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At least 1,081 records · Page 60Linked to original sources
PubMed1978

Further observations on the extramacular chromatic mechanisms.

Monochromatic targets presented at 30 degrees excentricity on orange, magenta and blue backgrouds are used. A small monochromatic light, 476 nm on orange, 551 nm on magenta and 621 nm on blue, is flashed at 3 cps-1 on the centre of the targets. The size of the targets is varied and their luminance adjusted using neutral filters until the flashing light is just not visible. This method allows the study of chromatic mechanism sensitivity and of retinal interactions (summation and inhibition). Some observations in normal as well as in pathological conditions are presented.

Adult↗
PubMed1988

Chromatic aftereffects associated with a night vision goggle simulation.

A visual perception experiment was conducted to determine the chromatic aftereffects of viewing a yellow-green field that simulated the display of current night vision goggles. Six females and two males served as subjects in a color-naming procedure. Subjects sequentially viewed an adaptation field, which was either yellow-green or white, and small colored targets presented on a CRT display. The time required to name the color of the targets was found to be dependent on the color of the adaptation field, the color of the target, and the interaction of these two variables. It was recommended that the effects of attenuation of the luminance of the night vision goggles be studied, and that color cockpit displays be redundantly coded whenever possible.

Adult↗
PubMedDate not supplied

[Chromatic component of the frog electroretinogram].

To single out the chromatic constituent of frog electroretinogram the method of great (superthreshold) differences between stimuli is used. The stimuli are presented as instantly replaced colour flashes. It is shown that the amplitude of the b-wave of the electroretinogram recorded during the replacement of the equally bright stimuli is determined only by their colour difference.

Animals↗
PubMed1985

Displacement thresholds for motion detection under conditions of chromatic adaptation.

The smallest, continuous target displacement which is sufficient to cause a sensation of movement was measured under conditions of chromatic adaptation. The experiments were carried out for test target and background field wavelengths which selectively isolate the activity of the colour mechanisms of the human eye. The results show that, when target detection is largely mediated by the red or green colour mechanism, a target displacement of 2-3' in the foveal region is sufficient to cause a reliable sensation of movement. These displacement thresholds show only a small change as a function of target contrast or background retinal illuminance level. Similar results were obtained when the colour of the test target was the same as that of the background field (e.g. green, yellow or red), when no attempt was made to isolate a single colour mechanism. Test target and background wavelengths which isolate the activity of the blue colour mechanism yield displacement thresholds in the range 5-7' and show a stronger dependence on target contrast and background retinal illuminance level. The experiments were repeated at several eccentricities and the results show that, for a test target and background field of the same colour and under conditions which isolate the green or red spectral response mechanism, the minimum target displacement required for motion detection appears to increase in a manner similar to the centre-width receptive-field size of broad-band, centre--surround transient neurons in the rhesus monkey retina [De Monasterio and Gouras (1975) J. Physiol., Lond. 251, 167-195].(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Ocular↗
PubMedDate not supplied

[Modelling the effect of photosynthetic enhancement and chromatic transitions].

A simple method is proposed and analysed which explains characteristic manifestation of the enchancement effect (2nd Emerson effect) and of chromatic transients effect (Blinks effect). The model is based on the hypothesis concerning the ATP/NADP concentrations ratio with a change of falling light wavelength. The model is suggested to reflect the behaviour of the reduction pentosophosphate cycle (Calvin cycle) under low illumination intensity, when the photosynthesis rate is determined only by ATP and NADP.H concentrations formed in the course of different photochemical reactions.

Adenosine Triphosphate↗
PubMedDate not supplied

Analogue chromatic continuous scale (ACCS): a new method for pain assessment.

A new pain rating scale, Analogue Chromatic Continuous Scale (ACCS), has been developed. The ACCS was tested in fifty consecutive patients suffering from pain of different origins, and compared with a simple descriptive scale (SDS) and a traditional 100 mm visual analogue scale (VAS). VAS and ACCS values showed a highly significant, positive correlation (r = 0.947, P less than 0.001). The means of the VAS and ACCS values, either considered as a whole or stratified according to SDS scores, did not differ significantly. The ACCS proved to be more sensitive than VAS (P less than 0.05), allowing a greater discrimination of grades of pain. Furthermore, the ACCS is very easy to use.

Adolescent↗
PubMedDate not supplied

[Comparative analysis of the rhythm assimilation reaction to chromatic and achromatic stimulation in children during the neonatal period].

Specificity of development of the acquisition of the rhythm of light flashes (driving) in the visual cortex depending on the light spectral composition and on age was revealed in healthy children. The index of driving for white, green and red light is minimal in the first two weeks of child's life and sharply increases in the period of 4--6 weeks. The difference between the optima of the driving reaction for green and red colors, appearing at this age, points to the development of cortical mechanisms, providing for the perception and analysis of color stimuli. In children born from diseased mothers the driving reaction is absent; chromatic stimuli cause paroxysmal activity. The significance of these parameters for early diagnosis of the cerebral functional disturbances is discussed.

Age Factors↗
PubMed1977

Localization in platelets of sodium 51Cr-chromate, 125I-antibody to whole membrane, and 3H-diisopropylfluorophosphate using electron microscopic autoradiography.

Platelets from the rabbit and rat, respectively, were incubated with sodium 51Cr-chromate and 3H-diisopropylfluorophosphate (3H-DFP) in the same manner as for platelet survival studies. A third isotope, 125I, was incorporated into a labeled antibody raised against a partially purified pig platelet membrane fraction. The 51Cr label was found to be concentrated predominantly in the cytoplasm, with a marked degree of association with mitochondria, whereas the tritium label appeared to be largely confined to the periphery of the platelet, particularly in association with the open canalicular system. The 125I-labeled antibody showed a very marked association with the plasma membrane and the open canalicular system, suggesting a membrane-bound affinity.

Animals↗
PubMed1977

A Goldmann perimeter with high luminance chromatic targets.

We have modified the original Goldmann perimeter by replacing the source and shutter by a Xenon arc source with maximum target luminance of 3183 cdm-2, and a quartz iodine lamp yielding maximum background luminance of 150 cdm-2, both measured at the bowl. Colorimetric and spectrophotometric specifications of the new colour targets are comparable to the original, but give luminance intensities equivalent to 318 cdm-2: levels only realized for the white target in the original system. Chromatic profiles are comparable to previous profiles for achromatic targets and the close correspondence between the retinal threshold gradients produced by the two methods simplifies comparison of data obtained with out instrument with those obtained from routine static perimetry. Under high luminance conditions we do not find the relative foveal scotoma for blue targets observed by other researchers. The use of photometrically equated targets well withi; the photopic levels is an improvement on present methods of colour perimetry.

Color↗