Differences In Spectral Sensitivity Research Articles

Comment on ‘Mesopic models / from brightness matching to visual performance in night-time driving: a review’ by M Eloholma, M Viikari, L Halonen, H Walkey, T Goodman, J Alferdinck, A Frieding, P Bodrogi and G Várad

A previous work summarized the history of the measurement of visual sensitivity to identify the problems inherent in mesopic photometry. The authors stated that in practical lighting applicatons, the detection and recognition of visual objects at or near visual threshold, and the reaction time needed to perceive objects in the visual field, are more relevant than the visual assessment of brightness. In this paper, Fotios comments on the study's results particularly on differences in spectral sensitivity between people of different nationalities. He emphasizes that brightness should not be relegated as it is a fundamental visual perception that is related to the amount of light present, and that in turn related to how well one can see. For their part, the authors of the previous study emphasize that visual task perception is not based on brightness itself but contrast.

Inherited colour vision deficiencies: From Dalton to molecular genetics

In recent years, great advances have been made in our understanding of the molecular basis of colour vision defects, as well as of the patterns of genetic variation in individuals with normal colour vision. Molecular genetic analyses have explained the diversity of types and degrees of severity in colour vision anomalies, their frequencies, pronounced individual variations in test results, etc. New techniques have even enabled the determination of John Dalton's real colour vision defect, 150 years after his death. Inherited colour vision deficiencies most often result from the mutations of genes that encode cone opsins. Cone opsin genes are linked to chromosomes 7 (the S or "blue" gene) and X (the L or "red" gene and the M or "green" gene). The L and M genes are located on the q arm of the X chromosome in a head-to-tail array, composed of 2 to 6 (typically 3) genes--a single L is followed by one or more M genes. Only the first two genes of the array are expressed and contribute to the colour vision phenotype. The high degree of homology (96%) between the L and M genes predisposes them to unequal recombination, leading to gene deletion or the formation of hybrid genes (comprising portions of both the L and M genes), explaining the majority of the common red-green colour vision deficiencies. The severity of any deficiency is influenced by the difference in spectral sensitivity between the opsins encoded by the first two genes of the array. A rare defect, S monochromacy, is caused either by the deletion of the regulatory region of the array or by mutations that inactivate the L and M genes. Most recent research concerns the molecular basis of complete achromatopsia, a rare disorder that involves the complete loss of all cone function. This is not caused by mutations in opsin genes, but in other genes that encode cone-specific proteins, e.g. channel proteins and transducin.

Cone deactivation kinetics and GRK1/GRK7 expression in enhanced S cone syndrome caused by mutations in NR2E3.

To determine the relationship between cone deactivation kinetics in patients with the enhanced S cone syndrome (ESCS) caused by mutations in NR2E3 and the immunoreactivity to G-protein-coupled receptor kinase 1 (GRK1) and GRK7. Electroretinogram (ERG) photoresponses were used to investigate activation kinetics of cones with a model of cone phototransduction. Deactivation kinetics of cones after bright flashes was quantified with a paired-flash ERG paradigm. Immunocytochemistry was performed with antibodies against cone opsins and kinases GRK1 and GRK7 in postmortem normal and ESCS retinal tissue. Activation kinetics of long/middle-wavelength-sensitive (L/M) cone-mediated responses in patients with ESCS were similar to those of normal L/M cones. Activation kinetics of ESCS short-wavelength-sensitive (S) cones, when compared with normal L/M cone responses evoked by the same stimulus, were slower by an amount consistent with the expected differences in spectral sensitivities. After bright flashes chosen to evoke identical activation kinetics, ESCS S cones deactivated much more slowly than ESCS or normal L/M cones. Normal human retina revealed strongly labeled cone outer segments with anti-GRK1 and anti-GRK7. In an ESCS retina, outer segments positive for L/M opsin were strongly labeled with anti-GRK1, whereas outer segments positive for S opsin showed no detectable GRK1 reactivity. GRK7 labeling was absent in all photoreceptors of the ESCS retina. The cone-dominant human retina resulting from NR2E3 mutations affords greater understanding of the physiological roles of GRK1 and GRK7 in human cone photoreceptors. Normal deactivation kinetics in human L/M cones can occur without GRK7 when GRK1 is present in ESCS, but does not occur when GRK7 is present but GRK1 is deficient in Oguchi disease. Lack of both GRK1 and GRK7 in S cones of patients with ESCS results in a more pronounced abnormality in deactivation kinetics and suggests the existence of partial compensation by either GRK when the other is deficient.

Evaluation of the LAI‐2000 Plant Canopy Analyzer to Estimate Leaf Area in Manually Defoliated Soybean

The LAI‐2000 Plant Canopy Analyzer provides a rapid estimate of leaf area index (LAI), but its accuracy and utility for estimating soybean [Glycine max (L.) Merr.] defoliation is unknown. This study evaluated minimum plot‐size requirements for manually defoliated soybean experiments using the LAI‐2000; compared LAI estimates using the LAI‐2000 with directly determined values for 0, 33, 67, and 100% manual defoliation levels; and compared estimates between two LAI‐2000 detector types having spectral sensitivity differences. The minimum plot size for obtaining accurate indirect estimates of LAI in defoliated canopies (0.89‐m height) with 0.38‐m row centers is six rows by 2.28 m and with 0.91‐m row centers and a canopy height of 0.81 m is four rows by 2 m plus an additional 1‐m defoliated area at the ends of the two middle rows. Indirect measurements of LAI with the wide‐blue detector, which is included on newer LAI‐2000 units, were statistically greater than directly determined values in 10 of 12 comparisons. Measurements with the narrow‐blue detector were the same as directly determined values in three of five comparisons in 1998 and 1999 but were statistically greater in 11 of 12 comparisons in 2000. Estimates with the wide‐blue detector were 9 and 2% greater than those with the narrow‐blue detector in 1999 and 2000, respectively.

Spectral sensitivity of larval and juvenile coral reef fishes: implications for feeding in a variable light environment

The spectral sensitivity of larval and juvenile stages of 3 species of coral reef fishes, Apogon compressus (Apogonidae), Pomacentrus amboinensis (Pomacentridae) and Premnas biaculeatus (Pomacentridae) has been investigated using feeding behaviour. Ontogenetic and taxonomic differences in spectral sensitivity were determined by establishing the minimum light intensity at which larvae and juveniles could strike prey at 12 restricted wavelength bands between 355 and 650 nm. Following construction of chromatic action spectra, the wavelength of maximum sensitivity (λmax) and the median wavelength (λP50) of the 3 species were found to be located close to 500 nm. All 3 species increased in sensitivity during growth, with A. compressus becoming the most sensitive prior to settlement. Ontogenetic shifts in spectral sensitivity towards longer wavelengths occurred in P. amboinensis and P. biaculeatus, but not in A. compressus. Spectral efficiency (wavelength-dependent efficiency of photon capture) was modelled for eutrophic and oligotrophic coral reef waters (Jerlov types Oceanic IA, Oceanic III and Coastal 1) at 2 different optical depths. Spectral efficiency was highest in the intermediate coral reef water type (JOIII) in all 3 larval fish taxa throughout early ontogeny, regardless of water depth. The results imply that the larvae would be able to feed across a broad spectrum of coral reef water types and depths.

Comparative study of spectral and antioxidant properties of pigments from the eyes of two Mysis relicta (Crustacea, Mysidacea) populations, with different light damage resistance

Retinal visual and screening pigments of two populations (one marine and the other freshwater) of the opossum shrimp Mysis relicta Loven (Crustacea, Mysidacea), which have different ocular tolerance to light, was investigated. Visual pigments were extracted by detergent and their bleaching difference spectra were determined. The difference between the visual pigment absorption maximum of the two populations correlated with their difference in spectral sensitivity. Using buffer or neutral methanol, a yellow pigment was extracted which had absorption maxima at 440 nm and 325 nm and bright blue fluorescence (λmax 415 nm). A screening pigment (ommochrome) with maximum at 525 nm was extracted by acid methanol, and was probably related to the group of ommines. The eyes of the lake population had 1.8–2.7 times less of this pigment than the eyes of the sea population. The sea population is more resistant to photo-induced accumulation of thiobarbituric acid-reactive substances in eye tissues. This resistance may be due to the higher ommochrome content.

Macular pigment densities derived from central and peripheral spectral sensitivity differences

Estimates of the density spectrum of the macular pigment (Wyszecki G, Stiles WS. Color Science: Concepts and Methods, Quantitative Data and Formulas. 1st ed. New York: Wiley, 1967); (Vos JJ. Literature review of human macular absorption in the visible and its consequences for the cone receptor primaries. Institute for Perception. Soesterberg, The Netherlands, 1972) are partially based on the difference between central and peripheral spectral sensitivities, measured under conditions chosen to isolate a single cone class (Stiles WS. Madrid: Union Internationale de Physique Pure et Appliquée. 1953:1:65–103). Such derivations assume that the isolated spectral sensitivity is the same at both retinal locations, save for the intervening macular pigment. If this is true, then the type of cone class mediating detection should not influence the calculated difference spectrum. To test this assumption, we measured central and peripheral spectral sensitivities in a deuteranope, a protanope and a normal trichromat observer: (a) for short-wave sensitive (S-) cone detection; and (b) for long-wave sensitive (L-) cone detection (deuteranope), for middle-wave sensitive (M-) cone detection (protanope) or for both L- and M-cone detection (normal trichromat). The difference spectra determined for L- or M-cone detection deviate significantly from those measured for S-cone detection, at wavelengths below 450 nm. A theoretical analysis suggests that the discrepancies are owing, in part, to regional variation in the optical density of the cone pigments; and that such receptor variation cannot be ignored when deriving the standard density spectrum of the macular pigment.

Electroretinographic evaluation of spectral sensitivity in yellow and silver eels (Anguilla anguilla).

Although differences in visual pigments between developmental stages of the European eel are well known, the expected differences in spectral sensitivity have not been demonstrated at the electrophysiological level. In fact, one past electroretinographic study led to the conclusion that in eels there is no change in scotopic sensitivity, with increasing sexual maturity. In the present experiments, electroretinograms (ERGs) were recorded from in situ eyecups of immobilized eels Anguilla anguilla (L.) caught in coastal running waters. It was shown that the ERG b-wave is as good an indicator of spectral sensitivity as the unmasked late receptor potential (LRP) which directly reflects the responsiveness of photoreceptors. Complete spectral-sensitivity curves, based on b-wave thresholds and on thresholds of LRP subsequently isolated by means of sodium iodate, have been obtained in the same eel. Using fitted amplitude-log intensity functions for threshold calculation, and two models for computer-assisted fitting of spectral-sensitivity curves, significant differences in lambda max were found between yellow and silver developmental stages of the eel, identified by ocular index measurements.

Spectral sensitivity of macaque monkeys measured with ERG flicker photometry

Macaque monkeys are widely used as a model species for investigations of the biology of human vision. Previous measurements suggest that the cone-based spectral sensitivity of these two primates is greatly similar, but perhaps not identical. We measured the photopic spectral sensitivity of 42 male macaque monkeys from two species (Macaca mulatta, M. fascicularis) using an objective index, electroretinogram flicker photometry. The variations among individuals and between the two species were very small and there was no evidence for any significant cone pigment polymorphism in this sample. There are small but systematic differences in spectral sensitivity between macaque monkeys and equivalently tested human subjects--the monkeys were slightly more sensitive to short wavelengths (< 520 nm) and slightly less sensitive to wavelengths longer than this value. The results obtained from the curve fitting of standard photopigment absorption spectra to the spectral-sensitivity functions suggest that the difference between human and macaque monkey spectral sensitivity principally reflects differences in the relative proportions of the long- and middle-wavelength cones in the retinas of the two species.

Psychophysical measurement of spectral sensitivity and color vision in red-light-reared tree shrews ( Tupaia belangeri)

The role of the spectral lighting environment on the post-natal development of spectral sensitivity and color vision was studied in tree shrews ( Tupaia belangeri) that were born and reared to adulthood in cyclic red light. Normal tree shrews are dichromats, possessing short-wavelength-sensitive (SWS) and long-wavelength-sensitive (LWS) cone receptors and a small population of rods. Red-lightrearing (RLR) produced differential stimulation of the cone types by effectively eliminating photic stimulation of the SWS cones, without depriving the LWS cones. Spectral sensitivity and color vision were measured behaviorally for RLR shrews and normal shrews under different ambient light levels. Spectral sensitivity functions were deutan-like, exhibiting maxima at ca 450 and 550 nm and a minimum at 510 nm. No significant differences in spectral sensitivity were observed between RLR and control animals. Furthermore, all animals demonstrated deutan-type dichromatic color vision evidenced by their ability to discriminate monochromatic lights from equally-bright achromatic lights except for a “neutral point” near 505 nm. These results demonstrate that a population of functional SWS cones survived the lack of post-natal photic stimulation. However, RLR shrews differed from controls in that they were poorer at making chromatic/achromatic discriminations. While no severe disorganization of color vision was evident, the poorer discrimination displayed by the RLR animals is likely the result of changes in post-receptoral visual mechanisms.

The photopic spectral sensitivity of the dorsal and ventral retinae of the chicken

The relative spectral sensitivities of the dorsal and ventral chicken (Gallus gallus) retinae were determined under photopic conditions by means of electroretinography and compared with data from the pigeon (Columba livid). Differences in spectral sensitivity between the dorsal and ventral chicken retinae appear only in the short wavelength range. In the chicken the dorsal retina is more sensitive to near UV light than the ventral retina relative to long wavelengths (beyond 470 nm), but both retinal areas are less sensitive to near UV than in the pigeon. The variation in relative near UV sensitivity is discussed in relation to recent data on the retinal distribution of different types of oil droplets in birds. The adaptive significance of near UV sensitivity is also discussed.

Spectral sensitivity and flicker fusion frequencies of the compound eye of salmon and wild‐type tsetse flies, Glossina morsitans

ABSTRACT. The spectral sensitivity and flicker fusion frequency (FFF) of wild‐type and salmon Glossina morsitans morsitans Westwood (Diptera, Glossinidae) were compared electroretinographically (ERG). Spectral sensitivity curves were similar in shape for dark‐adapted wild‐type and salmon flies, but salmon flies were over 100 times as sensitive as wild‐type flies over much of their sensitivity range. Estimation of the spectral absorption curve (from the differences in ERG sensitivities) for the pigment absent from (or present in low concentration in) the salmon eye suggests that the pigment is an ommochrome. FFF at threshold light intensities was similar in wild‐type and salmon flies, but at higher light intensity (1.3 °W/cm2) the FFF of salmon flies increased c. 200–300%, due to the capacity of the salmon eye to adapt rapidly to the flicker stimulus. Body weight had little effect upon spectral sensitivity and FFF. Wild‐type males were more sensitive to yellow‐green light and had higher FFF than did wild‐type females. Salmon males and females did not differ in spectral sensitivity, but females had higher FFF (when tested with 520‐nm light) than did males. Old wild‐type females did not differ from young females in either spectral sensitivity or FFF. However, old salmon females were more sensitive but had lower FFF than young salmon females. Food deprivation reduced spectral sensitivity and FFF in wild‐type males but not in salmon males. Irradiation (10.5 krad) reduced spectral sensitivity (c. 75–375%) and FFF (c. 30%) in wild‐type males. The greatly increased spectral sensitivity and FFF in salmon flies indicate that these flies may behave differently from wild‐type flies in the field. Differences in the way spectral sensitivity and flicker discrimination are affected by dark and light adaptation, and by such factors as age and sex, indicate that these measurements are of two independent phenomena.

Wavelength-specific ERG characteristics of pigmented- and white-eyed strains ofDrosophila

Previous electroretinographic (ERG) studies of white-eyed and red-eyed (wild-type)Drosophila melanogaster (Stark and Wasserman, 1972a) yielded results that were in agreement with Goldsmith's (1965) hypothesis that eye-color pigment absorption decreases the recruitment of contributions from peripheral ommatidia into the ERG. These screening pigments therefore produce wavelength-specific differences between these two strains (as well as within the red-eyed strain) in three ERG parameters, namely the magnitudes of the on- and off-transients and the slopes of the receptor potential energy-response functions. In the present study these three ERG parameters were each measured for constant receptor potential magnitudes (to remove the contribution of spectral sensitivityper se) at 13 wavelengths from 350 nm to 650 nm in the following strains:cn (having only pterins),bw (having only ommatins), wild (having both pigment classes), and two white-eyed strains,cn bw andw. Multiple linear regression analyses were carried out in order to determine the relationships between the foregoing three ERG parameters and parameters related to spectral sensitivity. These data lead us to the following conclusions: 1. Unexpected wavelength-dependent parameter differences exist in white-eyed flies. The slopes of the energy-response functions and the magnitudes of the transients all systematically vary and all correlate highly with the spectral sensitivity and with each other. This result implicates another spectrally selective factor other than pigment-determined recruitment in the ERG ofDrosophila. Several hypotheses about the nature of this factor are discussed. 2. Parameter differences attributable strictly to eye-color pigments were found when wild,cn, andbw strains were compared with white-eyed strains. These parameter differences varied linearly with screening pigment density, and multiple linear regression analyses accurately predicted the differences in spectral sensitivity produced by the eye-color pigments from the parameter differences of transient sizes and energy-response function slopes.

Spectral sensitivity of the compound eye in butterflies (Heliconius)

The spectral sensitivity of the compound eye in three butterfly species (Heliconius erato, H. numata, H, sara) was tested electrophysiologically in the wavelength region 310 to 650 nm. Sensitivity maxima were found at 370 to 390 nm, 450 to 470 nm, and 550 to 570 nm, for all species. The three sensitivity maxima are suggested to be due to different photoreceptor types effecting wave-length discrimination. An interspecies difference in spectral sensitivity was also found. The difference is suggested to be due to the relative number of photoreceptors of each type. In some of the present experiments a small discontinuity in sensitivity was found at 610 or 630 nm. It is probably caused by a selective reflection of these wavelengths from a tapetum.

Cat colour vision: one cone process or several?

1. Peripheral mechanisms that might contribute to colour vision in the cat have been investigated by recording from single units in the lateral geniculate and optic tract. Evidence is presented that the input to these cells comes from a single class of cones with a single spectral sensitivity.2. In cats with pupils dilated a background level of 10-30 cd/m(2) was sufficient to saturate the rod system for all units. When the rods were saturated, the spectral sensitivity of all units peaked at 556 nm; this was true both for centre and periphery of the receptive field. The spectral sensitivity curve was slightly narrower than the Dartnall nomogram. It could not be shifted by chromatic adaptation with red, green, blue or yellow backgrounds.3. In the mesopic range (0.1-10 cd/m(2)), the threshold could be predicted in terms of two mechanisms, a cone mechanism with spectral sensitivity peaking at 556 nm, and a rod mechanism with spectral sensitivity at 500 nm. The mechanisms were separated and their increment threshold curves measured by testing with one colour against a background of another colour. All units had input from both rods and cones. The changeover from rods to cones occurred at the same level of adaptation in both centre and periphery of the receptive field. Threshold for the cones was between 0.04 and 0.25 cd/m(2) with the pupil dilated, for a spot covering the centre of the receptive field.4. None of the results was found to vary between lateral geniculate and optic tract, with layer in the lateral geniculate, or with distance from area centralis in the visual field.5. The lack of evidence for more than one cone type suggests that colour discrimination in the cat may be a phenomenon of mesopic vision, based on differences in spectral sensitivity of the rods and a single class of cones.

Spectral Effects in the Comparison of Scintillators and Photomultipliers

Photomultiplier evaluation of scintillation performance is considered in the light of its marked dependence on spectral shape effects in the emission spectrum of the scintillator, in photon absorption of cell, reflector and photomultiplier window, and in the photoelectric conversion process. Relative pulse height data indicating gross differences in spectral sensitivity are presented for a group of 132 photomultipliers (types 6292 and 6342). A fluorescent converter for measuring the quantum output of liquid scintillators is described. Six scintillator solutions with fairly evenly spaced mean emission wavelengths from 3360 to 4660 A are evaluated for relative pulse height and relative photon output. Suggestions are presented for desirable methods for measuring the performance of scintillators.

Quantitative radiometric measurement of radioactive ores in the natural occurrence

The measurement of gamma radiation of radioactive ores in the natural deposit — directly in the face of a mine working or in a bore hole-permits determination of the radioactive element content in ores without collection of test samples and without chemical analyses. The accuracy of quantitative measurement by gamma rays depends to a considerable degree on correct interpretation of the spectral content of the gamma radiation measured. The gamma-ray spectra of radioactive ores is determined by the process of radiation dispersion and depends on the content of the ore. The intensity of gamma radiation registered by an ore seam depends on the cathode malarial of the counter (tungsten, copper, graphite) as a consequence of the difference in spectral sensitivity of various counters. The relationship of gamma — radiation intensity during measurement with a Geiger counter with various cathodes permits one to characterize the spectral composition of the ore's gamma radiation. In order to express the results in general units, microroentgens per hour, the radiometers are calibrated with an exact standard, but the calibration method does not exclude the radiometer reading dependence on the spectral sensitivity of the counters. In this article are determined the important conversion coefficients connecting gamma-radiation intensity with the content of radioactive elements in ore (see the table) during measurements on the ore seam surface or in borings. During measurements in borings the reverse dissemination of gamma rays having low energy is of great importance. By use of these coefficients calculations of the radioactive element content in ore from counter readings are carried out.