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ABSTRACT: Visual evoked potentials produced in response to a reversive checkerboard pattern presented in conditions of additive noise were recorded. Changes induced by noise in both the shapes of evoked potentials and the structure of the test stimulus were compared. The nature of changes in the shapes of evoked potentials was found to correlate with the nature of changes in the amplitude-frequency spectrum of the stimulus. These results support the gestalt psychology point of view that the visual system uses spatial frequency rather than discrete means for describing information.
Neuroscience and Behavioral Physiology 10/2009; 39(7):683-94.
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ABSTRACT: Previous studies have demonstrated that human contrast sensitivity curves have marked extremes [4]. This phenomenon has not yet been investigated. The present report describes studies of plots of frequency-contrast characteristics obtained using gratings with orientations of 0 degrees , 90 degrees , and 135 degrees . The results showed that: 1) periodically located extremes were marked on the averaged curve obtained using gratings with an orientation of 0 degrees , while use of gratings with orientations of 90 degrees and 135 degrees gave weak peaks; 2) on repeat testing, the amplitudes of extremes decreased sharply, to the level of disappearance by day 5 of testing. These data lead to the suggestion that the phenomenon of local extremes is not associated with random errors by the subjects but reflects the specific characteristics of information processing by the visual system.
Neuroscience and Behavioral Physiology 07/2009; 39(5):457-62.
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A V Merkul'ev
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ABSTRACT: Factors that lead to decreasing thresholds across repeated test sessions in Gollin incomplete figure test were investigated. In the first experiment, 4 tests with 5-day intervals and using same test figures, were conducted. Thresholds of recognition in each test and amplitude-frequency characteristics of test images were compared by correlation analysis. In the second investigation, 2 tests with 3-day intervals were conducted. In repeated tests, half figures were familiar to the subjects. In addition, half fragmented figures (both familiar an unfamiliar to the subjects) had such amplitude-frequency characteristics as in the first test. It was found that decreasing of thresholds was primary conditioned by optimization of mechanisms that work with statistical (not object) information.
Rossiĭskii fiziologicheskiĭ zhurnal imeni I.M. Sechenova / Rossiĭskaia akademiia nauk 09/2007; 93(8):886-97.
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ABSTRACT: Perception thresholds were measured for fragmented outline figures (the Gollin test). A new approach to the question of the perception of incomplete images was developed. In this approach, figure fragmentation consisted of masking with multiplicative texture-like noise--this interference was termed "invisible" masking. The first series of studies established that the "similarity" between the amplitude-frequency spectra of test figures and "invisible" masks, expressed as a linear correlation coefficient, had significant effects on the recognition thresholds of these figures. The second series of experiments showed that progressing formation of the figures was accompanied by increases in the correlation between their spatial-frequency characteristics and the corresponding characteristics of the incomplete figure, while the correlation with the "invisible" mask decreased. It is suggested that the ratio of the correlation coefficients, characterizing the "similarity" of the fragmented figure with the intact figure and the "invisible" mask, corresponds to the signal:noise ratio. The psychophysical recognition threshold for figures for naive subjects not familiar with the test image alphabet was reached after the particular level of fragmentation at which this ratio was unity.
Neuroscience and Behavioral Physiology 02/2006; 36(1):15-20.
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ABSTRACT: Measurements were made of the threshold of recognition of cumulatively forming line figures. The threshold value of the outline, expressed in pixels, depended on the length of the outline of the whole unfragmented figure. Relative threshold values were constant, and for the measures of figure fragments used in the present study, averaged 12.5%. A spatial frequency analysis of the test images was performed. Variation of the amplitude-frequency parameters of the spectra of the images of various figures with threshold fragmentation was minimal as compared with the variation of these parameters in figures with subthreshold or suprathreshold levels of fragmentation.
Neuroscience and Behavioral Physiology 02/2005; 35(1):83-7.
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ABSTRACT: We measured recognition thresholds of incomplete figure perception (the Gollin test). This test we regarded as a visual masking problem. Digital image processing permits us to measure the spatial properties and spatial frequency spectrum of the absent part of the image as the mask. Using a noise paradigm, we have measured the signal/noise ratio for Incomplete Figure. Recognition was worse with better spectral "similarity" between the figure and the "invisible" mask. At threshold, the spectrum of the fragmented image was equally similar to that of the "invisible" mask and complete image. We think the recognition thresholds for Gollin stimuli reflect the signal/noise ratio.
Rossiĭskii fiziologicheskiĭ zhurnal imeni I.M. Sechenova / Rossiĭskaia akademiia nauk 12/2004; 90(11):1348-55.
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ABSTRACT: The thresholds of recognition of line drawings of common objects were measured using the Gollin-test procedure, in which separate random line fragments are displayed cumulatively up to the point of recognition. It was shown that the mean percentage of contour displayed at threshold recognition for different images was always about 12.5%, despite inter-subject variability between 5% and 25%. The comparative and spatial-frequency analysis of the geometrical parameters of images was carried out for different levels of fragmentation (before threshold, at threshold, and for the complete contour). The magnitude information of the Fourier domain image of figures was characterized by maximum at low and high levels of fragmentation, but at recognition threshold fragmentation it was characterized by minimum variability.
Rossiĭskii fiziologicheskiĭ zhurnal imeni I.M. Sechenova / Rossiĭskaia akademiia nauk 07/2003; 89(6):731-7.
