Scotopic sensitivity in coyotes (Canis latrans).

The absolute scotopic limen for light intensity was measured for three 10-mo-old female coyotes. The methodology was similar to that used by Blough in determining psychophysical thresholds in pigeons. Three coyotes were operantly conditioned to depress one of two foot treadles, left or right, depending on the condition of the stimulus light. Scotopic adaptation curves for each coyote were generated. Nonlinear regression curves were then fitted to the raw data. The mean scotopic thresholds did not differ significantly. However, time to the curves' asymptotes did differ significantly for one of the coyotes. The adaptation curves showed a distinct rod-cone "break," and retinal histology confirmed that the coyote has a duplex retina with a preponderance of rods. In addition, electroretinographic analysis showed the relative contributions of rods and cones at various light intensities and indicated a rod-cone break at approximately 15 min. Scotopic spectral sensitivity curves were also generated. The coyotes' scotopic visual threshold is exceeded by the natural illumination available under many nocturnal conditions. The results are discussed in relation to the ecology of the species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Scotopic Sensitivity in Coyotes (Canis latrans)": Erratum.

Reports an error in the original article by Steven W. Horn and Philip N. Lehner (Journal of Comparative and Physiological Psychology, 1975[Nov], Vol 89[6], pp. 1070-1076). The corrected sentence beginning in the first line on page 1074 is published here. (The following abstract of this article originally appeared in record 2005-09231-001). Measured the absolute scotopic limen for light intensity for 3 10-mo-old female coyotes. The methodology was similar to that used by D. S. Blough (see record 1959-07701-001) in determining psychological thresholds in pigeons. Ss were operantly conditioned to depress 1 of 2 foot treadles, left or right, depending on the condition of the stimulus light. Scotopic adaptation curves for each S were generated. Nonlinear aggression curves were then fitted to the raw data. The mean scotopic thresholds did not differ significantly. However, time to the curves' asymptotes did differ significantly for 1 S. The adaptation curves showed a distinct rod-cone "break," and retinal histology confirmed that the coyote has a duplex retina with a preponderance of rods. In addition, electroretinographic analysis showed the relative contributions of rods and cones at various light intensities and indicated a rod-cone break at approximately 15 min. Scotopic spectral sensitivity curves were also generated. Ss' scotopic visual threshold was exceeded by the natural illumination available under many nocturnal conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of scotopic sensitivity in diurnal (Anas platyrhynchos) and crepuscular (Dendrocygna autumnalis) ducks.

Obtained scotopic visual adaptation curves from 4 mallard ducks. A curve of best fit was used to compare the mallards' mean adaptation curve to the curve previously reported for the black-bellied tree duck, a crepuscular species. The curves did not differ significantly in either their slopes or base levels (thresholds). The mallards' curve had a rod-cone "break" at approximately 25 min. This break was evident in the scotopic curve for pigeons but was absent from the black-bellied tree ducks' curve. Examination of retinal tissues indicated that the black-bellied tree ducks had significantly more rods and cones, and a larger rod-cone ratio than the mallards. The mallards' scotopic visual threshold was exceeded by the natural illumination present under several nocturnal conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biological and clinical responses of west African sheep to Crimean-Congo haemorrhagic fever virus experimental infection

Color and lightness constancy with respect to changing illumination was studied with three different perceptual tasks: ranking of colored papers according (1) to their lightness and (2) to their chromatic similarity in photopic, mesopic, and scotopic states of adaptation, and (3) recognition of remembered colored papers after changes of illumination in photopic vision. Constancy was found in the second task, only. Excitations of light receptors and luminance channels were computed to simulate the empirical rank orders. Results of the first task can be predicted with the hypothesis that luminance channels are activated, if lightness is asked for. Sequences arranged with respect to chromatic similarity were found independent of the illuminant spectra, even if the calculated rank orders of cone excitation were changed in the altered illumination.     

Patients with ocular hypertension have abnormal point scotopic thresholds in the superior hemifield

PURPOSE: To compare light- and fully dark-adapted thresholds at loci within the central visual field in patients with ocular hypertension and glaucoma. METHODS: Eighteen patients with chronic open angle glaucoma, 13 patients with ocular hypertension, and 24 age-matched normals were studied. The Humphrey automated perimeter with the standard background illumination of 31.5 apostilbs was used to determine photopic thresholds at 18 loci within 20 degrees of fixation. Fully dark-adapted thresholds were measured at the same loci after 30 minutes of dark adaptation by automatic, static campimetry. RESULTS: The glaucoma group showed elevated scotopic thresholds. Scotopic defects also were found in a significantly higher proportion of patients with ocular hypertension than in normals. These scotopic defects were predominantly in the superior hemifield. CONCLUSIONS: Scotopic threshold campimetry may identify the subgroup of patients with ocular hypertension who progress to develop glaucomatous field loss identifiable by standard photopic and mesopic perimetry.     

Away from a unisex psychology: individual differences in visual sensory and perceptual processes

Four tests of visual perception were given to twenty-five men and twenty-five women. These were a test of acuity, threshold for four field positions, visual persistence, and a measure of comfortable brightness. Subjects also completed five personality questionnaires. In most measures, differences were found to be related to sex rather than to personality factors. In fact, the analyses performed suggest that persenality tests do not measure equivalent processes in men and women. Correlational anaylsis showed all visual functions to be independent of one another with the exception of photopic acuity and scotopic threshold, which were highly correlated. Two new findings on the visual system emerged which have not been reported elsewhere: (i) Four distinct dark adaptation curves were produced, and have been labeled as exponential, flat-exponential, linear, and plateau. All subjects fell into one of these categories and showed a consistent trend to exhibit these curves for all field positions. (ii) Highly significant differences were found in sensitivity for the four visual fields, the upper field was superior, followed by the right, then left, with the lower visual field considerably poorer.     

Role of electroretinography in the prognosis of central retinal vein occlusion

The aim of the study is to evaluate the role of electroretinography in diagnosis of central retinal vein occlusion CRVO. There are two forms of this entity, each of them having a different prognosis. While haemorrhagic form has a better outcome, with fairly good prognosis for vision, ischaemic form usually develops many complications: macular oedema, neovascularisation of the retina or optic disk, neovascular glaucoma, and possible blindness. Three months after the onset, when oedema and retinal haemorrhages are usually resolved, it is possible to perform fundus fluorescein angiography (FFA) and make differentiation between the two forms of the disease. However, neovascular glaucoma may challenge the vision even before the diagnosis of ischaemic form becomes possible by observing the fundus or by performing FFA. Trying to foresee the course of the disease, and thus to help a patient with panretinal photocoagulation, we performed electroretinography (ERG) in each patient just after the onset of the disease. The prospective study included 40 patients with CROV which lasted less than three months and without any complication. Two parameters were examined: scotopic "b" wave and photopic b/a ration. By ERG action potentials from the retina after its stimulation with light, are recorded. Scotopic "b" wave generates in bipolar layer from Muller's and bipolar cells. Photopic b/a ratio is a ration of two waves, "b" and "a" in photopic conditions and is a good indicator of saturation of the retina with blood and oxygen. Visual acuity, applanation tonometry, examination of the fundus after dilatation of pupils with Sol. Mydriacili were performed in each patient. Each patient was examined by ERG in scotopic and photopic conditions. The results were as follows: Scotopic b wave per se could not indicate potential complications, while b/a ratio was a good predictor of possible complications when its value was less than 1.25. CONCLUSION: Electroretinography, which can be performed at any time after the onset of the disease may be a good indicator of retinal perfusion and oxygen saturation, by giving the ratio of b and a waves under photopic conditions. The status of Muller's cells and bipolar cells is reflected in the scotopic b wave. In a prospective study forty patients with CRVO of less than three months duration and without neovascularisation were studied with the use of ERG, both in scotopic and photopic conditions. Our results suggest that the b/a ratio may be a good predictor of the development of retinal, disk and iris neovascularisation by showing the degree of retinal ischaemia, while the scotopic b wave cannot be used for such evaluation. Predicting the new vessel development by ERG may save the useful vision and prevent a disastrous outcome, blinding and painful neovascular glaucoma by performing panretinal photocoagulation.     

Dopaminergic control of light-adaptive synaptic plasticity and role in goldfish visual behavior

Dopamine has been implicated in processes of retinal light and dark adaptation. In goldfish retina, horizontal cell dendrites elaborate neurite processes (spinules) into cone terminals, in a light- and dopamine-dependent manner. However, the functions of retinal dopamine and the horizontal cell spinules in visual behavior are unknown. These issues were addressed in behavioral, electroretinographic, and anatomical studies of normal fish and those with unilateral depletion of retinal dopamine induced by intraocular (i.o.) injections with 6-hydroxydopamine (6-OHDA). Dopamine interplexiform cells (DA-IPC) disappear within 2 weeks after 6-OHDA injection; cell bodies appear at the marginal zone within 6 weeks at which time neurites slowly reinnervate the retina with a sparse plexus over the next 12 months. We found that dopamine depletion increased light sensitivity at photopic but not scotopic backgrounds by 2.5 log units, an effect mimicked by i.o. injections of dopamine D1 and D2 antagonists. The ERG b-wave increment thresholds were the same for control and dopamine depleted eyes, indicating a normal transition from rod to cone systems in the ON pathway. Light-dependent spinule formation was reduced by about 60% in dopamine-depleted retinas, but returned to normal by 3 months and 9 months after injection in the entire retina, even areas not directly innervated with DA-IPC processes. Spinule formation in vivo was inhibited 50% with i.o. injection of SCH 23390 in control retinas as well as throughout 3 month 6-OHDA injected retinas, including DA-IPC free areas. This latter result indicates a volume effect of dopamine, diffusing laterally through the retina over several millimeters, in regulating spinules. We conclude that DA-IPCs regulate sensitivity to background at photopic levels not via the ON pathway, but perhaps the OFF pathway. Goldfish display both increased sensitivity to light and a normal Purkinje shift in the ERG b-wave whether or not horizontal cell spinules are present, indicating that dopamine control of photopic vision in fish is not mediated through light-induced spinule formation of horizontal cell dendrites.     

Inverse-intensity effect in duration of visible persistence.

Duration of visible persistence can vary inversely with stimulus intensity. This inverse-intensity effect is obtained by varying the intensity of the stimuli or of the background, provided that the variations extend into the mesopic range. A similar relationship—known as the Ferry-Porter law—holds for the critical frequency at fusion (CFF). The authors propose that studies of CFF, 2-pulse threshold, and visible persistence can be encompassed within 1 conceptual framework in which the effect is modeled by the progressive reduction in the temporal extent of the positive phase of the system's response as the level of light adaptation changes from scotopic to photopic. In this context, the authors present an integrative scheme in which G. Sperling and M. M. Sondhi's (1968) formal model and M. Coltheart's (1980) neurophysiological conjecture are shown to be compatible and complementary accounts of the effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical theories.

The chemical theories of the visual process advanced by Wald, Dartnall, and others are compared. Their adequacy for scotopic vision is substantial, while incomplete. Almost no theory successfully explains photopic vision. Evidence that rhodopsin is a light-sensitive enzyme is discussed, and it is conjectured that present extraction techniques do not permit comparison of in situ and in vitro data, particularly in the photopic case. (42 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dark adaptation in the American red squirrel (Tamiosciurus hudsonicus).

Used a behavioral tracking technique to investigate dark adaptation in 3 American red squirrels. Dark adaptation was fully completed within 30 min after the offset of the longest light-adaptation duration. An increase in visual sensitivity of more than 3 log units had taken place, and the final threshold (10-5 ml) was about 1 log unit above the scotopic threshold of a human tested in the same apparatus. A discontinuity occurred about 4 min after the start of dark adaptation when the Ss were light adapted for 4 min. No rod-cone break occurred when the Ss were not light adapted above room illumination. When colored test stimuli (red, yellow, and blue) were used after 4 min of light adaptation, rod-cone breaks occurred for each test stimulus. It is concluded that the tree squirrel possesses a functional duplex retina. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of the Night Vision Spectacles on patients with impaired night vision

BACKGROUND: The Night Vision Spectacles (NiViS) were developed by a consortium of European companies to assist individuals who suffer from impaired night vision. They consist of a head-mounted video camera (input) and binocular displays (output) connected to a portable computer processor, which uses an algorithm to enhance the luminance and contrast of the video image. METHODS: Eighteen patients with impaired night vision were tested, including those with retinitis pigmentosa (7), Usher syndrome (2), fundus albipunctatus (1) and complete (4) and incomplete (4) congenital stationary night blindness. Normal trichromats (3) and typical, complete achromats (2) acted as controls. A battery of tests assessed: visual acuity at 5 m (projection unit) and 1 m (chart) and at high and low contrasts; contrast sensitivity; absolute and increment threshold; the influence of glare; contrast motion detection; and hand-eye performance. The tests were performed, with and without the NiViS, at three adaptation levels: low scotopic (10(-3) cd/m2), high scotopic (10(-2) cd/m2) and mesopic (10(-1) cd/m2). RESULTS: At the low and high scotopic levels, the majority of patients showed improved performance on the visual acuity, contrast sensitivity and motion contrast tests with the NiViS. At the mesopic level, the advantage with the NiViS was greatly reduced, but still present for contrast sensitivity. CONCLUSION: Patients with impaired night vision can benefit from the NiViS when performing tasks involving contrast and motion perception. Those with normal visual fields and retaining good photopic vision will benefit more than those with constricted visual fields and impaired cone vision. Recommendations regarding desirable improvements of the NiViS and suitability for the individual patient are given.     

Defect of cold-sensitive response in calmodulin mutants of Paramecium and the restoration by cyclic nucleotide

In carp (Cyprinus) and goldfish (Carassius), long-wavelength cones are reported to be active under scotopic conditions. Using the electroretinogram (ERG), we tested another cyprinid fish, Danio aequipinnatus, which contains A1-based visual pigments and for which we had previously measured the spectral sensitivities of individual cones. Dark adaptation curves show a rod/cone break at about 45 min. When thoroughly dark-adapted, the spectral sensitivity function is broader than can be accounted for by self-screening of rhodopsin, but it can be modeled by an additive combination of rods and the 560-nm cones. Dim, red background light causes adaptation of rods and a broadening of the spectral sensitivity function, which can be simulated by increasing the proportion of cones in the model. Brighter red backgrounds adapt the 560-nm cones. Because of the effect of red adapting lights, the ERG evidence for the participation of long-wavelength cones close to visual threshold appears to be different in Danio than in the goldfish Carassius.     

Elevated levels of IL-8 in dengue hemorrhagic fever

AIMS: To characterise retinal function using electrophysiological and psychophysical tests in 17 patients with helicoidal peripapillary chorioretinal degeneration. METHODS: The electroretinogram (ERG) was recorded using gold foil corneal electrodes. The electro-oculogram (EOG) was recorded using a standard protocol. Dark adaptometry was recorded with an SST-1 dark adaptometer and colour vision assessed with Ishihara plates and Farnsworth D-15. RESULTS: All subjects had a recordable ERG. The amplitudes and implicit times of the a- and b-waves were within normal limits at all luminances in five subjects (age 21-70 years, mean 40 years). The ERG of six (age 26-55 years, mean 40.7 years) had subnormal amplitudes at all luminances, but normal implicit times, and six (age 38-81 years, mean 60.7 years) had abnormal ERGs with marked reduction of a- and b-waves, and delayed implicit times of the b-wave. The implicit times of the a-wave were normal in all subjects. A reduction in the b/a wave ratios was not found, nor was there selective loss of scotopic, mixed rod/cone, or cone responses. The light/dark ratio of the EOG was subnormal (150-185%) or abnormal (below 150%) in all but three subjects. Two patients with normal EOG showed normal ERGs in both eyes, but one had subnormal ERGs in both eyes. The scotopic sensitivity was normal in all subjects and dark adaptation showed a normal time course. Colour vision was normal in all patients. CONCLUSION: The results suggest that in most cases the function of the retinal pigment epithelium is affected by this disease before any changes in the function of the sensory retina are detectable by our methods, and that retinal dysfunction is focal rather than diffuse.     

Latent inhibition and overshadowing in conditioned emotional response conditioning with rats.

Tested whether unreinforced preexposure to one element of a compound CS would prevent that element from overshadowing the other element, using 64 male hooded COBS rats. Groups of Ss were given 20 preexposure trials to a light prior to conditioned emotional response (CER) conditioning or were given no pre-exposure. In CER conditioning, Ss received either a noise plus light or a noise followed by shock. In Ss given no pre-exposure, the presence of the light significantly attenuated conditioned suppression to the noise CS. However, in the pre-exposed compound-cue group no reduction in suppression to the noise CS was observed after 4 CER trials. After 8 CER trials, suppression to the noise CS was significantly attenuated. Latent inhibition temporarily reduced the extent to which the light CS overshadowed the noise CS. Overshadowing of the noise in the pre-exposed compound-cue group after 8 CER trials was not accompanied by any increase in suppression to the light CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electroretinogram: technique and clinical applications

INTRODUCTION: The retina is a neuronal membrane that covers the posterior part of the eye chamber and is formed by several layers. The retinal function can be synthesize as the light translation into nervous impulses in the optic nerve. MATERIAL AND METHODS: The ERG is the expression of the changes of the electrical potential in the retina after a luminous stimulus. There are different types of retinal stimulators specially flash, ganzfeld and pattern which are the most used in the clinical neurophysiological explorations. RESULTS: We expose the obtained responses, the morphology, amplitude and latencies of the (a) and (b) waves in scotopic and photopic conditions with ganzfeld or flash stimulator. In the ERG pattern we describe the waves for the transitory ERGP as well as for the Steady-State ERGP. We refer to the protocols proposed by the International Society of Electrophysiology of Vision (ISCEV). We mention the clinical applications of these techniques and we give our personal experience in diseases such retinitis pigmentosa, maculopathies, retinal degenerations, vascular diseases, cataracts and traumatic lesions of the retina.     

Cones survive rods in the light-damaged eye of the albino rat

Exposure to constant light causes extensive rod photoreceptor damage but spares the photopic system in albino rats. The rod branch of the dark-adaptation curve shows considerable elevation in threshold; the cone branch is hardly affected. Longer exposure and chromatic adaptation suggest that there are three cone mechanisms with peaks near wavelengths of 450,520, and 560 nanometers.     

Reexamination of spectral mechanisms in the rat (Rattus norvegicus).

Studied the spectral mechanisms of Long-Evans and Zucker rats in electrophysiological and behavioral experiments. The photopic electroretinogram was recorded (a) to rapidly flickering lights, (b) during the cone phase of dark adaptation, and (c) with a flicker photometric procedure. The consistent conclusion from both experiments is that the rat retina contains only a single photopic spectral mechanism. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A test of reciprocal inhibition: are anxiety and sexual arousal in women mutually inhibitory?

Tested J. Wolpe's (1958) prediction that autonomic sexual and anxiety arousal states are mutually inhibitory. Using a new physiological measure of female sexual arousal (vaginal blood volume), changes in 7 sexually experienced Ss (mean age 27 yrs) were compared during erotic video stimulation following anxiety and control stimulus preexposure and during anxiety and control stimulation following erotic stimulus preexposure. Consistent with reciprocal inhibition theory, when Ss were sexually aroused by erotic preexposure, anxiety arousal inhibited sexual arousal more rapidly than did an attention control stimulus. However, contrary to reciprocal inhibition theory, Ss became more rapidly aroused sexually following anxiety preexposure than following neutral preexposure. In the case of heart rate, changes were compared during erotic and neutral stimulation following anxiety preexposure and during anxiety arousal following erotic and neutral preexposure. Consistent with the literature to date, there were no heart rate changes that could be attributed to differential preexposure. Taken together, the results do not support Wolpe's reciprocal inhibition theory but do suggest a context interpretation: The way in which sexual and anxiety arousal states interact with each other may depend on the context in which Ss perceive the stimuli that generate these respective arousal states. The clinical implications of the findings are discussed. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of psychophysical and electrophysiological testing in early glaucoma

PURPOSE: To compare the sensitivity and specificity of a wide range of psychophysical and electrophysiological tests in the detection of early glaucomatous damage. METHODS: Forty-three normals and 43 patients with early glaucoma, some still without field defects, were tested with differential light threshold perimetry, short-wavelength automated perimetry, high-pass resolution perimetry, motion detection, flicker contrast sensitivity, flickering and isoluminantly matched letter tests, and pattern and flash electroretinography, including photopic, scotopic, oscillatory potentials, and 30 Hz flicker. Receiver operating characteristic analysis was applied to continuous variables derived from each of the tests. RESULTS: Most parameters reflected glaucomatous loss to some degree, even though only single variables were analyzed separately in the receiver operating characteristic analysis. The pattern electroretinogram and some of the letter acuity tests had the best sensitivity and specificity, followed by short-wavelength automated perimetry and high-pass resolution-perimetry. Motion detection, flicker contrast, and flash electroretinogram parameters scored poorly. Six patients with normal results on the Humphrey field test had abnormal results on many of the other tests. CONCLUSIONS: Applying different psychophysical and electrophysiological tests may add to our ability to detect early glaucomatous damage.