the superior colliculi.

Ultrastructural examination of the superior colliculi of mice intraocularly inoculated with the ME7 strain of scrapie showed vacuolation early in the course of infection. Brains were examined between 85-260 days after monocular inoculation with scrapie. The mean incubation period for the development of clinical disease was 302 days. Vacuolation was seen initially in the contralateral superior colliculus and subsequently in the ipsilateral colliculus. In coded trials light microscopical vacuolation was seen from 218 days but ultrastructural examination showed that sparse vacuoles were inconsistently present in either or both of the ipsilateral and contralateral colliculi from 85 days; frequent vacuoles were seen from 190 days. Scrapie-induced vacuoles were differentiated from vacuoles present in control tissue by the presence of loculation or by a limiting double membrane which showed protrusion or proliferation of the innermost lamella. Vacuolation was seen in neuronal perikarya, myelinated fibres, dendrites and axonal presynaptic terminals. Vacuoles of myelinated fibres were observed within myelin and possibly also in the inner tongue of oligodendroglial cytoplasm. Whorled membrane configurations were also seen. Tubulovesicular particles, 40 nm in diameter, were recognised in two scrapie-infected mice. It is suggested that some scrapie vacuoles arise as a result of incorporation of abnormal membrane into organelles, possibly mitochondria, in neuronal perikarya and neurites and probably also within oligodendroglial cytoplasm and myelin.

Animals↗
PubMedDate not supplied

[Facial motor responses to microstimulation of the superior colliculi in the white mouse].

Facial motor responses to microstimulation of different zones of the superior colliculi have been investigated in the albino mice craniotomized under thiopental anaesthesia. Local responses of the mystacial vibrissae, upper lip and eyelids were initiated by microstimulation of the rostral parts of the inner layers of the colliculus superior (high-frequency volleys of 5-7 pulses with a current limit of 35 microA). Sequential changes in the pattern of facial responses were observed within microelectrode traces indicating vertical orientation of facial motor representations in the superior colliculus. Some differences in the localization and pattern of facial responses in the right and left superior colliculi were revealed: 1) vibrissae and lip representations in the right superior colliculus occupy more extensive zone (vertical distribution from 300 to 2,300 microns) as compared to those in the left one (700-2,000 microns); 2) microstimulations of the right superior colliculus produce both uni- and bilateral vibrissal motor responses, whereas stimulation of the left superior colliculus evokes only unilateral responses. The duration of the latent period of the vibrissal and lip motor responses to stimulation of the right superior colliculus varied from 10 to 26 ms (16.1 +/- 2.4 ms; n = 199), to stimulation of the left one-from 10 to 18 ms (mean 14.9 +/- 1.8 ms; n = 55). It is suggested that polysynaptic motor responses to microstimulation of the superior colliculi are realized via the reticular and other premotor nuclei of the brain stem which have direct inputs from the superior colliculus and direct projections to the facial motor nucleus.

Animals↗
PubMed1986

Simultaneous unitary neuronal activity in both superior colliculi and its relation to eye movements in the cat.

The analysis of simultaneous unitary neuronal activity related to eye movement and recorded in both superior colliculi has shown a mirror-functioning image. Increase of the frequency discharge in a collicular unit, was associated with a decrease of the frequency discharge in the contralateral superior colliculus unit. This unitary neuronal reciprocal behaviour was observed each time a horizontal or oblique eye movement was produced. It is possible that this reciprocal functioning between neurones in both superior colliculi could exert an important influence on oculomotor brainstem structures. These results give a better idea of the role played by both superior colliculi in the control of conjugate eye movements.

Animals↗
PubMed1984

Effects of damage to superior colliculi and pre-tectum on movement discrimination in rhesus monkeys.

Eight rhesus monkeys (Macaca mulatta) were trained to detect an instantaneous lateral displacement of a small spot of light. The smallest movement for 79% correct performance was then determined. Severing the splenium of the corpus callosum, which has to be done to reveal the superior colliculi, had no effect on the movement threshold. But when the superior colliculi were damaged in addition, there was an initial substantial impairment in the detection of movement and a smaller but permanent elevation in the threshold. Only if the rostral superior colliculi and pretectum were spared, was there no change in threshold, and there was evidence that the pretectal rather than collicular damage may be more important in relation to movement discrimination. Tests with human observers performing the same task showed that the threshold can be elevated by imprecise fixation and accomodation, suggesting that the consequences of mid-brain damage on movement detection may be wholly or in large part attributed to oculomotor disorders.

Accommodation, Ocular↗
PubMed1987

Retinal ganglion cell survival and neurite regeneration requirements: the change from Müller cell dependence to superior colliculi dependence during development.

A study has been made of the effects of Müller conditioned media or neonatal superior collicular extracts on the survival in dissociate culture of retinal ganglion cells (RGC) from differently aged rats. Embryonic and neonatal RGC were identified either by retrograde horseradish peroxidase (HRP) or Thy-1 antibody labelling techniques. Müller conditioned media supported the survival, over 24 h in culture, of 85% of the RGC plated from 17-day embryos (E17); in contrast, superior collicular extract only maintained 45% of these RGC. With further development there was a decline in the survival enhancing effects of the Müller conditioned media and an increase in the survival due to superior collicular extracts: by postnatal day 12 (P12), the survival of RGC had declined to 20% in the Müller media, but had increased to over 90% in the colliculus extract. This transition in the dependence of RGC from Müller cells to superior colliculi was examined with homogeneous cultures of RGC, obtained using cell sorting techniques. RGC in these cultures showed the same transition in dependence from Müller cells to superior colliculi, indicating that the survival-enhancing effects were not mediated by the other intrinsic cells of the retina. The results suggest that the survival of RGC is at first dependent on the intrinsic glia of the retina and only later, as development proceeds, on the targets of the RGC in the superior colliculus. The normal RGC death period in the rat extends from near birth to about 6 days postnatal. The question then arises as to the timing of trophic support from Müller glia and from neurones in the tectum in relation to the duration of the normal RGC death period. This has been examined in the present work.

Animals↗
PubMedDate not supplied

[Function of the superior colliculi of the corpora quadrigemina during creation of a local focus of increased excitability in the mesencephalic reticular formation and sensomotor cortex].

In chronic experiments on waking rabbits, the foci of heightened excitability in the sensorimotor cortex and mesencephalic reticular formation affected in a similar way the background neuronal activity in the superior colliculi and that evoked by light stimuli. The effect was manifested in elimination of inhibitory pauses in the neuronal response to light stimulus and in a general increase of discharge frequency. Similarity of the cortical and reticular influences is due to their possible mediation by the same collicular interneurones participating in inhibitory pauses formation in the process of backward inhibition. Increased neuronal activity in the superior colliculi under the action of local foci in the sensorimotor cortex and mesencephalic reticular formation correlated with appearance of forelimb motor reaction to isolated light stimulus testifying to a formation of a functional connection between the visual and motor analyzers. Possible role of the superior colliculi in this process and their participation in the formation of a visually controlled reaction is discussed.

Animals↗
PubMed1982

The role of frontal eye-fields and superior colliculi in visual search and non-visual search in rhesus monkeys.

Rhesus monkeys were tested on a visual search task in which they had to find and retrieve a peanut from a display of visually similar but inedible objects. The speed with which they did so was measured. Animals in which the superior colliculi or frontal eye-fields had been removed took longer to find the peanut than two operated control groups. Animals with collicular lesions had longer latencies than those with frontal eye-fields removed. These two groups were also tested on a second task, non-visual search, in which a peanut was concealed in each of 25 identical holes. The animals' task was to retrieve all 25 peanuts as quickly as possible. The group with frontal eye-fields removed made significantly more return errors, i.e. returning to a hole already sampled, than the control group but, in contrast to the first task, the animals with collicular lesions were not impaired. The results are related to the physiological properties of frontal eye-fields and superior colliculi and to the effects of frontal cortical brain damage in man. It is suggested that the frontal eye-fields are concerned with internally organized, i.e. voluntary, eye scanning whereas the superior colliculi are concerned with the detection and location of targets which are then fixated involuntarily.

Animals↗
PubMedDate not supplied

Inhibition of labyrinthine nystagmus by visual fixation: effects of ablation of visual cortex and superior colliculi.

A study was conducted to destroy two specific areas of the cat's visual system in order to determine if these lesions would affect the visual inhibition of calorically-induced vestibular nystagmus. The occipital visual cortex was removed in eight cats and the superior colliculi were removed bilaterally in nine cats. Postoperative vestibular testing revealed no significant change in the electronystagmography tracings and response to visual fixation. These findings suggest that, in cats, the visual inhibition of labyrinthine nystagmus is not dependent upon the integrity of the visual cortex or superior colliculi. The hypothesis is brought forward that the visual inhibition of the vestibular nystagmus is merely a reflex of the brain stem to light stimulus, mediated via the cerebellum.

Animals↗
PubMedDate not supplied

The influence of activation of the superior colliculi on convulsive activity during picrotoxin kindling.

It has been demonstrated in experiments in rats in which kindling was induced by repeated subconvulsive doses of picrotoxin (1.0 mg/kg) that the bilateral microinjection of picrotoxin, bicuculline, and penicillin into the deep layers of the superior colliculi of the corpora quadrigemina leads to the appearance of a generator of pathologically intensified excitation. An increase in the latent period of the initial convulsive manifestations, the suppression of clonic-tonic convulsive attacks, as well as the prevention of generalized epileptic activity induced by the systemic utilization of picrotoxin were observed under the conditions of the appearance of a generator of pathologically intensified excitation. An inference was drawn regarding the role of the superior colliculi in the mechanisms of the suppression of convulsive activity and regarding their inclusion in the antiepileptic system.

Animals↗
PubMedDate not supplied

Abnormalities in grooming behavior and tryptophan hydroxylase activity in the superior colliculi in cats with pontile and frontal neocortical lesions.

Cats with pontile or frontal neocortical lesions display a dissociation of the appetitive and consummatory components of grooming behavior when their body surface is tactually stimulated, an abnormal behavior that waxes and wanes with the seasons of the year. Tryptophan hydroxylase activity is significantly decreased in the superior colliculi of cats with pontile lesions and of cats with frontal neocortical lesions. The results suggest that the change in tryptophan hydroxylase activity is mediated neuronally and is a transneuronal effect on the serotonergic input to the superior colliculi. Pharmacological manipulations of the serotonergic system in normal cats failed to induce the abnormal behavior, indicating that other factors are involved in the genesis of the abnormal behavior.

Animals↗
PubMed1980

The effect of ablation of frontal eye-fields and superior colliculi on visual stability and movement discrimination in rhesus monkeys.

The neurological basis of the maintenance of a stable visual scene by means of a corollary discharge mechanism was investigated. Monkeys were trained to detect and respond to sudden rapid movement of a small spot of light in an otherwise totally dark environment. There was no evidence that after removal of the frontal eye-fields, superior colliculi, or caudal superior temporal sulcus the animals confused real movement of the target with retinal image movement caused by changing the position of head and eyes. The result was confirmed by an examination of the ipsiversive turning that follows unilateral frontal eye-field or collicular ablation. If the turning is a compensation for apparent movement of the visual world when the eyes are moved it should not be present in total darkness. It was still present. The thresholds for the smallest detectable instantaneous displacement of the target were also measured. The threshold was impaired by bilateral superior colliculus lesions but not by removal of the frontal eye-fields or cortex of the caudal part of the superior temporal sulcus.

Animals↗
PubMed1994

Single retinal ganglion cells projecting bilaterally to the lateral geniculate nuclei or superior colliculi by way of axon collaterals in the cat.

In most mammals with frontalized eyes, retinal ganglion cells in the nasal or temporal retina send their axons to the contralateral or ipsilateral half, respectively, of the brain. Previous studies in the cat, however, have indicated a retinal region of "nasotemporal overlap" from which arise the retinal projections to both the contralateral and ipsilateral halves of the brain. The present study thus examined in the cat whether any retinal ganglion cells give rise to bifurcating axons that innervate both halves of the brain. By employing fluorescent retrograde double labeling, we investigated whether or not single retinal ganglion cells project bilaterally to the lateral geniculate nuclei or superior colliculi by way of axon collaterals. After Fast Blue was injected into the lateral geniculate nucleus on one side and Diamidino Yellow was injected contralaterally into the lateral geniculate nucleus, 100-200 ganglion cells in each retina were double labeled with both tracers. These double-labeled cells were distributed primarily in the temporal retina, including the region around the vertical meridian and, additionally, in the nasal retina. About 60-80% of the double-labeled cells had large cell bodies (more than 25 microns in diameter), and the others had medium-sized ones (15-25 microns in diameter). The pattern of distribution of double-labeled cells, which was observed after the combined injection into both superior colliculi, was similar to that seen after the combined injection into both lateral geniculate nuclei; more than 90% of double-labeled cells, however, were large.(ABSTRACT TRUNCATED AT 250 WORDS)

Amidines↗
PubMed1998

Spatiotemporal patterns of ontogenetic expression of parvalbumin in the superior colliculi of rats and rabbits.

We have examined the development of parvalbumin immunoreactivity in the superior colliculi (SC) of the perinatal and mature rats and rabbits. In mature animals, parvalbumin-expressing cells (PECs) and neuropil in the retinorecipient layers were distributed in a continuous single band extending throughout the entire extent of the colliculus, whereas those in the intermediate layers formed distinct, radially oriented patches. Parvalbumin was expressed for the first time on postconceptional day 34 (PCD 34, postnatal day 12) and PCD 42 (postnatal day 11) in the SC of rat and rabbit, respectively. During ensuing development, both the thickness of the parvalbumin-expressing band in the retinorecipient layers and the numbers of PECs in this band gradually increased, reaching adultlike values by PCD 44 and PCD 50 in the rat and rabbit, respectively. In the rat, monocular eye enucleations on PCD 23 resulted in approximately 55% reduction in the number of PECs in the retinorecipient layers of the contralateral colliculi examined on PCD 44 or PCD 50. Unilateral ablations of the entire visual cortex on PCD 23 (before the first corticotectal fibers from visual cortices reach the SC) or on PCD 28 (when about half of the corticotectal fibers have reached colliculus) resulted in, respectively, approximately 55% and approximately 25% relative reduction in the number of PECs in the retinorecipient layers of the ipsilateral colliculi examined on PCD 44 or PCD 50. We conclude that the ontogenetic expression of parvalbumin in most of PECs in the retinorecipient collicular layers is induced by the activity of the contralateral retinotectal and/or the activity of the ipsilateral corticotectal afferents.

Age Factors↗
PubMedDate not supplied

[Directional selectivity of neurons of the superior colliculi of the lamina quadrigemina in visually deprived rabbits].

The reactivity of neurones in the superior colliculi to the movement of the optic stimulus was studied in monocularly and binocularly deprived rabbits (MD and BD). Deprivation was effected by suturing the eyelids before the eyes opened. The neurones were classified into three groups by the degree of their directional selectivity (absolute, relative and zero). The effect of a prolonged (ten weeks or more) early MD consisted in the absence of collicular units with absolute selectivity. Proceeding from the existence of such units in the MD type rabbits in the third week of their life, it is suggested that prolongation of the MD time leads to their functional reduction. As the recorded characteristics of unit responses do not change in BD rabbits, it is assumed that the MD effect is not linked to limiting the function of vision and is just a consequence of a prolonged asymmetry of optic stimulation. The deprivation effect at the collicular level in different vertebrates is discussed.

Animals↗
PubMed1990

Evidence that superior colliculi are involved in the control of amygdala-kindled seizures.

The effects of bilateral high radiofrequency lesions of superior colliculus (SC) were studied on amygdala kindling. The results demonstrate that a selective destruction of the SC only slightly facilitated the development of kindling. However, the most remarkable effect was the increase of afterdischarge and motor seizure duration observed when SC-lesioned animals reached the generalized seizures. These data confirm that the superior colliculi participate in controlling the generalization of kindled seizures.

Amygdala↗
PubMed1975

Single-cell responses associated with rhythmic slow-wave potentials in rat superior colliculi.

The present study was designed to investigate the features of rhythmic slow-wave potentials in the superior colliculi of rats and to study the relationship between these potentials and the activity of single colliculi neurons. In contrast to studies in other portions of the visual system, rhythmic slow-wave potentials in the colliculi fell within a single limited range of frequencies from 9 to 26 cycl/sec. Single-cell recordings revealed that numerous collicular neurons were also responding rhythmically, with discharge frequencies generally coinciding with those established for collicular slow-wave potentials. In some animals slow-wave and single-cell potentials were recorded simultaneously through adjacent electrodes, and in all instances the frequency of discharge of single neurons coincided with the frequency of oscillation of the slow-wave potentials. These data suggest that rhythmic postsynaptic potentials in individual collicular neurons may be the mechanism by which rhythmic slow-wave potentials are generated.

Animals↗
PubMedDate not supplied

[Interaction of recovery cycles of evoked potentials in the cerebral cortex of the cat in response to stimulation of the superior colliculi and pulvinar].

Similar character of recovery cycles of evoked potentials in the visual cortex to electric stimulation of the superior colliculi (SC) and pulvinar was found in chronic experiments on alert cats irrespective of stimuli presentation order. In the association cortex preceding SC stimulation facilitated the response to test stimulation of pulvinar almost at all delays between the stimuli. If the pulvinar stimulation was applied as a conditioned stimulus, then the response to SC stimulation under intervals of 20-200 ms was depressed. The obtained data point to equivalence of the inputs from SC and pulvinar to the visual cortex, to different informational value of inputs from SC to the association and visual cortex, and to mutual function dependence of the inputs from SC and pulvinar to the association cortex.

Animals↗