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Journal ArticleDOI

Model of visual adaptation and contrast detection

George Sperling1
01 May 1970-Attention Perception & Psychophysics (Springer-Verlag)-Vol. 8, Iss: 3, pp 143-157
TL;DR: A three-component model of spatial vision is proposed, consisting of a feedback stage, a feedforward stage, and a threshold detector that correspond to physiological processes.
Abstract: A three-component model of spatial vision is proposed, consisting of (1) a feedback stage, (2) a feedforward stage, (3) a threshold detector. The components correspond to physiological processes; in particular, the feedforward control signal corresponds to the “surround’s” signal in the receptive fields of retinal ganglion cells. The model makes appropriate qualitative predictions of: (l)a square-root law (Δl ∞ l1/2) for detection at low luminances, (2) a Weber law (Δl ∞ l) at high luminances, (3) additivity of threshold masking effects at high background luminances, (4) receptive fields that, in the dark, consist only of an excitatory center and that, in the light, also contain inhibitory surrounds, (5) the variation of spatial characteristics of receptive fields depending on the temporal characteristic of the test stimulus used to measure them, (6) the subjective appearance of Mach bands, (7) sine-wave contrast-threshold transfer functions, (8) the frequent failure of disk-detection experiments to demonstrate inhibitory surrounds, and (9) various second-order threshold effects, such as reduced spatial integration for long-duration stimuli, reduced temporal integration for large-area stimuli, and the increased effect of background luminance on the detection of large-area stimuli. Predictions are improved by assuming there exist various sizes of receptive fields that determine thresholds jointly.

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Citations
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Journal ArticleDOI
TL;DR: It is shown that this particular mode reproduces some of the phenomenology of visual psychophysics, including spatial modulation transfer function determinations, certain metacontrast effects, and the spatial hysteresis phenomenon found in stereopsis.
Abstract: It is proposed that distinct anatomical regions of cerebral cortex and of thalamic nuclei are functionally two-dimensional. On this view, the third (radial) dimension of cortical and thalamic structures is associated with a redundancy of circuits and functions so that reliable signal processing obtains in the presence of noisy or ambiguous stimuli. A mathematical model of simple cortical and thalamic nervous tissue is consequently developed, comprising two types of neurons (excitatory and inhibitory), homogeneously distributed in planar sheets, and interacting by way of recurrent lateral connexions. Following a discussion of certain anatomical and physiological restrictions on such interactions, numerical solutions of the relevant non-linear integro-differential equations are obtained. The results fall conveniently into three categories, each of which is postulated to correspond to a distinct type of tissue: sensory neo-cortex, archior prefrontal cortex, and thalamus. The different categories of solution are referred to as dynamical modes. The mode appropriate to thalamus involves a variety of non-linear oscillatory phenomena. That appropriate to archior prefrontal cortex is defined by the existence of spatially inhomogeneous stable steady states which retain contour information about prior stimuli. Finally, the mode appropriate to sensory neo-cortex involves active transient responses. It is shown that this particular mode reproduces some of the phenomenology of visual psychophysics, including spatial modulation transfer function determinations, certain metacontrast effects, and the spatial hysteresis phenomenon found in stereopsis.

1,796 citations

Book ChapterDOI
TL;DR: It is suggested that competition solves a sensitivity problem that confronts all cellular systems: the noise-saturation dilemma.
Abstract: This article is the first of a series to globally analyse competitive dynamical systems. The article suggests that competition solves a sensitivity problem that confronts all cellular systems: the noise-saturation dilemma. Low energy input patterns can be registered poorly by cells due to their internal noise. High energy input patterns can be registered poorly by cells because their sensitivity approaches zero when all their sites are turned on. How do cells balance between the two equally deadly, but complementary, extremes of noise and saturation? How do cells achieve a Golden Mean?

648 citations

Journal ArticleDOI
TL;DR: The transformation of spatial patterns and their storage in short term memory by shunting neural networks are studied herein and various mechanisms are described for real-time regulation of the amount of contrast with which a pattern will be stored.
Abstract: The transformation of spatial patterns and their storage in short term memory by shunting neural networks are studied herein. Various mechanisms are described for real-time regulation of the amount of contrast with which a pattern will be stored. Parametric studies are described for the amount of contrast in the network responses to patterns presented at variable background or overall activity levels. Mechanisms for removing spurious peak splits and other disinhibitory responses are described. Furman's (1965) results on processing of patterns by shunting networks are generalized and reanalysed. Periodic responses (stable and unstable) corresponding to the time scale of slow cortical waves can be generated if a tonic input is set between two threshold activity levels. Their frequency as a function of tonic input size is unimodal. Order-preserving limit cycles are never found in STM; hence sustained slow oscillations as a mechanism for storing a pattern in STM are ruled out in favor of steady states (i.e., fast oscillations) with spatially graded activity levels. Such slow oscillations can, nonetheless, continuously retune the network's responsiveness to the patterns that perturb it.

271 citations

References
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Journal ArticleDOI
TL;DR: The contrast thresholds of a variety of grating patterns have been measured over a wide range of spatial frequencies and the results show clear patterns of uniformity in the response to grating noise.
Abstract: 1. The contrast thresholds of a variety of grating patterns have been measured over a wide range of spatial frequencies.2. Contrast thresholds for the detection of gratings whose luminance profiles are sine, square, rectangular or saw-tooth waves can be simply related using Fourier theory.3. Over a wide range of spatial frequencies the contrast threshold of a grating is determined only by the amplitude of the fundamental Fourier component of its wave form.4. Gratings of complex wave form cannot be distinguished from sine-wave gratings until their contrast has been raised to a level at which the higher harmonic components reach their independent threshold.5. These findings can be explained by the existence within the nervous system of linearly operating independent mechanisms selectively sensitive to limited ranges of spatial frequencies.

3,073 citations

Journal ArticleDOI
TL;DR: An improved version of the well-known interference fringe technique which theoretically allows a sinusoidal pattern of very high contrast to be formed directly on the retina to be obtained without prior modification by the optics of the eye is reported.
Abstract: If a scene containing fine spatial detail is viewed at constant high photopic luminance, there are two main factors which limit the perception of the fine detail-the quality of the optics of the eye forming the image on the retina and the ability of the retina (coupled to the brain) to resolve the details of that image. In the past there have been many theoretical studies of the potential resolving power of the optics based on consideration of diffraction and the chromatic and spherical aberrations of the eye. It is only recently that objective measurements of the quality of the optics of man in vivo have been obtained (Flamant, 1955; Westheimer & Campbell, 1962; Krauskopf 1962; R6hler, 1962). As will be demonstrated, it is not possible to use these findings to determine the relative weighting that should be given to the optics and the retina in determining a given threshold. This paper reports the results of experiments using an improved version of the well-known interference fringe technique (Le Grand, 1937; Byram 1944; Westheimer, 1960; Arnulf & Dupuy, 1960) which theoretically allows a sinusoidal pattern of very high contrast to be formed directly on the retina. The practical difficulty in using this technique is to obtain a light source of high intrinsic brightness and coherence with which to form high-luminance interference fringes on the retina; this has been solved by using a neon-helium gas laser. By decreasing the contrast (Fig. 1) of the interference fringes with another source of light it was possible to determine the contrasts on the retina at which the fringes are just detected. Thus a measure of the resolving power of the retina-brain is obtained without prior modification by the optics of the eye. Measurements have also been made of the visual resolution of external gratings whose intensity varied sinusoidally with distance across the gratings and which were imaged on to the retina by the optical components of the eye. By comparing the threshold contrasts of these external sinusoidal gratings with thresholds for sinusoidal fringes of the same spatial frequency formed through interference, the quality of the

1,600 citations

Journal ArticleDOI
TL;DR: The results clarify the nature of the fluctuations shown by an organism in response to a stimulus, and show that at the threshold it is the stimulus which is variable, and that the properties of its variation determine the fluctuations found between response and stimulus.
Abstract: 1. Direct measurements of the minimum energy required for threshold vision under optimal physiological conditions yield values between 2.1 and 5.7 x 10–10 ergs at the cornea, which correspond to between 54 and 148 quanta of blue-green light. 2. These values are at the cornea. To yield physiologically significant data they must be corrected for corneal reflection, which is 4 per cent; for ocular media absorption, which is almost precisely 50 per cent; and for retinal transmission, which is at least 80 per cent. Retinal transmission is derived from previous direct measurements and from new comparisons between the percentage absorption spectrum of visual purple with the dim-vision luminosity function. With these three corrections, the range of 54 to 148 quanta at the cornea becomes as an upper limit 5 to 14 quanta actually absorbed by the retinal rods. 3. This small number of quanta, in comparison with the large number of rods (500) involved, precludes any significant two quantum absorptions per rod, and means that in order to produce a visual effect, one quantum must be absorbed by each of 5 to 14 rods in the retina. 4. Because this number of individual events is so small, it may be derived from an independent statistical study of the relation between the intensity of a light flash and the frequency with which it is seen. Such experiments give values of 5 to 8 for the number of critical events involved at the threshold of vision. Biological variation does not alter these numbers essentially, and the agreement between the values measured directly and those derived from statistical considerations is therefore significant. 5. The results clarify the nature of the fluctuations shown by an organism in response to a stimulus. The general assumption has been that the stimulus is constant and the organism variable. The present considerations show, however, that at the threshold it is the stimulus which is variable, and that the properties of its variation determine the fluctuations found between response and stimulus.

1,028 citations

Journal ArticleDOI
TL;DR: In this paper, the reciprocal nature of these spatio-temporal interactions can be particularly clearly expressed if the threshold contrast is determined for a grating target whose luminance perpendicular to the bars is given by where m is the contrast, v the spatial frequency, and ƒ the temporal frequency of the target.
Abstract: T HE dependence of the form of the spatial contrast-sensitivity function for a square-wave test grating upon the duration of exposure of the target has been investigated by Schober and Hilz. 1 Kelly 2 has pointed out an analogous dependence of the form of the temporal contrast (modulation) sensitivity function upon the angular extent of the test target. The reciprocal nature of these spatio-temporal interactions can be particularly clearly ap­ preciated if the threshold contrast is determined for a grating target whose luminance perpendicular to the bars is given by where m is the contrast, v the spatial frequency, and ƒ the temporal frequency of the target. FIG. 2. Temporal contrast-sensitivity (reciprocal of threshold contrast) functions for different spatial frequencies. The points are the means of four measurements and the curves (two with dashed low-frequency sections) differ only in their positions along the contrast-sensitivity scale, O 0.5 cycle per degree, ● 4, ∆ 16, ▲ 22 cycles per degree. FIG. 1. Spatial contrast-sensitivity (reciprocal of threshold contrast) functions for different temporal frequencies. The points are the means of four measurements and the curves (one with a dashed low-frequency section) differ only in their positions along the contrast-sensitivity scale O 1 cycle per second, ● 6, ∆ 16, ▲ 22 cycles per second. Such a pattern was set up as a display on a cathode-ray oscil­ loscope and Figs. 1 and 2 show the results of threshold-contrast measurements made by the author (a well-corrected myope). Viewing was binocular at a distance of 2 m. The grating pattern subtended 2.5°×2.5° in the center of a 10°× 10° screen illuminated to the same mean luminance of 20 cd/m 2. The general similarity of the two sets of contrast-sensitivity functions is immediately evident but two features are particularly remarkable. First, the form of the fall-off in sensitivity at high

861 citations

Journal ArticleDOI
TL;DR: The concept of superposition has been found to be a useful and powerful one to apply to retinal function and an equation which enables calculations of responses to a wide range of visual stimuli is derived.

775 citations