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PubMed1994

Effect of endoscopic white light on the developing visual pathway: a histologic, histochemical, and behavioral study.

OBJECTIVE: We examined the potential teratogenic effect of endoscopic white light on the developing visual pathways. STUDY DESIGN: The right eye of chicken embryos (n = 22) was exposed to maximal endoscopic light intensity on day 10 of development. At day 17 of development the histologic characteristics of the light-exposed retinas were compared with those of the control embryos (n = 4). Normal functioning of the light-exposed eye was assessed by intravitreal injection of wheat germ agglutinin-horseradish peroxidase and observation of its axonal transport pattern to the diencephalic and mesencephalic visual centers. Axonal transport patterns were compared with those found in previous studies of normal embryos. Behavioral feeding patterns were compared between two groups of newly hatched chickens, one exposed to endoscopic light after hatching (n = 13) and the other, an unexposed control group (n = 12). RESULTS: No evidence of retinal damage, altered axonal transport or altered feeding patterns could be found between control and experimental animals. CONCLUSION: Endoscopic white light does not appear to be harmful to the developing retina and visual pathway.

Animals↗
PubMedDate not supplied

MR of visual pathways in patients with neurofibromatosis.

MR was performed on six patients clinically diagnosed as having neurofibromatosis. Owing to its multiplanar capability, MR greatly helped determine the extent of visual pathway disease. We attempted to find specific optimal pulse sequences for evaluating the prechiasmatic, chiasmatic, and retrochiasmatic visual system at 0.35 T. Using spin-echo techniques, we evaluated a T1-weighted sequence (TR 300 msec/TE 35 msec), an intermediate T2-weighted sequence (TR 1500 msec/TE 35 msec), and a T2-weighted sequence (TR 1500 msec/TR 70 msec). We found that the orbital and intracanalicular optic nerves were most accurately and easily seen with the T1-weighted sequence axially and coronally; the chiasm was best seen with the intermediate T2-weighted coronal sequence; and the retrochiasmatic visual pathway was optimally evaluated with T2-weighted spin-echo technique.

Child↗
PubMed1989

Glial fibrillary acidic protein (GFAP) from goldfish: its localisation in visual pathway.

An intermediate filament fraction, isolated from goldfish brain, contains a prominent protein having a molecular weight of 51 kDa. In normal goldfish visual pathway, this protein is present in tectum and tract, but not in optic nerve. A polyclonal antibody raised to this protein clearly labels ependymal glial profiles in tectum and parallel processes in the tract, whereas optic nerve is unlabelled; Müller fibres in the retina are also labelled. A similar, but less prominent, pattern of staining is observed with antibodies, raised elsewhere, against glial fibrillary acidic protein from human and porcine. These results suggest that the 51 kDa protein is a GFAP, demonstrate the heterogeneity of astrocytes in goldfish visual pathway, and are consistent with the idea that GFAP is well conserved in vertebrate phylogeny.

Animals↗
PubMed1975

[A light-independent function of the retina of rabbits. Examination on the energetic part of the visual pathway (author's transl)].

In this study a light-independent function of the retina of rabbits could be proved. For this purpose, the energetic part of the visual pathway was utilized, and its influence on the maturation of the testicles was examined. As a criterion of maturation, the pattern of the phosphatid-fatty acids was ascertained. The subdivision of the energetic part of the visual pathway into a photo-energetic and an autonomic-energetic component is proposed.

Animals↗
PubMed1984

Dissociated vertical deviation: evidence of abnormal visual pathway projection.

Abnormalities in visually evoked responses have been used to demonstrate abnormal optic nerve fibre projections in human albinos, who have anomalous nystagmoid movements. Using visually evoked potentials we tested the hypothesis that patients with dissociated vertical deviation (another group with anomalous nystagmoid movements) may have abnormal visual evoked responses similar to those of albinos. Patients with dissociated vertical deviation (both unilateral and alternating), patients with congenital esotropia without dissociated vertical deviation, and normal subjects were investigated. The results showed a very high incidence of abnormal visual evoked responses in patients with dissociated vertical deviation, while recordings from the other groups were normal. As well as suggesting the possibility of abnormalities of optic nerve fibre projections, the visual evoked responses showed a marked increase in latency in all patients with dissociated vertical deviation. These results occurred regardless of the visual acuity or amblyopia of the eyes tested. The possible existence of abnormal pathway projection in the presence of dissociated vertical deviation is discussed.

Evoked Potentials, Visual↗
PubMed1994

Neuronal selectivities to complex object features in the ventral visual pathway of the macaque cerebral cortex.

1. To infer relative roles of cortical areas at different stages of the ventral visual pathway, we quantitatively examined visual responses of cells in V2, V4, the posterior part of the inferotemporal cortex (posterior IT), and the anterior part of the inferotemporal cortex (anterior IT), using anesthetized macaque monkeys. 2. The critical feature for the activation was first determined for each recorded cell by using a reduction method. We started from images of three-dimensional complex objects and simplified the image of effective stimuli step by step by eliminating a part of the features present in the image. The simplest feature that maximally activated the cell was determined as the critical feature. The response to the critical feature was then compared with responses of the same cell to a routine set of 32 simple stimuli, which included white and black bars of four different orientations and squares or spots of four different colors. 3. Cells that responded maximally to particular complex object features were found in posterior IT and V4 as well as in anterior IT. The cells in posterior IT and V4 were, however, different from the cells in anterior IT in that many of them responded to some extent to some simple features, that the size of the receptive field was small, and that they intermingled in single penetrations with cells that responded maximally to some simple features. The complex critical features in posterior IT and V4 varied; they consisted of complex shapes, combinations of a shape and texture, and combinations of a shape and color. 4. We suggest that local neuronal networks in V4 and posterior IT play an essential role in the formation of selective responses to complex object features.

Animals↗
PubMed1983

[Morphological development of the primary visual pathway in the child].

This study concerns the development of the human primary visual pathway. The lateral geniculate nucleus (LGN), the principle thalamic relay to the visual cortex (area 17), has a population of neurons similar to that of the monkey, as identified by Golgi impregnation. Commonest neuron is the multipolar with a radiate or tufted dendritic tree, followed by the bipolar neuron with two or three diametrically opposed dendritic trunks and, more rarely, neurons with beaded dendrites and those with fine, axon-like dendritic processes, possibly interneurons. The dendritic tree of all neurons remains generally within a lamina, but some dendrites cross interlaminar zones. These zones contain neurons whose dendrites enter adjacent laminae. LGN neurons are identifiable at birth, and even earlier, and differ from their adult form by the presence of immature features (growth cones and numerous dendritic and somatic spines), most frequent at four months but disappearing completely by nine months post-natally, when the LGN has reached its "adult" volume. Two stages in the development of area 17 can be defined. The first is marked by rapid growth to its "adult" volume at about four months, and by intense synaptogenesis beginning in the foetus and reaching a maximum around eight months. The second stage is one of stabilization of volume of area 17 and loss of synapses to reach "adult" synaptic density around 11 years, at about 60 p. cent of maximum values. The formation of transitory morphological features in the first year coincides with a period of visual plasticity in the infant. Our observations can be correlated with clinical evaluations of visual activity during the preverbal stage, a period of great importance in the establishment of visual acuity, of stereopsis, and of oculomotor function, all very sensitive to the numerous forms of visual deprivation.

Animals↗
PubMed1981

Labelling by axonal transport of myelin-associated proteins in the rabbit visual pathway.

After intraocular injections of [3H]leucine, six regions of the visual pathway of adult rabbit were used to study the spatio-temporal pattern of the slow anterograde axonal transport of radioactive proteins associated with the particulate fraction, the water-soluble fraction and the myelin fraction. Unlike other fractions, myelin-associated labelled proteins represented a time-constant (for a given region) percentage of total tissue radioactivity. This percentage increased from the first half to the second half of the optic nerve and remained high in the chiasma and tract. The peak specific radioactivity of myelin decreased in the same direction. Myelin proteins were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and the labelling patterns obtained in different regions and at different survival times were compared. At the peak of myelin radioactivity of a given region the label was typically associated with four protein bands, L1, L2, L3 and L4, of 40000, 44000, 62000, and 68000 mol.wts. respectively. The basic protein, the proteolipid protein and the W1 component (mol.wt. 51000-53000) of the Wolfgram proteins were not significantly labelled. The radioactivity associated with the W2 component (mol.wt 60000) of the Wolfgram proteins could be derived from the closely migrating L3 component. At shorter survival times no clear labelling pattern could be detected. At longer survival times radioactivity was almost totally localized around band L3. The results presented underline the importance of choosing appropriate experimental conditions to obtain a consistent labelling pattern of myelin-associated proteins and to investigate the possible mechanism responsible for this phenomenon.

Animals↗
PubMed1982

Subtle disturbances of vision with compressive lesions of the anterior visual pathway measured by contrast sensitivity.

Contrast thresholds were determined for patients with compressive lesions of the chiasm or optic nerve but whose visual acuity was 20/20 on the Snellen scale. A generalized loss of contrast sensitivity for spatial frequencies ranging from 0.2 to 6.4 cycles per degree was found even in patients with normal color vision and full visual fields. After surgery was performed, improvements in the fields and color vision were seen in those patients who also showed a significant increase in their postoperative contrast sensitivity scores. Contrast sensitivity is shown to be a useful procedure for evaluating very mild visual complaints as well as for establishing early diagnosis and evaluation of surgical therapy in patients with compressive lesions of the anterior visual pathway.

Adult↗
PubMed1986

Monocular deprivation in kittens differently affects crossed and uncrossed visual pathways.

The effects of monocular deprivation (MD) on the crossed and uncrossed visual projections were studied using both electrophysiological and behavioural criteria. Our results show that Visual Evoked Potentials (VEPs) from the deprived eye (DE) in response to contrast reversing gratings are more reduced in the ipsilateral than in the contralateral cortex. This suggests a different sensitivity of the crossed and uncrossed visual pathways to MD. In the behavioural experiments comparable findings were obtained.

Animals↗
PubMed1995

High resolution magnetic resonance imaging of the anterior visual pathway in patients with optic neuropathies using fast spin echo and phased array local coils.

High resolution MRI of the anterior visual pathways was evaluated using frequency selective fat suppressed fast spin echo (FSE) sequences in conjunction with phased array local coils in patients with optic neuropathies. Fifteen normal controls and 57 patients were examined. Coronal T2 weighted fat suppressed FSE images were obtained in 11 minutes with an in plane resolution of 0.39 x 0.39 mm. The optic nerve and its sheath containing CSF were clearly differentiated. Central retinal vessels were often visible. In demyelinating optic neuritis and in anterior ischaemic optic neuropathy high signal within the nerve was readily delineated. Meningiomas and gliomas involving the optic nerve were precisely visualised both in the orbit and intracranially. Extrinsic compression of the optic nerves was readily visualised in carotid artery ectasia and dysthyroid eye disease. Enlarged subarachnoid spaces around the optic nerves were demonstrated in benign intracranial hypertension. High resolution MRI of the anterior visual pathway represents an advance in the diagnosis and management of patients presenting with optic neuropathy.

Adult↗
PubMed1984

Abnormal central visual pathways in the brain of an albino green monkey (Cercopithecus aethiops).

The visual pathways of an albino green monkey have been studied electrophysiologically and by autoradiographic methods. The monkey had a white coat and pink eyes; it had a strabismus and a nystagmus. When comparisons were made with normal macaque and green monkeys, several abnormalities could be defined. In the retina there was no foveal pit. A whole mount preparation showed a central area of high ganglion cell density in which the ganglion cells were significantly larger than the most central ganglion cells of a normal monkey. More peripheral retinal areas showed an apparently normal distribution of ganglion cell sizes and packing densities. Within the optic tract the number of uncrossed retinofugal fibers was less than normal, the part of the tract that represents central vision showing almost no uncrossed component. The uncrossed input to the lateral geniculate nucleus and to the superior colliculus was similarly reduced. Regions normally receiving ipsilateral afferents from the central retina were innervated exclusively by crossed afferents. The pathways to the magnocellular geniculate layers showed a more extensive abnormality than did the pathways to the parvicellular layers. Not only were the afferents to the geniculate layers abnormal, but the laminar pattern in the nucleus was also clear than normal in some parts of the nucleus, and there were a number of abnormal laminar fusions. Within the visual cortex it was possible to demonstrate a normal mapping of the contralateral visual field through the contralateral nasal retina and through the peripheral parts of the ipsilateral temporal retina. The central parts of the temporal retina mapped abnormally in the contralateral visual cortex, so that there was a monocular map of the central parts of the visual field forming as a mirror reversal of the normal map. The normal map of the contralateral hemifield formed columns that alternated with the abnormal map of the ipsilateral hemifield. The peripheral parts of the visual field were represented as ocular dominance columns, demonstrable electrophysiologically and also by the transneuronal transport of 3H-proline.

Animals↗
PubMed1995

Dysfunction of visual pathways in HIV-1 infection.

Foveal and conventional full field pattern-shift visual evoked potentials (f-VEPs and c-VEPs) were recorded bilaterally in 100 HIV seropositive homosexual men (HIVs) and in 40 age-matched healthy controls. In HIVs, both f-VEPs and c-VEPs revealed a significant mean increase in P100 latency (p < 0.001). In stage WR2 early conduction changes were detected in 17% of the stimulated eyes by f-VEPs and in 3% by c-VEPs. In patients with CD4 cell counts below 100/microliters a 33% reduction in the mean c-VEP amplitude was found (ANOVA p < 0.01). Multivariate analyses (MANCOVA) revealed that CD4 cell depletion was independently associated with lower (p < 0.01) and zidovudine treatment with higher c-VEP amplitudes (p < 0.05). Also patients with severe CD4 cell depletion showed a trend towards higher c-VEP amplitudes (p = 0.09) and lower f-VEP latencies (p = 0.08) after long lasting zidovudine treatment (Kruskal-Wallis test). Our data suggest that f-VEPs are a sensitive measure of subclinical optic fiber dysfunction in early HIV-1 infection and that axonal loss of optic fibers emerges with manifest immune deficiency. The inverse correlation of VEP changes and zidovudine treatment merits further studies on the question, whether inhibition of HIV replication may preserve visual pathway function.

Adult↗
PubMed1983

Inhibition of non-neuronal cell proliferation in the goldfish visual pathway affects the regenerative capacity of the retina.

Proliferating cells associated with the visual pathway were found in the present study to affect the regenerative capacity of the goldfish retina following optic nerve injury. The contribution of these cells to the process of regeneration was investigated in the goldfish visual system by reducing their proliferation in the optic tract and tecta, using X-irradiation. The regenerative ability of the retina was then evaluated by the following parameters: sprouting from retinal explants, protein synthesis in the retina and accumulation of radiolabeled transported components in the tectum. X-irradiation of the visual system at an early stage of the regeneration process had a promoting effect whereas irradiation at a later stage resulted in a reduced capacity to regenerate. The results are discussed with respect to the possibility that proliferating cells, possibly glia, exert two contradictory contributions: an inhibitory effect at the site of injury, whereas distal to it, a supportive, perhaps trophic effect.

Animals↗
PubMed1990

Phylogeny of putative cholinergic visual pathways through the pretectum to the hypothalamus in teleost fish.

Three patterns of pretectal organization can be discerned morphologically in teleosts. The taxonomic distribution of these pretectal patterns suggests that the intermediately complex pattern (seen in most teleost groups) has given rise to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). Two pretectal patterns (intermediately complex and elaborate) form part of similar, homologous visual pathways to the hypothalamus; the third pattern is involved in a nonhomologous pathway to the hypothalamus. Acetylcholinesterase (AChE) histochemistry was used in the present study in order to characterize these pretectal patterns further. It is demonstrated that AChE is a highly selective and reliable interspecific marker for all divisions of the superficial pretectum, the nucleus corticalis, the posterior pretectal nucleus (or nucleus glomerulosus) and portions of the inferior lobe. Therefore, the histochemical data support the hypothesis of a homology between the three patterns of pretectal organization in teleosts. Furthermore, the present data provide a basis for more specific investigations regarding the involvement of acetylcholine as a neurotransmitter within the visual pathways to the hypothalamus in teleosts.

Acetylcholinesterase↗
PubMed1994

Dolphin peripheral visual pathway in chronic unilateral ocular atrophy: complete decussation apparent.

Components of the peripheral visual pathway were examined in two bottlenose dolphins, Tursiops truncatus, each with unilateral ocular degeneration and scarring of 3 or more years' duration. In both animals, the optic nerve associated with the blind eye (right eye in Tg419 and left eye in Tt038) had a translucent, gel-like appearance upon gross examination. This translucency was also evident in the optic tract contralateral to the affected eye. In Tg419, myelinated axons of varying diameters were apparent in the left optic nerve, whereas the right optic nerve, serving the blind eye, appeared to be devoid of axons. In Tt038, myelinated axons were associated with the right optic nerve (serving the functional eye) and left optic tract but were essentially absent in the left optic nerve and right optic tract. Examined by light microscopy in serial horizontal sections, the optic chiasm of Tt038 was arranged along its central plane in segregated, alternating pathways for the decussation of right and left optic nerve fibers. Ventral to this plane, the chiasm was comprised of fibers from the left optic nerve, whereas dorsal to the central plane, fibers derived from the right optic nerve. Because of this architectural arrangement, the right and left optic nerves grossly appeared to overlap as they crossed the optic chiasm with the right optic nerve coursing dorsally to the left optic nerve. At the light and electron microscopic levels, the optic nerves and tracts lacking axons were well vascularized and dominated by glial cell bodies and glial processes, an expression of the marked glial scarring associated with postinjury axonal degeneration. The apparent absence of axons in one of the optic tract pairs (right in Tt038 and left in Tg419) supports the concept of complete decussation of right and left optic nerve fibers at the optic chiasm in the bottlenose dolphin.

Animal Diseases↗
PubMed1977

Aspects on the treatment of gliomas of the anterior visual pathway.

Partial excision of the glioma of the anterior visual pathway seemed to have no effect on the vision in 7 patients and had a negative effect in 2. These results support the opinion that no excision should be made in such tumours. However, the course of the disease in one exceptional patient raises doubts about the general validity of this rule. In this case the postulated chiasmal glioma proved to be an exophytic glioma arising in one intracranial optic nerve and compressing the other. Excision of the exophytic portion caused rapid and considerable improvement of vision in both eyes. Direct visualization by craniotomy was needed to separate this mode of growth from the common intrinsic growth of such tumours.

Adolescent↗
PubMed1989

Preliminary studies of cytokine-induced functional effects on the visual pathways in the rabbit.

Epidural visual evoked potentials (VEP) were used to study the role of cytokines in the induction of pathophysiologic changes associated with inflammation in the central nervous system (CNS) of the rabbit. In normal rabbits, intraocular injection of human recombinant interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF) increased the peak latency of the cortical VEP by more than 2 ms within 3 h of injection; equal volume injections of control substances had no effect. Alterations in conduction induced by IFN-gamma and TNF reversed within 24 h and could be reinduced by reinjection. Intraocular injection of recombinant human interleukin-1 beta (IL-1) induced a more progressive delay in conduction that peaked 24 h after intraocular challenge and reversed over the ensuing 48 h. Pathologic examination of the tissues indicated that the primary effect of these cytokines is on the vasculature and induces changes associated with inflammation. The results suggest that the acute reversible effects of cytokines on CNS function are associated with vascular events; further they support the sensitivity of the 'rabbit eye model' for studies on the pathophysiologic effect of inflammatory mediators on the CNS in vivo.

Animals↗