The initial stages of light and dark adaptation in the human visual system cannot be explained by a simple relation between sensitivity and pigment bleaching. We found changes in sensitivity in the goldfish ganglion cells similar to those seen in humans, and our results from experiments suggest that a change ...

Seedlings of tomato (Lycopersicon esculentum, Mill.) varied diurnally in their sensitivity to chilling temperatures. If chilled near the end of the dark period when they were most sensitive, the time taken to kill half of the seedlings was approximately 3 days, whereas in samples taken 4 hours after the onset ...

A procedure is proposed for computing the visual effectiveness of light incident on the retina considering the directional sensitivity of the underlying photoreceptor population. A half-sensitivity half-width measurement of the retinal directional sensitivity provides the basis for integrating a parabolic approximation to the directional sensitivity over the pupillary area penetrated ...

the foveal vision of certain patients afflicted with retinitis pigmentosa may be mediated solely by a long wavelength sensitivity (lws) mechanism, because (1) increment threshold data could always be fitted to a single template curve with unity slope, (2) test and field sensitivities differ only by a proportionality constant over ...

The effects of abrupt increases and decreases of light in one part of the retina on sensitivity in an adjacent part of the retina were studied under low scotopic conditions near absolute threshold. The basic finding is that a brief annular surround decreases sensitivity to test spots occurring near the ...

Spectral sensitivity curves for the freshwater perch were measured using an operant procedure. Sensitivity peaks were found at 530-560 nm and 660-680 nm. Compared with perch cone pigments (P530(2) and P617(2)), the red-shift of the maximum long wave length sensitivity suggested that opponent interactions between the cone types were responsible ...

Spectral sensitivities for small, brief lights presented on a neutral adapting field resemble the photopic luminosity function. The lights often appear achromatic near threshold. These findings are consistent with a hypothesis linking sensitivity to an independent class of nonopponent cells. To test this hypothesis, a variation of the Stiles two-color ...

Increment-threshold spectral sensitivity functions were taken foveally and at four other retinal locations with different sized test stimuli. For the fovea and parafovea at 4 degrees, a 1 degree, 250 msec stimulus of variable wavelength, flashed on a 1000 td white background yielded spectral sensitivity curves with three distinct maxima ...

Response patterns to complex visual stimuli were further analysed. Patterns were correlated with linear or non-linear components of the stimulus pattern at various wavelengths. Resulting correlograms revealed the spatial and spectral structure of receptive fields; they showed peaks or troughs according to whether that wavelength was associated with an increase ...

The triggered photocounting distribution (TPCD) of practical fields has been investigated. The moment generating function and the factorial moment are exactly deduced from theory and experimentally justified by the measurement of Gaussian-Lorentzian light. It is found that the first-order factorial moment of the TPCD has the spectral information of incident ...

By using a heterochromatic brightness-matching technique, in which the test and comparison field were presented in succession, spectral equal-brightness functions were measured in a dark-adapted state at a retinal illumination of 1000 photopic trolands at 6, 28, 45, and 65 degrees temporally to the fovea. In addition, the spectral equal-brightness ...

Spectrally opponent processes of ON-type retinal ganglion cells and the blue preference behavior were identified by parallel physiological and behavioral experiments in Rana pipiens. Spectral opponency of retinal ON-units was measured by recording from optic nerve terminals in the anterior thalamus, while the retina was stimulated by combinations of monochromatic ...

The spectral sensitivity of the pigeon Electroretinogram was determined at different times during the 24-hour cycle. These measures show that diurnal changes occur in the relative sensitivity of the electroretino-graphic responses to light stimuli of different wavelength. Diurnal variations occur despite the absence of rhythmic photoperiodic stimulation. It is suggested ...

A fast parallel approach to the spectral analysis of a time-varying signal is presented. The technique, which uses a light emitting diode array and an integrating photodiode array, can offer the potential of a thousand or more spectral points and data rates beyond 10 MHz.

Dark-active North American fireflies emit green bioluminescence and dusk-active species emit yellow, in general. Yellow light and yellow visual spectral sensitivity may be adaptations to increase the signal-to-noise (that is, foliage-reflected ambient light) ratio for sexual signaling during twilight. The peaks of the electroretinogram visual spectral sensitivities of four species ...

1. The light response of Balanus lateral eye photoreceptor was studied using intracellular recording and voltage clamp techniques. 2. The effect upon the light response of a prior depolarization was studied. Two effects were observed: a transient sensitization which appeared not to involve a change in time course, and a ...

We measured the visual sensitivity of the conger eel retina by means of its electroretinogram (e.r.g.) and whole nerve responses. The spectral sensitivity of the retina closely corresponded to a prediction based on the density spectrum of the conger visual pigment, measured in situ. The pigment density in the conger ...

Following three to four days of monocular light exclusion, the directional sensitivity of the retina was reduced at all areas tested. Changes in the shape of the Stiles-Crawford (SC) function were evident at both photopic and scotopic adaptation levels. The flattening of the SC functions was primarily a result of ...

Relative spectral sensitivity was measured at different intensity levels 45 degrees temporally during the cone-plateau period and in a dark-adapted state. Both heterochromatic brightness matching, flicker photometry, and threshold measurements were employed. The relative spectral sensitivity obtained during the cone-plateau period was found to coincide closely with the foveal luminosity ...

1. The retina of Leptograpsus contains five types of movable screening pigment. The positions of these were found under various conditions of illumination in the day and at night. 2. Intracellular recordings were made of the spectral responses of retinula cells R1-7 under the same conditions, with the eye in ...

A simple two-stage lateral-inhibition mechanism is described that permits edges due to changes in surface illumination and orientation to be distinguished directly in the retina from those due to changes in spectral reflectivity. It is based on the assumption that the spectral content of the reflected light changes acrpss a ...

Using both absolute threshold and flicker techniques, we measured the relative spectral sensitivity at different eccentricities during the cone-plateau period of the long-term dark-adaptation curve. With both techniques the relative spectral sensitivity tended to increase with eccentricity in the short-wave region of the spectrum. The results suggest that the relatively ...

When viewing a uniform field through a small aperture moved circularly before the pupil of the eye, many observers report a diffuse dim spot subtending roughly 1 degree visual angle, which rolls around the fixation point in synchrony with the motion of the aperture. Measurements of the Stiles-Crawford maximum for ...

About 20% of xiphophorin fish (Xiphophorus maculatus) dermal melanophores which were cultured in monolayer for 5 to 10 days responded to light directly, exhibiting reversible melanosome aggregation within a few minutes. In order to determine the spectral sensitivity for the light-response, absorbance changes due to the light-induced melanosome aggregation were ...

1. Microspectrophotometric measurements reveal four classes of photoreceptor in the retina of the cynomolgus monkey, Macaca fascicularis, which is known to possess colour vision similar to that of a normal human trichromat. 2. Although the eyes were removed in bright illumination, the densities of pigment were comparable to those we ...

The extrafoveal spectral sensitivity function was measured during dark adaptation at different intensity levels above the cone plateau of the long-term dark-adaptation curve using both flicker and heterochromatic brightness-matching techniques. During most of the cone-plateau period, the spectral sensitivity function was found to be photopic in form at all the ...

The absolute spectral response of solar cells is reported in the 400-1000-nm spectral region. Measurements were performed using two different types of monochromatic sources: amplitude-stabilized cw laser lines and interference filters with an incandescent lamp. Both types of calibration procedures use electrical substitution radiometry as the basis of traceability to ...

1. Receptor potentials in honeybee drone retinula cells were recorded with intracellular micro-electrodes in the dorsal part of the superfused retina. The light stimuli were sufficiently weak that the response amplitude was proportional to the intensity. 2. Responses to stimuli of different wave-lengths, although of different amplitude, all had the ...

It is well known that pupillary threshold shows a scotopic spectral behavior, even for foveal stimuli. However, when two scotopically balanced fields at different wavelengths are alternated, the pupil shows a constriction response at each transition, exposing innervation from chromatic mechanisms. Using a suitable model for pupillary innervation, this substitution ...

1. We define absolute sensitivity as (voltage/illuminance) and incremental sensitivity as the peak-to-peak amplitude of the first-order (Wiener) kernels. 2. Incremental sensitivity of the horizontal cells is the local slopes of the Michaelis-Menten equation and that of more proximal neurons is the Fechner slope. In a log-log plot, the former ...

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal-noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could ...

Uniocular occlusion (dark patching) of adults for a period of days produces marked reduction in the directional sensitivity of the eye (Stiles-Crawford effect). The effect reaches a maximum 3 to 5 days after the onset of patching. Recovery occurs in a comparable period. The second eye is not affected, and ...

The spectral sensitivity at the opponent stage of the visual system is traditionally measured by a hue-cancellation procedure. Comparison with a direct hue-matching method shows that cancellation overestimates short-wavelength sensitivity by as much as a factor of 30. The observation implies that different mechanisms control the perception of short-wavelength and ...

The intense excitation of an Ar(+) laser operating at 514 nm enhances the grating ghosts and general stray light within most double monochromators at wavelengths close to the exciting line. The I(2) filter technique provides an effective means of reducing this interference and, in so doing, makes possible the measurement ...

The phototactic responses of anuran amphibians to narrow-band monochromatic stimuli of equal quantum intensity were measured for the first time in eight new experiments. The unimodal spectral response, obtained from dark-adapted American toads (Bufo americanus), peaks near 626 THz of frequency (480 nm wavelength). The bimodal, U-shaped spectral response, obtained ...

The light sensitivity was determined on 14 psoriasis patients using two different light sources before, and after a three week period of systemic administration of 75 to 100 mg daily of the aromatic retinoid (ethyl ester of all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoic acid, Ro 10-9359 [1]). The results indicate that with this therapy, the ...

Intracellular hemoglobin detection by light microscopy in the Soret band (414nm) is a sensitive means of correlating morphology and biochemical function in studies of erythrpoiesis. Correct application of the technique requires a light source with strong emission in the near ultra-violet, a filter with a pass-band at 414nm, a preparation ...

Following complete bilateral tectal ablation, the ability to detect light recovers in about three weeks. The non-tectal retinal connections which may mediate detection are about one log unit less sensitive than the retinotectal connections. At moderate illumination levels, tectumless fish do not react visually to objects. Tectumless fish integrate luminous ...

Bdellovibrio underwent photooxidation by visible light in the presence of exogenous photosensitizer and by near-ultraviolet light (325 to 400 nm) in its absence. The colorless, host-dependent wild type was more sensitive to the lethal effect of light than was its pigmented, facultative parasitic mutant. The latter's ability to form colonies ...

Among squirrel monkeys (Saimiri sciureus) there are significant sex-related differences in visual sensitivity. As measured behaviorally in an increment-thershold task, a sample of males was found to be substantially less sensitive to long-wavelength (640-nanometer) light than a group of females tested in the same way, although the two groups showed ...

Properly functioning domestic television sets may induce seizures in epileptic patients (TV epilepsy). We investigated the effects of different types of visual stimuli on paroxysmal electroencephalographic (EEG) activity in 32 patients known to be sensitive to intermittent photic stimulation (stroboscopic light). We monitored sensitivity to patterns of horizontal and vertical ...

The spectrum of the carotenoid shift generated under continuous illumination in the GIC mutant of Rhodopseudomonas sphaeroides, which has a single carotenoid, has been examined under a variety of conditions expected to alter the size of the membrane potential. If the difference spectrum observed was due to a species with ...

Anatomical details in the ocular fundus can be seen with increased contrast when appropriate monochromatic illumination is used. This technique permits more accurate visualization and documentation than can be achieved with white light. This article reports the optimal spectral ranges for visualization of the different fundus structures. It describes and ...

Spectral sensitivity was measured by heterochromatic flicker photometry both in the fovea and at 45 degrees in the periphery, using a 1200 troland standard. At each location, sensitivity functions were obtained using both large and small targets. While the foveal functions were normal, the peripheral ones showed a large enhancement ...

A convenient spectral reference detector for the visible to 12-microm region has been developed. The device consists of a large area PVF(2) pyroelectric detector enclosed in a hemispherical light trap. Based on theoretical and experimental evaluations, the detector response is independent of wavelength to +/-1% over this spectral range.

In this paper, the fourth in a new series, we have examined the properties associated with illuminated sectors of the annular "sensitization" zone of the psychophysical Westheimer function. The results for one-, two-, and four-sector annular background fields indicate simple additivity of effects within the sensitization region when the flashing ...

The spectral sensitization of hardened dichromated gelatin to red light is carried out using methylene blue as sensitizer. The sensitized dichromated gelatin plate can be stored for over 1 month in an ammonia atmosphere without loss of photosensitivity. Holograms recorded in the sensitized dichromated gelatin using a He-Ne laser have ...

The California ground squirrel is a highly diurnal species previously thought to have an all-cone retina. This issue was re-examined in physiological and anatomical experiments. The electroretinogram (ERG) was used to measure the spectral sensitivity of the eye under different conditions of adaptation. The occurrence of a Purkinje shift could ...

Microdensitometric errors can result from various factors associated with the monochromator system, including imperfect monochromaticity of the light, incorrect setting of the wavelength, and non-uniform illumination of either the microscopic field or the objective aperture. Certain types of potential error are characteristic of particular instruments. Thus in the Vickers M85 ...

Small potential fluctuations ("bumps"), boyh spontaneous and light induced, can be recorded intracellularly from the photoreceptors of Drosophila melanogaster. Statistical analyses of these bumps in the spectral range, 400-600 nm, lead to the following interpretations; (a) For weak stimuli at least, these bumps are the quantal units of the receptor ...