scholarly journals THEORY AND MEASUREMENT OF VISUAL MECHANISMS

1939 ◽  
Vol 22 (3) ◽  
pp. 341-364 ◽  
Author(s):  
W. J. Crozier ◽  
A. H. Holway
Keyword(s):  
Angular Distance ◽  
Visual Sensitivity ◽  
Peripheral Retina ◽  
Test Image ◽  
Retinal Position ◽  
Threshold Response ◽  
Threshold Stimulus ◽  
The Central Nervous System ◽  
Quantitative Properties ◽  
Binocular Measurement

Monocular threshold stimulus intensities (ΔIo, photons) were measured along the 0–180° meridian of human retinae for three observers. The test image was small (= 0.08°) and of short duration (= 0.20 second). ΔIo was found to decrease as the angular distance from the fovea was increased. Actual counts of the number of retinal elements per mm.2 along the 0–180° meridian (Østerberg) were compared with the obtained results. No direct correlation was found to exist between visual sensitivity and the number of retinal elements. Binocular threshold stimuli were also measured along the same meridian. The form of the function relating binocular visual sensitivity and retinal position was discovered to be essentially similar to that for monocular sensitivity, but is more symmetrical about the center of the fovea. The magnitude of the binocular measurement is in each case smaller than that of the monocular threshold stimulus intensity for the more sensitive eye. The ratio is statistically equal to 1.4 (a fact which suggests Piper's rule). These results are shown to be consistent with the hypothesis that the process critical for the eventuation of the threshold response is localized in the central nervous system. They are not consistent with the view that the quantitative properties of visual data are directly determined by properties of the peripheral retina.

Establishing the Diagnosis

2009 ◽  
Author(s):  
Daniel A. Brinton ◽  
Charles P. Wilkinson
Keyword(s):  
Retinal Detachment ◽  
Posterior Pole ◽  
Peripheral Retina ◽  
Retinal Breaks ◽  
Yellow Color ◽  
Red Color ◽  
The Central Nervous System ◽  
Retinal Artery ◽  
Ciliary Artery ◽  
Choroidal Vessels

The differential diagnosis of rhegmatogenous retinal detachment includes secondary (nonrhegmatogenous) retinal detachment and other entities that may simulate a retinal detachment. Nonrhegmatogenous detachments are categorized as exudative (serous) and tractional detachments. Conditions that may be mistaken for retinal detachment include retinoschisis, choroidal detachment or tumors, and vitreous membranes. Sometimes benign findings in the peripheral retina are mistaken for retinal breaks. The most prominent feature of the fundus is the optic nerve head or disc, the only place in the human body that affords a direct view of a tract of the central nervous system. The foveola, the functional center of the fundus, is located in the center of the fovea, which has a diameter of about 5°. The macula is centered on the fovea and has a diameter of about 17°. The multiple branches of the central retinal artery are readily identifi ed by their bright red color and relatively narrow caliber. The multiple tributaries of the central retinal vein are recognized by their dark red color and relatively wider caliber. In a darkly pigmented fundus, the choroidal vessels in the posterior pole can be obscured from view, but in an eye with minimal pigment, they are readily visible. The venous tributaries of the choroid that make up the vortex veins are usually easily seen. The most prominent features of the choroidal venous system are the vortex ampullae, of which there are usually four (but sometimes more). They are located approximately in the 1-, 5-, 7-, and 11-o’clock meridians, just posterior to the equator. The horizontal meridians are usually identifiable by their radially oriented, long posterior ciliary nerves, and infrequently the long posterior ciliary artery can be seen adjacent to the nerve. The nerve is relatively broad and has a yellow color, and the artery is identifiable by its red color. The artery is usually inferior to the nerve temporally, and superior to it nasally (Figure 5–1).

MHC class II expression by β2 integrin (CD18)-positive microglia, macrophages and macrophage-like cells in rabbit retina

2008 ◽  
Vol 4 (4) ◽  
pp. 285-294 ◽  
Author(s):  
Wenbing Huang ◽  
Coral G. Chamberlain ◽  
Richard Y. Sarafian ◽  
Tailoi Chan-Ling
Keyword(s):  
Blood Vessels ◽  
Mhc Class Ii ◽  
Immune Surveillance ◽  
Class Ii ◽  
Developmental Expression ◽  
Peripheral Retina ◽  
Β2 Integrin ◽  
The Central Nervous System ◽  
Parenchymal Cells ◽  
Mhcii Expression

The aim of this study was to investigate the developmental expression of major histocompatibility complex class II (MHCII) by microglia and macrophages and their relationship to blood vessels in the retina, a representative tissue of the central nervous system. Such information is crucial to understanding the role of these cells in immune surveillance. Wholemount preparations of retinas from late embryonic, postnatal and adult rabbits were subjected to three-colour fluorescence microscopy using β2 integrin (CD18) and MHCII antibodies and biotinylated Griffonia simplicifolia B4 isolectin labelling of blood vessels. CD18+ cells consistently exhibited characteristics of macrophages or microglia in the vascularized and non-vascularized regions of the retina, respectively. At all ages, MHCII was expressed by a high proportion of cells in the vascularized region, which contained macrophage-like ‘parenchymal cells’ as well as typical perivascular macrophages. MHCII expression by ramified microglia, first detected on postnatal day 30, was lower in the peripheral retina and intermediate in the avascular region of the myelinated streak. The observed localization of MHCII+ cells in relation to blood vessels and location-dependent differences in MHCII expression point to the possibility that these cells may be distributed strategically within the retina to provide multiple lines of defence against immune challenge arriving via the retinal vasculature.

The morphological characterization and distribution of displaced ganglion cells in the anuran retina

1989 ◽  
Vol 3 (6) ◽  
pp. 551-561 ◽  
Author(s):  
Pál Tóth ◽  
Charles Straznicky
Keyword(s):  
Optic Nerve ◽  
Ganglion Cell ◽  
Ganglion Cells ◽  
Plexiform Layer ◽  
Cell Types ◽  
Dendritic Morphology ◽  
Peripheral Retina ◽  
Inner Plexiform Layer ◽  
Retinal Position ◽  
Retinal Distribution

AbstractThe number, dendritic morphology, and retinal distribution of displaced ganglion cells were studied in two anuran species, Xenopus laevis and Bufo marinus. Horseradish peroxidase or cobaltic lysine complex was applied to the cut end of the optic nerve, and the size, shape, and retinal position of retrogradely filled ganglion cells displaced into the inner nuclear layer were determined in retinal wholemount and sectioned material. Approximately 1% of ganglion cells in Xenopus and 0.1% in Bufo were found to be displaced. In both species, many of the previously described orthotopic ganglion cell types (Straznicky & Straznicky, 1988; Straznicky et al., 1990) were present among displaced ganglion cells. In Xenopus more displaced ganglion cells were found in the retinal periphery than in the retinal center, and they formed 3 or 4 distinct bands around the optic nerve head. In Bufo the incidence of displaced ganglion cells was higher along the visual streak than in the dorsal and ventral peripheral retina. These results indicate that the distribution of displaced ganglion cells approximates the retinal distribution of orthotopic ganglion cells. One of the likely mechanisms to account for this developmental paradox may be that the formation of the inner plexiform layer, adjacent to the ciliary margin, acts as a mechanical barrier by preventing the entry of some of the late developing ganglion cells into the ganglion cell layer.

Neural limitations of visual excitability: II. Retrochiasmal interaction

1959 ◽  
Vol 197 (6) ◽  
pp. 1237-1242 ◽  
Author(s):  
I. H. Wagman ◽  
W. S. Battersby
Keyword(s):  
Visual System ◽  
Visual Sensitivity ◽  
The Other ◽  
Test Flash ◽  
Retinal Position ◽  
Electrophysiological Data ◽  
Time Threshold ◽  
Maximum Increment ◽  
Trained Observers ◽  
Light Flashes

Binocular visual excitability changes were obtained from two trained observers by presenting a "conditioning" flash of light to one eye and a brief "test" flash to a homologous retinal position in the other. Interval between flashes ranged from –200 msec. (test flash preceding conditioning) to +600 msec. (test following onset of conditioning flash). Results showed that threshold rose when test preceded conditioning flash, reaching a maximum increment of 0.5 log ml at –25 msec. separation. When test was superimposed upon conditioning flash in time, threshold dropped sharply to reach a relatively constant but elevated value for the duration of the conditioning flash. No excitability changes were obtained, however, if the test and conditioning flashes were displaced so as to stimulate adjacent rather than "corresponding" retinal points. These findings indicate that central (retrochiasmal) factors can influence visual sensitivity, the magnitude of this influence varying with the spatial and the temporal relations between successive light flashes. This conclusion is compatible with recent electrophysiological data on excitability changes in the cerebral visual system.

Visual Detection Probability of “Sonar” Targets as a Function of Retinal Position and Brightness Contrast

1968 ◽  
Vol 10 (4) ◽  
pp. 403-412 ◽  
Author(s):  
Leroy L. Vallerie ◽  
James M. Link
Keyword(s):  
Detection Probability ◽  
Visual Detection ◽  
Angular Distance ◽  
Probability Of Detection ◽  
Brightness Contrast ◽  
Retinal Position ◽  
Peak Intensity

A study was carried out in the laboratory to determine the detectability of visual sonar targets as a function of retinal position and brightness contrast using a simulated sonar scope. Nine different retinal positions were investigated under photopic conditions of illumination. The target was approximately square and subtended 24 minutes of visual arc on a side. Average peak intensity of the sweep, which formed the target background was 9.12 FL. The results of the study were presented in terms of probability of detection curves. Equations were developed for determining the probability of detection given the target's normalized brightness intensity, expressed in Log ΔI/I, and its angular distance from the point of fixation.

Evidence for a Blood Ganglion Barrier in the Superior Cervical Ganglion of the Rat

1982 ◽  
Vol 40 ◽  
pp. 204-204
Author(s):  
D. M. DePace
Keyword(s):  
Blood Vessels ◽  
Superior Cervical Ganglion ◽  
Peripheral Nerves ◽  
Time Schedule ◽  
Transmission Electron ◽  
Cervical Ganglion ◽  
The Central Nervous System ◽  
Cervical Ganglia ◽  
Capillary Circulation ◽  
And Control

The majority of blood vessels in the superior cervical ganglion possess a continuous endothelium with tight junctions. These same features have been associated with the blood brain barrier of the central nervous system and peripheral nerves. These vessels may perform a barrier function between the capillary circulation and the superior cervical ganglion. The permeability of the blood vessels in the superior cervical ganglion of the rat was tested by intravenous injection of horseradish peroxidase (HRP). Three experimental groups of four animals each were given intravenous HRP (Sigma Type II) in a dosage of.08 to.15 mg/gm body weight in.5 ml of.85% saline. The animals were sacrificed at five, ten or 15 minutes following administration of the tracer. Superior cervical ganglia were quickly removed and fixed by immersion in 2.5% glutaraldehyde in Sorenson's.1M phosphate buffer, pH 7.4. Three control animals received,5ml of saline without HRP. These were sacrificed on the same time schedule. Tissues from experimental and control animals were reacted for peroxidase activity and then processed for routine transmission electron microscopy.

Effects of Hyperoxia on Lung Utrastructure

1970 ◽  
Vol 28 ◽  
pp. 26-27
Author(s):  
Gladys Harrison
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Light Microscopy ◽  
Oxygen Effects ◽  
Age Dependent ◽  
The Central Nervous System ◽  
The Subject ◽  
Space Age ◽  
Alveolar Septa ◽  
Extensive Damage

With the advent of the space age and the need to determine the requirements for a space cabin atmosphere, oxygen effects came into increased importance, even though these effects have been the subject of continuous research for many years. In fact, Priestly initiated oxygen research when in 1775 he published his results of isolating oxygen and described the effects of breathing it on himself and two mice, the only creatures to have had the “privilege” of breathing this “pure air”.Early studies had demonstrated the central nervous system effects at pressures above one atmosphere. Light microscopy revealed extensive damage to the lungs at one atmosphere. These changes which included perivascular and peribronchial edema, focal hemorrhage, rupture of the alveolar septa, and widespread edema, resulted in death of the animal in less than one week. The severity of the symptoms differed between species and was age dependent, with young animals being more resistant.

Presence of antibody in virus-infected brain cells of SSPE ferrets

1983 ◽  
Vol 41 ◽  
pp. 804-805
Author(s):  
Hannah R. Brown ◽  
Tammy L. Donato ◽  
Halldor Thormar
Keyword(s):  
Measles Virus ◽  
Plasma Cells ◽  
Subacute Sclerosing Panencephalitis ◽  
Protein A ◽  
Neutralizing Antibody ◽  
Brain Cells ◽  
Antibody Titers ◽  
A Cell ◽  
The Central Nervous System ◽  
The Brain

Measles virus specific immunoglobulin G (IgG) has been found in the brains of patients with subacute sclerosing panencephalitis (SSPE), a slowly progressing disease of the central nervous system (CNS) in children. IgG/albumin ratios indicate that the antibodies are synthesized within the CNS. Using the ferret as an animal model to study the disease, we have been attempting to localize the Ig's in the brains of animals inoculated with a cell associated strain of SSPE. In an earlier report, preliminary results using Protein A conjugated to horseradish peroxidase (PrAPx) (Dynatech Diagnostics Inc., South Windham, ME.) to detect antibodies revealed the presence of immunoglobulin mainly in antibody-producing plasma cells in inflammatory lesions and not in infected brain cells.In the present experiment we studied the brain of an SSPE ferret with neutralizing antibody titers of 1:1024 in serum and 1:512 in CSF at time of sacrifice 7 months after i.c. inoculation with SSPE measles virus-infected cells. The animal was perfused with saline and portions of the brain and spinal cord were immersed in periodate-lysine-paraformaldehyde (P-L-P) fixative. The ferret was not perfused with fixative because parts of the brain were used for virus isolation.

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