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At least 271 records · Page 15Linked to original sources
PubMed1999

Infantile cerebral aneurysms with visual pathway compression.

Intracranial aneurysms are rare in infancy. The commonest presentation is intracranial hemorrhage, but signs of mass effect are more frequent than in adults. We report 2 infants with cerebral aneurysms, one presenting with macrocephaly and another with strabismus. Both had visual loss and optic disc pallor; MRI revealed a suprasellar mass and anterior visual pathway compression. In both cases, the preoperative diagnosis was craniopharyngioma. It is essential to recognize that, although exceedingly uncommon, cerebral aneurysms do occur in infants and have features that differ from those in adults.

Calcinosis↗
PubMed1997

The prevalence of strabismus in congenital nystagmus: the influence of anterior visual pathway disease.

PURPOSE: To determine the influence of underlying visual system disorders on the risk of developing strabismus in children with congenital nystagmus. METHODS: We retrospectively reviewed 82 cases of congenital nystagmus from a pediatric ophthalmology referral practice. RESULTS: Strabismus was found in 50% of children with congenital nystagmus. The prevalence of strabismus was 82% in children with bilateral optic nerve hypoplasia, 53% in patients with albinism, 36% in children with congenital retinal dystrophies, and 17% in children with idiopathic congenital nystagmus. CONCLUSION: The risk that a child with congenital nystagmus will have strabismus develop can be predicted from the nature of the underlying visual disorder.

Adolescent↗
PubMed1999

[Long-term outcome of gliomas of the visual pathway in type 1 neurofibromatosis].

BACKGROUND: Optic gliomas are frequently associated with neurofibromatosis type 1 (NF1) and belong to the diagnostic criteria of NF1. Different growth rates require differentiated strategies for screening and observation. PATIENTS AND METHODS: 29 patients (25 children < 11 years, 4 adults > 18 years) with visual pathway tumors and NF1 were examined neurologically, ophthalmogically, by means of MRI and VEP. Results were set into context with preceding investigations (mean follow up time 6.5 years). RESULTS: 11 children showed a stable condition, 14 an unfavorable process with substantial loss of vision. Children with an unfavorable process showed a lower age at diagnosis (3.2 versus 5.8 years; p < 0.05), more frequently strabism (11/14 versus 1/11; p < 0.05), optic atrophy (12/14 versus 1/11; p < 0.05), pathological VEP (9/9 versus 2/10; p = 0.001), visual field defects (9/9 versus 1/9) and involvement of the optic chiasm (11/14 versus 3/11; p < 0.05) than children with a stable condition. 3 of 4 adults had no visual symptoms despite involvement of the optic chiasm. CONCLUSIONS: The crucial prognostic factor is the patient's age at the time of diagnosis. Optic gliomas which become symptomatic in early childhood (< 6 years) grow rapidly and require frequent ophthalmologic investigations and MRI. Tumors diagnosed in late childhood (> 6 years) do not progress, allowing for gradual extension of intervals between ophthalmological investigations.

Adolescent↗
PubMed1997

On the structure and function of the tectofugal visual pathway in laterally eyed birds.

Of the two visual systems in vertebrates, the tectofugal pathway has often been attributed to stimulus localization, while the thalamofugal pathway was thought to be involved in stimulus identification. This review provides evidence that the tectofugal pathway serves both functions. It is speculated that the initial task of the tectum is to localize an object and to guide the fixation movement. The object in focus is then analysed by the higher stations of the tectofugal system. The result of the analysis is fed into the optic tectum and is used for decision about the treatment of the object.

Animals↗
PubMed1994

Myelin repair by Schwann cells in the regenerating goldfish visual pathway: regional patterns revealed by X-irradiation.

In the regenerating goldfish optic nerves, Schwann cells of unknown origin reliably infiltrate the lesion site forming a band of peripheral-type myelinating tissue by 1-2 months, sharply demarcated from the adjacent new CNS myelin. To investigate this effect, we have interfered with cell proliferation by locally X-irradiating the fish visual pathway 24h after the lesion. As assayed by immunohistochemistry and EM, irradiation retards until 6 months formation of new myelin by Schwann cells at the lesion site, and virtually abolishes oligodendrocyte myelination distally, but has little or no effect on nerve fibre regrowth. Optic nerve astrocyte processes normally fail to re-infiltrate the lesion, but re-occupy it after irradiation, suggesting that they are normally excluded by early cell proliferation at this site. Moreover, scattered myelinating Schwann cells also appear in the oligodendrocyte-depleted distal optic nerve after irradiation, although only as far as the optic tract. Optic nerve reticular astrocytes differ in various ways from radial glia elsewhere in the fish CNS, and our observations suggest that they may be more permissive to Schwann cell invasion of CNS tissue.

Animals↗
PubMed1988

Normal visual pathway routing in dissociated vertical deviation.

Flash visually evoked cortical potentials have been recorded in three groups of age- and sex-matched subjects; one comprised of subjects with dissociated vertical deviation, one comprised of subjects with oculocutaneous albinism and one group of controls. The latency of the major positive (P2) component did not show statistically significant contralateral lateralization on monocular stimulation in either the dissociated vertical deviation group or the control group. Contralateral lateralization was found in the albino group at a statistically significant level (P less than 0.01). It is concluded that subjects with dissociated vertical deviation do not possess the typical albino optic pathway misrouting that has been reported.

Adolescent↗
PubMed2001

High-resolution spatio-temporal mapping of visual pathways using multi-electrode arrays.

The parallel processing of visual information was studied with penetrating microelectrode arrays. We studied the high-resolution visuotopic organization of cat primary visual cortex, and the encoding of simple visual stimuli by ensembles of ganglion cells in the isolated turtle retina. The high-resolution visuotopic organization of visual cortex is non-conformal. Regions of visual cortex separated by 400 mu may have receptive field centers that are separated by as much as 3 degrees, or they may superimpose. Ganglion cells are 'generalists', and are poor specifiers of the color of full field visual stimuli. Groups of 'luminosity' type ganglion cells can assist in the specification of stimulus color, but even individual 'chromatic' ganglion cells are not capable of quality color specification. These basic studies have relevance to the development of visual neuroprostheses based upon electrical stimulation of the retina and cortex.

Animals↗
PubMed1998

Evidence for spatial aliasing effects in the Y-like cells of the magnocellular visual pathway.

Several lines of evidence are provided indicating that our visual percept can be dominated by spatial aliasing for viewing conditions near those needed to see the spatial frequency doubled illusion. The apparent aliasing effect indicates that the underlying sampling array has a density 15-30% of that of M-cells, in agreement with the known proportion of Y-like M-cells (M(y)-cells). The presence of aliasing indicates, that there is a separate irregular array of M(y)-cells, and that their role is to rapidly convey information on retinal gain control to the brain rather than to act primarily as inputs to image motion computation.

Adaptation, Ocular↗
PubMed1981

[Multifocal ischemic lesions of the visual pathways (author's transl)].

Multiple ischemic lesions of the optic pathways may cause a number of complex visual field defects; their analysis is of substantial diagnostic significance, especially if the computer tomogram is negative. Perimetry is often complicated by an accompanying organic psychosyndrome.

Carotid Artery Diseases↗
PubMedDate not supplied

[Representation of the visual pathways in the retrosplenial area of the rat limbic cortex].

Visual inputs to field 29 of the limbic retrosplenial cortex have been studied by means of paired stimuli, i.e. photic and electrical stimulation of the anterodorsal nucleus (ADN). During stimulation of this nucleus, the evoked potentials in the field 29 decreased in the initial phase of visual stimulation, indicating the involvement of the ADN into the visual system. This finding confirms earlier morphological data [2]. Besides this, in the field 29 neurones were found which responded to light but not to ADN stimulation, suggesting the possibility of termination of different visual inputs on the neurones of the limbic cortex.

Animals↗
PubMedDate not supplied

Transneuronal retrograde transport of attenuated pseudorabies viruses within central visual pathways.

Pseudorabies virus (PRV) has been shown to be an effective transneuronal tracer within both the peripheral and the central nervous system. The only investigations of this virus in the visual system have examined anterograde transport of PRV from injection sites in the retina. In the present study, we injected attenuated forms of PRV into the primary visual cortex of both rats and cats to determine whether transneuronal retrograde infection would occur back to the retina. In rats, we made small injections into visual cortex of a strain of PRV (Bartha Blu) that contained a beta-galactosidase promoter insert. In cats, we injected PRV-M201 into area V1 of visual cortex. After a 2- to 4-day incubation period, we examined tissue from these animals for the presence of the beta-galactosidase marker (rats) or the virus itself (cats). Cortical PRV injections resulted in transneuronal retrograde infection of the lateral geniculate nucleus (LGN), thalamic reticular nucleus (TRN), and retina. PRV was retinotopically distributed in the pathway. In addition, double-labeling experiments in cats using an antibody against gamma-aminobutyric acid (GABA) were conducted to reveal PRV-labeled interneurons within the LGN and TRN. All TRN neurons were GABA+, as was a subset of LGN neurons. Only the subset of TRN neurons adjacent to the PRV-labeled sector of LGN was labeled with PRV. In addition, a subset of GABA+ interneurons in LGN was also labeled with PRV. We processed some tissue for electron microscopy to examine the morphology of the virus at various replication stages. No mature virions were detected in terminals from efferent pathways, although forms consistent with retrograde infection were encountered. We conclude that the PRV strains we have used produce a local infection that progresses primarily in the retrograde direction in the central visual pathways. The infection is transneuronal and viral replication maintains the intensity of the label throughout the chain of connected neurons, providing a means of examining detailed circuitry within the visual pathway.

Animals↗
PubMed1994

Network analysis of cortical visual pathways mapped with PET.

Brain metabolic mapping techniques, such as positron emission tomography (PET), can provide information about the functional interactions within entire neural systems. With the large quantity of data that can accumulate from a mapping study, a network analysis, which makes sense of the complex interactions among neural elements, is necessary. A network analysis was performed on data obtained from a PET study that examined both the changes in regional cerebral blood flow (rCBF) and interregional correlations among human cortical areas during performance of an object vision (face matching) and spatial vision (dot-location matching) task. Brain areas for the network were selected based on regions showing significant rCBF or interregional correlations between tasks. Anterior temporal and frontal lobe regions were added to the network using a principal components analysis. Interactions among selected regions were quantified with structural equation modeling. In the structural equation models, connections between brain areas were based on known neuroanatomy and the interregional correlations were used to calculate path coefficients representing the magnitude of the influence of each directional path. The combination of the anatomical network and interregional correlations created a functional network for each task. The functional network for the right hemisphere showed that in the object vision task, dominant path influences were among occipitotemporal areas, while in the spatial vision task, occipitoparietal interactions were stronger. The network for the spatial vision task also had a strong feedback path from area 46 to occipital cortex, an effect that was absent in the object vision task. There were strong interactions between dorsal and ventral pathways in both networks. Functional networks for the left hemisphere did not differ between tasks. Networks for the interhemispheric interactions showed that the dominant pathway in the right hemisphere also had stronger effects on homologous left hemisphere areas and are consistent with a hypothesis that intrahemispheric interactions were greater in the right hemisphere in both tasks, and that these influences were transmitted callosally to the left hemisphere.

Adult↗