Grey Target Research Articles

ストライプの形と検査野の横幅がホワイト効果と逆転ホワイト効果に及ぼす影響

Two experiments were designed to differentiate White's effect and an inverted White's effect. In White's effect, a gray target bordered by black stripes longer than white stripes appears darker than a target of the same physical luminance bordered by white stripes longer than black stripes when the luminance of the target area lies between the minimum and maximum luminance values of the inducing stripes. In an inverted White's effect, the direction of the effect is reversed when the target is either lighter or darker than both inducing stripes (Spehar, Clifford, & Agostini, 2002). Twenty undergraduates were asked to rate the brightness of a target area using a Munsell scale on the display. The results showed that both White's effect and an inverted White's effect were reproduced in any condition of Experiment 1 and 2. Experiment 1 showed that an inverted White's effect was affected by the shape of stripes, while White's effect was not Experiment 2 showed that an inverted White's effect was affected by the length of target area, while White's effect was not. The results support Spehar et al. (2002) that White's effect and an inverted White's effect are not mediated by the same mechanism.

Lightness constancy: Object identity and temporal integration

Studies of lightness constancy typically involve the comparison of two objects of the same shade that have been placed under different illuminations. In this study, we introduce factors such as object identity and immediate prior experience to measure the effect of these manipulations on constancy. In the first experiment, conditions sufficient to reproduce classical constancy failure (illumination difference, target values, articulation level) were determined. In the second experiment a lightness judgment was made for a gray target that was then seen to move into another illumination level for the second match. Motion was used in an attempt to stress the target?s identity. The shade was still judged significantly lighter when placed under the higher than under the lower illumination. Failure of constancy thus occurred even when object identity was not in question. In the third experiment a priming paradigm was used, to assess the strength of constancy: one shade would appear in one illumination level and another shade in the other illumination level. Motion was used to trick observers into thinking that only a single object was presented. The estimated shade varied as a function of the shade of the prime. In the last experiment, observers were asked to make another match when the object was removed from view: the match of its true color independent of illumination. The value of this match-from-memory was based on the value obtained in the higher illumination level. Taken together, the experiments show that through object identity, immediate prior experience can influence lightness in systematic fashion.

Grey Target Tracking and Self-Healing on Vehicular Sensor Networks

The wireless vehicular sensor network (VSN) has been very useful for many transportation application systems, but it does not operate like the traditional wireless sensor network. For safety reason, the vehicle-vehicle and vehicle-gateway communication modes must be stable. The motion of the vehicle, the environment of the roads, and other uncertain traffic conditions all pose challenges to the system. Therefore, how to keep link stability becomes an important issue. In this paper, we propose a scheme that uses grey target tracking to self-heal or reroute in advance the weak link on an alternative route as failure occurs and makes the whole vehicular sensor network more stable. Although this scheme increases the average latency and control overhead, it supports higher survivability and effective reflections on rerouting.

Grey target theory based equipment condition monitoring and wear mode recognition

Grey target theory is a newly developed method in grey system theory. Calculating with grey target theory, pattern recognition, mode gradation and optimal mode selection can be performed. Oil samples from one auto press line and one 16V280ZJA diesel engine were analyzed by analytical ferrograph. For every wear particle in every analytical result, the size and quantity were quantified together. And some corresponding series have been established. Grey target theory was applied and a “bull's-eye” was constructed. By calculating the approaching degrees, wear modes have been graded, in conjunction with the running conditions of the press line and the diesel engine for given operation modes. The order of existing wear modes from severe to benign has also been assessed. The results agree with the experts’ analysis. This is the first time that grey target theory has been applied in oil monitoring for wear mode recognition.

Spatial, temporal, and intensive determinants of dopamine release in the chick retina

The retinal dopaminergic system is a global regulator of retinal function. Apart from the fact that the rates of dopamine synthesis and release are increased by increasing illumination, the visual image parameters that influence dopaminergic function are mostly unknown. Roles for spatial and temporal frequency and image contrast are suggested by the effects of form-deprivation with a diffusing goggle. Form-deprivation reduces the rates of dopamine synthesis and release, and induces myopia, which is prevented by dopamine agonists. Our purpose here was to identify visual stimulus parameters that activate dopaminergic amacrine cells and elicit dopamine release. White Leghorn cockerels 4-7 days old were exposed to 2 h of form-deprivation, reduced light intensity, or stimuli of varied temporal or spatial frequency. Activation of dopaminergic neurons, labeled for tyrosine hydroxylase (TH), was assessed with immunocytochemistry for c-Fos, and dopamine release was measured by HPLC analysis of dopamine metabolite accumulation in the vitreous body. Form-deprivation did not reduce TH+ cell activation or vitreal dopamine metabolite accumulation any more than did neutral-density filters of approximately equal transmittance. TH+ cell activation and vitreal metabolite accumulation were not affected significantly by exposure to 2, 5, 10, 15, or 20 Hz stroboscopic stimulation on a dark background, or by sine-wave gratings of 0.089, 0.44, 0.89, 1.04, or 3.13 cycles/deg compared to a uniform gray target of equal mean luminance. These data indicate that the retinal dopaminergic system does not respond readily to short-term changes in visual stimulus parameters, other than light intensity, under the conditions of these experiments.

Rapid image-segmentation and perceptual transparency share a process which utilises X-junctions generated by temporal integration in the visual system.

Perceptual transparency requires local same-polarity X-junctions, which can also be generated by temporal integration under natural dynamic conditions. In this study, segmentation performance and target appearance were measured for a uniform gray target embedded in a random-dot frame presented with a temporally adjacent mask. Although static cues for both segmentation and transparency were unavailable, transparency was observed only when collinear same-polarity edges reduced backward masking, in both the fovea and the perifovea. These results suggest that the visual system has a common underlying mechanism for rapid segmentation and transparency, which utilises same-polarity X-junctions generated by temporal integration.

Brightness assimilation in bullseye displays

In simultaneous brightness contrast displays, a gray target square G B bordered by black appears brighter than an identical gray target square G W bordered by white. Here we demonstrate that this effect can be reversed if G B is surrounded by bands that alternate outward from black to white, while G W is surrounded by bands that alternate outward from white to black. With these simple “bullseye” displays assimilation generally occurs–– G B appears darker than G W. Experiments 1 and 2 used a 2AFC design with a 2.2 s display duration. The results of these experiments indicate that (i) substantial assimilation occurs for target Weber contrasts (relative to the gray background) of −0.25, 0, and 0.25, but assimilation was maximal when target contrast was −0.25 and decreased as target contrast increased, (ii) assimilation effects were the same whether the width of the four surround bands was 20% of the target or 40% of the target, and (iii) assimilation occurs with as few as 2 surround-bands and the magnitude of the effect increases slightly as the number of bands increase. When experiment 1 was re-run using the method of matching (experiment 3), however, the results changed dramatically: (moderate) assimilation effects were found only when target contrast was −0.25; when target contrast was 0.25, there was a brightness contrast effect; when target contrast was 0, there was no illusion. Assimilation effects in bullseye displays are not predicted by the CSF model described in DeValois and DeValois [Spatial Vision, Oxford University Press, New York, 1988], the anchoring model of Gilchrist et al. [Psychological Review, 106(4) (1999) 795], or Blakeslee and McCourt’s [Vision Research 39 (1999) 4361] ODOG model. We propose that this assimilation effect is the result of a contrast inhibition mechanism similar to that proposed by Chubb et al. [Proceedings for the National Academy of Science, vol. 86, 1989, p. 9631] to underlie contrast effects.

Inhibitory conditioning in honeybees.

Honeybees were rewarded with sucrose solution for choosing AX(a grey target, X, labelled with a distinctive stimulus, A) rather than ABX (a grey target labelled both with A and with another distinctive stimulus, B)-AX+/ABX- training. Tests of independent groups made after such training showed a clear preference not only for AX over ABX, but also for ABX over BX, and for X over BX. These experiments, along with some earlier ones to which they bring a new perspective, provide persuasive evidence, previously lacking, of inhibitory conditioning in honeybees.

54th annual meeting of the American Academy of Neurology, Denver, Colorado, April 13-20, 2002.

54th annual meeting of the American Academy of Neurology, Denver, Colorado, April 13-20, 2002.

The grey target method for risk evaluation of tubing in natural gas well

The application of Grey target theory to tubing corrosion is developed, and the risk evaluation of loss efficacy of the tubing corrosion in natural gas well of Zhongyuan oil field of China is cited as an instance for describing those works. The results indicate that the corrosion state of tubing can be represented quantitatively with the Grey target center grade r (x0,xi) and the judgment of risk level can be decided with the Grey evaluation grade. Therefore, the method is available for data processing and can be applied to the risk evaluation of complex corrosion systems such as tubing or pipeline in gas-oil field etc. Grey Target Methode zur Risikobeurteilung von Rohrleitungen in naturlichen Gasquellen Die Anwendung der Grey Target Theorie auf die Korrosion von Rohrleitungen wird entwickelt und die Risikobeurteilung der Rohrleitungskorrosion in naturlichen Gasquellen des Zhongyuan Olfeldes in China wird als Beispiel zur Beschreibung dieser Arbeiten angefuhrt. Die Ergebnisse zeigen an, dass der Korrosionszustand der Rohrleitung quantitativ durch den Grey Target Center Grad r (xx, xi) dargestellt und die Beurteilung des Risikolevels durch den Grey Evaluation Grad entschieden werden kann. Daher ist diese Methode fur die Datenverarbeitung geeignet und kann zur Risikobeurteilung von komplexen Korrosionssystemen wie z. B. Rohrleitungen von Gas-Ol-Feldern eingesetzt werden.

Induction in variants of White's effect: common or separate mechanisms?

In White's display the gray target surrounded more by black than white appears darker than the target of the same physical luminance surrounded more by white than black. Several subsequent studies have shown that this effect occurs only when the luminance of the test regions lies between the minimum and maximum luminance values of the inducing stripes. With targets either lighter or darker than both inducing stripes, the direction of the effect is reversed and the effect is known as the 'inverted' White's effect. Views differ on whether the classical and inverted White's effects are mediated by common or separate underlying mechanisms. We varied the aspect ratio of the test and inducing regions in the classical and inverted White's effects. Consistent with previously reported findings, we found that the direction of the classical effect did not depend on the amount of black or white border in immediate contact with the test patch. On the other hand, perceived lightness in the inverted White's effect was affected by such variations, suggesting that induction in classical and inverted White's configurations is governed by different mechanisms. These results confirm the critical importance of the interaction between luminance and geometric relationships in induced brightness.

Must all action halt during sensorimotor mismatch?

Gray's target article presents a model of consciousness that includes several ideas similar to those developed over the past century to explain how sensorimotor information is interpreted by the nervous system. This commentary discusses these ideas and introduces some additional hypotheses, also derived from sensorimotor investigations, that might help improve Gray's model.

Interocular suppression of a half-occluded region of stereoscopic images

We assessed the detectability d' of a monocular small gray dot target presented on a half-occluded region of stereoscopic three-dimensional background images by comparing it with that on a two-dimensional (2D) region. For our experiments we used a typical two-alternative temporal forced-choice procedure, in which the target was presented in one of two temporal intervals for approximately 67 ms, and observers selected the interval they believed to have contained the target by pressing the corresponding key. To vary target signal intensity, we changed the target contrast against the background. According to signal-detection theory, we converted the percent-correct data to detectability d' and found that the relationship between d' and the contrast of the target followed Legge's equation. We used Legge's equation to calculate the contrast threshold and found that the contrast threshold of the target on the half-occluded region was higher than that on the 2D region. This elevation of contrast threshold indicates that interocular suppression of the half-occluded region occurs more frequently than that of the 2D region. We also refer to the monocular performance of the human visual system.

Further Evidence of the Effect of Gradient on Lightness

Recently, Agostini and Galmonte (submitted for publication) reported a new effect of gradient on lightness. When two identical mid-gray squares are placed at the centre (white and black, respectively) of two crosses, the first cross having arms filled by a constant achromatic gradient from black (outer part) to white (inner part), and the second cross being the negative of the first one, the gray target surrounded by white appears much darker than that surrounded by black. In a simultaneous comparison, this phenomenon is much stronger than the classical lightness contrast effect. Further observations showed that the effect is quite robust also when the amount of black area is reduced and the gradient is discontinuous. When the gray targets are enlarged to fill the centres of the crosses, the effect is still stronger than that observed in the classical simultaneous lightness contrast display. Furthermore, the effect is independent of the shape of the configuration. The phenomenon can be explained by assuming that the gradient is perceived as a change of the level of illumination rather than as a change of the reflectance of the surfaces.

Prospects for a cognitive neuroscience of consciousness

AbstractIn this commentary, I point out some weaknesses in Gray's target article and, in the light of that discussion, I attempt to delineate the kinds of problem a cognitive neuroscience of consciousness faces on its way to a scientific understanding of subjective experience.

Flutter-like response in visual cortex of the semi-isolated turtle brain.

activity of nearby receptors in the eye that see an object becomes correlated (5). The lateral eye is highly sensitive to the flickering light from the overhead waves. A large component of the light reflected from grey targets centers at -2-4 Hz which is the peak of the temporal transfer function of the eye (Fig. 1B; 6, 7, 8). Phototransduction mechanisms set the underlying shape of the transfer function, which two inhibitory processes then sharpen and amplify (6, 7). As a result, the power spectrum of the spike train recorded from receptors viewing the grey target grows considerably in the range of 2-4 Hz (Fig. 1 B). In this paper we show that a consideration of the natural environment of an animal can lead to a better understanding of its visual system. The Limulus eye appears to be adapted to a particular feature of its environment-the flickering light reflected off the carapace of a potential mate. These light signals help males detect a female irrespective of the contrast of her carapace. Frequency tuning of vision is not unique to horseshoe crabs and has been observed in many animals, such as cats (9) and humans (10). Perhaps their lighting environment also deserves a closer look. Supported by NSF grant BNS9309539 and NIH grants MH4974 1 and EY00667.

The critical role of relative luminance relations in White's effect and grating induction

It has been proposed that both White's effect and the grating induction effect are examples of brightness induction phenomena modeled in terms of local spatial filters. We have shown that for these illusions to occur it is necessary that the luminance of the gray target elements falls between that of the inducing stripes of the square-wave pattern. This critical role of luminance relationships is not predicted by existing models of these illusions.

Varying the strength of the Munker-White effect by stereoscopic viewing.

In the Munker-White effect grey target bars appear lighter when they are flanked by white bars, and darker when they are flanked by black bars. It is shown that the effect is enhanced if the patterns are presented stereoscopically so that the grey bars appear either behind the grating, in which case they are seen as a rectangle that is occluded by the white bars of the grating, or in front of the grating, so that they form a transparent rectangle. These results are explained in terms of object perception: contrast enhances differences between an object and its surroundings, whereas assimilation reduces differences within an object.

Hyalomma truncatum (Acari; Ixodidae): evidence for the inability of adult ticks to discriminate between colours

Behavioural investigations into the perception and differentiation of coloured objects by unfed adult Hyalomma truncatum ticks revealed that silhouettes of blue, green, red and yellow colour, under illumination by a sun-simulating waveband spectrum, are perceived by the ticks and responded to equally by a directed response. Two green or dark grey rectangles each with a luminance contrast ratio of 5:1 against the white wall of the test arena in combination with an overlapping, equally sized dark grey or green target were consistently reached by ticks in a ratio of 2:1. Since the outer targets were occupied by the double number of ticks compared with the central silhouette this shows that the response is independent of the colour of the object. Investigations into target perception under monochromatic radiation of different wavelength ranges which were evenly adjusted in their irradiances revealed that ticks responded equally to a black target irradiated by blue, green, yellow and red light of wavelengths 428-472, 517-563, 549-591 and 606-654 nm, respectively. These results indicate the lack of true colour vision in H. truncatum.

Corticospinal axons and mechanism of target innervation in rat lumbar spinal cord

The aim of the present study is to investigate the mechanism by which outgrowing rat corticospinal (CS) axons innnervate their spinal gray target areas. This study was carried out with the use of anterogradely transported horseradish peroxidase or 1,1-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) after application in the sensorimotor cortex of rat pups varying in age between 5 days postnatal (P5) and 10 days postnatal (P10). The CS axons of neurons situated in the sensorimotor cortex have reached the ventral most parts of the dorsal funiculus at mid-lumbar spinal cord levels at the fifth postnatal day (P5). After a waiting period of 2 days some CS fibers change their direction and directly enter the adjacent spinal gray target areas. One day later, i.e., P8, CS target innervation by the formation of collateral branches can be observed. Finally, the development of collaterals by interstitial budding from their parent axons appears to be the major, but not the exclusive, mechanism by which CS axons innnervate the lumbar spinal gray matter target area.