Photopic spectral sensitivity of the cat

Spectral transmittance of animal intraocular lenses in comparison with the spectral properties of their biological lenses

PURPOSE

To determine the spectral transmittance of artificial intraocular lenses (IOLs) designed for various species (dog, cat, chinchilla, eagle, tiger) and compare them to the spectral properties of the biological lenses of these species.

METHODS

Twenty-seven IOLs were scanned with a spectrophotometer fitted with an integrating sphere.

RESULTS

All IOLs transmitted long wavelengths well before cutting off sharply at short wavelengths, with insignificant transmission below ca. 340 nm. In comparison with the IOLs, the biological lenses of the cat, dog, and probably the chinchilla transmitted significantly more short wavelengths. The spectral properties of the biological lenses of eagles and tigers, while uncertain, may be a closer match to the IOLs made for these species.

CONCLUSION

It is not known if there are any visual or behavioral consequences for animals caused by a mismatch between the spectral properties of their biological lenses and IOLs. However, following IOL implantation there might be a change in the perceived hue of objects due to the removal of UV wavelengths which form a normal part of the visible spectrum for these species and/or a decrease in sensitivity.

Diverse Cell Types, Circuits, and Mechanisms for Color Vision in the Vertebrate Retina

Synaptic interactions to extract information about wavelength, and thus color, begin in the vertebrate retina with three classes of light-sensitive cells: rod photoreceptors at low light levels, multiple types of cone photoreceptors that vary in spectral sensitivity, and intrinsically photosensitive ganglion cells that contain the photopigment melanopsin. When isolated from its neighbors, a photoreceptor confounds photon flux with wavelength and so by itself provides no information about color. The retina has evolved elaborate color opponent circuitry for extracting wavelength information by comparing the activities of different photoreceptor types broadly tuned to different parts of the visible spectrum. We review studies concerning the circuit mechanisms mediating opponent interactions in a range of species, from tetrachromatic fish with diverse color opponent cell types to common dichromatic mammals where cone opponency is restricted to a subset of specialized circuits. Distinct among mammals, primates have reinvented trichromatic color vision using novel strategies to incorporate evolution of an additional photopigment gene into the foveal structure and circuitry that supports high-resolution vision. Color vision is absent at scotopic light levels when only rods are active, but rods interact with cone signals to influence color perception at mesopic light levels. Recent evidence suggests melanopsin-mediated signals, which have been identified as a substrate for setting circadian rhythms, may also influence color perception. We consider circuits that may mediate these interactions. While cone opponency is a relatively simple neural computation, it has been implemented in vertebrates by diverse neural mechanisms that are not yet fully understood.

Temporal properties of colour opponent receptive fields in the cat lateral geniculate nucleus

The primordial form of mammalian colour vision relies on opponent interactions between inputs from just two cone types, 'blue' (S-) and 'green' (ML-) cones. We recently described the spatial receptive field structure of colour opponent blue-ON cells from the lateral geniculate nucleus of cats. Functional inputs from the opponent cone types were spatially coextensive and equally weighted, supporting their high chromatic and low achromatic sensitivity. Here, we studied relative cone weights, temporal frequency tuning and visual latency of cat blue-ON cells and non-opponent achromatic cells to temporally modulated cone-isolating and achromatic stimuli. We confirmed that blue-ON cells receive equally weighted antagonistic inputs from S- and ML-cones whereas achromatic cells receive exclusive ML-cone input. The temporal frequency tuning curves of S- and ML-cone inputs to blue-ON cells were tightly correlated between 1 and 48 Hz. Optimal temporal frequencies of blue-ON cells were around 3 Hz, whereas the frequency optimum of achromatic cells was close to 10 Hz. Most blue-ON cells showed negligible response to achromatic flicker across all frequencies tested. Latency to visual stimulation was significantly greater in blue-ON than in achromatic cells. The S- and ML-cone responses of blue-ON cells had on average, similar latencies to each other. Altogether, cat blue-ON cells showed remarkable balance of opponent cone inputs. Our results also confirm similarities to primate blue-ON cells suggesting that colour vision in mammals evolved on the basis of a sluggish pathway that is optimized for chromatic sensitivity at a wide range of spatial and temporal frequencies.

Color Representation Is Retinotopically Biased but Locally Intermingled in Mouse V1

Dichromatic vision is common in many mammals. However, color processing in the primary visual cortex (V1) of dichromatic mammals is relatively unknown compared to the trichromatic primates. In this study, we investigated the functional organization of color processing in mouse V1. The mouse retina has a graded expression pattern of two opsins along its dorsoventral axis. However, it is not clear whether and how this expression pattern is reflected in the cortical representation at local (several hundred microns) and areal (V1) level. Using in vivo two-photon calcium (Ca²⁺) imaging and wide-field Ca²⁺ imaging, we revealed that V1 neurons responded to S (UV)- and M (green)-opsin isolating stimuli with slightly biased color preference depending on retinotopic position in V1. This was consistent with the distribution of retinal opsins. At the cellular level, preferences for S- and M-opsin isolating stimuli were intermingled in a local region encompassing several hundred microns. These results suggest that functional organizations of color information are locally intermingled, but slightly biased depending on the retinotopic position in mouse V1.

Preliminary evidence for color stimuli discrimination in the Asian small-clawed otter (Aonyx cinerea)

Color discrimination ability can be determined through anatomy or perceptual ability. In this study we tested perceptual ability. Three Asian small-clawed otters (Aonyx cinerea), one male and two females, were trained via operant conditioning to discriminate stimuli within a training task. If they passed criteria for this task, they were tested on as many as six delayed matching-to-sample experimental tasks. These experimental tasks involved comparing varying saturations of the colors blue, green, and red against varying shades of gray, as well as against each other. The male reached criterion on five of the experimental tasks, indicating an ability to discriminate the stimuli. One female participated in only two tasks and did not achieve the criteria as set. The second female did not pass the training task, and thus was not experimentally tested. This study overall showed some early evidence that Asian small-clawed otters may have the ability to learn to discriminate different stimuli on the basis of color cues. Sensory studies conducted on two other otter species and the results of this study indicate that color vision may be a common trait across Lutrinae species.

Receptive field properties of color opponent neurons in the cat lateral geniculate nucleus

Most nonprimate mammals possess dichromatic ("red-green color blind") color vision based on short-wavelength-sensitive (S) and medium/long-wavelength-sensitive (ML) cone photoreceptor classes. However, the neural pathways carrying signals underlying the primitive "blue-yellow" axis of color vision in nonprimate mammals are largely unexplored. Here, we have characterized a population of color opponent (blue-ON) cells in recordings from the dorsal lateral geniculate nucleus of anesthetized cats. We found five points of similarity to previous descriptions of primate blue-ON cells. First, cat blue-ON cells receive ON-type excitation from S-cones, and OFF-type excitation from ML-cones. We found no blue-OFF cells. Second, the S- and ML-cone-driven receptive field regions of cat blue-ON cells are closely matched in size, consistent with specialization for detecting color contrast. Third, the receptive field center diameter of cat blue-ON cells is approximately three times larger than the center diameter of non-color opponent receptive fields at any eccentricity. Fourth, S- and ML-cones contribute weak surround inhibition to cat blue-ON cells. These data show that blue-ON receptive fields in cats are functionally very similar to blue-ON type receptive fields previously described in macaque and marmoset monkeys. Finally, cat blue-ON cells are found in the same layers as W-cells, which are thought to be homologous to the primate koniocellular system. Based on these data, we suggest that cat blue-ON cells are part of a "blue-yellow" color opponent system that is the evolutionary homolog of the blue-ON division of the koniocellular pathway in primates.

Evolution of colour vision in mammals

Colour vision allows animals to reliably distinguish differences in the distributions of spectral energies reaching the eye. Although not universal, a capacity for colour vision is sufficiently widespread across the animal kingdom to provide prima facie evidence of its importance as a tool for analysing and interpreting the visual environment. The basic biological mechanisms on which vertebrate colour vision ultimately rests, the cone opsin genes and the photopigments they specify, are highly conserved. Within that constraint, however, the utilization of these basic elements varies in striking ways in that they appear, disappear and emerge in altered form during the course of evolution. These changes, along with other alterations in the visual system, have led to profound variations in the nature and salience of colour vision among the vertebrates. This article concerns the evolution of colour vision among the mammals, viewing that process in the context of relevant biological mechanisms, of variations in mammalian colour vision, and of the utility of colour vision.

Elephants and human color-blind deuteranopes have identical sets of visual pigments

Being the largest land mammals, elephants have very few natural enemies and are active during both day and night. Compared with those of diurnal and nocturnal animals, the eyes of elephants and other arrhythmic species, such as many ungulates and large carnivores, must function in both the bright light of day and dim light of night. Despite their fundamental importance, the roles of photosensitive molecules, visual pigments, in arrhythmic vision are not well understood. Here we report that elephants (Loxodonta africana and Elephas maximus) use RH1, SWS1, and LWS pigments, which are maximally sensitive to 496, 419, and 552 nm, respectively. These light sensitivities are virtually identical to those of certain "color-blind" people who lack MWS pigments, which are maximally sensitive to 530 nm. During the day, therefore, elephants seem to have the dichromatic color vision of deuteranopes. During the night, however, they are likely to use RH1 and SWS1 pigments and detect light at 420-490 nm.

Animal colour vision--behavioural tests and physiological concepts

Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: 'what neural interactions underlie colour vision?' This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.

Orientation sensitivity of ganglion cells in primate retina

The two-dimensional shape of the receptive field center of macaque retinal ganglion cells was determined by measuring responses to drifting sinusoidal gratings of different spatial frequency and orientation. The responses of most cells to high spatial frequencies depended on grating orientation, indicating that their centers were not circularly symmetric. In general, center shape was well described by an ellipse. The major axis of the ellipse tended to point towards the fovea or perpendicular to this. Parvocellular pathway cells had greater center ellipticity than magnocellular pathway cells; the median ratio of the major-to-minor axis was 1.72 and 1.38, respectively. Parvocellular pathway cells also had centers that were often bimodal in shape, suggesting that they received patchy cone/bipolar cell input. We conclude that most ganglion cells in primate retina have elongated receptive field centers and thus show orientation sensitivity.

Visual analysis and image motion in locomoting cats

During locomotion, observers see a characteristic pattern of motion referred to as an optic flow field. To investigate how they make use of this pattern, we have developed a paradigm for testing visual function during locomotion. Foot placement was recorded while cats walked down an alley cluttered with a high density of small objects; the task was to avoid stepping on any object. In the experiments reported here, motion cues were eliminated by the use of low-frequency strobe lighting. In bright continuous light cats performed with great accuracy, and likewise at scotopic light levels. However, in strobe lighting their error rates increased more than threefold. This deterioration could not be attributed to lower acuity, since the cats' performance remained excellent when the light level was reduced well below that afforded by the strobe light. When very dim continuous light was combined with low-frequency strobe lighting, performance was substantially better than under strobe light alone. We conclude that motion-sensitive neurons make a major contribution to visual guidance of foot placement during locomotion. When strobe lighting is combined with very dim continuous light, even the minimal motion information available in the intervals between bright strobe flashes improves performance significantly. Cats were also trained to discriminate between complex patterns, and this discrimination was not affected by strobe lighting, suggesting that motion-sensitive neurons are not critical for this analysis.

Spectral tuning of dichromats to natural scenes

Multispectral images of natural scenes were collected from both forests and coral reefs. We varied the wavelength position of receptors in hypothetical dichromatic visual systems and, for each receptor pair estimated the percentage of discriminable points in natural scenes. The optimal spectral tuning predicted by this model results in photoreceptor pairs very like those of forest dwelling, dichromatic mammals and of coral reef fishes. Variations of the natural illuminants in forests have little or no effect on optimal spectral tuning, but variations of depth in coral reefs have moderate effects on the spectral placement of S and L cones. The ratio of S and L cones typically found in dichromatic mammals reduces the discriminability of forest scenes; in contrast, the typical ratio of S and L cones in coral reef fishes achieves nearly the optimal discrimination in coral reef scenes.

Distribution of S- and M-cones in normal and experimentally detached cat retina

The lectin peanut agglutinin (PNA) and antibodies to short (S)- and medium to long wavelength (M/L)-sensitive cones were utilized in order to define the relative distributions of the two spectral types of cone across the domestic cat's retina. These values, in turn, were compared to those from retinas that had been experimentally detached from the retinal pigment epithelium. The pattern of cone distribution in the normal cat's retina is established by the preponderance of M-cones that constitute between 80% and 90% of all cones. Their peak density of over 26,000 cells/mm(2) resides at the area centralis. Though M-cone density decreases smoothly to the ora serrata where they have densities as low as 2,200 cells/mm(2), the density decrease along the nasotemporal axis is slower,creating a horizontal region of higher cone density. S-cones constitute between 10% and 20% of all cones, the number being quite variable even between individual animals of similar age. The highest S-cone densities are found in three distinct locations: at the superior far periphery near the ora serrata, immediately at the area centralis itself, and in a broad zone comprising the central and lower half of the inferior hemiretina. S-cones in the cat retina do not form a regular geometrical array at any eccentricity. As for the detached cat retina, the density of labeled S-cone outer segments (OS) decreases rapidly as early as 1 day postdetachment and continues decreasing to day 28 when the density of cones labeling with anti-S opsin has dropped to less than 10% of normal. This response points to a profound difference between rods and cones; essentially all rods, including those without OS, continue to express their opsin even in long-term detachments. The implications of these results for visual recovery after retinal reattachment are discussed.

The distribution and nature of colour vision among the mammals

1. An oft-cited view, derived principally from the writings of Gordon L. Walls, is that relatively few mammalian species have a capacity for colour vision. This review has evaluated that proposition in the light of recent research on colour vision and its mechanisms in mammals. 2. To yield colour vision a retina must contain two or more spectrally discrete types of photopigment. While this is a necessary condition, it is not a sufficient one. This means, in particular, that inferences about the presence of colour vision drawn from studies of photopigments, the precursors of photopigments, or from nervous system signals must be accepted with due caution. 3. Conjoint signals from rods and cones may be exploited by mammalian nervous systems to yield behavioural discriminations consistent with the formal definition of colour vision. Many mammalian retinas are relatively cone-poor, and thus there are abundant opportunities for such rod/cone interactions. Several instances were cited in which animals having (apparently) only one type of cone photopigment succeed at colour discriminations using such a mechanism. it is suggested that the exploitation of such a mechanism may not be uncommon among mammals. 4. Based on ideas drawn from natural history, Walls (1942) proposed that the receptors and photopigments necessary to support colour vision were lost during the nocturnal phase of mammalian history and then re-acquired during the subsequent mammalian radiations. Contemporary examination of photopigment genes along with the utilization of better techniques for identifying rods and cones suggest a different view, that the earliest mammals had retinas containing some cones and two types of cone photopigment. Thus the baseline mammalian colour vision is argued to be dichromacy. 5. A consideration of the broad range of mammalian niches and activity cycles suggests that many mammals are active during photic periods that would make a colour vision capacity potentially useful. 6. A systematic survey was presented that summarized the evidence for colour vision in mammals. Indications of the presence and nature of colour vision were drawn both from direct studies of colour vision and from studies of those retinal mechanisms that are most closely associated with the possession of colour vision. Information about colour vision can be adduced for species drawn from nine mammalian orders.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of ambient illumination on the spatial properties of the center and surround of Y-cell receptive fields

The primary goal of this study was to expand the description of the filtering properties of the Y-cell receptive field, by quantitatively characterizing the spatial filtering properties of the receptive field's center-and-surround components as a function of adapting light level. A range of more than five orders of magnitude in retinal illuminance were covered, including the vast majority of the cat's functional range of vision. Recordings were taken from optic tract fibers of Y cells in cats under general anesthesia. Sinusoidal gratings and a stimulus designed to selectively probe the properties of the surround mechanism were used. The cells' responses to these stimuli were fit to a Gaussian center-surround receptive-field model, in which six parameters define the properties of the center and surround. Fits were made independently to data collected at each light level and changes in the values of the model's parameters with illuminance are reported. A set of equations that summarize the changes in parameter values is given. From these summary equations, reasonable estimates of the parameters' values can be determined across a wide range of illuminances. Hence, a quantitative model of the spatial properties of the center and surround of the Y-cell receptive field can now be derived from these equations for most of the levels of retinal illuminance experienced by a Y cell. The consistency between the description provided by our equations and results from earlier work is considered.

The rod-cone shift and its effect on ganglion cells in the cat's retina

We examined how several characteristics of cat retinal ganglion cells--receptive field size, spatial resolution, and centre-surround antagonism--change with background illumination. Spectral sensitivity was also measured to see how these changes depend on the rod-cone shift. The radius of the centre mechanism changed very little across the mesopic range. The absence of a change can be attributed to the connections rods make with cones, and to the small spatial spread of rods which connect to a cone. The highest spatial frequency to which a cell could respond dropped sharply with falling background illumination. This loss of spatial resolution is due partly to increasing receptive field size, and partly to loss of contrast gain. Centre-surround antagonism approached zero as background illumination fell. The loss of antagonism could have been due to either a change in the subtractive relationship between centre and surround, or due to a loss of surround strength relative to centre strength; the latter was shown to be the case.

Spectral sensitivity of monocularly deprived cats

The reports of rod-dominated psychophysical spectral sensitivity from the deprived eye of monocularly lid-sutured (MD) monkeys are intriguing but difficult to reconcile with the absence of any reported deprivation effects in retina. As most studies of MD retina have been from cat, we have examined psychophysically the increment threshold spectral sensitivity of MD cats using both reaction time and simultaneous two-choice behavioral procedures. Although the deprived eyes exhibited an absolute increment threshold sensitivity deficit, both rod and cone spectral sensitivity functions were obtained on large white backgrounds. This normal transition from rod to cone vision, as background luminance increased, was also found in threshold vs. intensity functions. Using their deprived eye, some cats exhibited a rod spectral sensitivity function when a smaller, normally photopic, background was used providing some support for a hypothesis that the rod-dominated spectral sensitivity observed in monkey may represent detection of scattered stimulus light. Alternatively monocular deprivation may reveal a rod-dominated mechanism which exists in monkey but not in cat.

Luminance sensitivity recovers quickly in monocularly deprived cats

We measured increment thresholds, using a reaction time or two-choice behavioral technique, in three cats monocularly deprived of normal vision for 14-16 months. Luminance increment thresholds could be obtained as early as nine days after lid opening and improved by 0.5-2.0 log units over the next few weeks. Also, visual reaction times decreased during the sensitivity improvement. When compared to the data for grating discrimination, these results suggest that visual recovery from monocular deprivation may proceed at different rates for different psychophysical discriminations.

Physiology of HI horizontal cells in the primate retina

Two types of recording were obtained from horizontal cells in the superfused eyecup preparation of the retina of Macaca mulatta . Injection of horseradish peroxidase showed that one class of responses was generated by the cell body of H I horizontal cells. The origin of the other type of responses was not identified morphologically, but they were strikingly similar to those recorded from the axonal arborization of axon-bearing horizontal cells of other mammalian species. The soma of H I cells responded with graded hyperpolarizations to increasing changes in diffuse white-light illumination. Threshold responses were obtained with stimulus intensities above electroretinogram (ERG) b -wave threshold; this was taken as an indication of cone input to this part of the cell. Responses to low-intensity stimuli were small, sustained hyperpolarizations; at intermediate intensities, the hyperpolarizations were initiated by a prominent transient component and were followed by a small rod after-effect at stimulus termination; with bright flashes, the transient component was abolished and the rod after-effect became larger. The spectral input of the H I cell body was tested with chromatic stimuli matching the spectral sensitivity of primate cone pigments: responses to all wavelengths were hyperpolarizations. Spectral sensitivity values for the different wavelengths and a comparison of the spectral amplitude–intensity curves for 450 nm, 540 nm and 630 nm wavelengths suggested that H I cell bodies had a non-specific, broad-band sensitivity to mid-spectral wavelengths. Thus more than one spectrally sensitive mechanism was involved in the generation of their response and they were not univariant. This was supported by the morphological observation that the clusters of terminal dendritic branchlets of H I cells had the same arrangement and distance from each other as the overlying cone inner segments, suggesting that these cells contact cones in an indiscriminate fashion. The other class of horizontal cell responses were characterized by a lower threshold, a larger amplitude with low intensity stimuli, a steeper increment in amplitude with increasing intensity, a saturation at moderate levels of illumination and a prominent rod after-effect in response to bright-light stimuli. We concluded that these responses were generated by the axon terminal of H I horizontal cells, that receives synaptic input from rods. Thus H I horizontal cells belong to the luminosity type, are not involved in the processing of colour contrast and are homologous to the axon-bearing horizontal cells of other mammalian retinas.

The refractive structure and optical properties of the isolated crystalline lens of the cat

Direct measurements of the shape and internal refractive index distribution of the isolated cat lens were used to construct individual optical models of the lenses from the left eyes of five cats. The right eyes were used in a companion study of the optics of the cat eye. The lens refractive index spatial distribution and dispersion were measured with a specially designed Pulfrich areal refractometer. Agreement of calculated ray paths through these models with the observed paths of laser beam fans incident parallel to, and at an oblique angle to the lens axis indicates that the models, which contain no freely adjustable parameters, are good physical and optical representations of the isolated (accommodated) crystalline lenses.

Color vision in the dog

The color vision of three domestic dogs was examined in a series of behavioral discrimination experiments. Measurements of increment-threshold spectral sensitivity functions and direct tests of color matching indicate that the dog retina contains two classes of cone photopigment. These two pigments are computed to have spectral peaks of about 429 nm and 555 nm. The results of the color vision tests are all consistent with the conclusion that dogs have dichromatic color vision.

The effects of beta-adrenergic agonists on cone systems in the cat eye

The effects of the beta-adrenergic agonist nylidrin and the beta 2-adrenergic agonist clenbuterol on electroretinogram and optic nerve response were studied in the isolated and arterially perfused, light-adapted cat eye. Two cone mechanisms, short wavelength-sensitive and long wavelength-sensitive, were functionally separated by means of intense yellow adaptation. A reversible increase in b-wave amplitude in response to nylidrin or clenbuterol was observed for the cone systems. Both drugs also caused a reversible alteration in configuration of the optic nerve response, mainly a depression of the late components related in time to the changes in the electroretinogram. These observations suggest that beta-adrenergic mechanisms are involved in cone systems. The greater increase in b-wave amplitude on 558-nm stimulation and preliminary evidence for greater increase in sensitivity observed in the V-log I function compared with 439 nm further suggest that the short and long wavelength cone systems are affected differently by beta-adrenergic agonists.