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 901 records · Page 50Linked to original sources
PubMed1997

Early impairment of foveal magno- and parvocellular pathways in juxta chiasmal tumours.

Foveal pathway visual function was assessed in 11 patients having tumours extending into the suprasellar region but without evidence of visual impairment as assessed by visual acuity and Bjerrum screen campimetry. Psychophysical and routine visual evoked potential (VEP) measurements were obtained from the eye ipsilateral to the maximal suprasellar extension. The sensitivity of luminance and chromatic pathways was assessed psychophysically by measuring increment thresholds for white and red flashes of light presented on a white adapting field. Temporal sensitivity was assessed psychophysically by measuring threshold modulation sensitivity for sinusoidally modulating stimuli (de Lange attenuation characteristic). The patient group showed approximately equal significant psychophysical losses in chromatic, luminance and temporal sensitivities relative to normal controls. Midline VEP P100 latencies of the patient group did not significantly differ from those of the normal control group. It is concluded that tumours extending into the suprasellar region can cause foveal pathway dysfunction affecting both magno- and parvocellular pathways, even in the presence of normal visual acuity and fields suggesting a more widespread and insidious abnormality of the visual pathways in this condition than previously thought.

Adenoma↗
PubMed1977

The role of the ventral lateral geniculate nucleus and posterior thalamus in intensity discrimination in rats.

The role of several subcortical structures in intensity discrimination was studies by examining the effects of localized lesions on intensity and orientation discrimination. In experiment 1 rats with lesions confined to the ventral lateral geniculate nucleus (LGNv) or posterior thalamus were specifically impaired on postoperative acquisition of the intensity discrimination compared with sham operated controls or rats with destruction of the superior colliculi. The lesions had no effect on the orientation discrimination unless the primary visual pathways were also damaged. The effects of LGNv damage on intensity discrimination were confirmed with much smaller lesions in experiment 2. In experiment 3 it was shown that postoperative retention of the intensity discrimination is also specifically impaired by destruction of LGNv. The results are related to the possiblility that information about intensity and pattern is coded in separate visual pathways.

Animals↗
PubMed1997

Activation and inactivation steps in the visual transduction pathway.

Recent genetic, biochemical and electrophysiological evidence has provided insights into the molecular identity of the substance responsible for bleaching desensitization in vision. Studies examining the molecular defects that cause delayed dark adaptation suggest that the desensitizing substance is recognized by rhodopsin kinase and/or arrestin and, therefore, is probably a complex comprising all-trans-retinal and opsin.

Animals↗
PubMed1998

The cupped disc. Who needs neuroimaging?

OBJECTIVE: To determine the incidence of positive neuroradiologic studies in consecutive patients with glaucoma associated with normal intraocular pressure and to compare the psychophysical and clinical characteristics of these eyes with eyes with disc cupping associated with intracranial masses. DESIGN: Retrospective case-controlled study. PARTICIPANTS: Fifty-two eyes of 29 patients with glaucoma associated with normal intraocular pressure and 44 eyes of 28 control patients with compressive lesions were reviewed. INTERVENTION: The medical records of consecutive glaucoma patients with normal intraocular pressure who underwent brain magnetic resonance imaging or computed tomography scanning as part of a diagnostic evaluation between January 1, 1985, and July 1, 1995, were reviewed. A masked reading of optic nerve photographs and visual fields was performed by one observer. A similar analysis was performed on a control group of consecutive patients with nonglaucomatous optic nerve cupping with known intracranial mass lesions. MAIN OUTCOME MEASURES: The neuroradiologic findings, clinical characteristics, optic nerve head appearance, and patterns of visual field loss were compared between groups. RESULTS: None of the patients diagnosed with glaucoma had neuroradiologic evidence of a mass lesion involving the anterior visual pathway. Compared to control subjects, patients with glaucoma were older (P = 0.0001), had better visual acuity (P = 0.002), greater vertical loss of neuroretinal rim tissue (P = 0.0001), more frequent optic disc hemorrhages (P = 0.01), less neuroretinal rim pallor (P = 0.0001), and more nerve fiber bundle visual field defects aligned at the horizontal midline (P = 0.0001). Visual acuity less than 20/40, vertically aligned visual field defects, optic nerve pallor in excess of cupping, and age younger than 50 years were 77%, 81%, 90%, and 93% specific for nonglaucomatous cupping associated with compressive lesions, respectively. CONCLUSIONS: Anterior visual pathway compression is an uncommon finding in the neuroradiologic evaluation of patients with a presumptive diagnosis of normal-tension glaucoma. Younger age, lower levels of visual acuity, vertically aligned visual field defects, and neuroretinal rim pallor may increase the likelihood of identifying an intracranial mass lesion.

Adolescent↗
PubMed1990

Altitudinal hemianopia; a clinical and anatomical entity or a mere coincidence? Case report and review of literature.

Many lesions along the visual pathway from the retina to the occipital cortex can cause a horizontal hemianopia. The anatomy of the visual pathway is reviewed in an attempt to clarify how and where this visual field defect develops. A case is presented in which two ischemic occipital infarcts caused a bilateral inferior horizontal hemianopia and complex visual hallucinations. Previous cases of occipital lesions resulting in an altitudinal hemianopia are reviewed.

Aged↗
PubMed1997

Transsynaptic degeneration of lateral geniculate bodies in blind children: in vivo MR demonstration.

PURPOSE: To investigate signal alterations in the thalamic lateral geniculate bodies of blind patients compatible with transsynaptic degeneration of these nuclei caused by pregeniculate or postgeniculate interruption of the visual pathway. METHODS: Six patients were selected from a group of blind children in our care. Four had cerebral palsy caused by periventricular leukomalacia, one had infantile neuroaxonal dystrophy, and one had Chiari I malformation and hydrocephalus, which was worsened by bilateral ischemic lesions of the occipital lobes. MR examinations (obtained at 0.5 T) were reviewed retrospectively by two neuroradiologists, with particular attention to the visual pathway. RESULTS: Symmetric, focal areas of T2 prolongation were found at the precise site of the lateral geniculate bodies. CONCLUSION: Anterograde (pregeniculate) and retrograde (postgeniculate) transsynaptic degeneration of the second neurons of the visual pathway produce alterations in MR signal.

Arnold-Chiari Malformation↗
PubMed2003

Concordance of high-pass resolution perimetry and frequency-doubling technology perimetry results in glaucoma: no support for selective ganglion cell damage.

PURPOSE: To compare the results of frequency-doubling technology perimetry (FDT), assumed to test the magnocellular visual pathway, and high-pass resolution perimetry (HRP), assumed to test the parvocellular visual pathway, in patients with ocular hypertension or glaucoma. PATIENTS AND METHODS: Forty-eight consecutive patients with glaucoma or ocular hypertension, covering the entire range of optic nerve function from normal to severely damaged, were examined on the same day using FDT and HRP. RESULTS: There was a linear correlation between both global and local indices in FDT and HRP (r = -0.84 P<0.0001 and r = 0.8 P<0.001, respectively). The HRP and FDT classifications agreed in 32 of the 48 (67%) eyes (Cohen kappa = 0.5). There was no significant difference between the ability of the different techniques to detect abnormality. CONCLUSION: The observations in the present study indicate either that both cell populations are similarly affected by glaucomatous damage or that both methods measure activity in the same cell populations.

Adult↗
PubMed2007

Imaging anatomy of the vestibular and visual systems.

PURPOSE OF REVIEW: This review will outline the imaging anatomy of the vestibular and visual pathways, using computed tomography and magnetic resonance imaging, with emphasis on the more recent developments in neuroimaging. RECENT FINDINGS: Technical advances in computed tomography and magnetic resonance imaging, such as the advent of multislice computed tomography and newer magnetic resonance imaging techniques such as T2-weighted magnetic resonance cisternography, have improved the imaging of the vestibular and visual pathways, allowing better visualization of the end organs and peripheral nerves. Higher field strength magnetic resonance imaging is a promising tool, which has been used to evaluate and resolve fine anatomic detail in vitro, as in the labyrinth. Advanced magnetic resonance imaging techniques such as functional magnetic resonance imaging and diffusion tractography have been used to identify cortical areas of activation and associated white matter pathways, and show potential for the future identification of complex neuronal relays involved in integrating these pathways. SUMMARY: The assessment of the various components of the vestibular and the visual systems has improved with more detailed research on the imaging anatomy of these systems, the advent of high field magnetic resonance scanners and multislice computerized tomography, and the wider use of specific techniques such as tractography which displays white matter tracts not directly accessible until now.

Afferent Pathways↗
PubMed1987

Corticocortical projections to the monkey temporal lobe with particular reference to the visual processing pathways.

Cortico-cortical connections occurring within the temporal lobe and afferent projections to the temporal cortex particularly from the prefrontal and parahippocampal areas were studied in the monkey by means of retrograde axonal transport of horseradish peroxidase (HRP) or wheat-germ-agglutinin-conjugated HRP (WGA-HRP). In particular, 0.1-0.3 microliter of 50% HRP or 5% WGA-HRP was injected into various parts of the temporal cortex, i.e. the rostral (TEr), the caudal (TEc), and the most caudal (TEO) parts of the inferotemporal cortex, the superior temporal gyrus, and the temporal pole (TG), and in the upper bank of the inferior arcuate sulcus in the frontal lobe. Labeled cells, which represent cells of origin of association fibers projecting to the injection site, appeared in various cortical regions. The main findings of the present study are the following. The temporal pole (TG) receives fibers almost exclusively from the most rostral part of the TE. The rostral part of the TE receives many fibers from both the caudal part of the TE and the TEO. The caudal part of the TE receives fibers from the TEO, and the TEO from the prestriate cortex (OA and OB). Taking these findings together, the morphological basis of the "step-wise" progression of visual impulses from the prestriate cortex to the TEO, TE and finally to the TG is clearly presented. The superior temporal gyrus (TA or area 22) receives most fibers from the dorsolateral frontal gyrus, while the inferotemporal cortex (TE or areas 21 and 20) receives most fibers from the ventrolateral frontal gyrus (inferior frontal convexity). Both the temporal pole (TG) and the inferotemporal cortex (TE) receives a fair number of fibers from the parahippocampal region (TH and TF).

Animals↗
PubMed2006

Surgical lesion of the anterior optic tract abolishes polarotaxis in tethered flying locusts, Schistocerca gregaria.

Many insects can detect the polarization pattern of the blue sky and rely on polarization vision for sky compass orientation. In laboratory experiments, tethered flying locusts perform periodic changes in flight behavior under a slowly rotating polarizer even if one eye is painted black. Anatomical tracing studies and intracellular recordings have suggested that the polarization vision pathway in the locust brain involves the anterior optic tract and tubercle, the lateral accessory lobe, and the central complex of the brain. To investigate whether visual pathways through the anterior optic tract mediate polarotaxis in the desert locust, we transected the tract on one side and tested polarotaxis (1) with both eyes unoccluded and (2) with the eye of the intact hemisphere painted black. In the second group of animals, but not in the first group, polarotaxis was abolished. Sham operations did not impair polarotaxis. The experiments show that the anterior optic tract is an indispensable part of visual pathways mediating polarotaxis in the desert locust.

Animals↗
PubMed2005

Lymphatic drainage from esophagogastric tract: feasibility of endoscopic CT lymphography for direct visualization of pathways.

PURPOSE: To evaluate the feasibility of an endoscopic computed tomographic (CT) lymphography technique with submucosal injection of iopamidol for direct visualization of lymphatic drainage pathways in dogs and in patients with operable esophageal cancer. MATERIALS AND METHODS: With institutional animal committee approval, a total of 2 mL of undiluted iopamidol was injected into the esophageal (n = 6) or gastric (n = 3) submucosa in nine dogs by using a flexible endoscope. Multi-detector row CT images (section thickness, 1.25 mm) were obtained before contrast material injection and during the 10 minutes after injection. The animals were euthanized so that their lymphatic anatomy could be examined. With ethical committee approval and patient informed consent, nine patients with esophageal cancer also underwent CT lymphography with peritumoral injection of 2 mL of iopamidol, followed by esophagectomy and regional lymph node dissection with CT lymphographic guidance. The histopathologic features of dissected nodes, including sentinel lymph nodes (SLNs), were examined. RESULTS: CT lymphography depicted the direct connection of lymphatic drainage vessels with enhanced and/or unenhanced nodes (ie, SLNs) as early as within 5 minutes after contrast material injection in all subjects. All 13 SLNs in dogs (1.4 nodes per animal) and 18 SLNs in patients (two nodes per patient) were found and dissected at the correct location by using CT lymphographic guidance. In patients, histopathologic examination revealed the high predictive value of CT lymphographic-guided SLN biopsy: Only one of the preoperatively identified SLNs in three patients and both SLNs and adjacent nodes in two patients were positive for metastasis; all resected nodes in the remaining four patients were negative. CONCLUSION: Endoscopic CT lymphography is a feasible method for visualizing the direct connection between and the accurate anatomic location of SLNs and lymphatic drainage vessels.

Aged↗
PubMed1991

Localization of visual field defects in multiple sclerosis.

Demyelinating plaques can occur throughout the central nervous system in multiple sclerosis, possibly involving the visual pathways at any location. The proper evaluation of visual field defects in multiple sclerosis patients enables the optometrist to become a part of the health care team in monitoring the severity and progression of the disease. Three case reports are presented which illustrate the variable presentations and the proper interpretation of findings to localize demyelinating plaques in the visual pathways.

Adult↗
PubMed1993

Longitudinal comparison of temporal-modulation perimetry with white-on-white and blue-on-yellow perimetry in ocular hypertension and early glaucoma.

We obtained data over 3 years on temporal-modulation perimetry (TMP), standard automated [white-on-white (W/W)] perimetry, and short-wavelength-sensitive [blue-on-yellow (B/Y)] perimetry in ocular hypertensive (OH) patients and patients with early glaucomatous visual-field loss (EG). Evidence of visual-field defects was obtained with the use of both B/Y perimetry and TMP in the majority of OH and EG eyes that demonstrated progression on W/W perimetry as well as in all stable EG eyes. Using the nerve-fiber-bundle pattern to compare testing procedures, we determined that these defects were generally as extensive or more extensive than the concurrent W/W abnormalities. In terms of location over the 3 years of testing, TMP and B/Y defects were reasonably consistent in the EG eyes, somewhat less consistent in the OH eyes demonstrating progression, and both inconsistent and infrequent in the stable OH eyes. The greatest degree of overlap occurred between the location of defects obtained by use of the higher TMP frequencies (8 and 16 Hz) and that of defects obtained by use of B/Y perimetry. Since these two methods are thought to isolate different visual mechanisms subserved by different visual pathways, these results suggest that early glaucomatous visual-field damage as revealed by TMP and B/Y perimetry may not be specific to a single visual pathway.

Color Perception Tests↗
PubMed1998

Multimodality visual evoked potentials in evaluating visual dysfunction in optic neuritis.

Visual information is processed via multiple, parallel channels. The present study examined the clinical feasibility of multimodality visual evoked potentials (VEPs) in optic neuritis. We recorded transient VEPs to 30' checkerboard patterns, chromatic and achromatic sinusoidal gratings and apparent motion, and steady-state VEPs to achromatic gratings in 15 normal controls and 14 patients. VEPs to 30' checks were abnormal in 10 eyes (7 patients); however, considering all five modalities, abnormal responses were seen in 20 eyes (12 patients). Abnormality rates were not equal among the visual stimuli, which thus suggested possible dysfunction of individual subdivisions in the visual pathways. We conclude that use of multimodality VEPs may increase both understanding of the pathophysiology of the visual pathways and diagnostic yield.

Adult↗
PubMed1995

[Abnormalities of pattern reversal evoked visual potential in patients with defined multiple sclerosis].

The pattern reversal visual evoked potential with checks of 14' and 28' was retrospectivelly studied in 28 patients with definite multiple sclerosis. We observed abnormal responses in 27/28 (96.4%) patients, in 31/36 (86%) of symptomatic eyes, and in 16/20 (80%) of asymptomatic eyes. When we classified the abnormalities in each eye according to the findings obtained with each check, there was a correlation between the pattern of abnormalities and the severity of visual involvement. Occasionally there were isolated abnormalities of N75 or only in P100 obtained with 28' checks. In conclusion the methodology applied was very sensible in detecting abnormalities in visual pathway. We could classify the findings in each eye and correlate them with the severity of visual involvement. The findings showed uneven distribution of lesions in visual pathway, affecting preferentially the central vision afferents.

Adult↗
PubMed1990

Properties of area 17/18 border neurons contributing to the visual transcallosal pathway in the cat.

In a series of physiological experiments, a total of 203 neurons at the Area 17/18 border were recorded with a callosal link either demonstrated by antidromic or transsynaptic activation from stimulating electrodes located in the homotopic contralateral hemisphere (CH), or in the splenial segment of the corpus callosum (CC). Forty-four percent of the transcallosal cells could also be driven from stimulating electrodes in or just above the lateral geniculate nucleus (OR1). The majority (69%) of transcallosal neurons were classifiable as belonging to the complex family (B and C cells) and most of these were found in the supragranular laminae and in lamina 4A. The ocular dominance distribution of transcallosal cells was trimodal, consisting of roughly equal numbers of monocularly dominated and binocularly balanced neurons. Estimates of conduction time and synaptic delay were obtained for neurons driven from CH, CC, and from OR1, and in most instances the response latency was short enough to suggest a monosynaptic input from either the ipsi- or contra-lateral hemisphere. The distribution of transcallosal conduction times showed that S cells, as a class, had significantly faster conduction than cells of the complex family but otherwise there was no obvious signs of multimodality in the distribution curve. An analysis of the synaptic delays in transcallosal activation produced a mean of 0.6 to 0.7 ms but some were too short to be consistent with a transsynaptic drive, suggesting that some cells with an antidromic drive may have been included in the transsynaptic category. Results are interpreted in terms of the contribution made by the corpus callosum to stereoscopic vision.

Animals↗
PubMed1993

Pseudorandom binary sequence stimulation applied to the visual evoked response. Normative data and a comparative study with pattern and flash stimulation.

The investigation of patients who are unable to fixate the pattern visual stimulus generally requires the use of diffuse flash stimulation to elicit the visual evoked response. However, by comparison with pattern, flash stimulation has proved relatively insensitive in identifying lesions of the visual pathway. We investigated a more complex method of flash stimulation. A pseudorandom binary sequence has been used to generate the diffuse visual evoked response stimulus. The pseudorandom binary sequence, rather than producing a single flash, switches in a pseudorandom fashion between two levels of illumination. The result is a diffuse visual stimulus approximating band-limited white noise. The series is periodic, enabling signal averaging to be performed. By applying the methods of random signal analysis, the impulse or transient response of the visual pathway can be determined. Our normal pseudo-random binary sequence visual evoked response impulse function, derived from 29 normal subjects, had the morphologic characteristics of the conventional flash visual evoked response and a major positive component (P100), whose latency mean and standard deviation closely matched that of our normative pattern visual evoked response. However, the P100 amplitude standard deviation was significantly greater than that produced by conventional pattern and flash stimulation. We investigated 140 patients by means of pattern, flash and pseudorandom binary sequence stimulation. The pseudorandom binary sequence visual evoked response proved to be almost 12 times more effective than flash visual evoked response in detecting lesions of the visual system.

Adolescent↗
PubMed1984

Mapping of functional activity in the falcon visual system with [14C] 2-deoxyglucose.

[14C] 2-Deoxyglucose uptake was mapped in the brain of one awake falcon which had one eye covered during the experiment, with the aim of providing tentative data on the identification of this bird's visual centers. Most of the structures with increased [14C] 2-Deoxyglucose uptake receive information from the exposed eye. Labeling was rather symmetrical in the hyperstriatum which receives bilateral projections from the visual thalamic centers. The results are largely consistent with what is known about the visual pathways in pigeons and owls. The falcon's visual Wulst as detected by the [14C] 2-Deoxyglucose labeling, is proportionally larger than that found in the pigeon. This result is consistent with the marked representation of the binocular visual field in the falcon's Wulst.

Animals↗