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Results for “Superior Colliculi”

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PubMed1992

Single retinal ganglion cells sending axon collaterals to the bilateral superior colliculi: a fluorescent retrograde double-labeling study in the Japanese monkey (Macaca fuscata).

Single retinal ganglion cells projecting bilaterally to the superior colliculi (SC) by way of axon collaterals were revealed in the Japanese monkey (Macaca fuscata). After injecting Fast blue into the SC on one side and Diamidino yellow into the SC on the opposite side, some retinal ganglion cells were double-labeled with both tracers. Most of them were large cells (more than 25 microns in diameter), and were localized in a narrow strip around the vertical meridian of the retina on each side. This retinal area roughly corresponds to the reported strip of nasotemporal overlap, where both crossed and uncrossed retinofugal projections arise.

Amidines↗
PubMed1995

A retrograde double-labeling study of uni- and bilaterally projecting retinal ganglion cells that project to the superior colliculi after unilateral eye removal at birth in the albino rat.

By injecting Fluoro-Gold and Evans-Blue into the right and left superior colliculi of the normal adult albino rats, bilaterally projecting retinal ganglion cells were labeled in the ventrotemporal crescent accounting for 37.9% of all the labeled cells, whereas in 0- and 5-day unilaterally enucleated rats these were found in the lower half of the retina accounting for 64.8% and 80.6%, respectively. Furthermore, they tended to have larger somata (type I cells).

Animals↗
PubMed1993

Bilateral projections of single retinal ganglion cells to the lateral geniculate nuclei and superior colliculi in the albino rat.

Employing fluorescent retrograde double/triple labeling, we investigated bilateral projections of single retinal ganglion cells to the lateral geniculate nuclei (LGN) and superior colliculi (SC) in the albino rat. After separate injections of Fast Blue (FB) and Diamidino Yellow (DY), respectively, into the right and left LGN, a large number of retrogradely-labeled cells were distributed all over the retina contralateral to each injection. Ipsilaterally projecting ganglion cells, which were labeled with one tracer injected into the LGN, were found predominantly in the lower-temporal retinal region; approximately 56% (120-140 cells per retina) of them were further labeled with the other tracer injected into the contralateral LGN. The vast majority of these double-labeled cells were of large type (more than 20 microns in diameter). Similar findings were obtained after separate injections of FB and DY, respectively, into the right and left SC, or respectively, into the right SC and left LGN. After separate injections of FB, DY and rhodamine-B-isothiocyanate, respectively, into the bilateral LGN and unilateral SC, or respectively, into the unilateral LGN and bilateral SC, a number of cells triple-labeled with all tracers were localized in the lower-temporal retinal region; most of them were of large type. Thus, the bilateral projections from the lower-temporal retinal region representing binocular vision in the rat are indicated to be achieved not only by separate populations of ganglion cells each exclusively serving one side of the brain, but also by axon collaterals from single ganglion cells; the ganglion cells projecting bilaterally to the LGN or/and SC are primarily of large type corresponding probably to the Y cell in the cat retina.

Amidines↗
PubMed1998

Unilateral enucleation of adult rats does not effect the synapse-to-neuron ratio within the stratum griseum superficiale of the superior colliculi.

Ninety-day-old hooded male rats were anaesthetised with an intraperitoneal injection of a mixture of xylazine and ketamine and had their right eyes removed. Groups of non-enucleated control and enucleated rats were killed at either 150 or 390 days of age by intracardiac perfusion with fixatives. Stereological methods were used to estimate the synapse-to-neuron ratios within the stratum griseum superficiale (SGS) layers of both the ipsi- and contra-lateral superior colliculi. The enucleation had no significant effects on this ratio irrespective of the side or age of the brains examined. This experiment shows that a constant synapse-to-neuron ratio may be maintained within the SGS layer of the rat superior colliculus despite the inevitable loss of synaptic contacts due to the anterograde transneuronal degeneration initiated by the enucleation.

Animals↗
PubMed1996

Discrimination learning of grating orientation in visually deprived cats and the role of the superior colliculi.

Four cats deprived binocularly of pattern vision (BD cats), 4 control cats reared also in the laboratory (C cats), and 4 normal wild cats (N cats) were trained to discriminate gratings of progressively smaller difference in orientation. Differences in learning were found only in fine orientation discriminations. The stage of 15 degrees orientation difference was learned by 4 N cats, 2 C cats, and 1 BD cat. After the discrimination training, the superior colliculi were ablated in 2 C cats and 2 BD cats. In contrast to C cats, the BD cats were very deficient and failed to relearn even a horizontal versus vertical orientation discrimination. Thus, an abnormal neural strategy used by BD cats diminished their deficit in grating discrimination learning.

Animals↗
PubMed1976

Increase by visual stimuli in turnover of 5-hydroxytryptamine in the superior colliculi of the rabbit.

1. Irregular light falshes were played on to one eye of dark adapted rabbits for periods of 20-80 min. The concentration of 5-hydroxyindol-3-ylacetic acid (5-HIAA) and of 5-hydroxytryptamine (5-HT) were estimated in left and right superior colliculi, thalami and hippocampi. 2. In rabbits exposed to such visual stimuli for 30-60 min, there was an increase in the 5-HIAA content of the colliculus contralateral to the stimulated retina which aberaged 17% (P = 0-02), but no rise was seen if the exposure was shortened to 20 or prolonged to 80 min. At no time was there a difference in 5-HIAA content between right and left thalamus or right and left hippocampus. 3. Stationary or strictly repetitive visual stimuli produced no difference between the 5-HIAA content of left and right superior colliculus. 4. No difference in 5-HT concentration between the two colliculi was found after any form of visual stimulation, nor did any changes occur in the other parts of the brain which were examined. 5. Irregular, prolonged visual stimualtion thus appears to activate tryptaminergic neurones terminating in the colliculi. The possibility is discussed that the 5-HT released at this site might act as a brake to neuronal activity under conditions when habituation to the stimuli is not yet complete.

Animals↗
PubMed1985

[Oscillating potentials of the retina and superior colliculi and correlations with neuronal activity].

The oscillatory potentials of retina and superior colliculus induced with photostimuli were studied in unanesthetized rabbits. Increasing intensity of light flashes induces a better correlation of the responses in these structures. A common genesis of the oscillatory processes and neuronal activity was revealed. The peculiarities of formation of the short-latency responses in the superior colliculus and the specificity of generation of the responses of photostimuli of extreme brightness, are discussed.

Animals↗
PubMed2001

Convergence of Y and non-Y channels onto single neurons in the superior colliculi of the cat.

Receptive field properties of single neurons in the cat superior colliculus were examined following selective conduction-block of Y-type fibers in contralateral optic nerve. Although the responses evoked by photic stimuli presented via the Y-blocked eye were significantly weaker than those evoked by stimuli presented via the normal eye, > 85% of collicular cells were binocular. Furthermore, when binocular cells were stimulated via the Y-blocked eye their median upper cut-off velocity (100 degrees /s) was significantly lower than that (400 degrees /s) for stimuli presented via the normal eye. Thus, there is a substantial degree of excitatory convergence of Y- and non-Y- information channels on single collicular neurons and the responses to high velocity of motion appear to depend on the integrity of Y-type input.

Action Potentials↗
PubMed1981

[Analysis of current source density in the superior colliculi of cats in response to punctate visual stimulation].

The EPs in the cat superior colliculus to the punctiform light stimulation were of negative polarity and did not show the potential reversion. The region of EP recording was from 0.1 to 0.9 mm (stratum griseum superficiale). The field potential profile was subjected to the current source density analysis to determine the location and sequence of the current sources and sinks after punctiform light stimulation. The earliest current sink was observed at the depth 0.6--0.8 mm, the later and the most prominent local one--at 0.2--0.3 mm. The EPs to punctiform light stimuli seem to indicate more precisely the location of afferent synapses.

Animals↗
PubMed1983

[Laminar distribution of current sources in the superior colliculi of the rabbit upon stimulation of the optic nerve].

The evoked potential field in the rabbit superior colliculus was subjected to the current source density analysis to determine the location and sequence of the current sinks and sources after electrical stimulation of the optic nerve. The earliest current sink was observed in the middle part of the stratum griseum superficiale. The later and the most prominent current sinks were observed in the upper part and in the deep part of the stratum griseum superficiale. The time course of the current sinks and sources was in correspondence with the main components of the evoked potential. The results permit indicating the location of afferent synapses and sequence of their activation.

Animals↗
PubMedDate not supplied

[The functional connections of the supraoptic and suprachiasmatic nuclei of the anterior hypothalamus with the superior colliculi].

Interrelation of single hypothalamic (supraoptic--SO and suprachiasmatic--SCH nuclei) and light stimuli at the level of superior colliculus (SC) were studied during chronic experiments in waking rabbits. Short-term inhibitory and the subsequent facilitatory effects of the hypothalamic stimuli on SC responses induced by light flashes were established. The foregoing light stimulus caused inhibitory effect on formation of hypothalamo-collicular responses induced by SO and SCH nuclei stimulation. The final result of the anterior hypothalamic effect on SC function is the vector value of the mechanism of interrelation between the hypothalamic inputs in this structure.

Animals↗
PubMed1986

[Effect of stimulation of the superior colliculi of the tectum mesencephali on the motor neurons of the neck muscles of the cat].

Postsynaptic potentials evoked by stimulation of three points of the superior colliculus in motoneurons of neck muscles were studied in experiments on cats under chloralosenembutal anesthesia. Stimulation of ipsilateral superior colliculus evoked EPSP with latencies ranging from 1.5 to 3.5 ms in 49 motoneurons. Stimulation of contralateral superior colliculus evoked EPSP with latencies ranging from 1.5 to 3.0 ms in 63 motoneurons and IPSP with latencies ranging from 2.6 to 5.0 ms in 10 motoneurons. It is suggested that the recorded postsynaptic potentials are mono- and disynaptic.

Animals↗
PubMed1985

[Relation between the spatial characteristics of the receptive fields of the superior colliculi of the cat and the rate of movement of a photic stimulus].

The receptive fields of visual cells in superficial and intermediate layers of the cat superior colliculus were investigated: their boundaries, size, shape, dependence on the velocity of stimulus. The size of the excitatory zone decreased whereas the firing rate of the cells increased when the velocity 3 +/- 180 degrees.S-1 was changed. That was typical of both directionally and non-directionally selective cells. The mechanism of directional selectivity is discussed.

Animals↗