Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Visual Pathways”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
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↗
PubMed1982

[Assessment of lesions in various sections of the visual pathway].

The suitability of ultrasonography, computer tomography and Octopus perimetry is illustrated with reference to an investigation carried out in 60 patients. First, the characteristic symptoms are described, depending on the localization of the lesion in the visual pathway. Then the advantages and disadvantages of the various examination methods are compared. In the orbita, echography is the most accurate method in the anterior segments, while the balance shifts increasingly in favor of CT toward the retrobulbar region. As far as intracranial tumors are concerned, there is good correlation between CT and VF findings in the case of sellar processes and pathologic changes of the midline and occipital lobe. In the frontotemporal region, on the other hand, VF defects are found in only one-half of the cases, while in the case of vascular lesions there is no apparent correlation between perimetry findings and the size of the lesion demonstrated on the computer tomogram. The importance of the Octopus for early recognition of such lesions is discussed.

Hemianopsia↗
PubMed1998

Bilaterally projecting neurons in the two visual pathways of chicks.

By means of a double-labeling technique, we have investigated the organization of the bilateral thalamo-Wulst and tecto-rotundal projections in 2-day old chicks. After injecting fluorogold (FG) into one side of the visual Wulst and rhodamine B isothiocyanate (RITC) into the other side of the visual Wulst, the labeled neurons in the nucleus geniculatus lateralis pars dorsalis (GLd) were examined. Although the distribution areas of ipsilaterally and contralaterally labeled neurons overlap partly, very few double-labeled neurons were found (only 0.01% double-labeled neurons). This suggests that the ipsilateral and contralateral projections to the Wulst come from different neuronal populations of the thalamus. The FG and RITC were also injected into the rotundal nuclei (Rt) on each side of the thalamus and the labeled neurons in the optic tectum (TeO) were examined. In the TeO, the distribution areas of the neurons labeled ipsilaterally and contralaterally to Rt overlap completely and we found that up to 45% of the tectal cells were double-labeled by both FG and RITC. Therefore, many tectal neurons have axon collaterals so that they project to the Rt on both sides of the thalamus and must send information simultaneously to both sides of the brain. The differences in the structural organization of the two visual pathways are discussed with reference to the transmission of information to higher centers on both sides of the brain.

Animals↗
PubMed1994

Abnormal connectivity of the visual pathways in human albinos demonstrated by susceptibility-sensitized MRI.

We studied activation of the human visual cortex (VC) using susceptibility-sensitized MRI at 1.5 Tesla. Three albinos and six healthy controls underwent a series of monocular and binocular photic flash stimulation. Monocular stimulation in albinos caused predominant contralateral activation with a small, well-delineated area in the anterior part of the VC in the ipsilateral hemisphere. This finding was consistent with a chiasmal crossing anomaly in albinism. All controls had symmetric patterns of activation during monocular stimulation. Functional MRI represents a promising method for evaluation of the visual pathways in humans.

Adolescent↗
PubMed1982

Surgical and intensification procedures for defining visual pathways with cobaltous-lysine.

The introduction of heavy metals directly into living neuronal tissue has received little attention as a method for defining connections in the vertebrate nervous system. Procedures are described for the use of cobaltous-lysine to trace visual pathways with light microscopy. The success of the technique depends on a number of variables including: the method by which the tracer is applied, the survival period, and the method of intensification. Best results were obtained by soaking the optic nerve of living animals in the filling solution for 24 hr and by using a modification of the Timm's silver sulfide intensification procedure. Several factors that lead to poor results are discussed. Cobaltous-lysine is capable of both anterograde and retrograde labeling and can fill very sparse projections. Furthermore, the success of the fill can, at times, be evaluated prior to histology.

Animals↗
PubMed1978

Delayed visual evoked potentials with bilateral disease of the posterior visual pathway.

A man of 51 years presented with sudden onset of a confusional state and marked visual deterioration. The computerised transaxial tomogram showed a mass in the corpus callosum which had spread to involve both cerebral hemispheres. The visual evoked potential to pattern stimulus was delayed by about 20 ms. Necropsy confirmed the presence of an astrocytoma of the corpus callosum involving the optic radiation and occipital cortex on both sides. The anterior visual pathway was normal.

Astrocytoma↗
PubMed1983

Rapid decompression of anterior intracranial visual pathways with bromocriptine.

Bromocriptine mesylate (2-bromo-alpha-ergocryptine) has proved to be useful in reducing the size of prolactin-secreting pituitary adenomas, but little evidence has accumulated about its effectiveness within the first two weeks of therapy. The patient described herein showed a rapid reduction in the size of the suprasellar extension of a prolactinoma and a dramatic improvement of the primary visual field abnormalities within two weeks of starting bromocriptine therapy. This experience exemplifies the potential use of the drug in acutely decompressing the anterior intracranial visual pathways.

Adenoma↗
PubMed1992

Separate visual pathways for perception and action.

Accumulating neuropsychological, electrophysiological and behavioural evidence suggests that the neural substrates of visual perception may be quite distinct from those underlying the visual control of actions. In other words, the set of object descriptions that permit identification and recognition may be computed independently of the set of descriptions that allow an observer to shape the hand appropriately to pick up an object. We propose that the ventral stream of projections from the striate cortex to the inferotemporal cortex plays the major role in the perceptual identification of objects, while the dorsal stream projecting from the striate cortex to the posterior parietal region mediates the required sensorimotor transformations for visually guided actions directed at such objects.

Animals↗
PubMed1976

Organization of the tectofugal visual pathway in the pigeon: a retrograde transport study.

In birds, superficial laminae of the optic tectum receive a massive retinal input; the tectum in turn projects upon the nucleus rotundus thalami, which then sends its efferents to the ectostriatal core of the telencephalon. To examine the detailed organization of this principal ascending visual pathway, small injections of the marker horseradish peroxidase (HRP) were placed in various sites throughout the ectostriatum (E) or nucleus rotundus (Rt) in pigeons. Analysis of the resulting patterns of retrograde labeling indicates the tectofugal pathway to be comprised of at least five different channels. Cells which lie at various depths in the stratum griseum centrale (SGC) of the tectum project upon distinct subdivisions of nucleus rotundus. Anterior portions of Rt receive input from superficial-most cells in the SGC, while medial and more caudal portions of Rt are projected upon by deeper SGC neurons. A ventral subdivision of Rt was found to receive its primary input from two pretectal nuclei. Additional inputs to all portions of Rt arise from nucleus reticularis superior thalami. The various subdivisions of rotundus in turn project upon distinct portions of the ectostriatum. Thus, the segregation between the different input classes into Rt is largely retained at the telencephalic level. In contrast, the nucleus triangularis, a dorso-medial extension of Rt which receives its input from the deepest of all SGC neurons, sends its efferents to all parts of the ectostriatum.

Animals↗
PubMed1987

The scale of the visual pathways of mouse and rat.

Photoreceptors and neurons at various levels to cortex have been counted in mouse and rat. The ratios of neuron numbers (rat/mouse) are similar to the ratio of retinal areas or the squared ratio of eye sizes; so to a first approximation the two species have linearly scaled eyes, equal photoreceptor spacings (in micron), and visual pathways scaled numerically by the number of photoreceptors. With supplementary data from the literature, some of the functional implications of the design can be evaluated level by level. Overall, there is structural and computational economy, or even parsimony.

Animals↗
PubMed1986

Involvement of posterior visual pathways by optic nerve gliomas.

We describe the computed tomographic (CT) findings in seven children with optic nerve gliomas extending posterior to the chiasm. These tumors spread along the optic tracts and in five of seven cases, involved the lateral geniculate bodies and adjacent optic radiations. The propensity for these tumors to extend along both the anterior and posterior visual pathways aids in their diagnosis. An MR scan was obtained in one patient and identified an unexpected site of tumor extension as well as the mass seen by CT.

Child↗
PubMed1996

Discrimination performance and resolution capacity of uncrossed visual pathways in one-eyed albino rats.

Our recent study has demonstrated that adult rats with one eye removed at birth (OEB) relearn a discrimination between alternating black and white stripes, 30 mm wide each, oriented horizontally and vertically faster than control rats monocularly enucleated in adulthood (OET), when relearning is carried out after lesions of the visual cortex and transections of the optic tract contralateral to the remaining eye. Yet, we could not obtain the corresponding results in the acquisition of the discrimination following the same surgical treatments: OEBs did master the discrimination, whereas OETs did not. We hypothesized that a large discrepancy in OETs' performance between the acquisition and relearning occurred because the stripes were close to the limit of the resolution capacity of the uncrossed visual pathways (UXVPs), and hence that a better performance of OEBs was to indicate an increase in the resolution capacity, which resulted from reorganization of the UXVPs brought about by monocular enucleation at birth. To test the hypothesis we tried to approximate the limit of the resolution capacity of the UXVPs in OEBs and OETs using seven different sized test stripes ranging from 20 to 5 mm in width after both OEBs and OETs had relearned the discrimination of the 30 mm training stripes following the same surgical treatments mentioned above. It was found that the median width of the smallest stripes for OETs to discriminate was 10 mm, and that of OEBs 7.5 mm. Although OETs could not discriminate the smallest stripes which OEBs could, they were able to discriminate stripes one third smaller than those hypothesized. Based on these findings the possibility was discussed that the acquisition as well as the relearning of the discrimination of the 30 mm stripes mediated by the UXVPs in OEBs and OETs might not be influenced by the resolution capacity, but mostly, if not entirely, by the size of the visual field.

Animals↗