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 145 records · Page 8Linked to original sources
PubMed1994

Responses of neurons in the parietal and temporal visual pathways during a motion task.

The visual cortex of macaque monkeys has been divided into two functional streams that have been characterized in terms of sensory processing (color/form vs motion) and in terms of behavioral goals (object recognition vs spatial orientation). As a step toward unifying these two views of cortical processing, we compared the behavioral modulation of sensory signals across the two streams in monkeys trained to do a visual short-term memory task. We recorded from individual neurons in areas MT, MST, 7a, and V4 while monkeys performed a delayed match-to-sample task using direction of motion as the matching criterion. This task allowed us to determine if sensory responses were modulated by extraretinal signals related to the direction of the remembered sample. We sorted neuronal responses as a function of the remembered direction and calculated a modulation index, MI = (maximum response--minimum response)/(maximum response + minimum response). In the motion pathway, we found virtually no extraretinal signals in MT (average MI = 0.11 +/- 0.01 SE, 66 cells), but progressively stronger extraretinal signals in later stages, that is, MST (average MI = 0.17 +/- 0.01 SE, 57 cells) and 7a (average MI = 0.23 +/- 0.02 SE, 46 cells). In contrast to MT, strong extraretinal signals for direction matching were found in V4 (average MI = 0.28 +/- 0.02 SE, 94 cells), a relatively early stage of the color/form pathway, even though this pathway is not generally viewed as playing a major role in motion processing. Some cells in V4 were also tested while the animals performed a color matching task. These cells showed memory-related modulation of their response when either color or direction was used as the matching criterion. We conclude that extraretinal signals related to the match-to-sample task may be stronger in the temporal (color/form) pathway than in the parietal (motion) pathway, regardless of the stimulus dimension involved. Furthermore, our results indicate that the temporal pathway is capable of making a significant contribution to motion processing in tasks where motion can be considered as a cue for the identification of object attributes.

Analysis of Variance↗
PubMed1994

Correlational imaging of thalamocortical coupling in the primary visual pathway of the human brain.

While the anatomy of the human brain is well defined, the functional connectivity of its structures is far less understood. Modern neuroimaging techniques offer the unique opportunity of visualizing physiologic activation in central nervous structures and of identifying the elements underlying distributed networks for information processing. Following improved spatial resolution of deoxyhemoglobin-sensitive magnetic resonance imaging, we were able to detect simultaneous signal changes in the lateral geniculate nucleus and primary visual cortex during periodic photic stimulation. Visualization of coupled activation by cross-correlation analysis resulted in the first demonstration of thalamocortical interaction in the primary visual pathway of the intact human brain.

Adult↗
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↗
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↗