We examined the retinal cone topography in sexually mature individuals from four species of Pacific salmonid fishes by using semithin plastic sections. We identified variations in cone density and cone arrangements and noted the presence of putative ultraviolet (UV) cones. Putative UV cones were found over an area extending dorsotemporally ...

Psychophysical research has documented the existence of three processes in light adaptation: a fast subtractive process, a divisive process that is fast at light onset and slower at light offset, and a very slow subtractive process (Hayhoe et al., 1987). In the neural model developed here, the fast subtractive process ...

We have developed a high-resolution imaging technique, based on speckle interferometry, for the objective determination of the cone spacing in the living human fovea. The spatial resolution attained with this technique is theoretically diffraction limited by the pupil size. However, the highest frequency that we measure varies greatly among subjects, ...

In order to better understand the nature of long-wavelength (L) and middle-wavelength (M) cone input into spectral sensitivity functions and determine the reliability with which it is possible to predict L:M cone inputs, we developed analytical methods to determine confidence intervals for L:M cone input for spectral sensitivity functions or ...

In all mammals, the mitochondria of the cones of the retina are concentrated in the inner segment. Uniquely in tree-shrews (Tupaia, Scandentia, Mammalia), a "megamitochondrion" exhibiting highly specialized systems of densely packed cristae and a very electron dense matrix, is located apically in the inner segment. The ellipsoid is a ...

Video time-lapse microscopy has made it possible to document growth cone motility during axon navigation in the intact brain. This approach prompted us to reanalyze the hypothesis, originally derived from observations of fixed tissue, that growth cone form is position-specific. The behaviors of Dil-labeled retinal axon growth cones were tracked ...

Retinas of adult teleost fish can regenerate after injury. Two important issues regarding this phenomenon are the assembly of the regenerated retina and the neuronal images of the visual scene that the regenerated retina produces. Here we report experiments in which the visual pigment content of photoreceptors derived from native ...

The aim of this study was to develop a fast test for local photoreceptor alignment. Photoreceptor alignment is an important indicator of retinal integrity. Digitized images of fundus reflectance were obtained for 20-30 pupil entry positions with a custom built scanning laser ophthalmoscope (SLO). The data permitted the calculation of ...

The retina of mammals contains various amounts of cone photoreceptors that are relatively evenly distributed and display a radially or horizontally oriented area of peak density. In most mammalian species two spectrally different classes of cone can be distinguished with various histochemical and physiological methods. These cone classes occur in ...

Blue acaras (Aequidens pulcher, Cichlidae) were reared for 1 yr in white or monochromatic "red", "green" and "blue" lights to study the function and control mechanisms of horizontal cell (HC) spinules in the synaptic pedicles of cones. Ratios of spinules per synaptic ribbon (S/R) were determined in tangential sections in ...

Retinoid trafficking between the photoreceptors and pigmented epithelium is probably mediated by interphotoreceptor retinoid-binding protein (IRBP), a 124-145 kDa glycolipoprotein in mammals and amphibians. In these animals, IRBP is composed of four homologous regions (modules) 300 amino acids in length. We have determined the primary structure of zebrafish IRBP and ...

The action spectrum of the optomotor response in goldfish was measured to investigate which of the four cone types involved in color vision contributes to motion detection. In the dark-adapted state, the action spectrum showed a single maximum in the range of 500-520 nm, and resembled the rod spectral sensitivity ...

PURPOSE: To determine the origin of the tapetal-like reflex (TLR) in carriers of X-linked retinitis pigmentosa. METHODS: Spectral fundus reflectance of carriers of X-linked retinitis pigmentosa was measured and compared with that of normal subjects. The influence of visual pigment was determined by measuring the density difference, that is, the ...

The topography and spectral characteristics of mammalian photoreceptors correlate with both, the present ecological demands and the evolutionary history. The South American Opossum is a marsupial mammal with unspecialized habitus and crepuscular lifestyle. A sparse population of cones (max. = 3000/mm2) can be differentiated into four subtypes by morphological, topographical ...

In this study the dynamic properties of goldfish horizontal cell (HC) receptive fields were evaluated. The size of HC receptive fields increases up to about 60 msec after stimulus onset, and then reduces to a smaller end value. They can therefore not adequately be described by the cable equation. Estimates ...

Short-wavelength-sensitive (S-) cone-mediated thresholds have been used to study the early stages of visual loss, but due to the effects of non-neural factors (pupil size, lenticular density, macular pigment density) S-cone thresholds are often of limited clinical utility. The current study evaluates four possible effects of non-neural factors on S-cone ...

The confusion points of dichromats are derived from the constant-luminance planes of trichromats, protanopes and deuteranopes experimentally defined by heterochromatic-flicker photometry: (1) the zero-luminance planes of the observers considered in this experiment intersect almost exactly in a line that crosses the plane of the chromaticity diagram in the tritanopic-confusion point ...

Mammalian color vision is mediated by light-sensitive pigments in retinal cone cells. Biochemical studies on native mammalian cone visual pigments are seriously hampered by their low levels and instability. We describe a novel approach for their functional expression, employing the baculovirus system in combination with histidine tagging to allow future ...

By means of asymmetric color matching, the effects of steady-state chromatic adaptation on the color appearance of briefly presented chromatic flashes were investigated. The adapting and test lights were of equal luminance (35 cd/m2) and differed from the standard grey adapting light either along the L-2M (red and green), or ...

Motion reversal effects (the apparent reversal of the direction of motion of a high frequency sinusoidal grating) have been attributed to aliasing by the cone mosaic [Coletta et al. (1990). Vision Research, 30, 1631-1648] and postreceptoral layers [Anderson & Hess (1990). Vision Research, 30, 1507-1515] in human observers. We present ...

AIMS: The short wavelength sensitive (S) cone electroretinograms (ERGs) were examined in two patients with the complete type of congenital stationary night blindness (CSNB). METHODS: Ganzfeld spectral flashes in the presence of strong white adapting fields were used to elicit the S cone ERGs. RESULTS: The S cone ERG b-wave ...

On the basis of the early primate neurophysiological recordings, it was thought that the different cone types of the primate retina project selectively into the centre and surround of the receptive fields of cone opponent neurons, and more recently this view has been reasserted on the basis of physiological results. ...

Patients with retinitis pigmentosa (RP) show delayed inner retinal responses as measured by the cone ERG response to a 30 Hz stimulus. To determine the extent to which this delay results from abnormalities of cone phototransduction, cone ERGs to single flashes were obtained from 21 patients with RP and a ...

To test whether the binocular contour rivalry mechanism is tritanopic, we presented isoluminant, rival stimuli visible only via the short-wavelength-sensitive (S) cones. We stimulated only the S cones with violet gratings superimposed on a bright yellow field that adapted the responses of the middle- and long-wavelength-sensitive (M and L) cones. ...

In the vertebrate retina, the light responses of post-receptor neurons depend on the ambient or background illumination. Using intracellular recording, we have found that a circadian clock regulates the light responses of dark-adapted fish cone horizontal cells. Goldfish were maintained on a 12-hr light/12-hr dark cycle. At different times of ...

Color appearance judgments revealed fundamental differences in visual processing of incremental and decremental lights. First, the balance of cone activation required for a light to appear achromatic was different for increments and decrements (Judd, 1940; Helson & Michels, 1948). Second, adaptation--the visual system's adjustment to background light--affected achromatic decrements more ...

Photocurrents of cones in the retinas of a small fish, Danio aequipinnatus (Cyprinidae) were recorded with suction pipette electrodes. Spectral sensitivity was measured between 277 and 697 nm. Four spectral classes of cone were found, with lambdamax at 560, 480, 408, and 358 nm. For the latter, we provide the ...

Slope of terrain is an important orienting gradient affecting the goal-directed locomotion of animals. Its significance was assessed in experiment 1 by training rats to find in darkness a feeder on the top of a low cone (80-cm base, 0- to 4-cm high). A computerized infrared tracking system monitoring the ...

1. Optical reflectance spectra of the fovea were measured in ten subjects with normal colour vision, ten protanopes and seven deuteranopes. Four conditions were used: perpendicular and oblique angle of incident and reflected light on the retina, both in a dark-adapted and a fully bleached state. 2. The spectra were ...

The various classes of photoreceptor cells found in vertebrate retinae are organized in specific patterns, which are important for visual function. It is not known how these patterns are achieved during development. The chick retina provides an excellent model system in which to investigate this issue, containing cone opsins red, ...

1. The action of N-methyl-D-aspartate (NMDA) on cone horizontal cells was studied in in vitro goldfish retinas superfused with a bicarbonate-based Ringer solution that contained D-serine (0.5 microM), a glycine analogue, but no added Mg2+. Horizontal cell light responses and electrical coupling were assessed by monitoring responses to full-field stimuli ...

The growth cone is generally regarded as the basic unit of neuronal organization concerned with development of connections within the nervous system. The discussion below illustrates that the growth cone itself can be subdivided into distinct units of organization. It is this functional compartmentalization which enables the growth cone to ...

At the retinal level, the strategies utilized by biological visual systems allow them to outperform machine vision systems, serving to motivate the design of electronic or "smart" sensors based on similar principles. Design of such sensors in silicon first requires a model of retinal information processing which captures the essential ...

Using optic filters, we analyzed the wave-length specificity of photoparoxysmal responses (PPR) in photosensitive patients with idiopathic generalized epilepsy (IGE). We specified the wavelength spectrum approximately 700 nm (660-720 nm) as the only visible spectrum essential for eliciting PPR in some normal trichromat IGE patients and showed that any flashing ...

Surround enhancement (sensitization) is a poorly understood form of network adaptation in which the kinetics of the responses of retinal neurons to test stimuli become faster, and absolute sensitivity of the responses increases with increasing level of steady, surrounding light. Surround enhancement has been observed in all classes of retinal ...

Determination of the primary structures of six kinds of vertebrate visual pigments enabled us to classify them into four groups of cone-type pigments. The phylogenetic tree demonstrated that an ancestor of vertebrate visual pigments evolved into four kinds of cone-type pigments, from one of which rhodopsins diverged. Tetrachromatic color vision ...

PURPOSE: To determine the functional defects in two male patients with progressive cone dystrophy and hybrid L-M cone pigment genes. METHODS: Clinical evaluation, standard electroretinography, and electrooculography were performed in two affected patients and two family members. Measurements of spectral sensitivity and transient tritanopia were made in both patients. RESULTS: ...

Recent physiological evidence suggests that cones do not light adapt at low light levels. To assess whether adaptation is cone-selective at low light levels, the red-green detection mechanism was isolated. Thresholds were measured with a large test flash, which stimulated the L and M cones in different fixed amplitude ratios, ...

In this report we have characterized the photopigments mediating circadian phase shifts in retinal degenerate (rd) mice. In aged rd/rd mice, which lack detectable opsin, high performance liquid chromatography (HPLC) was used to quantify the photopigment chromophore 11-cis-retinaldehyde. This chromophore was photoisomerized in whole eyes, suggesting the presence of a ...

The influence of center-surround antagonism on light adaptation in cone photoreceptors was investigated by intracellular recording from red-sensitive cones in the retina of the turtle, Pseudemys scripta elegans. Test flashes of 0.15-mm diameter were applied at the center of background fields of 0.25-mm or 2.2-mm diameter. Immediately upon expanding the ...

PURPOSE: Blue-on-yellow (B-on-Y) perimetry assesses the S-cone visual field under yellow adaptation. Glaucomatous field defects have been shown to appear earlier and to be larger in B-on-Y perimetry than in standard perimetry. An upper limit to the use of B-on-Y perimetry is set by the separation of the S-cones from ...

In recent years a number of electrophysiological and psychophysical observations have suggested that the temporal properties of the human longwave- and middlewave-sensitive cones might be different. However, until now the issue has remained unresolved, despite its obvious importance. We have succeeded in probing, electrophysiologically, the temporal properties of the two ...

Chromatic-discrimination thresholds were measured for light mixtures lying along individually determined tritan axes and an axis of constant short-wavelength-sensitive- (S-) cone stimulation for 30 color-normal observers (age range 22-77 years). The stimulus was a foveally viewed 2 degrees, circular bipartite field consisting of a standard and a test light. Heterochromatic ...

About 3% of all mouse photoreceptors are cones. An earlier electrophysiological study indicated that there were two classes of cone in the mouse retina having peak sensitivities (lambda max) of about 360 nm and 511 nm. Recent immunocytochemical results show there are two types of cones that have distinctive regional ...

The outer plexiform layer of the retina contains a neural circuit in which cone synaptic terminals are electrically coupled and release glutamate onto wide-field and narrow-field horizontal cells. These are also electrically coupled and feed back through a GABAergic synapse to cones. In cat this circuit's structure is known in ...

PURPOSE: Ethambutol can cause optic neuropathy and deficiencies in color-opponent visual processing in patients treated for tuberculosis. In fish, Ethambutol induces color vision deficiencies similar to those observed in humans and affects color coding in retinal ganglion cells. Color opponency in fish is mainly mediated by a horizontal cell feedback ...

The study examined the time taken to reach and touch keys positioned both within and just outside the traditional reach envelope, as well as within and just outside the region of easy visibility, defined as being within a 30 degrees cone centered on the line of sight. Movements were required ...

Microelectrodes were used to record from red and green cones of the turtle Pseudemys scripta elegans. The purpose of this study was to determine the action spectra of the red and green cone photopigments, and to look closely for direct interactions between the two cone classes. An isolated retina preparation ...

The temporal response of cone inputs to macaque retinal ganglion cells were compared with cone-specific sinusoidal modulation used to isolate each cone type. For all cell types of the parvocellular (PC) pathway, temporal responsivity was similar for short (S)-, middle (M)-, and long (L)-wavelength-sensitive cone inputs, apart from small latency ...

Temporal contrast sensitivity data were collected with sine-wave-modulated lights for achromatic, chromatic, and silent-cone-substitution stimuli. Achromatic (556- and 642-nm lights in phase) and chromatic (556- and 642-nm lights in counterphase) modulation sensitivities were measured at a constant time-average retinal illuminance of 1256 trolands (Td) and chromaticity of 595 nm. These ...