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At least 91 records · Page 5Linked to original sources
PubMed1985

Abnormal visual pathways in normally pigmented cats that are heterozygous for albinism.

The various forms of albinism affect about one in 10,000 births in the United States. An additional 1 to 2 percent of the population has normal pigmentation but is heterozygous and carries a recessive allele for albinism. The retinogeniculocortical pathways were studied in normally pigmented cats that carry a recessive allele for albinism. The cats exhibited abnormalities in their visual pathways similar to those present in homozygous albinos. These results imply that visual anomalies like those found in albinos may be present in 1 to 2 percent of the human population.

Albinism↗
PubMed1988

Transneuronal transport of WGA-HRP in immature rat visual pathways.

Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to study transneuronal transport in the developing rat visual pathways. Intraocular injections of WGA-HRP were made in neonatal albino rat pups at different ages from the day of birth, postnatal day 0 (P0), to one month of age. Transneuronal labeling in geniculostriate fibers and in tectoparabigeminal terminals was observed as early as P1 and showed little change with eye-opening. However, at early ages, consistent transneuronal labeling was found to require injection of up to 4 times the amount of tracer (0.18 mg WGA-HRP) as adults (0.04 mg WGA-HRP), delivered in two injections. Control injections of HRP alone produced heavy anterograde labeling at all ages, without requiring increased injections. The results suggest that transneuronal transport precedes synaptic transmission, and may illustrate a mechanism for exchanging molecules between neurons. One explanation for the requirement of increased tracer is that axonal and/or transneuronal transport of WGA-HRP may be selectively limited to certain cells in the postnatal retina.

Aging↗
PubMed1977

[A comparison between pneumatography and tomography (tomodensitometry) for examination of the visual pathway (author's transl)].

The author describes the possibilities of x-ray examination of the extra- and intracranial parts of the visual pathway. After a survey of pneumatography of the orbit a comparison with pneumoencephalography and tomodensitometry (EMI-scanner) is made. Tomodensitometry must be regarded as a significant advance in neuroradiological examination because it is not dangerous and easy to perform. The indications for complementary pneumoencephalography are discussed in detail.

Arachnoiditis↗
PubMed1979

[Disturbances of the pupil reflex associated with lesions of the upper visual pathway (author's transl)].

In six patients with ischemic lesions of the visual pathways above the lateral geniculate body, the pupil light reflex was investigated under perimetric conditions. The size of the lesions--in four cases caused by lateralized cerebral infarction, in two cases by complicated migraine attacks--was certified by neurological examination and by angiography or computerized tomography respectively. The recordings were done with a portable pupillograph measuring the infrared light reflected from the iris. A Tübinger perimeter served as stimulator. All patients except one, whose visual fields recovered quickly and completely, showed parallel tracings concerning the sensory and the pupillographic profiles, in the older lesions as well as in the recent ones.

Adult↗
PubMed1990

[Analysis of electrically evoked response (EER) in relation to the central visual pathway of the cat (1). Wave shape of the cat EER].

To analyze the Electrically evoked response (EER) in relation to the central visual pathway, the authors studied the properties of wave patterns and peak latencies of EER in 35 anesthetized adult cats. The cat EER showed two early positive waves on outward current (cornea cathode) stimulus and three or four early positive waves on inward current (cornea anode) stimulus. These waves were recorded within 50 ms after stimulus onset, and were the most consistent components in cat EER. The stimulus threshold for EER showed a less individual variation than amplitude. The difference of stimulus threshold between outward and inward current stimulus was also essentially negligible. The stimulus threshold was higher in early components than in late components. The peak latency of EER became shorter and the amplitude became higher, as the stimulus intensity was increased. However, this tendency was reversed and some wavelets started to appear when the stimulus was extremely strong. The recording using short stimulus duration and bipolar electrodes enabled us to reduce the electrical artifact of EER. These results obtained from cats were compared with those of humans and rabbits.

Animals↗
PubMed1991

[Analysis of electrically evoked response (EER) in relation to the central visual pathway of the cat (2). Response characteristics of the lateral geniculate neurons].

To analyze the electrically evoked response (EER) in relation to the central visual pathway, the response characteristics of the lateral geniculate neurons (LGNs) of the EER in 35 anesthetized adult cats were studied. Responses of the LGNs showed interindividual variation of more than one log unit in terms of the stimulus threshold for electrical stimuli. As the stimulus intensity increased, the spikes with constant latencies were recorded, which showed bursts with much stronger stimuli. The latencies of the spikes were closely correlated with those of negative components of EER. The LGNs were divided into two major groups by the latency. The periodical and alternative excitation of these neurons contributed to form the first negative wave of EER. The latency of these two major groups of LGNs was reversed when the electrode polarity was changed. At higher stimulus intensities, the components with short latency became dominant and those with longer latency were suppressed. The above results suggested that the periodical excitation of LGNs and the formation of the prominent EER components may result from the interaction between on- and off-type retinal ganglion cells and amacrine cells. It was also suggested that the origins of the wavelets in negative waves of EER at strong stimuli are the bursts of the spikes of the visual cortex neurons.

Animals↗
PubMed1992

Critical frequency of photic driving: which part of the visual pathway do we examine?

Studies on critical frequency of photic driving were performed on patients with optic atrophy, moderately expressed suprachiasmal lesions and normal subjects. A reduction was present only in optic atrophy patients. The critical frequency of photic driving showed significant correlations with visual acuity and differential light sensitivity of the areas located within 15 degrees from the fixation point. The correlation proved higher for foveal sensitivity expressed in non-logarithmic rather than in logarithmic units, the opposite being the case for the sensitivity of parafoveal areas. It may be concluded that critical frequency of photic driving is conditioned by the cortical projection zones and visual pathways corresponding to the central 15 degrees of the visual field, but with predominant role of foveal projections.

Adolescent↗
PubMed1988

[Lesions of the posterior visual pathways: clinical presentation and mechanisms of functional restoration].

The present paper begins with a brief discussion of general clinical features found in patients with lesions of the posterior visual pathways. The author goes on to discuss various mechanisms of restitution of function in the central nervous system, including activation of neural pathways subserved by spared neurons, metabolic modulations, and neural plasticity.

Brain Damage, Chronic↗
PubMed1989

Organization of astrocytes in the visual pathways of the goldfish: an immunohistochemical study.

We have used antisera directed against glial cytoskeletal proteins to examine the distribution and organization of astrocytes in the visual pathways of the goldfish. We describe two different types of cells, which may be distinguished by their unique cytoskeletal proteins. Antibodies raised against a 48 Kd optic nerve protein react with stellate astrocytes in the optic nerve but virtually no glial cells in the brain (although blood vessels and the meninges in the brain were stained). The optic nerve astrocytes form a dense meshwork of processes through which the optic fibers pass. The intraorbital and intracranial segments of the nerve are divided into fascicles, each bounded by a glia limitans, which extend across the optic chiasm. Astroglial cells in the brain bind antibodies raised against a 50 Kd brain cytoskeletal protein. These antibodies show a very limited cross-reactivity with optic nerve cells. Brain astrocytes have filiform profiles and most appear to be deployed as radial glia. The glial fabric of the brain, as revealed by these antibodies, is far more loosely woven than that of the optic nerve. There is a sharp boundary between the two types of glial cells, immediately behind the optic chiasm. Glial processes in the optic tracts arise from cells in the preoptic area, whereas those in the optic tectum arise from cells that reside locally. In the optic tract, a glia limitans was often difficult to discern, whereas in the tectum one was always evident and composed of endfeet at the pial extremities of radial glial processes. These findings are discussed both in the context of previous observations by other workers as well as with regard to their possible functional implications.

Animals↗
PubMed1983

Hereditary neuropathy with upper motor-neuron, visual pathway, and autonomic disorders.

A 42-year-old man had progressive distal weakness and muscle atrophy, stocking-type sensory loss, upper motor-neuron and visual pathway lesions, and dysautonomia. Electrodiagnostic tests revealed a generalized sensorimotor peripheral neuropathy that largely involved axons. Low recumbent and upright norepinephrine levels implied a peripheral autonomic defect. Sural nerve biopsy showed mild abnormalities of medium and small size fibers. The patient's mother and two brothers were also affected. Other causes of peripheral motor, sensory, and autonomic failure were eliminated. This kinship does not fit any generally accepted classification of hereditary neuropathies.

Adult↗
PubMed1973

Genetic abnormality of the visual pathways in a "white" tiger.

"White"tigers show an inherited reduction of pigment, produced by an autosomal recessive gene. The brain of one of these tigers shows an abnormality of the visual pathways similar to abnormalities that are associated with albinism in many other mammals. There is a close relationship between the reduced pigment formation, the pathway abnormality, and strabismus.

Albinism↗
PubMed1983

A visual pathway that mediates fear-conditioned enhancement of acoustic startle.

Eighty rats received 10 light-shock pairings on two successive days. Seventy-two h after the final training session, subjects received lesions directed at the primary visual areas (deep and superficial layers of the superior colliculus, dorsal lateral geniculate nucleus, pretectal nuclei, visual cortex and thalamic reticular nucleus) and at the nuclei of the lateral lemniscus and reticularis pontis caudalis, proposed components of a primary acoustic startle circuit in the rat. Control animals were sham operated. One day later, all animals were tested for startle by presenting noise bursts of 3 different intensities in the presence or absence of the light conditioned stimulus. Potentiated startle (the difference between light-noise vs noise-alone trials) was significantly attenuated or eliminated by lesions directed at the dorsal nucleus of the lateral geniculate, deep layers of the superior colliculus, visual cortex, and the posteroventral region of the nucleus of the lateral lemniscus. Lesions directed at pretectal nuclei, superficial layers of the superior colliculus, thalamic reticular nucleus, nucleus reticularis pontis caudalis or dorsal nucleus of the lateral lemniscus did not attenuate potentiated startle. The results suggest that the visual pathway that mediates potentiated startle goes from the retina to the dorsal lateral geniculate nucleus to visual cortex to deep layers of superior colliculus and down to the postero-ventral region of the lateral lemniscus where acoustic startle is modulated.

Acoustic Stimulation↗
PubMed1991

A detailed model of the primary visual pathway in the cat: comparison of afferent excitatory and intracortical inhibitory connection schemes for orientation selectivity.

In order to arrive at a quantitative understanding of the dynamics of cortical neuronal networks, we simulated a detailed model of the primary visual pathway of the adult cat. This computer model comprises a 5 degrees x 5 degrees patch of the visual field at a retinal eccentricity of 4.5 degrees and includes 2048 ON- and OFF-center retinal beta-ganglion cells, 8192 geniculate X-cells, and 4096 simple cells in layer IV in area 17. The neurons are implemented as improved integrate-and-fire units. Cortical receptive fields are determined by the pattern of afferent convergence and by inhibitory intracortical connections. Orientation columns are implemented continuously with a realistic receptive field scatter and jitter in the preferred orientations. We first show that realistic ON-OFF-responses, orientation selectivity, velocity low-pass behaviour, null response, and responses to spot stimuli can be obtained with an appropriate alignment of geniculate neurons converging onto the cortical simple cell (Hubel and Wiesel, 1962) and in the absence of intracortical connections. However, the average receptive field elongation (length to width) required to obtain realistic orientation tuning is 4.0, much higher than the average observed elongation. This strongly argues for additional intracortical mechanisms sharpening orientation selectivity. In the second stage, we simulated five different inhibitory intracortical connection patterns (random, local, sparse-local, circular, and cross-orientation) in order to investigate the connection specificity necessary to achieve orientation tuning. Inhibitory connection schemes were superimposed onto Hubel and Wiesel-type receptive fields with an elongation of 1.78. Cross-orientation inhibition gave rise to different horizontal and vertical orientation tuning curves, something not observed experimentally. A combination of two inhibitory schemes, local and circular inhibition (a weak form of cross-orientation inhibition), is in good agreement with observed receptive field properties. The specificity required to establish these connections during development is low. We propose that orientation selectivity is caused by at least three different mechanisms ("eclectic" model): a weak afferent geniculate bias, broadly tuned cross-orientation inhibition, and some iso-orientation inhibition. The most surprising finding is that an isotropic connection scheme, circular inhibition, in which a cell inhibits all of its postsynaptic target cells at a distance of approximately 500 microns, enhances orientation tuning and leads to a significant directional bias. This is caused by the embedding of cortical cells within a columnar structure and does not depend on our specific assumptions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Visual receptive fields and response properties of neurons in human temporal lobe and visual pathways.

Recordings were made from depth electrodes placed in medial temporal and occipital lobes for the localization of seizure foci in patients with medically intractable psychomotor epilepsy. Electrodes were located in the amygdala and at three rostrocaudal levels of the hippocampal formation including the posterior hippocampal gyrus, which lies medial to the portion of the geniculostriate pathway which passes through the temporal lobe. 1. Approximately 10 per cent of single units recorded from microelectrodes chronically implanted in medial temporal sites were visually responsive. Some of the units in the posterior hippocampal gyrus displayed receptive field characteristics similar to those reported in lower primates, including circular or linear shape, monocular or binocular response, variable (1 to 10 deg) receptive field size, retinotopic organization and sustained or transient response. 2. Visually responsive units were also recorded from lateral geniculate nucleus, pulvinar nucleus and occipital cortex, and their basic response form and latencies compared with the short latency visually responsive cells in medial temporal lobe. 3. The heterogeneity of receptive field characteristics in the medial temporal lobe is consistent with the existence of more than one visual input to this region, while their retinotopic relationship differentiates these receptive fields from those of units studied in the inferior temporal lobe of lower primates. 4. Properties of visual pathways in this region are discussed in relation to several types of temporal lobe function and to memory. Recordings from these neurons offer a rare opportunity for comparison of central visual response properties and receptive field characteristics of humans with those reported in animal studies.

Adult↗
PubMed1990

Our treatment philosophy of gliomas of the anterior visual pathways.

Therapeutic strategy and clinical course of 28 low grade gliomas of the anterior visual tract were analyzed and compared with results of quantitative microscopic examination. Children operated on between 1978 and 1987 were divided into four groups according to the tumor site. DNA microfluorometry and image analysis of bioptic material were used for an objective differentiation between morphologically almost identical gliomas classified as pilocytic astrocytomas (grade I). Six cases of posttraumatic gliosis were examined as controls. Results were tested with factor analysis and by multiple comparison procedures. Significant differences between quantitative parameters of tumors located along the visual pathway were found with the use of computer-aided microscopy. These results corresponded with the clinical experience and patient's outcome. A radical surgical intervention (without additional oncologic therapy) was recommended for patients with intraorbital gliomas which revealed favorable quantitative microscopic features.

Astrocytoma↗
PubMed1986

2',3'-cyclic nucleotide 3'-phosphohydrolase activity in rat visual pathways with experimental allergic encephalomyelitis.

The enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) is one of the important markers for myelin synthesis or demyelination. We measured the CNPase activities in the visual pathway tissues of Lewis strain rats with experimental allergic encephalomyelitis (EAE) induced by inoculation of myelin basic protein from the brain. The enzyme activities in the retina, optic nerve, optic chiasma and lateral geniculate body were reduced to about 50-80% of that of controls at 15 days after myelin basic protein inoculation when symptoms of EAE were most severe. However, the activities recovered at 19 days except in the retina when the symptoms of EAE disappeared. Furthermore, the activities of the optic nerve and chiasma increased to a level higher than that of the controls at this time. By histopathological study, infiltration of inflammatory cells and focal demyelination were found in the optic nerve and lumbar spinal cord at 15 days after myelin basic protein inoculation. It was considered that the reduction of CNPase activity and its recovery and increase reflect demyelination and activation of oligodendroglia for remyelination, respectively.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1990

Spread of vesicular stomatitis virus along the visual pathways after retinal infection in the mouse.

Vesicular stomatitis virus (VSV) was injected into the left eyeball of 3-week-old mice and it infected the retinal ganglion cells. The infection spread rapidly along the visual pathways to the postsynaptic neurons in the contralateral superior collicle (SC) and lateral geniculate body (LGB). The distributional pattern of the viral immunoreactivity indicated an anterograde axonal transport of the infectious material. A subsequent spread to the ganglion cells of the right retina further indicated retrograde axonal VSV transport. Within the retina the infection spread from the ganglion cells to the pigment epithelium. Although a transneuronal spread of the VSV infection was observed, no VSV budding from or uptake in synaptic membranes was demonstrated ultrastructurally in the retina or the superior collicle. In the retina virions budded from the perikaryal and dendritic plasma membranes of the ganglion cells as well as from the nerve cell bodies of the inner and outer nuclear layers, but not from the receptor segments. In the superior collicle budding was also observed from the plasma membranes of nerve cell bodies and dendrites. In contrast, the intraocular injection of Sendai virus caused a limited retinal ganglion cell infection, with no further propagation in the retina or to the SC or LGB.

Animals↗